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Sample records for 18f-labeled rgd dimer

  1. Sulfonation of Tyrosine as a Method to Improve Biodistribution of Peptide-Based Radiotracers: Novel (18)F-Labelled Cyclic RGD Analogues.

    PubMed

    Haskali, Mohammad Baqir; Denoyer, Delphine; Noonan, Wayne; Cullinane, Carleen; Rangger, Christine; Pouliot, Normand; Haubner, Roland; Roselt, Peter D; Hicks, Rodney J; Hutton, Craig A

    2017-02-13

    The labeling of peptides with positron emitting radionuclides has long held the promise of a wide range of PET agents possessing high affinity and selectivity. Not surprisingly, controlling the biodistribution of these agents has proven to be a major challenge in their successful application. Modification of peptide hydrophilicity in order to increase renal clearance has been a common endeavor to improve overall biodistribution. Herein, we examine the effect of site-specific sulfonation of tyrosine moieties in cyclic(RGDyK) peptides as a means to enhance their hydrophilicity and improve their biodistribution. The novel sulfonated cyclic(RGDyK) peptides were conjugated directly to 4-nitrophenyl 2-[18F]fluoropropionate and the biodistribution of the radiolabeled peptides was compared with that of their non-sulfonated, clinically relevant counterparts, [18F]GalactoRGD and [18F]FPPRGD2. Site-specific sulfonation of the tyrosine residues was shown to increase hydrophilicity and improve biodistribution of the RGD peptides, despite contributing just 79 Da towards the MW, compared with 189 Da for both the 'Galacto' and mini-PEG moieties, suggesting this may be a broadly applicable approach to enhancing biodistribution of radiolabelled peptides.

  2. 18F-Labeling Using Click Cycloadditions

    PubMed Central

    Ross, Tobias L.

    2014-01-01

    Due to expanding applications of positron emission tomography (PET) there is a demand for developing new techniques to introduce fluorine-18 (t1/2 = 109.8 min). Considering that most novel PET tracers are sensitive biomolecules and that direct introduction of fluorine-18 often needs harsh conditions, the insertion of 18F in those molecules poses an exceeding challenge. Two major challenges during 18F-labeling are a regioselective introduction and a fast and high yielding way under mild conditions. Furthermore, attention has to be paid to functionalities, which are usually present in complex structures of the target molecule. The Cu-catalyzed azide-alkyne cycloaddition (CuAAC) and several copper-free click reactions represent such methods for radiolabeling of sensitive molecules under the above-mentioned criteria. This minireview will provide a quick overview about the development of novel 18F-labeled prosthetic groups for click cycloadditions and will summarize recent trends in copper-catalyzed and copper-free click 18F-cycloadditions. PMID:25003110

  3. One-step 18F labeling of biomolecules using organotrifluoroborates

    PubMed Central

    Liu, Zhibo; Lin, Kuo-Shyan; Bénard, François; Pourghiasian, Maral; Kiesewetter, Dale O; Perrin, David M; Chen, Xiaoyuan

    2017-01-01

    Herein we present a general protocol for the functionalization of biomolecules with an organotrifluoroborate moiety so that they can be radiolabeled with aqueous 18F fluoride (18F−) and used for positron emission tomography (PET) imaging. Among the β+-emitting radionuclides, fluorine-18 (18F) is the isotope of choice for PET, and it is produced, on-demand, in many hospitals worldwide. Organotrifluoroborates can be 18F-labeled in one step in aqueous conditions via 18F–19F isotope exchange. This protocol features a recently designed ammoniomethyltrifluoroborate, and it describes the following: (i) a synthetic strategy that affords modular synthesis of radiolabeling precursors via a copper-catalyzed ‘click’ reaction; and (ii) a one-step 18F-labeling method that obviates the need for HPLC purification. Within 30 min, 18F-labeled PET imaging probes, such as peptides, can be synthesized in good chemical and radiochemical purity (>98%), satisfactory radiochemical yield of 20–35% (n > 20, non-decay corrected) and high specific activity of 40–111 GBq/µmol (1.1–3.0 Ci/µmol). The entire procedure, including the precursor preparation and 18F radiolabeling, takes 7–10 d. PMID:26313478

  4. Synthesis and Reactivity of (18)F-Labeled α,α-Difluoro-α-(aryloxy)acetic Acids.

    PubMed

    Khotavivattana, Tanatorn; Calderwood, Samuel; Verhoog, Stefan; Pfeifer, Lukas; Preshlock, Sean; Vasdev, Neil; Collier, Thomas L; Gouverneur, Véronique

    2017-02-03

    In this work, we describe the (18)F-labeling of α,α-difluoro-α-(aryloxy)acetic acid derivatives and demonstrate that these building blocks are amenable to post-(18)F-fluorination functionalization. Protodecarboxylation offers a new entry to (18)F-difluoromethoxyarene, and the value of this approach is further demonstrated with coupling processes leading to representative (18)F-labeled TRPV1 inhibitors and TRPV1 antagonists.

  5. 18F-Labelled Intermediates for Radiosynthesis by Modular Build-Up Reactions: Newer Developments

    PubMed Central

    Ermert, Johannes

    2014-01-01

    This brief review gives an overview of newer developments in 18F-chemistry with the focus on small 18F-labelled molecules as intermediates for modular build-up syntheses. The short half-life (<2 h) of the radionuclide requires efficient syntheses of these intermediates considering that multistep syntheses are often time consuming and characterized by a loss of yield in each reaction step. Recent examples of improved synthesis of 18F-labelled intermediates show new possibilities for no-carrier-added ring-fluorinated arenes, novel intermediates for tri[18F]fluoromethylation reactions, and 18F-fluorovinylation methods. PMID:25343144

  6. F-18 Labeled RGD Probes Based on Bioorthogonal Strain-Promoted Click Reaction for PET Imaging.

    PubMed

    Kim, Hye Lan; Sachin, Kalme; Jeong, Hyeon Jin; Choi, Wonsil; Lee, Hyun Soo; Kim, Dong Wook

    2015-04-09

    A series of fluorine-substituted monomeric and dimeric cRGD peptide derivatives, such as cRGD-ADIBOT-F (ADIBOT = azadibenzocyclooctatriazole), di-cRGD-ADIBOT-F, cRGD-PEG5-ADIBOT-F, and di-cRGD-PEG5-ADIBOT-F, were prepared by strain-promoted alkyne azide cycloaddition (SPAAC) reaction of the corresponding aza-dibenzocyclooctyne (ADIBO) substituted peptides with a fluorinated azide 3. Among these cRGD derivatives, di-cRGD-PEG5-ADIBOT-F had the highest binding affinity in a competitive binding assay compared to other derivatives and even the original cRGDyk. On the basis of the in vitro study results, di-cRGD-PEG5-ADIBOT-(18)F was prepared from a SPAAC reaction with (18)F-labeled azide and subsequent chemo-orthogonal scavenger-assisted separation without high performance liquid chromatography (HPLC) purification in 92% decay-corrected radiochemical yield (dcRCY) with high specific activity for further in vivo positron emission tomography (PET) imaging study. In vivo PET imaging study and biodistribution data showed that this radiotracer allowed successful visualization of tumors with good tumor-to-background contrast and significantly higher tumor uptake compared to other major organs.

  7. Convergent synthesis and evaluation of (18)F-labeled azulenic COX2 probes for cancer imaging.

    PubMed

    Nolting, Donald D; Nickels, Michael; Tantawy, Mohammed N; Yu, James Y H; Xie, Jingping; Peterson, Todd E; Crews, Brenda C; Marnett, Larry; Gore, John C; Pham, Wellington

    2012-01-01

    The overall objectives of this research are to (i) develop azulene-based positron emission tomography (PET) probes and (ii) image COX2 as a potential biomarker of breast cancer. Several lines of research have demonstrated that COX2 is overexpressed in breast cancer and that its presence correlates with poor prognoses. While other studies have reported that COX2 inhibition can be modulated and used beneficially as a chemopreventive strategy in cancer, no viable mechanism for achieving that approach has yet been developed. This shortfall could be circumvented through in vivo imaging of COX2 activity, particularly using sensitive imaging techniques such as PET. Toward that goal, our laboratory focuses on the development of novel (18)F-labled COX2 probes. We began the synthesis of the probes by transforming tropolone into a lactone, which was subjected to an [8 + 2] cycloaddition reaction to yield 2-methylazulene as the core ring of the probe. After exploring numerous synthetic routes, the final target molecule and precursor PET compounds were prepared successfully using convergent synthesis. Conventional (18)F labeling methods caused precursor decomposition, which prompted us to hypothesize that the acidic protons of the methylene moiety between the azulene and thiazole rings were readily abstracted by a strong base such as potassium carbonate. Ultimately, this caused the precursors to disintegrate. This observation was supported after successfully using an (18)F labeling strategy that employed a much milder phosphate buffer. The (18)F-labeled COX2 probe was tested in a breast cancer xenograft mouse model. The data obtained via successive whole-body PET/CT scans indicated probe accumulation and retention in the tumor. Overall, the probe was stable in vivo and no defluorination was observed. A biodistribution study and Western blot analysis corroborate with the imaging data. In conclusion, this novel COX2 PET probe was shown to be a promising agent for cancer imaging

  8. Convergent synthesis and evaluation of 18F-labeled azulenic COX2 probes for cancer imaging

    PubMed Central

    Nolting, Donald D.; Nickels, Michael; Tantawy, Mohammed N.; Yu, James Y. H.; Xie, Jingping; Peterson, Todd E.; Crews, Brenda C.; Marnett, Larry; Gore, John C.; Pham, Wellington

    2013-01-01

    The overall objectives of this research are to (i) develop azulene-based positron emission tomography (PET) probes and (ii) image COX2 as a potential biomarker of breast cancer. Several lines of research have demonstrated that COX2 is overexpressed in breast cancer and that its presence correlates with poor prognoses. While other studies have reported that COX2 inhibition can be modulated and used beneficially as a chemopreventive strategy in cancer, no viable mechanism for achieving that approach has yet been developed. This shortfall could be circumvented through in vivo imaging of COX2 activity, particularly using sensitive imaging techniques such as PET. Toward that goal, our laboratory focuses on the development of novel 18F-labled COX2 probes. We began the synthesis of the probes by transforming tropolone into a lactone, which was subjected to an [8 + 2] cycloaddition reaction to yield 2-methylazulene as the core ring of the probe. After exploring numerous synthetic routes, the final target molecule and precursor PET compounds were prepared successfully using convergent synthesis. Conventional 18F labeling methods caused precursor decomposition, which prompted us to hypothesize that the acidic protons of the methylene moiety between the azulene and thiazole rings were readily abstracted by a strong base such as potassium carbonate. Ultimately, this caused the precursors to disintegrate. This observation was supported after successfully using an 18F labeling strategy that employed a much milder phosphate buffer. The 18F-labeled COX2 probe was tested in a breast cancer xenograft mouse model. The data obtained via successive whole-body PET/CT scans indicated probe accumulation and retention in the tumor. Overall, the probe was stable in vivo and no defluorination was observed. A biodistribution study and Western blot analysis corroborate with the imaging data. In conclusion, this novel COX2 PET probe was shown to be a promising agent for cancer imaging and

  9. Enhanced Aqueous Suzuki–Miyaura Coupling Allows Site-Specific Polypeptide 18F-Labeling

    PubMed Central

    2013-01-01

    The excesses of reagents used in protein chemistry are often incompatible with the reduced or even inverse stoichiometries used for efficient radiolabeling. Analysis and screening of aqueous Pd(0) ligand systems has revealed the importance of a guanidine core and the discovery of 1,1-dimethylguanidine as an enhanced ligand for aqueous Suzuki–Miyaura cross-coupling. This novel Pd catalyst system has now allowed the labeling of small molecules, peptides, and proteins with the fluorine-18 prosthetic [18F]4-fluorophenylboronic acid. These findings now enable site-specific protein 18F-labeling under biologically compatible conditions using a metal-triggered reaction. PMID:23991754

  10. New Chelators for Low Temperature Al(18)F-Labeling of Biomolecules.

    PubMed

    Cleeren, Frederik; Lecina, Joan; Billaud, Emilie M F; Ahamed, Muneer; Verbruggen, Alfons; Bormans, Guy M

    2016-03-16

    The Al(18)F labeling method is a relatively new approach that allows radiofluorination of biomolecules such as peptides and proteins in a one-step procedure and in aqueous solution. However, the chelation of the {Al(18)F}(2+) core with the macrocyclic chelators NOTA or NODA requires heating to 100-120 °C. Therefore, we have developed new polydentate ligands for the complexation of {Al(18)F}(2+) with good radiochemical yields at a temperature of 40 °C. The stability of the new Al(18)F-complexes was tested in phosphate buffered saline (PBS) at pH 7.4 and in rat serum. The stability of the Al(18)F-L3 complex was found to be comparable to that of the previously reported Al(18)F-NODA complex up to 60 min in rat serum. Moreover, the biodistribution of Al(18)F-L3 in healthy mice showed the absence of in vivo defluorination since no significant bone uptake was observed, whereas the major fraction of activity at 60 min p.i. was observed in liver and intestines, indicating hepatobiliary clearance of the radiolabeled ligand. The acyclic chelator H3L3 proved to be a good lead candidate for labeling of heat-sensitive biomolecules with fluorine-18. In order to obtain a better understanding of the different factors influencing the formation and stability of the complex, we carried out more in-depth experiments with ligand H3L3. As a proof of concept, we successfully conjugated the new AlF-chelator with the urea-based PSMA inhibitor Glu-NH-CO-NH-Lys to form Glu-NH-CO-NH-Lys(Ahx)L3, and a biodistribution study in healthy mice was performed with the Al(18)F-labeled construct. This new class of AlF-chelators may have a great impact on PET radiochemical space as it will stimulate the rapid development of new fluorine-18 labeled peptides and other heat-sensitive biomolecules.

  11. sup 18 F-labeled insulin: A prosthetic group methodology for incorporation of a positron emitter into peptides and proteins

    SciTech Connect

    Shai, Y.; Kirk, K.L.; Channing, M.A.; Dunn, B.B.; Lesniak, M.A.; Eastman, R.C.; Finn, R.D.; Roth, J.; Jacobson, K.A. )

    1989-05-30

    In the present study we synthesize {sup 18}F-labeled insulin of high specific radioactivity. A new prosthetic group methodology, in which ({sup 18}F)fluoride displaces a bromide group of 4-(bromomethyl)-benzoylamine intermediates, was used. The 4-(fluoromethyl)benzoyl product was chemically stable. {sup 18}F-Labeled insulin retains the essential biological properties of native insulin, as measured in vitro by binding to insulin receptors on human cells and stimulation of glucose metabolism in rat adipocytes. The overall process can be carried out speedily to yield a product of sufficient purity to permit in vivo studies. The method appears to be applicable to a wide variety of peptides.

  12. Impact of Multiple Negative Charges on Blood Clearance and Biodistribution Characteristics of 99mTc-Labeled Dimeric Cyclic RGD Peptides

    PubMed Central

    2015-01-01

    This study sought to evaluate the impact of multiple negative charges on blood clearance kinetics and biodistribution properties of 99mTc-labeled RGD peptide dimers. Bioconjugates HYNIC-P6G-RGD2 and HYNIC-P6D-RGD2 were prepared by reacting P6G-RGD2 and P6D-RGD2, respectively, with excess HYNIC-OSu in the presence of diisopropylethylamine. Their IC50 values were determined to be 31 ± 5 and 41 ± 6 nM, respectively, against 125I-echistatin bound to U87MG glioma cells in a whole-cell displacement assay. Complexes [99mTc(HYNIC-P6G-RGD2)(tricine)(TPPTS)] (99mTc-P6G-RGD2) and [99mTc(HYNIC-P6D-RGD2)(tricine)(TPPTS)] (99mTc-P6D-RGD2) were prepared in high radiochemical purity (RCP > 95%) and specific activity (37–110 GBq/μmol). They were evaluated in athymic nude mice bearing U87MG glioma xenografts for their biodistribution. The most significant difference between 99mTc-P6D-RGD2 and 99mTc-P6G-RGD2 was their blood radioactivity levels and tumor uptake. The initial blood radioactivity level for 99mTc-P6D-RGD2 (4.71 ± 1.00%ID/g) was ∼5× higher than that of 99mTc-P6G-RGD2 (0.88 ± 0.05%ID/g), but this difference disappeared at 60 min p.i. 99mTc-P6D-RGD2 had much lower tumor uptake (2.20–3.11%ID/g) than 99mTc-P6G-RGD2 (7.82–9.27%ID/g) over a 2 h period. Since HYNIC-P6D-RGD2 and HYNIC-P6G-RGD2 shared a similar integrin αvβ3 binding affinity (41 ± 6 nM versus 31 ± 5 nM), the difference in their blood activity and tumor uptake is most likely related to the nine negative charges and high protein binding of 99mTc-P6D-RGD2. Despite its low uptake in U87MG tumors, the tumor uptake of 99mTc-P6D-RGD2 was integrin αvβ3-specific. SPECT/CT studies were performed using 99mTc-P6G-RGD2 in athymic nude mice bearing U87MG glioma and MDA-MB-231 breast cancer xenografts. The SPECT/CT data demonstrated the tumor-targeting capability of 99mTc-P6G-RGD2, and its tumor uptake depends on the integrin αvβ3 expression levels on tumor cells and neovasculature. It was concluded that

  13. (18)F-labeled positron emission tomographic radiopharmaceuticals in oncology: an overview of radiochemistry and mechanisms of tumor localization.

    PubMed

    Vallabhajosula, Shankar

    2007-11-01

    Molecular imaging is the visualization, characterization, and measurement of biological processes at the molecular and cellular levels in a living system. At present, positron emission tomography/computed tomography (PET/CT) is one the most rapidly growing areas of medical imaging, with many applications in the clinical management of patients with cancer. Although [(18)F]fluorodeoxyglucose (FDG)-PET/CT imaging provides high specificity and sensitivity in several kinds of cancer and has many applications, it is important to recognize that FDG is not a "specific" radiotracer for imaging malignant disease. Highly "tumor-specific" and "tumor cell signal-specific" PET radiopharmaceuticals are essential to meet the growing demand of radioisotope-based molecular imaging technology. In the last 15 years, many alternative PET tracers have been proposed and evaluated in preclinical and clinical studies to characterize the tumor biology more appropriately. The potential clinical utility of several (18)F-labeled radiotracers (eg, fluoride, FDOPA, FLT, FMISO, FES, and FCH) is being reviewed by several investigators in this issue. An overview of design and development of (18)F-labeled PET radiopharmaceuticals, radiochemistry, and mechanism(s) of tumor cell uptake and localization of radiotracers are presented here. The approval of clinical indications for FDG-PET in the year 2000 by the Food and Drug Administration, based on a review of literature, was a major breakthrough to the rapid incorporation of PET into nuclear medicine practice, particularly in oncology. Approval of a radiopharmaceutical typically involves submission of a "New Drug Application" by a manufacturer or a company clearly documenting 2 major aspects of the drug: (1) manufacturing of PET drug using current good manufacturing practices and (2) the safety and effectiveness of a drug with specific indications. The potential routine clinical utility of (18)F-labeled PET radiopharmaceuticals depends also on

  14. Synthesis and preliminary evaluation of [18F]-labeled 2-oxoquinoline derivatives for PET imaging of cannabinoid CB2 receptor

    PubMed Central

    Turkman, Nashaat; Paolillo, Vincenzo; Shavrin, Aleksander; Yeh, Hsin Hsien; Flores, Leo; Soghomonian, Suren; Ravinovich, Brian; Volgin, Andrei; Gelovani, Juri; Alauddin, Mian

    2011-01-01

    Introduction The cannabinoid receptor type 2 (CB2) is an important target for development of drugs and imaging agents for diseases, such as neuroinflammation, neurodegeneration, and cancer. Recently we reported synthesis and results of in vitro receptor binding of a focused library of fluorinated 2-oxoquinoline derivatives as CB2 receptor ligands. Some of the compounds demonstrated as good CB2-specific ligands with Ki values in the nanomolar to sub-nanomolar concentrations; therefore, we pursued the development of their 18F-labeled analogues that should be useful for PET imaging of CB2 receptor expression. Here, we report the radiosynthesis of two 18F-labeled 2-oxoquinoline derivatives, and preliminary in vitro and ex-vivo evaluation of one compound as a CB2-specific radioligand. Methods 4-[18F]Fluorobenzyl amine [18F]-3 was prepared by radiofluorination of 4-cyano-N,N,N-trimethylanilinium triflate salt followed by reduction with LiAlH4 and then coupled with acid chlorides 11 and 12 to afford [18F]-13 and [18F]-14. In vitro CB2 receptor binding assay was performed using U87 cells transduced with CB2- and CB1-receptor. Ex-vivo autoradiography was performed with [18F]-14 on spleen, CB2- and CB1-expressing and wild type U87 subcutaneous tumors grown in mice. Results The radiochemical yields of [18F]-13 and [18F]-14 were 10%-15.0% with an average of 12% (n=10); radiochemical purity was > 99% with specific activity 1200 mCi/μmole. The dissociation constant Kd for [18F]-14 was 3.4 nM. Ex-vivo autoradiography showed accumulation of [18F]-14 in the CB2-expressing tumor. Conclusion Two new [18F]-labeled CB2 ligands have been synthesized. Compound [18F]-14 appears to be a potential PET imaging agent for the assessment of CB2 receptor expression in vivo. PMID:22226022

  15. Design, synthesis and evaluation of (18)F-labeled bradykinin B1 receptor-targeting small molecules for PET imaging.

    PubMed

    Zhang, Zhengxing; Kuo, Hsiou-Ting; Lau, Joseph; Jenni, Silvia; Zhang, Chengcheng; Zeisler, Jutta; Bénard, François; Lin, Kuo-Shyan

    2016-08-15

    Two fluorine-18 ((18)F) labeled bradykinin B1 receptor (B1R)-targeting small molecules, (18)F-Z02035 and (18)F-Z02165, were synthesized and evaluated for imaging with positron emission tomography (PET). Z02035 and Z02165 were derived from potent antagonists, and showed high binding affinity (0.93±0.44 and 2.80±0.50nM, respectively) to B1R. (18)F-Z02035 and (18)F-Z02165 were prepared by coupling 2-[(18)F]fluoroethyl tosylate with their respective precursors, and were obtained in 10±5 (n=4) and 22±14% (n=3), respectively, decay-corrected radiochemical yield with >99% radiochemical purity. (18)F-Z02035 and (18)F-Z02165 exhibited moderate lipophilicity (LogD7.4=1.10 and 0.59, respectively), and were stable in mouse plasma. PET imaging and biodistribution studies in mice showed that both tracers enabled visualization of the B1R-positive HEK293T::hB1R tumor xenografts with better contrast than control B1R-negative HEK293T tumors. Our data indicate that small molecule antagonists can be used as pharmacophores for the design of B1R-targeting PET tracers.

  16. A high-affinity [18F]-labeled phosphoramidate peptidomimetic PSMA-targeted inhibitor for PET imaging of prostate cancer

    PubMed Central

    Ganguly, Tanushree; Dannoon, Shorouk; Hopkins, Mark R.; Murphy, Stephanie; Cahaya, Hendry; Blecha, Joseph E.; Jivan, Salma; Drake, Christopher R.; Barinka, Cyril; Jones, Ella F.; VanBrocklin, Henry F.; Berkman, Clifford E.

    2015-01-01

    Introduction In this study, a structurally modified phosphoramidate scaffold, with improved prostate-specific membrane antigen (PSMA) avidity, stability and in vivo characteristics, as a PET imaging agent for prostate cancer (PCa), was prepared and evaluated. Methods p-Fluorobenzoyl-aminohexanoate and 2-(3-hydroxypropyl)glycine were introduced into the PSMA-targeting scaffold yielding phosphoramidate 5. X-ray crystallography was performed on the PSMA/5 complex. [18F]5 was synthesized, and cell uptake and internalization studies were conducted in PSMA(+) LNCaP and CWR22Rv1 cells and PSMA(−) PC-3 cells. In vivo PET imaging and biodistribution studies were performed at 1 and 4 h post injection in mice bearing CWR22Rv1 tumor, with or without blocking agent. Results The crystallographic data showed interaction of the p-fluorobenzoyl group with an arene-binding cleft on the PSMA surface. In vitro studies revealed elevated uptake of [18F]5 in PSMA(+) cells (2.2% in CWR22Rv1 and 12.1% in LNCaP) compared to PSMA(−) cells (0.08%) at 4 h. In vivo tumor uptake of 2.33% ID/g and tumor-to-blood ratio of 265:1 was observed at 4 h. Conclusions We have successfully synthesized, radiolabeled and evaluated a new PSMA-targeted PET agent. The crystal structure of the PSMA/5 complex highlighted the interactions within the arene-binding cleft contributing to the overall complex stability. The high target uptake and rapid non-target clearance exhibited by [18F]5 in PSMA(+) xenografts substantiates its potential use for PET imaging of PCa. Advances in Knowledge The only FDA-approved imaging agent for PCa, Prostascint®, targets PSMA but suffers from inherent shortcomings. The data acquired in this manuscript confirmed that our new generation of [18F]-labeled PSMA inhibitor exhibited promising in vivo performance as a PET imaging agent for PCa and is well-positioned for subsequent clinical trials. Implications for Patient Care Our preliminary data demonstrate that this tracer possesses

  17. Fluorine-18 labeling of small molecules: the use of 18F-labeled aryl fluorides derived from no-carrier-added [18F]fluoride as labeling precursors.

    PubMed

    Wuest, F

    2007-01-01

    The favourable long-half life, the ease of production and the low energy of the emitted positron make 18F an ideal radionuclide for PET imaging. Radiochemistry of 18F basically relies on two distinctive types of reactions: nucleophilic and electrophilic reactions. All syntheses of 18F-labeled radiotracers are based on either [18F]fluoride ion or [18F]fluorine gas as simple primary labeling precursors which are obtained directly from the cyclotron. They can be applied either directly to the radiosynthesis or they can be transformed into more complex labeling precursors enabling the multi-step build-up of organic tracer molecules. The topic of this review is a survey on the application of several 18F-labeled aryl fluorides as building blocks derived from no-carrier-added (n.c.a.) [18F] fluoride to build up small monomeric PET radiotracers at high specific radioactivity by multi-step synthesis procedures.

  18. Synthesis and in vitro and in vivo evaluation of an (18)F-labeled neuropeptide Y analogue for imaging of breast cancer by PET.

    PubMed

    Hofmann, Sven; Maschauer, Simone; Kuwert, Torsten; Beck-Sickinger, Annette G; Prante, Olaf

    2015-04-06

    Imaging of Y1R expression in breast cancer is still a challenging task. Herein, we report a suitable (18)F-labeled high-molecular-weight glycopeptide for imaging of peripheral neuropeptide Y (NPY) Y1 receptor (Y1R)-positive tumors by preclinical small-animal positron emission tomography (PET). The Y1R-preferring NPY [F(7),P(34)]NPY analogue was functionalized with an alkyne-bearing propargylglycine (Pra) in position 4. The corresponding fluoroglycosylated (FGlc) peptide analogue [Pra(4)(FGlc),F(7),P(34)]NPY and its (18)F-labeled analogue were synthesized by click chemistry-based fluoroglycosylation. The radiosynthesis was performed by (18)F-fluoroglycosylation starting from the 2-triflate of the β-mannosylazide and the alkyne peptide [Pra(4),F(7),P(34)]NPY. The radiosynthesis of the(18)F-labeled analogue was optimized using a minimum amount of peptide precursor (40 nmol), proceeding with an overall radiochemical yield of 20-25% (nondecay corrected) in a total synthesis time of 75 min with specific activities of 40-70 GBq/μmol. In comparison to NPY and [F(7),P(34)]NPY, in vitro Y1R and Y2R activation studies with the cold [Pra(4)(FGlc),F(7),P(34)]NPY on stably transfected COS-7 cells displayed a high potency for the induction of Y1R-specific inositol accumulation (pEC50 = 8.5 ± 0.1), whereas the potency at Y2R was significantly decreased. Internalization studies on stably transfected HEK293 cells confirmed a strong glycopeptide-mediated Y1R internalization and a substantial Y1R subtype selectivity over Y2R. In vitro autoradiography with Y1R-positive MCF-7 tumor tissue slices indicated high specific binding of the (18)F-labeled glycopeptide, when binding was reduced by 95% ([Pra(4),F(7),P(34)]NPY) and by 86% (BIBP3226 Y1R antagonist) in competition studies. Biodistribution and small-animal PET studies on MCF-7 breast tumor-bearing nude mice revealed radiotracer uptake in the MCF-7 tumor of 1.8%ID/g at 20 min p.i. and 0.7%ID/g at 120 min p.i. (n = 3-4), increasing

  19. Preparation of 18F-labeled peptides using the copper(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition.

    PubMed

    Gill, Herman S; Marik, Jan

    2011-10-13

    An optimized procedure for preparing fluorine-18 ((18)F)-labeled peptides by the copper-catalyzed azide-alkyne 1,3-dipolar cyloaddition (CuAAC) is presented here. The two-step radiosynthesis begins with the microwave-assisted nucleophilic (18)F-fluorination of a precursor containing a terminal p-toluenesulfonyl, terminal azide and polyethylene glycol backbone. The resulting (18)F-fluorinated azide-containing building block is coupled to an alkyne-decorated peptide by the CuAAC. The reaction is accelerated by the copper(I)-stabilizing ligand bathophenanthroline disulfonate and can be performed in either reducing or nonreducing conditions (e.g., to preserve disulfide bonds). After an HPLC purification, (18)F-labeled peptide can be obtained with a 31 ± 6% radiochemical yield (n = 4, decay-corrected from (18)F-fluoride elution) and a specific activity of 39.0 ± 12.4 Ci μmol(-1) within 77 ± 4 min.

  20. In vivo biodistribution of two ( sup 18 F)-labelled muscarinic cholinergic receptor ligands: 2-( sup 18 F)- and 4-( sup 18 F)-fluorodexetimide

    SciTech Connect

    Wilson, A.A.; Scheffel, U.A.; Dannals, R.F.; Stathis, M.; Ravert, H.T.; Wagner, H.N. Jr. )

    1991-01-01

    Two ({sup 18}F)-labelled analogues of the potent muscarinic cholinergic receptor (m-AChR) antagonist, dexetimide, were evaluated as potential ligands for imaging m-AChR by positron emission tomography (PET). Intravenous administration of both 2-({sup 18}F)- or 4-({sup 18}F)-fluorodexetimide resulted in high brain uptake of radioactivity in mice. High binding levels were observed in m-AChR rich areas, such as cortex and striatum, with low levels in the receptor-poor cerebellum. Uptake of radioactivity was saturable and could be blocked by pre-administration of dexetimide or atropine. Drugs with different sites of action were ineffective at blocking receptor binding. The results indicate that both radiotracers are promising candidates for use in PET studies.

  1. RGD-based PET tracers for imaging receptor integrin αv β3 expression.

    PubMed

    Cai, Hancheng; Conti, Peter S

    2013-05-15

    Positron emission tomography (PET) imaging of receptor integrin αv β3 expression may play a key role in the early detection of cancer and cardiovascular diseases, monitoring disease progression, evaluating therapeutic response, and aiding anti-angiogenic drugs discovery and development. The last decade has seen the development of new PET tracers for in vivo imaging of integrin αv β3 expression along with advances in PET chemistry. In this review, we will focus on the radiochemistry development of PET tracers based on arginine-glycine-aspartic acid (RGD) peptide, present an overview of general strategies for preparing RGD-based PET tracers, and review the recent advances in preparations of (18) F-labeled, (64) Cu-labeled, and (68) Ga-labeled RGD tracers, RGD-based PET multivalent probes, and RGD-based PET multimodality probes for imaging receptor integrin αv β3 expression.

  2. Synthesis and pre-clinical evaluation of an 18F-labeled single-chain antibody fragment for PET imaging of epithelial ovarian cancer

    PubMed Central

    Sharma, Sai Kiran; Wuest, Melinda; Way, Jenilee D; Bouvet, Vincent R; Wang, Monica; Wuest, Frank R

    2016-01-01

    Anti-CA125 antibodies have been used in immunoassays to quantify levels of shed antigen in the serum of patients who are under surveillance for epithelial ovarian cancer (EOC). However, there is currently no molecular imaging probe in the clinic for the assessment of CA125 expression in vivo. The present study describes the development of an 18F-labeled single-chain variable fragment (scFv) for PET imaging of CA125 in preclinical EOC models. Anti-CA125 scFv was derived from MAb-B43.13 by recombinant expression of the fragment in E.coli. Fragment scFv-B43.13 was purified via immobilized metal affinity chromatography and characterized for antigen binding via immuno-staining and flow cytometry. Prosthetic group N-succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) was used for radiolabeling of scFv-B43.13. Preclinical ovarian cancer models were developed based on ovarian cancer cell lines OVCAR3 (CA125-positive) and SKOV3 (CA125-negative) in NIH-III mice. The radiopharmacological profile of 18F-labeled scFv-B43.13 ([18F]FBz-scFv-B43.13) was studied with PET. [18F]FBz-scFv-B43.13 was prepared in radiochemical yields of 3.7 ± 1.8% (n = 5) at an effective specific activity of 3.88 ± 0.76 GBq/µmol (n = 5). The radiotracer demonstrated selective uptake in CA125-positive OVCAR3 cells and virtually no uptake in CA125-negative SKOV3 cells. Standardized uptake values (SUV) of radioactivity uptake in OVCAR3 tumors was 0.5 (n = 3) and 0.3 (n = 2) in SKOV3 tumors after 60 min post injection (p.i.). PMID:27508105

  3. Early identification of antigen-specific immune responses in vivo by [18F]-labeled 3'-fluoro-3'-deoxy-thymidine ([18F]FLT) PET imaging.

    PubMed

    Aarntzen, Erik H J G; Srinivas, Mangala; De Wilt, Johannes H W; Jacobs, Joannes F M; Lesterhuis, W Joost; Windhorst, Albert D; Troost, Esther G; Bonenkamp, Johannes J; van Rossum, Michelle M; Blokx, Willeke A M; Mus, Roel D; Boerman, Otto C; Punt, Cornelis J A; Figdor, Carl G; Oyen, Wim J G; de Vries, I Jolanda M

    2011-11-08

    Current biomarkers are unable to adequately predict vaccine-induced immune protection in humans with infectious disease or cancer. However, timely and adequate assessment of antigen-specific immune responses is critical for successful vaccine development. Therefore, we have developed a method for the direct assessment of immune responses in vivo in a clinical setting. Melanoma patients with lymph node (LN) metastases received dendritic cell (DC) vaccine therapy, injected intranodally, followed by [(18)F]-labeled 3'-fluoro-3'-deoxy-thymidine ([(18)F]FLT) PET at varying time points after vaccination. Control LNs received saline or DCs without antigen. De novo immune responses were readily visualized in treated LNs early after the prime vaccination, and these signals persisted for up to 3 wk. This selective [(18)F]FLT uptake was markedly absent in control LNs, although tracer uptake in treated LNs increased profoundly with as little as 4.5 × 10(5) DCs. Immunohistochemical staining confirmed injected DC dispersion to T-cell areas and resultant activation of CD4(+) and CD8(+) T cells. The level of LN tracer uptake significantly correlates to the level of circulating antigen-specific IgG antibodies and antigen-specific proliferation of T cells in peripheral blood. Furthermore, this correlation was not observed with [(18)F]-labeled fluoro-2-deoxy-2-D-glucose. Therefore, [(18)F]FLT PET offers a sensitive tool to study the kinetics, localization, and involvement of lymphocyte subsets in response to vaccination. This technique allows for early discrimination of responding from nonresponding patients in anti-cancer vaccination and aid physicians in individualized decisionmaking.

  4. Fully automated production of diverse 18F-labeled PET tracers on the ELIXYS multi-reactor radiosynthesizer without hardware modification

    PubMed Central

    Lazari, Mark; Collins, Jeffrey; Shen, Bin; Farhoud, Mohammed; Yeh, Daniel; Maraglia, Brandon; Chin, Frederick T.; Nathanson, David A.; Moore, Melissa; van Dam, R. Michael

    2015-01-01

    Fully-automated radiosynthesizers are continuing to be developed to meet the growing need for the reliable production of positron emission tomography (PET) tracers made under current good manufacturing practice (cGMP) guidelines. There is a current trend towards supporting “kit-like” disposable cassettes that come preconfigured for particular tracers, thus eliminating the need for cleaning protocols between syntheses and enabling quick transitions to synthesizing other tracers. Though ideal for production, these systems are often limited for the development of novel tracers due to pressure, temperature, and chemical compatibility considerations. This study demonstrates the versatile use of the ELIXYS fully-automated radiosynthesizer to adapt and produce eight different 18F-labeled PET tracers of varying complexity. Methods Three reactor syntheses of D-[18F]FAC, L-[18F]FMAU, and D-[18F]FEAU along with the one reactor syntheses of D-[18F]FEAU, [18F]FDG, [18F]FLT, [18F]Fallypride, [18F]FHBG, and [18F]SFB were all produced using ELIXYS without the need for any hardware modifications or reconfiguration. Synthesis protocols were adapted, and slightly modified from literature, but not fully optimized. Furthermore, [18F]FLT, [18F]FDG, and [18F]Fallypride were produced sequentially on the same day and used for preclinical imaging of A431 tumor-bearing SCID mice and wild-type BALB/c mice, respectively. To assess future translation to the clinical setting, several batches of tracers were subjected to a full set of quality control tests. Results All tracers were produced with radiochemical yields comparable to those in literature. [18F]FLT, [18F]FDG, and [18F]Fallypride were successfully used to image the mice with results consistent with literature. All tracers subjected to clinical quality control tests passed. Conclusion The ELIXYS radiosynthesizer facilitates rapid tracer development and is capable of producing multiple 18F-labeled PET tracers suitable for clinical

  5. Synthesis of a potent and selective (18)F-labeled delta-opioid receptor antagonist derived from the Dmt-Tic pharmacophore for positron emission tomography imaging.

    PubMed

    Ryu, Eun Kyoung; Wu, Zhanhong; Chen, Kai; Lazarus, Lawrence H; Marczak, Ewa D; Sasaki, Yusuke; Ambo, Akihiro; Salvadori, Severo; Ren, Chuancheng; Zhao, Heng; Balboni, Gianfranco; Chen, Xiaoyuan

    2008-03-27

    Identification and pharmacological characterization of two new selective delta-opioid receptor antagonists, derived from the Dmt-Tic pharmacophore, of potential utility in positron emission tomography (PET) imaging are described. On the basis of its high delta selectivity, H-Dmt-Tic--Lys(Z)-OH (reference compound 1) is a useful starting point for the synthesis of (18)F-labeled compounds prepared by the coupling of N-succinimidyl 4-[ (18)F]fluorobenzoate ([(18)F]SFB) with Boc-Dmt-Tic--Lys(Z)-OH under slightly basic conditions at 37 degrees C for 15 min, deprotection with TFA, and HPLC purification. The total synthesis time was 120 min, and the decay-corrected radiochemical yield of [(18)F]- 1 was about 25-30% ( n = 5) starting from [(18)F]SFB ( n = 5) with an effective specific activity about 46 GBq/micromol. In vitro autoradiography studies showed prominent uptake of [ (18)F]- 1 in the striatum and cortex with significant blocking by 1 and UFP-501 (selective delta-opioid receptor antagonist), suggesting high specific binding of [(18)F]- 1 to delta-opioid receptors. Noninvasive microPET imaging studies revealed the absence of [(18)F]- 1 in rat brain, since it fails to cross the blood-brain barrier. This study demonstrates the suitability of [ (18)F]- 1 for imaging peripheral delta-opioid receptors.

  6. Radiosynthesis and Evaluation of an 18F-Labeled Positron Emission Tomography (PET) Radioligand for Metabotropic Glutamate Receptor Subtype 4 (mGlu4)

    PubMed Central

    2015-01-01

    Four 4-phthalimide derivatives of N-(3-chlorophenyl)-2-picolinamide were synthesized as potential ligands for the PET imaging of mGlu4 in the brain. Of these compounds, N-(3-chloro-4-(4-fluoro-1,3-dioxoisoindolin-2-yl)phenyl)-2-picolinamide (3, KALB001) exhibited improved binding affinity (IC50 = 5.1 nM) compared with ML128 (1) and was subsequently labeled with 18F. When finally formulated in 0.1 M citrate buffer (pH 4) with 10% ethanol, the specific activity of [18F]3 at the end of synthesis (EOS) was 233.5 ± 177.8 GBq/μmol (n = 4). The radiochemical yield of [18F]3 was 16.4 ± 4.8% (n = 4), and the purity was over 98%. In vivo imaging studies in a monkey showed that the radiotracer quickly penetrated the brain with the highest accumulation in the brain areas known to express mGlu4. Despite some unfavorable radiotracer properties like fast washout in rodent studies, [18F]3 is the first 18F-labeled mGlu4 radioligand, which can be further modified to improve pharmacokinetics and brain penetrability for future human studies. PMID:25330258

  7. Synthesis and Evaluation of 18F-labeled Pyridaben Analogues for Myocardial Perfusion Imaging in Mice, Rats and Chinese mini-swine

    PubMed Central

    Mou, Tiantian; Zhao, Zuoquan; You, Linyi; Li, Yesen; Wang, Qian; Fang, Wei; Lu, Jie; Peng, Cheng; Zhang, Xianzhong

    2016-01-01

    This study reports three novel 18F-labeled pyridaben analogues for potential myocardial perfusion imaging (MPI). Three precursors and the corresponding nonradioactive compounds were synthesized and characterized. The radiolabeled tracers were obtained by substituting tosyl with 18F. The total radiosynthesis time of these tracers was 70–90 min. Typical decay-corrected radiochemical yields were 47–58%, with high radiochemical purities (>98%). Tracers were evaluated as MPI agents in vitro, ex vivo and in vivo. In the mouse biodistribution study, all three radiotracers showed high initial heart uptake (34–54% ID/g at 2 min after injection) and fast liver clearance. In the microPET imaging study, [18F]Fmpp2 produced heart images with good quality in both mice and rats. In the whole-body PET/CT images of mini-swine, [18F]Fmpp2 showed excellent initial heart standardized uptake value (SUV) (7.12 at 5 min p.i.) and good retention (5.75 at 120 min p.i.). The heart/liver SUV ratios were 4.12, 5.42 and 5.99 at 30, 60 and 120 min after injection, respectively. The favorable biological properties of [18F]Fmpp2 suggest that it is worth further investigation as a potential MPI agent. PMID:27646847

  8. Noninvasive positron emission tomography imaging of cell death using a novel small-molecule probe, (18)F labeled bis(zinc(II)-dipicolylamine) complex.

    PubMed

    Wang, Hongliang; Tang, Xiaolan; Tang, Ganghua; Huang, Tingting; Liang, Xiang; Hu, Kongzhen; Deng, Huaifu; Yi, Chang; Shi, Xinchong; Wu, Kening

    2013-08-01

    The synthetic bis(zinc(II)-dipicolylamine) (DPAZn2) coordination complexes are known to have a high specific and selective affinity to target the exposed phosphatidylserine (PS) on the surface of dead and dying cells. An (18)F-labeled DPAZn2 complex (4-(18)F-Fluoro-benzoyl-bis(zinc(II)-dipicolylamine), (18)F-FB-DPAZn2) as positron emission tomography (PET) tracer was developed and evaluated for in vivo imaging of tumor treated with a chemical agent. The in vitro cell stain studies revealed that fluorescent DPAZn2 complexes (Dansyl-DPAZn2) stained the same cells (apoptotic and necrotic cells) as fluorescein isothiocyanate (FITC) labeled Annexin V (FITC-Annexin V). The radiosynthesis of (18)F-FB-DPAZn2 was achieved through the amidation the precursor bis(2,2'-dipicolylamine) derivative (DPA2) with the prosthetic group N-succinimidyl-4-[(18)F]-fluorobenzoate ((18)F-SFB) and chelation with zinc nitrate. In the biodistribution study, the fast clearance of (18)F-FB-DPAZn2 from blood and kidney was observed and high uptake in liver and intestine within 90 min postinjection was also found. For the PET imaging, significantly higher tumor uptake of (18)F-FB-DPAZn2 was observed in the adriamycin (ADM)-treated Hepa1-6 hepatocellular carcinoma-bearing mice than that in the untreated tumor-model mice, while a slightly decreased tumor uptake of (18)F-FDG was found in the ADM-treated tumor-bearing mice. The results indicate that (18)F-FB-DPAZn2 has the similar capability of apoptosis detection as FITC-Annexin V and seems to be a potential PET tracer for noninvasive evaluation and monitoring of anti-tumor chemotherapy. The high uptake of (18)F-FB-DPAZn2 in the abdomen needs to optimize the structure for improving its pharmacokinetics characteristics in the future work.

  9. Synthesis and evaluation of 18F-labeled ATP competitive inhibitors of topoisomerase II as probes for imaging topoisomerase II expression

    PubMed Central

    Daumar, Pierre; Zeglis, Brian M.; Ramos, Nicholas; Divilov, Vadim; Sevak, Kuntal Kumar; Pillarsetty, NagaVaraKishore; Lewis, Jason S.

    2015-01-01

    Type II topoisomerase (Topo-II) is an ATP-dependent enzyme that is essential in the transcription, replication, and chromosome segregation processes and, as such, represents an attractive target for cancer therapy. Numerous studies indicate that the response to treatment with Topo-II inhibitors is highly dependent on both the levels and the activity of the enzyme. Consequently, a non-invasive assay to measure tumoral Topo-II levels has the potential to differentiate responders from non-responders. With the ultimate goal of developing a radiofluorinated tracer for positron emission tomography (PET) imaging, we have designed, synthesized, and evaluated a set of fluorinated compounds based on the structure of the ATP-competitive Topo-II inhibitor QAP1. Compounds 18 and 19b showed inhibition of Topo-II in in vitro assays and exhibited moderate, Topo-II level dependent cytotoxicity in SK-BR-3 and MCF-7 cell lines. Based on these results, 18F-labeled analogs of these two compounds were synthesized and evaluated as PET probes for imaging Topo-II overexpression in mice bearing SK-BR-3 xenografts. [18F]-18 and [18F]-19b were synthesized from their corresponding protected tosylated derivatives by fluorination and subsequent deprotection. Small animal PET imaging studies indicated that both compounds do not accumulate in tumors and exhibit poor pharmacokinetics, clearing from the blood pool very rapidly and getting metabolized over. The insights gained from the current study will surely aid in the design and construction of future generations of PET agents for the non-invasive delineation of Topo-II expression. PMID:25240701

  10. Synthesis and evaluation of an (18) F-labeled derivative of F3 for targeting surface-expressed nucleolin in cancer and tumor endothelial cells.

    PubMed

    Lam, Phoebe Y H; Hillyar, Christopher R T; Able, Sarah; Vallis, Katherine A

    2016-10-01

    The surface overexpression of nucleolin provides an anchor for the specific attachment of biomolecules to cancer and angiogenic endothelial cells. The peptide F3 is a high-affinity ligand of the nucleolin receptor (NR) that has been investigated as a carrier to deliver biologically active molecules to tumors for both therapeutic and imaging applications. A site-specific PEGylated F3 derivative was radiolabeled with [(18) F]Al-F. The binding affinity and cellular distribution of the compound was assessed in tumor (H2N) and tumor endothelial (2H-11) cells. Specific uptake via the NR was demonstrated by the siRNA knockdown of nucleolin in both cell lines. The partition and the plasma stability of the compound were assessed at 37°C. The enzyme-mediated site-specific modification of F3 to give NODA-PEG-F3 (NP-F3) was achieved. Radiolabeling with [(18) F]Al-F gave (18) F-NP-F3. (18) F-NP-F3 demonstrated high affinity for cancer and tumor endothelial cells. The siRNA knockdown of nucleolin resulted in a binding affinity reduction of 50% to 60%, confirming cell surface binding via the NR. NP-F3 was stable in serum for 2 h. (18) F-NP-F3 is reported as the first (18) F-labeled F3 derivative. It was obtained in a site-specific, high-yield, and efficient manner and binds to surface NR in the low nanomolar range, suggesting it has potential as a tumor and angiogenesis tracer.

  11. PET imaging of apoptosis in tumor-bearing mice and rabbits after paclitaxel treatment with 18F-Labeled recombinant human His10-annexin V

    PubMed Central

    Qin, Haidong; Zhang, Ming-Rong; Xie, Lin; Hou, Yanjie; Hua, Zichun; Hu, Minjin; Wang, Zizheng; Wang, Feng

    2015-01-01

    Monitoring response to chemo- or radiotherapy is of great importance in clinical practice. Apoptosis imaging serves as a very useful tool for the early evaluation of tumor response. The goal of this study was PET imaging of apoptosis with 18F-labeled recombinant human annexin V linked with 10 histidine tag (18F-rh-His10-annexin V) in nude mice bearing an A549 tumor and rabbits bearing a VX2 lung cancer after paclitaxel therapy. 18F-rh-His10-annexin V was prepared by conjugation of rh-His10-annexin V with N-succinimidyl 4-[18F]fluorobenzoate. Biodistribution was determined in mice by the dissection method and small-animal PET. Single-dose paclitaxel (175 mg/m2) was used to induce apoptosis in A549 and VX2 tumor models. 18F-rh-His10-annexin V was injected into A549 mice and VX rabbits to acquire dynamic and static PET images 72 h after paclitaxel treatment. The uptake of 18F-rh-His10-annexin V in apoptotic cells 4 h after induction was 6.45±0.52 fold higher than that in non-induced cells. High focal uptake of 18F-rh-His10-annexin V was visualized in A549 (SUVmax: 0.35±0.13) and VX2 (0.41±0.23) tumor models after paclitaxel treatment, whereas lower uptake was found in the corresponding tumors before treatment (A549 SUVmax: 0.04±0.02; VX2: 0.009±0.002). The apoptotic index was 75.61±11.56% in the treated VX2 cancer, much higher than that in the untreated VX2 (8.03±2.81%). This study demonstrated the feasibility of 18F-rh-His10-annexin V for the detection of apoptosis after chemotherapy in A549 and VX2 tumor models. PMID:25625024

  12. Radiosynthesis and preliminary PET evaluation of (18)F-labeled 2-(1-(3-fluorophenyl)-2-oxo-5-(pyrimidin-2-yl)-1,2-dihydropyridin-3-yl)benzonitrile for imaging AMPA receptors.

    PubMed

    Yuan, Gengyang; Jones, Graham B; Vasdev, Neil; Liang, Steven H

    2016-10-01

    To prompt the development of (18)F-labeled positron emission tomography (PET) tracers for the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, we have prepared (18)F-labeled 2-(1-(3-fluorophenyl)-2-oxo-5-(pyrimidin-2-yl)-1,2-dihydropyridin-3-yl)benzonitrile ([(18)F]8). The radiosynthesis was achieved by a one-pot two-step method that utilized a spirocyclic hypervalent iodine(III) mediated radiofluorination to prepare the (18)F-labeled 1-bromo-3-fluorobenzene ([(18)F]15) intermediate with K(18)F. A subsequent copper(I) iodide mediated coupling reaction was carried out with 2-(2-oxo-5-(pyrimidin-2-yl)-1,2-dihydropyridin-3-yl)benzonitrile (10) to [(18)F]8 in 10±2% uncorrected radiochemical yield relative to starting (18)F-fluoride with >99% radiochemical purity and 29.6±7.4Gbq/μmol specific activity at the time of injection. PET imaging studies with the title radiotracer in normal mice demonstrated good brain uptake (peak standardized uptake value (SUV)=2.3±0.1) and warrants further in vivo validation.

  13. Molecular Imaging of Breast Cancer: Role of RGD Peptides.

    PubMed

    Chakravarty, Rubel; Chakraborty, Sudipta; Dash, Ashutosh

    2015-01-01

    Breast cancer is the leading cause of cancer deaths among women of all ages worldwide. With advances in molecular imaging procedures, it has been possible to detect breast cancer in its early stage, determine the extent of the disease to administer appropriate therapeutic protocol and also monitor the effects of treatment. By accurately characterizing the tumor properties and biological processes involved, molecular imaging can play a crucial role in minimizing the morbidity and mortality associated with breast cancer. The integrin αvβ3 plays an important role in breast cancer angiogenesis and is expressed on tumor endothelial cells as well as on some tumor cells. It is a receptor for the extracellular matrix proteins with the exposed arginine-glycine-aspartic acid (RGD) tripeptide sequence and therefore RGD peptides can preferentially bind to integrin αvβ3. In this context, targeting tumor vasculature or tumor cells by RGD-based probes is a promising strategy for molecular imaging of breast cancer. Using RGD-based probes, several preclinical studies have employed different imaging modalities such as positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), ultrasound and optical imaging for visualization of integrin αvβ3 expression in breast cancer models. Limited clinical trials using (18)F-labeled RGD peptides have also been initiated for non-invasive detection and staging of breast cancer. Herein, we provide a comprehensive overview of the latest advances in molecular imaging of breast cancer using RGD peptide-based probes and discuss the challenges and opportunities for advancement of the field. The reported strategies for molecular imaging of breast cancer using RGD peptide-based probes holds promise for making clinically translatable advances that can positively impact the overall diagnostic and therapeutic processes and result in improved quality of life for breast cancer patients.

  14. Preclinical Evaluation of 18F-Labeled Anti-HER2 Nanobody Conjugates for Imaging HER2 Receptor Expression by ImmunoPET

    PubMed Central

    Vaidyanathan, Ganesan; McDougald, Darryl; Choi, Jaeyeon; Koumarianou, Eftychia; Weitzel, Douglas; Osada, Takuya; Lyerly, H. Kim; Zalutsky, Michael R.

    2016-01-01

    The human growth factor receptor type 2 (HER2) is overexpressed in breast as well as other types of cancer. ImmunoPET, a noninvasive imaging procedure that could assess HER2 status in both primary and metastatic lesions simultaneously, could be a valuable tool for optimizing application of HER2-targeted therapies in individual patients. Herein, we have evaluated the tumor targeting potential of the 5F7 anti-HER2 Nanobody (single-domain antibody fragment; ~13 kDa) after 18F labeling by two methods. Methods The 5F7 Nanobody was labeled with 18F using the novel residualizing label N-succinimidyl 3-((4-(4-18F-fluorobutyl)-1H-1,2,3-triazol-1-yl)methyl)-5-(guanidinomethyl)benzoate (18F-SFBTMGMB; 18F-RL-I) and also via the most commonly utilized 18F protein labeling prosthetic agent, N-succinimidyl 3-18F-fluorobenzoate (18F-SFB). For comparison, 5F7 Nanobody was also labeled using the residualizing radioiodination agent N-succinimidyl 4-guanidinomethyl-3-125I-iodobenzoate (125I-SGMIB). Paired label (18F/125I) internalization assays and biodistribution studies were performed on HER2-expressing BT474M1 breast carcinoma cells and in mice with BT474M1 subcutaneous xenografts, respectively. Micro positron emission tomography/computed tomography (microPET/CT) imaging of 5F7 Nanobody labeled using 18F-RL-I also was performed. Results Internalization assays indicated that intracellularly retained radioactivity for 18F-RL-I-5F7 was similar to that for co-incubated 125I-SGMIB-5F7, while that for 18F-SFB-5F7 was lower than co-incubated 125I-SGMIB-5F7 and decreased with time. BT474M1 tumor uptake of 18F-RL-I-5F7 was 28.97 ± 3.88 %ID/g at 1 h and 36.28 ± 14.10 %ID/g at 2 h, reduced by >90% trastuzumab blocking, indicating HER2-specificity of uptake, and also 26–28% higher (P < 0.05) than that of 18F-SFB-5F7. At 2 h, the tumor-to-blood ratio for 18F-RL-I-5F7 (47.4 ± 13.1) was significantly higher (P < 0.05) than for 18F-SFB-5F7 (25.4 ± 10.3); however, kidney uptake was 28–36

  15. Distribution and binding of 18F-labeled and 125I-labeled analogues of ACI-80, a prospective molecular imaging biomarker of disease: a whole hemisphere post mortem autoradiography study in human brains obtained from Alzheimer's disease patients.

    PubMed

    Gulyás, Balázs; Spenger, Christian; Beliczai, Zsuzsa; Gulya, Károly; Kása, Péter; Jahan, Mahabuba; Jia, Zhisheng; Weber, Urs; Pfeifer, Andrea; Muhs, Andreas; Willbold, Dieter; Halldin, Christer

    2012-01-01

    One of the major pathological landmarks of Alzheimer's disease and other neurodegenerative diseases is the presence of amyloid deposits in the brain. The early non-invasive visualization of amyloid is a major objective of recent diagnostic neuroimaging approaches, including positron emission tomography (PET), with an eye on follow-up of disease progression and/or therapy efficacy. The development of molecular imaging biomarkers with binding affinity to amyloid in the brain is therefore in the forefront of imaging biomarker and radiochemistry research. Recently, a dodecamer peptide (amino acid sequence=QSHYRHISPAQV; denominated D1 or ACI-80) was identified as a prospective ligand candidate, binding with high ex vivo affinity to L-Aβ-amyloid (K(d): 0.4 μM). In order to assess the ligand's capacity to visualize amyloid in Alzheimer's disease (AD), two (125)I labeled and three (18)F labeled analogues of the peptide were synthesized and tested in post mortem human autoradiography experiments using whole hemisphere brain slices obtained from deceased AD patients and age matched control subjects. The (18)F-labeled radioligands showed more promising visualization capacity of amyloid that the (125)I-labeled radioligands. In the case of each (18)F radioligands the grey matter uptake in the AD brains was significantly higher than that in control brains. Furthermore, the grey matter: white matter uptake ratio was over ~2, the difference being significant for each (18)F-radioligands. The regional distribution of the uptake of the various radioligands systematically shows a congruent pattern between the high uptake regions and spots in the autoradiographic images and the disease specific signals obtained in adjacent or identical brain slices labeled with histological, immunohistochemical or autoradiographic stains for amyloid deposits or activated astrocytes. The present data, using post mortem human brain autoradiography in whole hemisphere human brains obtained from deceased

  16. 18F-FP-PEG2-β-Glu-RGD2: A Symmetric Integrin αvβ3-Targeting Radiotracer for Tumor PET Imaging

    PubMed Central

    Tang, Ganghua; Yao, Shaobo; Yao, Baoguo; Wang, Hongliang; Nie, Dahong; Liang, Xiang; Tang, Caihua; He, Shanzhen

    2015-01-01

    Radiolabeled cyclic arginine-glycine-aspartic (RGD) peptides can be used for noninvasive determination of integrin αvβ3 expression in tumors. In this study, we performed radiosynthesis and biological evaluation of a new 18F-labeled RGD homodimeric peptide with one 8-amino-3,6-dioxaoctanoic acid (PEG2) linker on the glutamate β-amino group (18F-FP-PEG2-β-Glu-RGD2) as a symmetric PET tracer for tumor imaging. Biodistribution studies showed that radioactivity of 18F-FP-PEG2-β-Glu-RGD2 was rapidly cleared from blood by predominately renal excretion. MicroPET-CT imaging with 18F-FP-PEG2-β-Glu-RGD2 revealed high tumor contrast and low background in A549 human lung adenocarcinoma-bearing mouse models, PC-3 prostate cancer-bearing mouse models, and orthotopic transplanted C6 brain glioma models. 18F-FP-PEG2-β-Glu-RGD2 exhibited good stability in vitro and in vivo. The results suggest that this tracer is a potential PET tracer for tumor imaging. PMID:26397833

  17. Synthesis and Evaluation of Two 18F-Labeled 6-Iodo-2-(4′-N,N-dimethylamino)phenylimidazo[1,2-a]pyridine Derivatives as Prospective Radioligands for β-Amyloid in Alzheimer’s Disease

    PubMed Central

    Cai, Lisheng; Chin, Frederick T.; Pike, Victor W.; Toyama, Hiroshi; Liow, Jeih-San; Zoghbi, Sami S.; Modell, Kendra; Briard, Emmanuelle; Shetty, H. Umesha; Sinclair, Kathryn; Donohue, Sean; Tipre, Dnyanesh; Kung, Mei-Ping; Dagostin, Claudio; Widdowson, David A.; Green, Michael; Gao, Weiyi; Herman, Mary M.; Ichise, Masanori; Innis, Robert B.

    2014-01-01

    This study evaluated 18F-labeled IMPY [6-iodo-2-(4′-N,N-dimethylamino)phenylimidazo[1,2-a]pyridine] derivatives as agents for imaging β-amyloid plaque with positron emission tomography (PET). The precursor for radiolabeling and reference compounds was synthesized in up to five steps from commercially accessible starting materials. One of the two N-methyl groups of IMPY was substituted with either a 3-fluoropropyl (FPM-IMPY) or a 2-fluoroethyl (FEM-IMPY) group. FPM-IMPY and FEM-IMPY were found to have moderate affinity for Aβ- aggregates with Ki = 27 ± 8 and 40 ± 5 nM, respectively. A “one-pot” method for 18F-2-fluoroethylation and 18F-3-fluoropropylation of the precursor was developed. The overall decay-corrected radiochemical yields were 26–51%. In PET experiments with normal mouse, high uptake of activity was obtained in the brain after iv injection of each probe: 6.4% ID/g for [18F]FEM-IMPY at 1.2 min, and 5.7% ID/g for [18F]FPM-IMPY at 0.8 min. These values were similar to those of [123I/125I]IMPY (7.2% ID/g at 2 min). Polar and nonpolar radioactive metabolites were observed in both plasma and brain homogenates after injection of [18F]FEM or [18F]FPM-IMPY. In contrast to the single-exponential washout of [123I/125I]IMPY, the washouts of brain activity for the two fluorinated analogues were biphasic, with an initial rapid phase over 20 min and a subsequent much slower phase. Residual brain activity at 2 h, which may represent polar metabolites trapped in the brain, was 4.5% ID/g for [18F]FEM-IMPY and 2.1% ID/g for [18F]FPM-IMPY. Substantial skull uptake of [18F]fluoride was also clearly observed. With a view to slow the metabolism of [18F]FEM-IMPY, an analogue was prepared with deuteriums substituted for the four ethyl hydrogens. However, D4-[18F]FEM-IMPY showed the same brain uptake and clearance as the protio analogue. Metabolism of the [18F]FEM-IMPY was appreciably slower in rhesus monkey than in mouse. Autoradiography of postmortem brain sections

  18. N-Succinimidyl 3-((4-(4-[18F]fluorobutyl)-1H-1,2,3-triazol-1-yl)methyl)-5-(guanidinomethyl)benzoate ([18F]SFBTMGMB): A Residualizing Label for 18F-labeling of internalizing biomolecules

    PubMed Central

    Vaidyanathan, Ganesan; McDougald, Darryl; Choi, Jaeyeon; Pruszynski, Marek; Koumarianou, Eftychia; Zhou, Zhengyuan; Zalutsky, Michael R.

    2015-01-01

    Residualizing labeling methods for internalizing peptides and proteins are designed to trap the radionuclide inside the cell after intracellular degradation of the biomolecule. The goal of this work was to develop a residualizing label for the 18F-labeling of internalizing biomolecules based on a template used successfully for radioiodination. N-succinimidyl 3-((4-(4-[18F]fluorobutyl)-1H-1,2,3-triazol-1-yl)methyl)-5-(bis-Boc-guanidinomethyl)benzoate (Boc2-[18F]SFBTMGMB) was synthesized by click reaction of an azide precursor and [18F]fluorohexyne in 8.5 ± 2.8% average decay-corrected radiochemical yield (n =15). An anti-HER2 nanobody 5F7 was labeled with 18F using [18F]SFBTMGMB ([18F]RL-I), obtained by the deprotection of Boc2-[18F]SFBTMGMB, in 31.2 ± 6.7% (n =5) conjugation efficiency. Thus labeled nanobody had a radiochemical purity of >95%, bound to the HER2-expressing BT474M1 breast cancer cells with an affinity of 4.7 ± 0.9 nM, and had an immunoreactive fraction of 62–80%. In summary, a novel residualizing prosthetic agent for labeling biomolecules with 18F has been developed. An anti-HER2 nanobody was labeled using this prosthetic group with retention of affinity and immunoreactivity to HER2. PMID:26645790

  19. RGD modified polymers: biomaterials for stimulated cell adhesion and beyond.

    PubMed

    Hersel, Ulrich; Dahmen, Claudia; Kessler, Horst

    2003-11-01

    Since RGD peptides (R: arginine; G: glycine; D: aspartic acid) have been found to promote cell adhesion in 1984 (Cell attachment activity of fibronectin can be duplicated by small synthetic fragments of the molecule, Nature 309 (1984) 30), numerous materials have been RGD functionalized for academic studies or medical applications. This review gives an overview of RGD modified polymers, that have been used for cell adhesion, and provides information about technical aspects of RGD immobilization on polymers. The impacts of RGD peptide surface density, spatial arrangement as well as integrin affinity and selectivity on cell responses like adhesion and migration are discussed.

  20. RGD-Xyloside Conjugates Prime Glycosaminoglycans

    PubMed Central

    Tran, Vy M.; Victor, Xylophone V.; Yockman, James W.; Kuberan, Balagurunathan

    2010-01-01

    Glycosaminoglycans (GAG) play decisive roles in various cardio-vascular & cancer-associated processes. Changes in the expression of GAG fine structures, attributed to deregulation of their biosynthetic and catabolic enzymes, are hallmarks of vascular dysfunction and tumor progression. Wide spread role of GAG chains in blood clotting, wound healing and tumor biology has led to the development of modified GAG chains, GAG binding peptides and GAG based enzyme inhibitors as therapeutic agents. Xylosides, carrying hydrophobic aglycone, are known to induce GAG biosynthesis in various systems. Given the important roles of GAG chains in vascular and tumor biology, we envision that RGD-conjugated xylosides could be targeted to activated endothelial and cancer cells, which are known to express αvβ3 integrin, and thereby, modulate the pathological processes. To accomplish this vision, xylose residue was conjugated to linear and cyclic RGD containing peptides using click chemistry. Our results demonstrate that RGD-conjugated xylosides are able to prime GAG chains in various cell types, and future studies are aimed toward evaluating potential utility of such xylosides in treating myocardial infarction as well as cancer-associated thrombotic complications. PMID:20717719

  1. Does ligand-receptor mediated competitive effect or penetrating effect of iRGD peptide when co-administration with iRGD-modified SSL?

    PubMed

    Zhang, Wei-Qiang; Yu, Ke-Fu; Zhong, Ting; Luo, Li-Min; Du, Ruo; Ren, Wei; Huang, Dan; Song, Ping; Li, Dan; Zhao, Yang; Wang, Chao; Zhang, Xuan

    2015-12-01

    Ligand-mediated targeting of anticancer therapeutic agents is a useful strategy for improving anti-tumor efficacy. It has been reported that co-administration of a tumor-penetrating peptide iRGD (CRGDK/RGPD/EC) enhances the efficacy of anticancer drugs. Here, we designed an experiment involving co-administration of iRGD-SSL-DOX with free iRGD to B16-F10 tumor bearing mice to examine the action of free iRGD. We also designed an experiment to investigate the location of iRGD-modified SSL when co-administered with free iRGD or free RGD to B16-F10 tumor bearing nude mice. Considering the sequence of iRGD, we selected the GPDC, RGD and CRGDK as targeting ligands to investigate the targeting effect of these peptides compared with iRGD on B16-F10 and MCF-7 cells, with or without enzymatic degradation. Finally, we selected free RGD, free CRGDK and free iRGD as ligand to investigate the inhibitory effect on RGD-, CRGDK- or iRGD-modified SSL on B16-F10 or MCF-7 cells. Our results indicated that iRGD targeting to tumor cells was ligand-receptor mediated involving RGD to αv-integrin receptor and CRGDK to NRP-1 receptor. Being competitive effect, the administration of free iRGD would not be able to further enhance the anti-tumor activity of iRGD-modified SSL. There is no need to co-administrate of free iRGD with the iRGD-modified nanoparticles for further therapeutic benefit.

  2. Integrin‐Targeting Fluorescent Proteins: Exploration of RGD Insertion Sites

    PubMed Central

    Sonntag, Michael H.; Schill, Jurgen

    2017-01-01

    Abstract The potential of the fluorescent protein scaffold to control peptide sequence functionality is illustrated by an exploration of fluorescent proteins as novel probes for targeting integrins. A library of fluorescent mCitrine proteins with RGD motifs incorporated at several positions in loops within the protein main chain was generated and characterized. Amino acid mutations to RGD as well as RGD insertions were evaluated: both led to constructs with typical mCitrine fluorescent properties. Screening experiments against four human integrin receptors revealed two strong‐binding constructs and two selective integrin binders. The effect of the site of RGD incorporation illustrates the importance of the protein scaffold on RGD sequence functionality, leading to fluorescent protein constructs with the potential for selective integrin targeting. PMID:28004511

  3. Clinical Experience with (18)F-Labeled Small Molecule Inhibitors of Prostate-Specific Membrane Antigen.

    PubMed

    Rowe, Steven P; Gorin, Michael A; Salas Fragomeni, Roberto A; Drzezga, Alexander; Pomper, Martin G

    2017-04-01

    Prostate cancer (PCa) is the most common noncutaneous malignancy diagnosed in men. Despite the large number of men who will suffer from PCa at some point during their lives, conventional imaging modalities for this important disease (contrast-enhanced computed tomography, bone scan, and MR imaging) have provided only marginal to moderate success in appropriately guiding patient management in certain clinical contexts. In this review, the authors discuss radiofluorinated small molecule radiotracers that have been developed to bind to the transmembrane glycoprotein prostate-specific membrane antigen, a target that is nearly universally overexpressed on PCa epithelial cells.

  4. An improved strategy for the synthesis of [18F]-labeled arabinofuranosyl nuclosides

    PubMed Central

    Zhang, Hanwen; Cantorias, Melchor V.; Pillarsetty, NagaVaraKishore; Burnazi, Eva M.; Cai, Shangde; Lewis, Jason S.

    2012-01-01

    The expression of the herpes simplex virus type-1 thymidine kinase (HSV1-tk) gene can be imaged efficaciously using a variety of 2′-[18F]fluoro-2′-deoxy-1-b-D-arabinofuranosyl-uracil derivatives [[18F]-FXAU, X= I(iodo), E(ethyl), and M(methyl)]. However, the application of these derivatives in clinical and translational studies has been impeded by their complicated and long syntheses (3–5 h). To remedy these issues, in the study at hand we have investigated whether microwave or combined catalysts could facilitate the coupling reaction between sugar and nucleobase and, further, have probed the feasibility of establishing a novel approach for [18F]-FXAU synthesis. We have demonstrated that the rate of the trimethylsilyl trifluoromethanesulfonate (TMSOTf)-catalyzed coupling reaction between the 2-deoxy-sugar and uracil derivatives at 90°C can be significantly accelerated by microwave-driven heating or by the addition of Lewis acid catalyst (SnCl4). Further, we have observed that the stability of the α- and β-anomers of [18F]-FXAU derivatives differs during the hydrolysis step. Using the microwave-driven heating approach, overall decay-corrected radiochemical yields of 19–27% were achieved for [18F]-FXAU in 120 min at a specific activity of >22 MBq/nmol (595 Ci/mmol). Ultimately, we believe that these high yielding syntheses of [18F]-FIAU, [18F]-FMAU and [18F]-FEAU will facilitate routine production for clinical applications. PMID:22819195

  5. Improved 18F Labeling of Peptides with a Fluoride-Aluminum-Chelate Complex

    PubMed Central

    McBride, William J.; D’Souza, Christopher A.; Sharkey, Robert M.; Karacay, Habibe; Rossi, Edmund A.; Chang, Chien-Hsing; Goldenberg, David M.

    2010-01-01

    We reported previously the feasibility to radiolabel peptides with fluorine-18 (18F) using a rapid, one-pot, method that first mixes 18F− with Al3+, and then binds the (Al18F)2+ complex to a NOTA ligand on the peptide. In this report, we examined several new NOTA ligands and determined how temperature, reaction time, and reagent concentration affected the radiolabeling yield. Four structural variations of the NOTA ligand had isolated radiolabeling yields ranging from 5.8% to 87% under similar reaction conditions. All of the Al18F NOTA complexes were stable in vitro in human serum and those that were tested in vivo also were stable. The radiolabeling reactions were performed at 100°C and the peptides could be labeled in as little as five minutes. The IMP467 peptide could be labeled up to 115 GBq/μmol (3100 Ci/mmol), with a total reaction and purification time of 30 min without chromatographic purification. PMID:20540570

  6. 18F-Labeled Silicon-Based Fluoride Acceptors: Potential Opportunities for Novel Positron Emitting Radiopharmaceuticals

    PubMed Central

    Bernard-Gauthier, Vadim; Wängler, Carmen; Wängler, Bjoern; Schirrmacher, Ralf

    2014-01-01

    Background. Over the recent years, radiopharmaceutical chemistry has experienced a wide variety of innovative pushes towards finding both novel and unconventional radiochemical methods to introduce fluorine-18 into radiotracers for positron emission tomography (PET). These “nonclassical” labeling methodologies based on silicon-, boron-, and aluminium-18F chemistry deviate from commonplace bonding of an [18F]fluorine atom (18F) to either an aliphatic or aromatic carbon atom. One method in particular, the silicon-fluoride-acceptor isotopic exchange (SiFA-IE) approach, invalidates a dogma in radiochemistry that has been widely accepted for many years: the inability to obtain radiopharmaceuticals of high specific activity (SA) via simple IE. Methodology. The most advantageous feature of IE labeling in general is that labeling precursor and labeled radiotracer are chemically identical, eliminating the need to separate the radiotracer from its precursor. SiFA-IE chemistry proceeds in dipolar aprotic solvents at room temperature and below, entirely avoiding the formation of radioactive side products during the IE. Scope of Review. A great plethora of different SiFA species have been reported in the literature ranging from small prosthetic groups and other compounds of low molecular weight to labeled peptides and most recently affibody molecules. Conclusions. The literature over the last years (from 2006 to 2014) shows unambiguously that SiFA-IE and other silicon-based fluoride acceptor strategies relying on 18F− leaving group substitutions have the potential to become a valuable addition to radiochemistry. PMID:25157357

  7. Synthesis and evaluation of 18F labeled alanine derivatives as potential tumor imaging agents

    PubMed Central

    Wang, Limin; Zha, Zhihao; Qu, Wenchao; Qiao, Hongwen; Lieberman, Brian P.; Plössl, Karl; Kung, Hank F.

    2012-01-01

    Introduction This paper reports the synthesis and labeling of 18F alanine derivatives. We also investigate their biological characteristics as potential tumor imaging agents mediated by alanine-serine-cysteine preferring (ASC) transporter system. Methods Three new 18F alanine derivatives were prepared from corresponding tosylate-precursors through a two-step labelling reaction. In vitro uptake studies to evaluate and to compare these three analogs were carried out in 9L glioma and PC-3 prostate cancer cell lines. Potential transport mechanisms, protein incorporation and stability of 3-(1-[18F]fluoromethyl)-L-alanine (L[18F]FMA) were investigated in 9L glioma cells. Its biodistribution was determined in a rat-bearing 9L tumor model. PET imaging studies were performed on rat bearing 9L glioma tumors and transgenic mouse carrying spontaneous generated M/tomND tumor (mammary gland adenocarcinoma). Results New 18F alanine derivatives were prepared with 7–34% uncorrected radiochemical yields, excellent enantiomeric purity (>99%) and good radiochemical purity (>99%). In vitro uptake of the L-[18F]FMA in 9L glioma and PC-3 prostate cancer cells was higher than those observed for other two alanine derivatives and [18F]FDG in first 1 h. Inhibition of cell uptake studies suggested that L-[18F]FMA uptake in 9L glioma was predominantly via transport system ASC. After entering into cells, L-[18F]FMA remained stable and was not incorporated into protein within 2 h. In vivo biodistribution studies demonstrated that L-[18F]FMA had relatively high uptake in liver and kidney. Tumor uptake was fast, reaching a maximum within 30 min. The tumor-to-muscle, tumor-to-blood and tumor-to-brain ratios at 60 min post injection were 2.2, 1.9 and 3.0, respectively. In PET imaging studies, tumors were visualized with L-[18F]FMA in both 9L rat and transgenic mouse. Conclusion L-[18F]FMA showed promising properties as a PET imaging agent for up-regulated ASC transporter associated with tumor proliferation. PMID:22542392

  8. 18F-labeled FECNT: a selective radioligand for PET imaging of brain dopamine transporters.

    PubMed

    Goodman, M M; Kilts, C D; Keil, R; Shi, B; Martarello, L; Xing, D; Votaw, J; Ely, T D; Lambert, P; Owens, M J; Camp, V M; Malveaux, E; Hoffman, J M

    2000-01-01

    Fluorine-18 labeled 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nort ropane (FECNT) was synthesized in the development of a dopamine transporter (DAT) imaging ligand for positron emission tomography (PET). The methods of radiolabeling and ligand synthesis of FECNT, and the results of the in vitro characterization and in vivo tissue distribution in rats and in vivo PET imaging in rhesus monkeys of [18F]FECNT are described. Fluorine-18 was introduced into 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nort ropane (4) by preparation of 1-[18F]fluoro-2-tosyloxyethane (2) followed by alkylation of 2beta-carbomethoxy-3beta-(4-chlorophenyl)nortropane (3) in 21% radiochemical yield (decay corrected to end of bombardment [EOB]). Competition binding in cells stably expressing the transfected human DAT serotonin transporter (SERT) and norepinephrine transporter (NET) labeled by [3H]WIN 35428, [3H]citalopram, and [3H]nisoxetine, respectively, indicated the following order of DAT affinity: GBR 12909 > CIT > 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(3-fluoropropyl) nortropane (FPCT) > FECNT. The affinity of FECNT for SERT and NET was 25- and 156-fold lower, respectively, than for DAT. Blocking studies were performed in rats with a series of transporter-specific agents and demonstrated that the brain uptake of [18F]FECNT was selective and specific for DAT-rich regions. PET brain imaging studies in monkeys demonstrated high [18F]FECNT uptake in the caudate and putamen that resulted in caudate-to-cerebellum and putamen-to-cerebellum ratios of 10.5 at 60 min. [18F]FECNT uptake in the caudate/putamen peaked in less than 75 min and exhibited higher caudate- and putamen-to-cerebellum ratios at transient equilibrium than reported for 11C-WIN 35,428, [11C]CIT/RTI-55, or [18F]beta-CIT-FP. Analysis of monkey arterial plasma samples using high performance liquid chromatography determined that there was no detectable formation of lipophilic radiolabeled metabolites capable of entering the brain. In equilibrium displacement experiments with CIT in rhesus monkeys, radioactivity in the putamen was displaced with an average half-time of 10.2 min. These results indicate that [18F]FECNT is a radioligand that is superior to 11C-WIN 35,428, [11C]CIT/RTI-55, [18F]beta-CIT-FP, and [18F]FPCT for mapping brain DAT in humans using PET.

  9. Single-scan rest/stress imaging 18F-labeled flow tracers

    PubMed Central

    Alpert, Nathaniel; Dean Fang, Yu-Hua; Fakhri, Georges El

    2012-01-01

    Purpose: The authors report a novel measurement strategy to obtain both rest and stress blood flow during a single, relatively short, scan session. Methods: Measurement of rest-stress myocardial blood flow with long-lived tracers usually requires separate scan sessions to remove the confounding effects of residual radioactivity concentration in the blood and tissue. The innovation of this method is to treat the rest-stress scan as a single entity in which the flow parameters change due to pharmacological challenge. With this approach the fate of a tracer molecule is naturally accounted for, no matter if it was introduced during the rest or stress phase of the study. Two new dual-injection kinetic models are considered that represent the response to pharmacological stress as a transitional or transient increase of myocardial blood flow. The authors present the theory of the method followed by the specific application of the theory to 18F-Flurpiridaz, a new myocardial flow-imaging agent. Results: Myocardial blood flow was accurately and precisely estimated from a single-scan rest/stress study for the long half-lived tracer 18F-Flurpiridaz. By accounting for the time-dependence of the kinetic parameters, the proposed models achieved good accuracy and precision (5%) under different vasodilators and different ischemic states. Conclusions: Detailed simulations predict that accurate and precise rest-stress blood flow measurements can be obtained in 20–30 min. PMID:23127055

  10. Galloyl-RGD as a new cosmetic ingredient

    PubMed Central

    2014-01-01

    Background The cosmetics market has rapidly increased over the last years. For example, in 2011 it reached 242.8 billion US dollars, which was a 3.9% increase compared to 2010. There have been many recent trials aimed at finding the functional ingredients for new cosmetics. Gallic acid is a phytochemical derived from various herbs, and has anti-fungal, anti-viral, and antioxidant properties. Although phytochemicals are useful as cosmetic ingredients, they have a number of drawbacks, such as thermal stability, residence time in the skin, and permeability through the dermal layer. To overcome these problems, we considered conjugation of gallic acid with a peptide. Results We synthesized galloyl-RGD, which represents a conjugate of gallic acid and the peptide RGD, purified it by HPLC and characterized by MALDI-TOF with the aim of using it as a new cosmetic ingredient. Thermal stability of galloyl-RGD was tested at alternating temperatures (consecutive 4°C, 20°C, or 40°C for 8 h each) on days 2, 21, 41, and 61. Galloyl-RGD was relatively safe to HaCaT keratinocytes, as their viability after 48 h incubation with 500 ppm galloyl-RGD was 93.53%. In the group treated with 50 ppm galloyl-RGD, 85.0% of free radicals were removed, whereas 1000 ppm galloyl-RGD suppressed not only L-DOPA formation (43.8%) but also L-DOPA oxidation (54.4%). Conclusions Galloyl-RGD is a promising candidate for a cosmetic ingredient. PMID:25103826

  11. New Methods for Labeling RGD Peptides with Bromine-76

    PubMed Central

    Lang, Lixin; Li, Weihua; Jia, Hong-Mei; Fang, De-Cai; Zhang, Shushu; Sun, Xilin; Zhu, Lei; Ma, Ying; Shen, Baozhong; Kiesewetter, Dale O.; Niu, Gang; Chen, Xiaoyuan

    2011-01-01

    confirmed by decreased tumor uptake after co-administration of unlabeled dimeric RGD peptides. The energy barrier of the transition state of bromination for the dimethoxybenzoyl group was about 9 kcal/mol lower than that for the tyrosine residue. In conclusion, the newly developed N-succinimidyl-2, 6-dimethoxybenzoate molecule can be used either for one step labeling through pre-conjugation or as the precursor for a Br-76 labeled prosthetic group for indirect labeling. Radiobromination on a dimethoxybenzoyl group has selectivity over radiobromination on tyrosine. The energy barrier difference of the transition states of bromination between the dimethoxybenzoyl group and the tyrosine residue may account for the reaction selectivity when both groups are present in the same molecule. PMID:21938262

  12. [Status and advances of RGD molecular imaging in lung cancer].

    PubMed

    Yue, Ning; Yuan, Shuanghu; Yang, Guoren

    2014-12-01

    Lung cancer has been one of the most common and the highest mortality rates malignant tumors at home and abroad. Sustained angiogenesis was not only the characteristic of malignant tumors, but also the foundation of tumor proliferation, invasion, recurrence and metastasis, it was also one of the hot spots of treatments in lung cancer biology currently. Integrins played an important part in tumor angiogenesis. Arg-Gly-Asp (RGD) peptides could combine with integrins specifically, and the application of radionuclide-labeled RGD molecular probes enabled imaging of tumor blood vessels to reflect its changes. The lung cancer imaging of RGD peptides at home and abroad in recent years was reviewed in this article.

  13. RGD-FasL Induces Apoptosis in Hepatocellular Carcinoma

    PubMed Central

    Liu, Zhongchen; Wang, Juan; Yin, Ping; Qiu, Jinhua; Liu, Ruizhen; Li, Wenzhu; Fan, Xin; Cheng, Xiaofeng; Chen, Caixia; Zhang, Jiakai; Zhuang, Guohong

    2009-01-01

    Despite impressive results obtained in animal models, the clinical use of Fas ligand (FasL) as an anticancer drug is limited by severe toxicity. Systemic toxicity of death ligands may be prevented by using genes encoding membrane-bound death ligands and by targeted transgene expression through either targeted transduction or targeted transcription. Selective induction of tumor cell death is a promising anticancer strategy. A fusion protein is created by fusing the extracellular domain of Fas ligand (FasL) to the peptide arginine-glycine-aspartic acid (RGD) that selectively targets avβ3-integrins on tumor endothelial cells. The purpose of this study is to evaluate the effects of RGD-FasL on tumor growth and survival in a murine hepatocellular carcinoma (HCC) tumor model. Treatment with RGD-FasL displaying an obvious suppressive effect on the HCC tumor model as compared to that with FasL (p < 0.05) and resulted in a more additive effect on tumor growth delay in this model. RGD-FasL treatment significantly enhanced mouse survival and caused no toxic effect, such as weight loss, organ failure, or other treatment-related toxicities. Apoptosis was detected by flow cytometric analysis and TUNEL assays; those results also showed that RGD-FasL is a more potent inducer of cell apoptosis for H22 and H9101 cell lines than FasL (p < 0.05). In conclusion, RGD-FasL appears to be a low-toxicity selective inducer of tumor cell death, which merits further investigation in preclinical and clinical studies. Furthermore, this approach offers a versatile technology for complexing target ligands with therapeutic recombinant proteins. To distinguish the anti-tumor effects of FasL in vivo, tumor and liver tissues were harvested to examine for evidence of necrotic cells, tumor cells, or apoptotic cells by Hematoxylin and eosin (H&E) staining. PMID:19728930

  14. RGD based peptide amphiphiles as drug carriers for cancer targeting

    NASA Astrophysics Data System (ADS)

    Saraf, Poonam S.

    Specific interactions of ligands with receptors is one of the approaches for active targeting of anticancer drugs to cancer cells. Over expression of integrin receptors is a physiological manifestation in several cancers and is associated with cancer progression and metastasis, which makes it an attractive target for cancer chemotherapy. The peptide sequence for this integrin recognition is the Arg-Gly-Asp (RGD). Self-assembly offers a unique way of presenting ligands to target receptors for recognition and binding. This study focuses on development of integrin specific peptide amphiphile self-assemblies as carriers for targeted delivery of paclitaxel to αvbeta 3 integrin overexpressing cancers. Amphiphiles composed of conjugates of different analogs of RGD (linear, cyclic or glycosylated) and aliphatic fatty acid with or without 8-amino-3,6-dioxaoctanoic acid (ADA) as linker were synthesized and characterized. The amphiphiles exhibited Critical Micellar Concentration in the range of 7-30 μM. Transmission electron microscopy images revealed the formation of spherical micelles in the size range of 10-40 nm. Forster Resonance Energy Transfer studies revealed entrapment of hydrophobic dyes within a tight micellar core and provided information regarding the cargo exchange within micelles. The RGD micelles exhibited competitive binding with 55% displacement of a bound fluorescent probe by the cyclic RGD micelles. The internalization of fluorescein isothiocynate (FITC) loaded RGD micelles was significantly higher in A2058 melanoma cells compared to free FITC within 20 minutes of incubation at 37°C. The same micelles showed significantly lower internalization at 4°C and on pretreatment with 0.45M sucrose confirming endocytotic uptake of the RGD micellar carriers. The IC50 of paclitaxel in A2058 melanoma cells was lower when treated within RGD micelles as compared to treatment of free drug. On the other hand, IC50 values increased by 2 to 9 fold for micellar treatment

  15. The dimers of cyanamide

    NASA Astrophysics Data System (ADS)

    Moffat, J. B.

    Ab initio calculations have been performed on various dimeric forms of cyanamide. The "nondissociative" dimerization of cyanamide leads to cyclic molecules all of which are unstable with respect to cyanamide. However, the molecules produced by "dissociative" dimerization are stable relative to cyanamide. Dicyandiamide is found to be the most stable of nine dimeric configurations.

  16. Immobilization of RGD peptide on HA coating through a chemical bonding approach.

    PubMed

    Yang, Chunli; Cheng, Kui; Weng, Wenjian; Yang, Chunyu

    2009-11-01

    In this work, Arg-Gly-Asp (RGD) sequence containing peptide was immobilized on hydroxyapatite (HA) coatings through a chemical bonding approach in two steps, surface modification with 3-aminopropyltriethoxysilane (APTES) and RGD immobilization. The results indicate that RGD has been successfully immobilized on HA coatings. Comparing with physical adsorption coatings, the chemically bonded RGD on the coatings shows much better anti-wash-out ability. Since RGD is able to recognize cell-membrane integrins on biointerfaces, the present method will be an effective way to favor interaction of cells with HA coatings.

  17. Cyclic RGD-poly(ethylene glycol)-polyethyleneimine is more suitable for glioblastoma targeting gene transfer in vivo.

    PubMed

    Zhan, Changyou; Qian, Jun; Feng, Linglin; Zhong, Gaoren; Zhu, Jianhua; Lu, Weiyue

    2011-08-01

    Arginine-glycine-aspartic acid (RGD) is a widely chosen ligand to improve the specific gene targeting transfection efficiency of polyethyleneimine (PEI) in vivo. However, the optimal RGD conjugating mode, RGD-poly(ethylene glycol)-PEI (RGD-PEG-PEI) or RGD-PEI-methoxyl poly(ethylene glycol) (RGD-PEI-mPEG) still remains controversial. In this study, RGD-PEG-PEI and RGD-PEI-mPEG were synthesized and compared with respects to their glioblastoma cell-binding capability and tumor-targeting ability of their complexes with plasmid DNA. These results demonstrated that RGD-PEG-PEI/plasmid enhanced green fluorescent protein (pEGFP)-N2 complexes had higher binding affinities with U87 cells than RGD-PEI-mPEG/pEGFP-N2 complexes. The gene transfection was also performed on U87 cells in vitro and in vivo. In vitro, both of the RGD-modified PEI derivatives enhanced the gene transfection efficiency to some extent. However, all of the complexes (with or without RGD modification) had high transfection efficiency. The biodistribution of RGD-PEG-PEI/pEGFP-N2 complexes in mice bearing subcutaneous glioblastomas were significantly greater than that of RGD-PEI-mPEG/pEGFP-N2 complexes, suggesting a more efficient gene transfection in vivo. In the RGD-PEG-PEI, the use of a PEG spacer was particularly important. These results indicated that RGD-PEG-PEI was more suitable for targeted gene transfer in vivo.

  18. MicroPET Imaging of Integrin αvβ3 Expressing Tumors Using 89Zr-RGD Peptides

    PubMed Central

    Jacobson, Orit; Zhu, Lei; Niu, Gang; Weiss, Ido D.; Szajek, Lawrence P.; Ma, Ying; Sun, Xilin; Yan, Yongjun; Kiesewetter, Dale O.; Liu, Shuang; Chen, Xiaoyuan

    2011-01-01

    Purpose The dimeric transmembrane integrin, αvβ3, is a well-investigated target by different imaging modalities through suitably labeled arginine–glycine–aspartic acid (RGD) containing peptides. In this study, we labeled four cyclic RGD peptides with or without PEG functional groups: c(RGDfK) (denoted as FK), PEG3-c(RGDfK) (denoted as FK-PEG3), E[c(RGDfK)]2 (denoted as [FK]2), and PEG4-E[PEG4-c(RGDfK)]2 (denoted as [FK]2-3PEG4), with 89Zr (t1/2=78.4 h), using the chelator desferrioxamine-p-SCN (Df) for imaging tumor integrin αvβ3. Methods The Df conjugated RGD peptides were subjected to integrin αvβ3 binding assay in vitro using MDA-MB-435 breast cancer cells. The 89Zr-labeled RGD peptides were then subjected to small animal positron emission tomography (PET) and direct tissue sampling biodistribution studies in an orthotopic MDA-MB-435 breast cancer xenograft model. Results All four tracers, 89Zr-Df-FK, 89Zr-Df-FK-PEG3, 89Zr-Df-[FK]2, and 89Zr-Df-[FK]2-3PEG4, were labeled in high radiochemical yield (89±4%) and high specific activity (4.07–6 MBq/µg). Competitive binding assay with 125I-echistatin showed that conjugation of the RGD peptides to the Df chelator did not have significant impact on their integrin αvβ3 binding affinity and the dimeric peptides were shown to be more potent than the monomers. In agreement with binding results, tumor uptake of 89Zr-Df-[FK]2 and 89Zr-Df-[FK]2-3PEG4 was significantly higher (4.32±1.73%ID/g and 4.72±0.66%ID/g, respectively, at 2 h post-injection) than the monomers 89Zr-Df-FK and 89Zr-Df-FK-PEG3 (1.97±0.38%ID/g and 1.57±0.49%ID/g, respectively, at 2 h post-injection). Out of the four labeled peptides, 89Zr-Df-[FK]2-3PEG4 gave the highest tumor-to-background ratio (18.21±2.52 at 2 h post-injection and 19.69±3.99 at 4 h post-injection), with the lowest uptake in metabolic organs. Analysis of late time points biodistribution data revealed that the uptake in the tumor was decreased, along with increase in the

  19. RNA Dimerization Promotes PKR Dimerization and Activation

    PubMed Central

    Heinicke, Laurie A.; Wong, C. Jason; Lary, Jeffrey; Nallagatla, Subba Rao; Diegelman-Parente, Amy; Zheng, Xiaofeng; Cole, James L.; Bevilacqua, Philip C.

    2009-01-01

    The double-stranded RNA (dsRNA)-activated protein kinase (PKR) plays a major role in the innate immune response in humans. PKR binds dsRNA non-sequence specifically and requires a minimum of 15 bp dsRNA for one protein to bind and 30 bp dsRNA to induce protein dimerization and activation by autophosphorylation. PKR phosphorylates eIF2α, a translation initiation factor, resulting in the inhibition of protein synthesis. We investigated the mechanism of PKR activation by an RNA hairpin with a number of base pairs intermediate between these 15 to 30 bp limits: HIV-I TAR RNA, a 23 bp hairpin with three bulges that is known to dimerize. To test whether RNA dimerization affects PKR dimerization and activation, TAR monomers and dimers were isolated from native gels and assayed for RNA and protein dimerization. To modulate the extent of dimerization, we included TAR mutants with different secondary features. Native gel mixing experiments and analytical ultracentrifugation indicate that TAR monomers bind one PKR monomer and that TAR dimers bind two or three PKRs, demonstrating that RNA dimerization drives the binding of multiple PKR molecules. Consistent with functional dimerization of PKR, TAR dimers activated PKR while TAR monomers did not, and RNA dimers with fewer asymmetrical secondary structure defects, as determined by enzymatic structure mapping, were more potent activators. Thus, the secondary structure defects in the TAR RNA stem function as antideterminants to PKR binding and activation. Our studies support that dimerization of a 15–30 bp hairpin RNA, which effectively doubles its length, is a key step in driving activation of PKR and provide a model for how RNA folding can be related to human disease. PMID:19445956

  20. Tumor penetrability and anti-angiogenesis using iRGD-mediated delivery of doxorubicin-polymer conjugates.

    PubMed

    Wang, Ke; Zhang, Xiaofeng; Liu, Yang; Liu, Chang; Jiang, Baohong; Jiang, Yanyan

    2014-10-01

    Tumor-penetrating peptide, iRGD (internalizing RGD, CRGDK/RGPD/EC) with the similar affinity to αv integrins as conventional RGD cyclopeptide could enhance the tumor penetrability of drugs by binding to neuropilin-1 (NRP-1) that over-expressed on both angiogenic blood vessels and tumor cells. Comparing with our previous study, in which a RGD cyclopeptide (RGDyC) was bound to PEGylated polyamidoamine (PAMAM) dendrimer with doxorubicin (DOX) by acid-sensitive cis-aconityl linkage (PEG-PAMAM-cis-aconityl-DOX, PPCD), the present study selected iRGD instead of previous RGD to produce iRGD-PPCD conjugate. The effect of iRGD-mediated PPCD on tumor penetration was compared with the conventional RGD ones via administration of RGDs-modified PPCD (iRGD/RGDs-PPCD) and co-administration of RGDs and PPCD (iRGD/RGD + PPCD). C6 cells were selected as the cell model owing to the highest expression of αv integrins and NRP-1 among four tumor cell lines. In vitro cytotoxicity and cellular uptake showed no significant difference between RGD-PPCD and iRGD-PPCD, but glioma spheroid penetration study showed that RGD-PPCD, iRGD-PPCD and iRGD + PPCD penetrated into C6 spheroids with a depth of 115 μm, 144 μm and 150 μm, respectively, indicating that the iRGD-mediated PPCD delivery system had a stronger penetrating ability than the RGD ones. In vivo results also demonstrated the superiority of iRGD system over RGD ones. After systemic administration, iRGD-mediated PPCD increased tumor vascular permeability, decreased tumor vascular density and average vascular diameter. Correspondingly, the iRGD system exhibited stronger penetration ability, higher accumulation in brain tumor. The median survival time of iRGD + PPCD, iRGD-PPCD and RGD-PPCD treatment groups were 61, 57.5 and 43.5 days. The present findings strongly suggested that the iRGD-mediated drug delivery system could significantly improve the efficacy of tumor therapy through enhancing tumor accumulation and penetration as

  1. Tumor-Penetrating iRGD Peptide Inhibits Metastasis

    PubMed Central

    Sugahara, Kazuki N.; Braun, Gary B.; de Mendoza, Tatiana Hurtado; Kotamraju, Venkata Ramana; French, Randall P.; Lowy, Andrew M.; Teesalu, Tambet; Ruoslahti, Erkki

    2014-01-01

    Tumor-specific tissue-penetrating peptides deliver drugs into extravascular tumor tissue by increasing tumor vascular permeability through interaction with neuropilin (NRP). Here we report that a prototypic tumor-penetrating peptide iRGD (amino acid sequence: CRGDKGPDC) potently inhibits spontaneous metastasis in mice. The anti-metastatic effect was mediated by the NRP-binding RXXK peptide motif (CendR motif), and not by the integrin-binding RGD motif. iRGD inhibited migration of tumor cells and caused chemorepulsion in vitro in a CendR- and NRP-1-dependent manner. The peptide induced dramatic collapse of cellular processes and partial cell detachment, resulting in the repellent activity. These effects were prominently displayed when the cells were seeded on fibronectin, suggesting a role of CendR in functional regulation of integrins. The anti-metastatic activity of iRGD may provide a significant additional benefit when this peptide is used for drug delivery to tumors. PMID:25392370

  2. Identification of Angiogenesis Rich-Viable Myocardium using RGD Dimer based SPECT after Myocardial Infarction

    PubMed Central

    Lee, Min Su; Park, Hyun Soo; Lee, Byung Chul; Jung, Jae Ho; Yoo, Jung Sun; Kim, Sang Eun

    2016-01-01

    Cardiac healing after myocardial ischemia is a complex biological process. Advances in understanding of wound healing response have paved the way for clinical testing of novel molecular imaging to improve clinical outcomes. A key factor for assessing myocardial viability after ischemic injury is the evaluation of angiogenesis accompanying increased expression of integrin αvβ3. Here, we describe the capability of an αvβ3 integrin-targeting SPECT agent, 99mTc-IDA-D-[c(RGDfK)]2, for identification of ischemic but viable myocardium, i.e., hibernating myocardium which is crucial to predict functional recovery after revascularization, the standard care of cardiovascular medicine. In vivo SPECT imaging of rat models with transient coronary occlusion showed significantly high uptake of 99mTc-IDA-D-[c(RGDfK)]2 in the ischemic region. Comparative measurements with 201Tl SPECT and 18F-FDG PET, then, proved that such prominent uptake of 99mTc-IDA-D-[c(RGDfK)]2 exactly matched the hallmark of hibernation, i.e., the perfusion-metabolism mismatch pattern. The uptake of 99mTc-IDA-D-[c(RGDfK)]2 was non-inferior to that of 18F-FDG, confirmed by time-course variation analysis. Immunohistochemical characterization revealed that an intense signal of 99mTc-IDA-D-[c(RGDfK)]2 corresponded to the vibrant angiogenic events with elevated expression of αvβ3 integrin. Together, these results establish that 99mTc-IDA-D-[c(RGDfK)]2 SPECT can serve as a sensitive clinical measure for myocardial salvage to identify the patients who might benefit most from revascularization. PMID:27283041

  3. High affinity recognition of a Phytophthora protein by Arabidopsis via an RGD motif.

    PubMed

    Senchou, V; Weide, R; Carrasco, A; Bouyssou, H; Pont-Lezica, R; Govers, F; Canut, H

    2004-02-01

    The RGD tripeptide sequence, a cell adhesion motif present in several extracellular matrix proteins of mammalians, is involved in numerous plant processes. In plant-pathogen interactions, the RGD motif is believed to reduce plant defence responses by disrupting adhesions between the cell wall and plasma membrane. Photoaffinity cross-linking of [125I]-azido-RGD heptapeptide in the presence of purified plasma membrane vesicles of Arabidopsis thaliana led to label incorporation into a single protein with an apparent molecular mass of 80 kDa. Incorporation could be prevented by excess RGD peptides, but also by the IPI-O protein, an RGD-containing protein secreted by the oomycete plant pathogen Phytophthora infestans. Hydrophobic cluster analysis revealed that the RGD motif of IPI-O (positions 53-56) is readily accessible for interactions. Single amino acid mutations in the RGD motif in IPI-O (of Asp56 into Glu or Ala) resulted in the loss of protection of the 80-kDa protein from labelling. Thus, the interaction between the two proteins is mediated through RGD recognition and the 80-kDa RGD-binding protein has the characteristics of a receptor for IPI-O. The IPI-O protein also disrupted cell wall-plasma membrane adhesions in plasmolysed A. thaliana cells, whereas IPI-O proteins mutated in the RGD motif (D56A and D56E) did not.

  4. microPET Imaging of Glioma Integrin (alpha-v, beta-3) Expression Using Cu-64-Labeled Tetrameric RGD Peptide

    SciTech Connect

    Wu, Yun; Zhang, , Xianzhong; Xiong, , Zhengming; Cheng, Zhen; Fisher, Darrell R.; Liu, Shu-hong; Gambhir, Sanjiv S.; Chen, Xiaoyuan

    2005-10-01

    Integrins ?v?3 and ?v?5 play a critical role in tumor-induced angiogenesis and metastasis, and have become promising diagnostic indicators and therapeutic targets of tumors. Radiolabeled RGD peptides that are integrin-specific may be used for non-invasive imaging of integrin expression level as well as for integrin-targeted radionuclide therapy. We previously conjugated a series of mono- and dimeric RGD peptides with 1,4,7,10-tetraazacyclododecane-N, N?,N??,N???-tetraacetic acid (DOTA) and labeled these with copper-64 for microPET imaging in various mouse xenograft models. The copper-64 tracers showed ?v?3-selective tumor uptake, but the magnitude of tumor uptake was relatively low, the tumor washout was rapid, and non-target organ/tissue retention was high. In this study we developed a tetrameric RGD peptide tracer 64Cu-DOTA-E{l_brace}E[c(RGDfK)]2{r_brace}2 for positron emission tomography (PET) imaging of integrin ?v?3 expression in a subcutaneous U87MG glioma xenograft model in female athymic nude mice. The RGD tetramer showed significantly higher integrin binding affinity than the corresponding mono- and dimeric RGD analogs, most likely due to polyvalency effect. The radiolabeled peptide showed rapid blood clearance (0.61 ? 0.01%ID/g at 30 min and 0.21 ? 0.01 %ID/g at 4 h postinjection (p.i.), respectively) and predominantly renal excretion. Tumor uptake was rapid and high and the tumor washout was slow (9.93 ? 1.05 %ID/g at 30 min p.i. and 4.56 ? 0.51 %ID/g at 24 h post-injection). The metabolic stability of 64Cu-DOTA-E{l_brace}E[c(RGDfK)]2{r_brace}2 was determined in mouse blood, urine, and liver and kidney homogenates at different times after tracer injection. The average fractions of intact tracer in these organs at 1 h were approximately 70, 58, 51 and 26 percent, respectively. Non-invasive microPET imaging studies showed significant tumor uptake and good contrast in the subcutaneous tumor-bearing mice, which agreed well with the biodistribution results

  5. Recombinant decorsin: dynamics of the RGD recognition site.

    PubMed Central

    Krezel, A. M.; Ulmer, J. S.; Wagner, G.; Lazarus, R. A.

    2000-01-01

    Decorsin is an antagonist of integrin alphaIIbbeta3 and a potent platelet aggregation inhibitor. A synthetic gene encoding decorsin, originally isolated from the leech Macrobdella decora, was designed, constructed, and expressed in Escherichia coli. The synthetic gene was fused to the stII signal sequence and expressed under the transcriptional control of the E. coli alkaline phosphatase promoter. The protein was purified by size-exclusion filtration of the periplasmic contents followed by reversed-phase high-performance liquid chromatography. Purified recombinant decorsin was found to be indistinguishable from leech-derived decorsin based on amino acid composition, mass spectral analysis, and biological activity assays. Complete sequential assignments of 1H and proton bound 13C resonances were established. Stereospecific assignments of 21 of 25 nondegenerate b-methylene groups were determined. The RGD adhesion site recognized by integrin receptors was found at the apex of a most exposed hairpin loop. The dynamic behavior of decorsin was analyzed using several independent NMR parameters. Although the loop containing the RGD sequence is the most flexible one in decorsin, the conformation of the RGD site itself is more restricted than in other proteins with similar activities. PMID:10975565

  6. The RGD finger of Del-1 is a unique structural feature critical for integrin binding

    SciTech Connect

    Schürpf, Thomas; Chen, Qiang; Liu, Jin-huan; Wang, Rui; Springer, Timothy A.; Wang, Jia-huai

    2012-11-13

    Developmental endothelial cell locus-1 (Del-1) glycoprotein is secreted by endothelial cells and a subset of macrophages. Del-1 plays a regulatory role in vascular remodeling and functions in innate immunity through interaction with integrin {alpha}{sub V}{beta}{sub 3}. Del-1 contains 3 epidermal growth factor (EGF)-like repeats and 2 discoidin-like domains. An Arg-Gly-Asp (RGD) motif in the second EGF domain (EGF2) mediates adhesion by endothelial cells and phagocytes. We report the crystal structure of its 3 EGF domains. The RGD motif of EGF2 forms a type II' {beta} turn at the tip of a long protruding loop, dubbed the RGD finger. Whereas EGF2 and EGF3 constitute a rigid rod via an interdomain calcium ion binding site, the long linker between EGF1 and EGF2 lends considerable flexibility to EGF1. Two unique O-linked glycans and 1 N-linked glycan locate to the opposite side of EGF2 from the RGD motif. These structural features favor integrin binding of the RGD finger. Mutagenesis data confirm the importance of having the RGD motif at the tip of the RGD finger. A database search for EGF domain sequences shows that this RGD finger is likely an evolutionary insertion and unique to the EGF domain of Del-1 and its homologue milk fat globule-EGF 8. The RGD finger of Del-1 is a unique structural feature critical for integrin binding.

  7. RGD functionalized polymeric nanoparticles targeting periodontitis epithelial cells for the enhanced treatment of periodontitis in dogs.

    PubMed

    Yao, Wenxin; Xu, Peicheng; Zhao, Jingjing; Ling, Li; Li, Xiaoxia; Zhang, Bo; Cheng, Nengneng; Pang, Zhiqing

    2015-11-15

    Long term retention of antimicrobials with effective drug concentration in gingival crevicular fluid (GCF) is of vital importance for the treatment of chronic periodontitis. In this study, a novel epithelial cell-targeting nanoparticle drug delivery system by conjugating minocycline-loaded poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) nanoparticles (NP-MIN) with RGD peptide were developed and administrated locally for targeting periodontitis epithelial cells and enhancing the treatment of periodontitis in dogs. Biodegradable NP-MIN was made with an emulsion/solvent evaporation technique. RGD peptide was conjugated to the surface of nanoparticles via Maleimide group reaction with hydrosulfide in RGD peptide (RGD-NP-MIN). Transmission electron microscopy examination and dynamic light scattering results revealed that RGD-NP-MIN had a sphere shape, with a mean diameter around 106nm. In vitro release of minocycline from RGD-NP-MIN showed that RGD modification did not change the remarkable sustained releasing characteristic of NP-MIN. To elucidate the interaction of RGD-NP and epithelial cells, RGD-NP binding, uptake and cellular internalization mechanisms by calu-3 cells were investigated. It was shown RGD modification significantly enhanced nanoparticles binding and uptake by Calu-3 cells, and RGD-NP uptake was an energy-dependent process through receptor-mediated endocytosis. Both clathrin-associated endocytosis and caveolae-dependent endocytosis pathway were involved in the RGD-NP uptake, and the intracellular transport of RGD-NP was related to lysosome and Golgi apparatus. Finally, in vivo pharmacokinetics of minocycline in the periodontal pockets and anti-periodontitis effects of RGD-NP-MIN on periodontitis-bearing dogs were evaluated. After local administration of RGD-NP-MIN, minocycline concentration in gingival crevicular fluid decreased slowly and maintained an effective drug concentration for a longer time than that of NP-MIN. Anti-periodontitis effects

  8. Activatable iRGD-based peptide monolith: Targeting, internalization, and fluorescence activation for precise tumor imaging.

    PubMed

    Cho, Hong-Jun; Lee, Sung-Jin; Park, Sung-Jun; Paik, Chang H; Lee, Sang-Myung; Kim, Sehoon; Lee, Yoon-Sik

    2016-09-10

    A disulfide-bridged cyclic RGD peptide, named iRGD (internalizing RGD, c(CRGDK/RGPD/EC)), is known to facilitate tumor targeting as well as tissue penetration. After the RGD motif-induced targeting on αv integrins expressed near tumor tissue, iRGD encounters proteolytic cleavage to expose the CendR motif that promotes penetration into cancer cells via the interaction with neuropilin-1. Based on these proteolytic cleavage and internalization mechanism, we designed an iRGD-based monolithic imaging probe that integrates multiple functions (cancer-specific targeting, internalization and fluorescence activation) within a small peptide framework. To provide the capability of activatable fluorescence signaling, we conjugated a fluorescent dye to the N-terminal of iRGD, which was linked to the internalizing sequence (CendR motif), and a quencher to the opposite C-terminal. It turned out that fluorescence activation of the dye/quencher-conjugated monolithic peptide probe requires dual (reductive and proteolytic) cleavages on both disulfide and amide bond of iRGD peptide. Furthermore, the cleavage of the iRGD peptide leading to fluorescence recovery was indeed operative depending on the tumor-related angiogenic receptors (αvβ3 integrin and neuropilin-1) in vitro as well as in vivo. Compared to an 'always fluorescent' iRGD control probe without quencher conjugation, the dye/quencher-conjugated activatable monolithic peptide probe visualized tumor regions more precisely with lower background noise after intravenous injection, owing to the multifunctional responses specific to tumor microenvironment. All these results, along with minimal in vitro and in vivo toxicity profiles, suggest potential of the iRGD-based activatable monolithic peptide probe as a promising imaging agent for precise tumor diagnosis.

  9. RGD-fatty alcohol-modified docetaxel liposomes improve tumor selectivity in vivo.

    PubMed

    Li, Yinghuan; Zheng, Xuelian; Sun, Yi; Ren, Zhao; Li, Xuemei; Cui, Guohui

    2014-07-01

    The tripeptide arginine-glycine-aspartate (RGD) was conjugated with various fatty alcohols to obtain RGDOCnH2n+1 (n=8, 10, 12, 14, 16, 18), which were incorporated into the bilayer of docetaxel liposomes to improve their tumor specificity. The fatty alcohols were accepted as linking groups to insert the tetrapeptide RGDX (X=amino acid) into the bilayer of liposomes. RGDX was previously shown to be a potent ligand to target tumor cell-surface integrin receptors, whereas RGD was not shown to have this ability. We hypothesized that RGD-fatty alcohol conjugates lacking the fourth amine X can guide liposomes to tumors without reducing their binding affinity to integrins. Antitumor activity, pharmacokinetics and biodistribution studies were evaluated in mice inoculated with S180 sarcoma. Compared with unmodified liposomes, RGD-fatty alcohol-modified liposomes successfully delivered significantly more docetaxel to tumors, which led to significant tumor weight loss and increased tumor docetaxel concentrations accompanied by reduced liver accumulation. Improved affinity of RGD-fatty alcohols to integrins was also confirmed on A375 cell model. Further comparisons among the tumor-targeting capacities of liposomes containing RGD-fatty alcohols, RGDF-fatty alcohols and RGDV-fatty acids demonstrated that RGD-fatty alcohols were as effective as the other two tetrapeptide derivatives. Therefore, a simplified tumor-targeting delivery system using RGD-fatty alcohols was developed.

  10. Targeting In-Stent-Stenosis with RGD- and CXCL1-Coated Mini-Stents in Mice

    PubMed Central

    Weinandy, Stefan; Schreiber, Fabian; Megens, Remco T. A.; Theelen, Wendy; Smeets, Ralf; Jockenhövel, Stefan; Gries, Thomas; Möller, Martin; Klee, Doris; Weber, Christian; Zernecke, Alma

    2016-01-01

    Atherosclerotic lesions that critically narrow the artery can necessitate an angioplasty and stent implantation. Long-term therapeutic effects, however, are limited by excessive arterial remodeling. We here employed a miniaturized nitinol-stent coated with star-shaped polyethylenglycole (star-PEG), and evaluated its bio-functionalization with RGD and CXCL1 for improving in-stent stenosis after implantation into carotid arteries of mice. Nitinol foils or stents (bare metal) were coated with star-PEG, and bio-functionalized with RGD, or RGD/CXCL1. Cell adhesion to star-PEG-coated nitinol foils was unaltered or reduced, whereas bio-functionalization with RGD but foremost RGD/CXCL1 increased adhesion of early angiogenic outgrowth cells (EOCs) and endothelial cells but not smooth muscle cells when compared with bare metal foils. Stimulation of cells with RGD/CXCL1 furthermore increased the proliferation of EOCs. In vivo, bio-functionalization with RGD/CXCL1 significantly reduced neointima formation and thrombus formation, and increased re-endothelialization in apoE-/- carotid arteries compared with bare-metal nitinol stents, star-PEG-coated stents, and stents bio-functionalized with RGD only. Bio-functionalization of star-PEG-coated nitinol-stents with RGD/CXCL1 reduced in-stent neointima formation. By supporting the adhesion and proliferation of endothelial progenitor cells, RGD/CXCL1 coating of stents may help to accelerate endothelial repair after stent implantation, and thus may harbor the potential to limit the complication of in-stent restenosis in clinical approaches. PMID:27192172

  11. RGD-based active targeting of novel polycation liposomes bearing siRNA for cancer treatment.

    PubMed

    Yonenaga, Norihito; Kenjo, Eriya; Asai, Tomohiro; Tsuruta, Atsushi; Shimizu, Kosuke; Dewa, Takehisa; Nango, Mamoru; Oku, Naoto

    2012-06-10

    For the purpose of systemic delivery of siRNA, we previously developed polycation liposomes (PCLs) containing dicetylphosphate-tetraethylenepentamine (DCP-TEPA) as an effective siRNA carrier. In the present study, to endow these PCLs (TEPA-PCL) actively target cancer cells and angiogenic vessels, we decorated the PCLs with cyclic RGD, by using cyclic RGD-grafted distearoylphosphatidylethanolamine-polyethylene glycol (DSPE-PEG), and investigated the usefulness of this type of carrier (RGD-PEG-PCL) for active targeting. Firstly, the gene-silencing efficacy of siRNA for luciferase (siLuc2) formulated in RGD-PEG-PCL (RGD-PEG-PCL/siLuc2) was examined in vitro by using B16F10-luc2 murine melanoma cells stably expressing the luciferase 2 gene, where the siRNA was grafted with cholesterol at the 3'-end of the sense strand (siRNA-C) for the stable association of the siRNA with the PCL. RGD-PEG-PCL/siLuc2 showed high knockdown efficiency compared with siLuc2 formulated in PEGylated TEPA-PCL without cyclic RGD (PEG-PCL). Next, the gene-silencing efficacy of RGD-PEG-PCL/siLuc2 was examined in vivo by use of B16F10-luc2 lung metastatic model mice. The intravenous injection of RGD-PEG-PCL/siLuc2 showed high knockdown efficiency against metastatic B16F10-luc2 tumors in the lungs of the mice, as assessed with an in vivo imaging system. These data strongly suggest that systemic and active targeting siRNA delivery using RGD-PEG-PCL is useful for cancer RNAi therapy.

  12. RGD-Targeted Ultrasound Contrast Agent for Longitudinal Assessment of Hep-2 Tumor Angiogenesis In Vivo

    PubMed Central

    Hu, Qiao; Wang, Xiao-Yan; Kang, Li-Ke; Wei, Hai-Ming; Xu, Chun-Mei; Wang, Tao; Wen, Zong-Hua

    2016-01-01

    Objective To prepare arginine-glycine-aspartate (RGD)-targeted ultrasound contrast microbubbles (MBs) and explore the feasibility of their use in assessing dynamic changes in αvβ3 integrin expression in a murine model of tumor angiogenesis. Methods RGD peptides were conjugated to the surfaces of microbubbles via biotin-avidin linkage. Microbubbles bearing RADfK peptides were prepared as controls. The RGD-MBs were characterized using an Accusizer 780 and optical microscopy. The binding specificity of the RGD-MBs for ανβ3-expressing endothelial cells (bEnd.3) was demonstrated in vitro by a competitive inhibition experiment. In an in vivo study, mice bearing tumors of three different stages were intravenously injected with RGD-MBs and subjected to targeted, contrast-enhanced, high-frequency ultrasound. Subsequently, tumors were harvested and sectioned for immunofluorescence analysis of ανβ3 expression. Results The mean size of the RGD-MBs was 2.36 ± 1.7 μm. The RGD-MBs showed significantly higher adhesion levels to bEnd.3 cells compared to control MBs (P < 0.01). There was rarely binding of RGD-MBs to αvβ3-negative MCF-7 cells. Adhesion of the RGD-MBs to the bEnd.3 cells was significantly inhibited following treatment with anti-alpha(v) antibodies. The quantitative acoustic video intensity for high-frequency, contrast-enhanced ultrasound imaging of subcutaneous human laryngeal carcinoma (Hep-2) tumor xenografts was significantly higher in small tumors (19.89 ± 2.49) than in medium tumors (11.25 ± 2.23) and large tumors (3.38 ± 0.67) (P < 0.01). Conclusions RGD-MBs enable noninvasive in vivo visualization of changes in tumor angiogenesis during tumor growth in subcutaneous cancer xenografts. PMID:26862757

  13. Photochemical dimerization of organic compounds

    DOEpatents

    Crabtree, Robert H.; Brown, Stephen H.; Muedas, Cesar A.; Ferguson, Richard R.

    1992-01-01

    At least one of selectivity and reaction rate of photosensitized vapor phase dimerizations, including dehydrodimerizations, hydrodimerizations and cross-dimerizations of saturated and unsaturated organic compounds is improved by conducting the dimerization in the presence of hydrogen or nitrous oxide.

  14. [Expression and bioactivity effects to Hela of recombinant toxin protein rLj-RGD3 from Lampetra japonica].

    PubMed

    Zhang, Piqiao; Wang, Jihong; Liu, Xin; Chu, Dan; Li, Qingwei

    2009-05-01

    Lj-RGD3 was a toxin from the saliva gland of Lampetra japonica. To study the anti-tumor function of rLj-RGD3 and confirm its biological status and significance, we extracted total RNA from the saliva gland and amplified the cDNA of Lj-RGD3 by RT-PCR. The cDNA of Lj-RGD3 was 357 bp long and encoded a polypeptide composed of 118 amino acids including 2 cysteines, 17 histidines and 3 RGD (Arg-Gly-Asp) motifs. We cloned the cDNA into the plasmid pET23b, and expressed the recombinant protein rLj-RGD3 in Escherichia coli BL21. Fusion rLj-RGD3 with the C-terminal his-tag was a 15 kD soluble protein. Using the His-Bind affinity chromatography, we purified rLj-RGD3. Furthermore, we determined the biological activities of rLj-RGD3. To examine the ability of rLj-RGD3 inhibiting Hela cells proliferation, we used MTT assay. The results showed that, rLj-RGD3 inhibited bFGF induced proliferation of Hela cells in a dose-dependent manner, the IC50 value was 2.6 micromol/L. Hoechst staining assay revealed that, the nuclei of the cells treated with rLj-RGD3 were stained much brighter than that of untreated cells due to chromatin condensation. Furthermore, the DNA ladder patterns from the cells treated with rLj-RGD3 were also observed. These results demonstrated that rLj-RGD3 could induce apoptosis of Hela cells. Cell adhesion, migration and invasion are critical processes in tumor metastasis. rLj-RGD3 significantly inhibited adhesion of Hela cells to vironectin in a dose-dependent manner. In order to determine the effect of rLj-RGD3 on Hela cells migration toward bFGF, we used Transwell containing insert filter. rLj-RGD3 showed a significant inhibition on Hela cells migration, the inhibition rate was 60%. In the invasion assay, the Matrigel and Transwell were used to imitate environment in vivo. The results of invasion assay revealed that, rLj-RGD3 significantly inhibited bFGF induced invasion of Hela cells. Taken together, these results revealed that rLj-RGD3 had typical functions

  15. 18F-labeled Single-Stranded DNA Aptamer for PET Imaging of Protein Tyrosine Kinase-7 Expression

    PubMed Central

    Wang, Lu; Wang, Zhe; Yang, Xiangyu; Dewhurst, Andrew; Ma, Ying; Zhu, Guizhi; Niu, Gang; Kiesewetter, Dale O.; Vasdev, Neil; Liang, Steven H.; Chen, Xiaoyuan

    2016-01-01

    Protein tyrosine kinase-7 (PTK7), a member of receptor tyrosine kinase superfamily initially identified as colon carcinoma kinase-4 (CCK-4), is highly expressed in various human malignancies. Its expression was found to correlate with aggressive biological behaviors such as increased cell proliferation, invasiveness and migration. Despite the importance and unmet need of imaging PTK7 in vivo, there is currently no clinically-relevant method to visualize tumoral PTK7 expression noninvasively such as PET or SPECT. This study aims to develop a specific, selective and high affinity PET radioligand based on single-stranded DNA (ssDNA) aptamer to address this challenge. Methods Sgc8, a 41-oligonucleotide that targets to PTK7, was labeled with F-18 using a two-step radiochemical synthesis, which featured a direct one-step radiofluorination on the distinctive spirocyclic hypervalent iodine(III) precursor to give 18F-fluorobenzyl azide followed by copper mediated “click” conjugation with Sgc8-alkyne. 18F-Sgc8 was evaluated in vitro and in vivo in two cell lines, HCT116 and U87MG, which express high and low amounts of PTK7, respectively. Results Sgc8 was labeled efficiently with F-18 in an isolated radiochemical yield of 62 ± 2%, non-decay-corrected (ndc) based on 18F-fluorobenzyl azide. 18F-Tr-Sgc8 was found to possess high affinity binding to both cell lines, with IC50 values for HCT116 as 2.7 ± 0.6 nM and U87MG as 16.9 ± 2.1 nM. In vivo PET imaging clearly visualized PTK7 expression in HCT116 xenografted mice with tumor uptake of 0.76 ± 0.09 %ID/g at 30 min post-injection (p.i.) for the subcutaneous tumor model and greater than 1.5 %ID/g for the liver metastasis model. U87MG xenograft tumors had much lower tracer accumulation (0.13 ± 0.06 %ID/g at 30 min p.i.), which was consistent with the lower expression of PTK7 in this tumor model. The labeled aptamer was rapidly cleared from the blood through the kidneys and bladder to give high tumor-to-blood and tumor-to-muscle ratios of 7.29 ± 1.51 and 10.25 ± 2.08, respectively. Conclusions The F-18 radiolabeling methodology shown here is a very robust procedure for labeling aptamers and similar chemical moieties, and can be applied to many different targets. Quantification of PTK7 using 18F-Tr-Sgc8 may be suitable for clinical translation and might help in the future to select and monitor appropriate therapies. PMID:26315836

  16. A high-affinity [18F]-labeled phosphoramidate peptidomimetic PSMA-targeted inhibitor for PET imaging of prostate cancer

    DOE PAGES

    Ganguly, Tanushree; Dannoon, Shorouk; Hopkins, Mark R.; ...

    2015-06-09

    Here in this study, a structurally modified phosphoramidate scaffold, with improved prostate-specific membrane antigen (PSMA) avidity, stability and in vivo characteristics, as a PET imaging agent for prostate cancer (PCa), was prepared and evaluated. p-Fluorobenzoyl-aminohexanoate and 2-(3-hydroxypropyl)glycine were introduced into the PSMA-targeting scaffold yielding phosphoramidate 5. X-ray crystallography was performed on the PSMA/5 complex. [18F]5 was synthesized, and cell uptake and internalization studies were conducted in PSMA(+) LNCaP and CWR22Rv1 cells and PSMA(-) PC-3 cells. In vivo PET imaging and biodistribution studies were performed at 1 and 4 h post injection in mice bearing CWR22Rv1 tumor, with or without blockingmore » agent. The crystallographic data showed interaction of the p-fluorobenzoyl group with an arene-binding cleft on the PSMA surface. In vitro studies revealed elevated uptake of [18F]5 in PSMA(+) cells (2.2% in CWR22Rv1 and 12.1% in LNCaP) compared to PSMA(-) cells (0.08%) at 4 h. In vivo tumor uptake of 2.33% ID/g and tumor-to-blood ratio of 265:1 was observed at 4 h. In conclusion, we have successfully synthesized, radiolabeled and evaluated a new PSMA-targeted PET agent. The crystal structure of the PSMA/5 complex highlighted the interactions within the arene-binding cleft contributing to the overall complex stability. The high target uptake and rapid non-target clearance exhibited by [18F]5 in PSMA(+) xenografts substantiates its potential use for PET imaging of PCa.« less

  17. Novel 18F labeling strategy for polyester-based NPs for in vivo PET-CT imaging.

    PubMed

    Di Mauro, Primiano Pio; Gómez-Vallejo, Vanessa; Baz Maldonado, Zuriñe; Llop Roig, Jordi; Borrós, Salvador

    2015-03-18

    Drug-loaded nanocarriers and nanoparticulate systems used for drug release require a careful in vivo evaluation in terms of physicochemical and pharmacokinetic properties. Nuclear imaging techniques such as positron emission tomography (PET) are ideal and noninvasive tools to investigate the biodistribution and biological fate of the nanostructures, but the incorporation of a positron emitter is required. Here we describe a novel approach for the (18)F-radiolabeling of polyester-based nanoparticles. Our approach relies on the preparation of the radiolabeled active agent 4-[(18)F]fluorobenzyl-2-bromoacetamide ([(18)F]FBBA), which is subsequently coupled to block copolymers under mild conditions. The labeled block copolymers are ultimately incorporated as constituent elements of the NPs by using a modified nano coprecipitation method. This strategy has been applied in the current work to the preparation of peptide-functionalized NPs with potential applications in drug delivery. According to the measurements of particle size and zeta potential, the radiolabeling process did not result in a statistically significant alteration of the physicochemical properties of the NPs. Moreover, radiochemical stability studies showed no detachment of the radioactivity from NPs even at 12 h after preparation. The radiolabeled NPs enabled the in vivo quantification of the biodistribution data in rats using a combination of imaging techniques, namely, PET and computerized tomography (CT). Low accumulation of the nanoparticles in the liver and their elimination mainly via urine was found. The different biodistribution pattern obtained for the "free" radiolabeled polymer suggests chemical and radiochemical integrity of the NPs under investigation. The strategy reported here may be applied to any polymeric NPs containing polymers bearing a nucleophile, and hence our novel strategy may find application for the in vivo and noninvasive investigation of a wide range of NPs.

  18. The effect of RGD density on osteoblast and endothelial cell behavior on RGD-grafted polyethylene terephthalate surfaces.

    PubMed

    Chollet, Celine; Chanseau, Christel; Remy, Murielle; Guignandon, Alain; Bareille, Reine; Labrugère, Christine; Bordenave, Laurence; Durrieu, Marie-C

    2009-02-01

    Hybrid materials combining polyethylene terephthalate and different types of cells (endothelial and osteoblastic cells) have been developed thanks to the covalent grafting of different densities of RGD containing peptides onto the polymer surface. Biomimetic modifications were performed by means of a three-step reaction procedure: creation of COOH functions, coupling agent grafting and the immobilization of the RGDC peptides. High resolution mu-imager was used to evaluate RGD densities (varying between 0.6 and 2.4 pmol/mm(2)) and has exhibited the stability of the surface grafted peptides when treated in harsh conditions. The efficiency of this route for biomimetic modification of a PET surface was demonstrated by measuring the adhesion of MC3T3 and HSVEC cells and by focal adhesion observation. Results obtained prove that a minimal RGDC density of 1 pmol/mm(2) is required to improve MC3T3 and HSVEC cells responses. Indeed, cells seeded onto a RGDC-modified PET with a density higher than 1 pmol/mm(2) were able to establish focal adhesion as visualized by fluorescence microscope compared to cells immobilized onto unmodified PET and RGDC-modified PET with densities lower than 1 pmol/mm(2). Moreover, the number of focal contacts was enhanced by the increase of RGDC peptide densities grafted onto the material surface. With this study we proved that the density of peptides immobilized on the surface is a very important parameter influencing osteoblast or endothelial cell adhesion and focal contact formation.

  19. Biomimetic Hybrid Nanofiber Sheets Composed of RGD Peptide-Decorated PLGA as Cell-Adhesive Substrates.

    PubMed

    Shin, Yong Cheol; Lee, Jong Ho; Kim, Min Jeong; Park, Ji Hoon; Kim, Sung Eun; Kim, Jin Su; Oh, Jin-Woo; Han, Dong-Wook

    2015-05-29

    In biomedical applications, there is a need for tissue engineering scaffolds to promote and control cellular behaviors, including adhesion, proliferation and differentiation. In particular, the initial adhesion of cells has a great influence on those cellular behaviors. In this study, we concentrate on developing cell-adhesive substrates applicable for tissue engineering scaffolds. The hybrid nanofiber sheets were prepared by electrospinning poly(lactic-co-glycolic acid) (PLGA) and M13 phage, which was genetically modified to enhance cell adhesion thru expressing RGD peptides on their surface. The RGD peptide is a specific motif of extracellular matrix (ECM) for integrin receptors of cells. RGD peptide-decorated PLGA (RGD-PLGA) nanofiber sheets were characterized by scanning electron microscopy, immunofluorescence staining, contact angle measurement and differential scanning calorimetry. In addition, the initial adhesion and proliferation of four different types of mammalian cells were determined in order to evaluate the potential of RGD-PLGA nanofiber sheets as cell-adhesive substrates. Our results showed that the hybrid nanofiber sheets have a three-dimensional porous structure comparable to the native ECM. Furthermore, the initial adhesion and proliferation of cells were significantly enhanced on RGD-PLGA sheets. These results suggest that biomimetic RGD-PLGA nanofiber sheets can be promising cell-adhesive substrates for application as tissue engineering scaffolds.

  20. Novel Approach to Prepare {sup 99m}Tc-Based Multivalent RGD Peptides

    SciTech Connect

    Shuang Liu

    2012-10-24

    This project presents a novel approach to prepare the {sup 99m}Tc-bridged multivalent RGD (arginine-glycine-aspartate) peptides. This project will focus on fundamentals of {sup 99m}Tc radiochemistry. The main objective of this project is to demonstrate the proof-of-principle for the proposed radiotracers. Once a kit formulation is developed for preparation of the {sup 99m}Tc-bridged multivalent RGD peptides, various tumor-bearing animal models will be used to evaluate their potential for SPECT (single photon-emission computed tomography) imaging of cancer. We have demonstrated that (1) multimerization of cyclic RGD peptides enhances the integrin {alpha}{sub v}{beta}{sub 3} bonding affinity and radiotracer tumor uptake; (2) addition of G{sub 3} or PEG{sub 4} linkers makes it possible for two RGD motifs in 3P-RGD{sub 2} and 3G-RGD{sub 2} to achieve simultaneous integrin {alpha}{sub v}{beta}{sub 3} binding; and (3) multimers are actually bivalent (not multivalent), the presence of extra RGD motifs can enhance the tumor retention time of the radiotracer.

  1. Dimers in nucleating vapors

    NASA Astrophysics Data System (ADS)

    Lushnikov, A. A.; Kulmala, M.

    1998-09-01

    The dimer stage of nucleation may affect considerably the rate of the nucleation process at high supersaturation of the nucleating vapor. Assuming that the dimer formation limits the nucleation rate, the kinetics of the particle formation-growth process is studied starting with the definition of dimers as bound states of two associating molecules. The partition function of dimer states is calculated by summing the Boltzmann factor over all classical bound states, and the equilibrium population of dimers is found for two types of intermolecular forces: the Lennard-Jones (LJ) and rectangular well+hard core (RW) potentials. The principle of detailed balance is used for calculating the evaporation rate of dimers. The kinetics of the particle formation-growth process is then investigated under the assumption that the trimers are stable with respect to evaporation and that the condensation rate is a power function of the particle mass. If the power exponent λ=n/(n+1) (n is a non-negative integer), the kinetics of the process is described by a finite set of moments of particle mass distribution. When the characteristic time of the particle formation by nucleation is much shorter than that of the condensational growth, n+2 universal functions of a nondimensional time define the kinetic process. These functions are calculated for λ=2/3 (gas-to-particle conversion in the free molecular regime) and λ=1/2 (formation of islands on surfaces).

  2. Application of click-click chemistry to the synthesis of new multivalent RGD conjugates

    PubMed Central

    Galibert, Mathieu; Sancey, Lucie; Renaudet, Olivier; Coll, Jean-Luc; Dumy, Pascal; Boturyn, Didier

    2010-01-01

    New multivalent RGD-containing macromolecules were designed by exploiting two orthogonal chemoselective ligations. They were next applied to a competitive cell adhesion assay and used for the non invasive optical imaging of tumour in small animals. PMID:20835451

  3. [The synthesis of RGD peptide derivatives containing glutaric and adipic residues].

    PubMed

    Vigorov, A Iu; Demin, A M; Nizova, I A; Krasnov, V P

    2014-01-01

    A method of the synthesis of RGD peptide derivatives containing glutaric or adipic residues linked with α-amino group of L-arginine and allowing carrying out their coupling with other biomolecules and nanoparticles.

  4. RGD-functionalized ultrasmall iron oxide nanoparticles for targeted T1-weighted MR imaging of gliomas

    NASA Astrophysics Data System (ADS)

    Luo, Yu; Yang, Jia; Yan, Yu; Li, Jingchao; Shen, Mingwu; Zhang, Guixiang; Mignani, Serge; Shi, Xiangyang

    2015-08-01

    We report a convenient approach to prepare ultrasmall Fe3O4 nanoparticles (NPs) functionalized with an arginylglycylaspartic acid (RGD) peptide for in vitro and in vivo magnetic resonance (MR) imaging of gliomas. In our work, stable sodium citrate-stabilized Fe3O4 NPs were prepared by a solvothermal route. Then, the carboxylated Fe3O4 NPs stabilized with sodium citrate were conjugated with polyethylene glycol (PEG)-linked RGD. The formed ultrasmall RGD-functionalized nanoprobe (Fe3O4-PEG-RGD) was fully characterized using different techniques. We show that these Fe3O4-PEG-RGD particles with a size of 2.7 nm are water-dispersible, stable, cytocompatible and hemocompatible in a given concentration range, and display targeting specificity to glioma cells overexpressing αvβ3 integrin in vitro. With the relatively high r1 relaxivity (r1 = 1.4 mM-1 s-1), the Fe3O4-PEG-RGD particles can be used as an efficient nanoprobe for targeted T1-weighted positive MR imaging of glioma cells in vitro and the xenografted tumor model in vivo via an active RGD-mediated targeting pathway. The developed RGD-functionalized Fe3O4 NPs may hold great promise to be used as a nanoprobe for targeted T1-weighted MR imaging of different αvβ3 integrin-overexpressing cancer cells or biological systems.We report a convenient approach to prepare ultrasmall Fe3O4 nanoparticles (NPs) functionalized with an arginylglycylaspartic acid (RGD) peptide for in vitro and in vivo magnetic resonance (MR) imaging of gliomas. In our work, stable sodium citrate-stabilized Fe3O4 NPs were prepared by a solvothermal route. Then, the carboxylated Fe3O4 NPs stabilized with sodium citrate were conjugated with polyethylene glycol (PEG)-linked RGD. The formed ultrasmall RGD-functionalized nanoprobe (Fe3O4-PEG-RGD) was fully characterized using different techniques. We show that these Fe3O4-PEG-RGD particles with a size of 2.7 nm are water-dispersible, stable, cytocompatible and hemocompatible in a given concentration

  5. Effect of RGD-functionalization and stiffness modulation of polyelectrolyte multilayer films on muscle cell differentiation

    PubMed Central

    Gribova, Varvara; Gauthier-Rouvière, Cécile; Albigès-Rizo, Corinne; Auzely-Velty, Rachel; Picart, Catherine

    2014-01-01

    Skeletal muscle tissue engineering holds promise for the replacement of muscle due to an injury and for the treatment of muscle diseases. Although RGD substrates have been widely explored in tissue engineering, there is no study aimed at investigating the combined effects of RGD nanoscale presentation and matrix stiffness on myogenesis. In the present work, we use polyelectrolyte multilayer films made of poly(L-lysine) (PLL) and poly(L-glutamic) acid (PGA) as substrates of tunable stiffness that can be functionalized by a RGD adhesive peptide to investigate important events in myogenesis, including adhesion, migration, proliferation and differentiation. C2C12 myoblasts were used as cellular models. RGD presentation on soft films and increased film stiffness could both induce cell adhesion, but integrins involved in adhesion were different in case of soft and stiff films. Moreover, soft films with RGD peptide appeared to be the most appropriate substrate for myogenic differentiation while the stiff PLL/PGA films significantly induced cell migration, proliferation and inhibited myogenic differentiation. The ROCK kinase was found to be involved in myoblast response to the different films. Indeed, its inhibition was sufficient to rescue the differentiation on stiff films, but no significant changes were observed on stiff films with the RGD peptide. These results suggest that different signaling pathways may be activated depending on mechanical and biochemical properties of the multilayer films. This study emphasizes the superior advantage of the soft PLL/PGA films presenting the RGD peptide in terms of myogenic differentiation. This soft RGD-presenting film may be further used as coating of various polymeric scaffolds for muscle tissue engineering. PMID:23261924

  6. Characterization of bioactive RGD peptide immobilized onto poly(acrylic acid) thin films by plasma polymerization

    NASA Astrophysics Data System (ADS)

    Seo, Hyun Suk; Ko, Yeong Mu; Shim, Jae Won; Lim, Yun Kyong; Kook, Joong-Ki; Cho, Dong-Lyun; Kim, Byung Hoon

    2010-11-01

    Plasma surface modification can be used to improve the surface properties of commercial pure Ti by creating functional groups to produce bioactive materials with different surface topography. In this study, a titanium surface was modified with acrylic acid (AA) using a plasma treatment and immobilized with bioactive arginine-glycine-aspartic acid (RGD) peptide, which may accelerate the tissue integration of bone implants. Both terminals containing the -NH2 of RGD peptide sequence and -COOH of poly(acrylic acid) (PAA) thin film were combined with a covalent bond in the presence of 1-ethyl-3-3-dimethylaminopropyl carbodiimide (EDC). The chemical structure and morphology of AA film and RGD immobilized surface were investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), atomic force microscopy (AFM), and scanning electron microscopy (SEM). All chemical analysis showed full coverage of the Ti substrate with the PAA thin film containing COOH groups and the RGD peptide. The MC3T3-E1 cells were cultured on each specimen, and the cell alkaline phosphatase (ALP) activity were examined. The surface-immobilized RGD peptide has a significantly increased the ALP activity of MC3T3-E1 cells. These results suggest that the RGD peptide immobilization on the titanium surface has an effect on osteoblastic differentiation of MC3T3-E1 cells and potential use in osteo-conductive bone implants.

  7. Heterogeneous dimer peptide-conjugated polylysine dendrimer-Fe3O4 composite as a novel nanoscale molecular probe for early diagnosis and therapy in hepatocellular carcinoma.

    PubMed

    Shen, Jian-Min; Li, Xin-Xin; Fan, Lin-Lan; Zhou, Xing; Han, Ji-Min; Jia, Ming-Kang; Wu, Liang-Fan; Zhang, Xiao-Xue; Chen, Jing

    2017-01-01

    A novel nanoscale molecular probe is formulated in order to reduce toxicity and side effects of antitumor drug doxorubicin (DOX) in normal tissues and to enhance the detection sensitivity during early imaging diagnosis. The mechanism involves a specific targeting of Arg-Gly-Asp peptide (RGD)-GX1 heterogeneous dimer peptide-conjugated dendrigraft poly-l-lysine (DGL)-magnetic nanoparticle (MNP) composite by αvβ3-integrin/vasculature endothelium receptor-mediated synergetic effect. The physicochemical properties of the nanoprobe were characterized by using transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, dynamic light scattering (DLS), and vibrating sample magnetometer. The average diameter of the resulting MNP-DGL-RGD-GX1-DOX nanoparticles (NPs) was ~150-160 nm by DLS under simulate physiological medium. In the present experimental system, the loading amount of DOX on NPs accounted for 414.4 mg/g for MNP-DGL-RGD-GX1-DOX. The results of cytotoxicity, flow cytometry, and cellular uptake consistently indicated that the MNP-DGL-RGD-GX1-DOX NPs were inclined to target HepG2 cells in selected three kinds of cells. In vitro exploration of molecular mechanism revealed that cell apoptosis was associated with the overexpression of Fas protein and the significant activation of caspase-3. In vivo magnetic resonance imaging and biodistribution study showed that the MNP-DGL-RGD-GX1-DOX formulation had high affinity to the tumor tissue, leading to more aggregation of NPs in the tumor. In vivo antitumor efficacy research verified that MNP-DGL-RGD-GX1-DOX NPs possessed significant antitumor activity and the tumor inhibitory rate reached 78.5%. These results suggested that NPs could be promising in application to early diagnosis and therapy in hepatocellular carcinoma as a specific nanoprobe.

  8. Heterogeneous dimer peptide-conjugated polylysine dendrimer-Fe3O4 composite as a novel nanoscale molecular probe for early diagnosis and therapy in hepatocellular carcinoma

    PubMed Central

    Shen, Jian-Min; Li, Xin-Xin; Fan, Lin-Lan; Zhou, Xing; Han, Ji-Min; Jia, Ming-Kang; Wu, Liang-Fan; Zhang, Xiao-Xue; Chen, Jing

    2017-01-01

    A novel nanoscale molecular probe is formulated in order to reduce toxicity and side effects of antitumor drug doxorubicin (DOX) in normal tissues and to enhance the detection sensitivity during early imaging diagnosis. The mechanism involves a specific targeting of Arg-Gly-Asp peptide (RGD)-GX1 heterogeneous dimer peptide-conjugated dendrigraft poly-l-lysine (DGL)–magnetic nanoparticle (MNP) composite by αvβ3-integrin/vasculature endothelium receptor-mediated synergetic effect. The physicochemical properties of the nanoprobe were characterized by using transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, dynamic light scattering (DLS), and vibrating sample magnetometer. The average diameter of the resulting MNP–DGL–RGD-GX1–DOX nanoparticles (NPs) was ~150−160 nm by DLS under simulate physiological medium. In the present experimental system, the loading amount of DOX on NPs accounted for 414.4 mg/g for MNP–DGL–RGD-GX1–DOX. The results of cytotoxicity, flow cytometry, and cellular uptake consistently indicated that the MNP–DGL–RGD-GX1–DOX NPs were inclined to target HepG2 cells in selected three kinds of cells. In vitro exploration of molecular mechanism revealed that cell apoptosis was associated with the overexpression of Fas protein and the significant activation of caspase-3. In vivo magnetic resonance imaging and biodistribution study showed that the MNP–DGL–RGD-GX1–DOX formulation had high affinity to the tumor tissue, leading to more aggregation of NPs in the tumor. In vivo antitumor efficacy research verified that MNP–DGL–RGD-GX1–DOX NPs possessed significant antitumor activity and the tumor inhibitory rate reached 78.5%. These results suggested that NPs could be promising in application to early diagnosis and therapy in hepatocellular carcinoma as a specific nanoprobe. PMID:28243083

  9. Collective motion of dimers.

    PubMed

    Penington, Catherine J; Korvasová, Karolína; Hughes, Barry D; Landman, Kerry A

    2012-11-01

    We consider a discrete agent-based model on a one-dimensional lattice and a two-dimensional square lattice, where each agent is a dimer occupying two sites. Agents move by vacating one occupied site in favor of a nearest-neighbor site and obey either a strict simple exclusion rule or a weaker constraint that permits partial overlaps between dimers. Using indicator variables and careful probability arguments, a discrete-time master equation for these processes is derived systematically within a mean-field approximation. In the continuum limit, nonlinear diffusion equations that describe the average agent occupancy of the dimer population are obtained. In addition, we show that multiple species of interacting subpopulations give rise to advection-diffusion equations. Averaged discrete simulation data compares very well with the solution to the continuum partial differential equation models. Since many cell types are elongated rather than circular, this work offers insight into population-level behavior of collective cellular motion.

  10. Bone healing of commercial oral implants with RGD immobilization through electrodeposited poly(ethylene glycol) in rabbit cancellous bone.

    PubMed

    Park, Jin-Woo; Kurashima, Kazuya; Tustusmi, Yusuke; An, Chang-Hyeon; Suh, Jo-Young; Doi, Hisashi; Nomura, Naoyuki; Noda, Kazuhiko; Hanawa, Takao

    2011-08-01

    Immobilization of RGD peptides on titanium (Ti) surfaces enhances implant bone healing by promoting early osteoblastic cell attachment and subsequent differentiation by facilitating integrin binding. Our previous studies have demonstrated the efficacy of RGD peptide immobilization on Ti surfaces through the electrodeposition of poly(ethylene glycol) (PEG) (RGD/PEG/Ti), which exhibited good chemical stability and bonding. The RGD/PEG/Ti surface promoted differentiation and mineralization of pre-osteoblasts. This study investigated the in vivo bone healing capacity of the RGD/PEG/Ti surface for biomedical application as a more osteoconductive implant surface in dentistry. The RGD/PEG/Ti surface was produced on an osteoconductive implant surface, i.e. the grit blasted micro-rough surface of a commercial oral implant. The osteoconductivity of the RGD/PEG/Ti surface was compared by histomorphometric evaluation with an RGD peptide-coated surface obtained by simple adsorption in rabbit cancellous bone after 2 and 4 weeks healing. The RGD/PEG/Ti implants displayed a high degree of direct bone apposition in cancellous bone and achieved greater active bone apposition, even in areas of poor surrounding bone. Significant increases in the bone to implant contact percentage were observed for RGD/PEG/Ti implants compared with RGD-coated Ti implants obtained by simple adsorption both after 2 and 4 weeks healing (P<0.05). These results demonstrate that RGD peptide immobilization on a Ti surface through electrodeposited PEG may be an effective method for enhancing bone healing with commercial micro-rough surface oral implants in cancellous bone by achieving rapid bone apposition on the implant surface.

  11. The effect of conjugating RGD into 3D alginate hydrogels on adipogenic differentiation of human adipose-derived stromal cells.

    PubMed

    Kang, Sun-Woong; Cha, Byung-Hyun; Park, Honghyun; Park, Kwang-Sook; Lee, Kuen Yong; Lee, Soo-Hong

    2011-05-12

    The effects of RGD peptide conjugation to alginate hydrogel on the adipogenic differentiation of ASCs was investigated. After 3 d of culture, RGD-modified alginate hydrogels significantly stimulated FAK and integrin α1 gene expressions and vinculin expression in ASCs. In addition, RGD-modified alginate hydrogels significantly enhanced the adipogenic differentiation of human ASCs to exhibit higher expression levels of oil red O staining and adipogenic genes compared to those of the control group (unmodified gels). These results suggest potential applications of RGD-modified alginate gels for adipose tissue regeneration.

  12. Systemic Administration of siRNA via cRGD-containing Peptide

    PubMed Central

    Huang, Yuanyu; Wang, Xiaoxia; Huang, Weiyan; Cheng, Qiang; Zheng, Shuquan; Guo, Shutao; Cao, Huiqing; Liang, Xing-Jie; Du, Quan; Liang, Zicai

    2015-01-01

    Although small interfering RNAs (siRNAs) have been demonstrated to specifically silence their target genes in disease models and clinical trials, in vivo siRNA delivery is still the technical bottleneck that limits their use in therapeutic applications. In this study, a bifunctional peptide named RGD10-10R was designed and tested for its ability to deliver siRNA in vitro and in vivo. Because of their electrostatic interactions with polyarginine (10R), negatively charged siRNAs were readily complexed with RGD10-10R peptides, forming spherical RGD10-10R/siRNA nanoparticles. In addition to enhancing their serum stability by preventing RNase from attacking siRNA through steric hindrance, peptide binding facilitated siRNA transfection into MDA-MB-231 cells, as demonstrated by FACS and confocal microscopy assays and by the repressed expression of target genes. When RGD10 peptide, a receptor competitor of RGD10-10R, was added to the transfection system, the cellular internalization of RGD10-10R/siRNA was significantly compromised, suggesting a mechanism of ligand/receptor interaction. Tissue distribution assays indicated that the peptide/siRNA complex preferentially accumulated in the liver and in several exocrine/endocrine glands. Furthermore, tumor-targeted delivery of siRNA was also demonstrated by in vivo imaging and cryosection assays. In summary, RGD10-10R might constitute a novel siRNA delivery tool that could potentially be applied in tumor treatment. PMID:26300278

  13. RGD-conjugated albumin nanoparticles as a novel delivery vehicle in pancreatic cancer therapy.

    PubMed

    Ji, Shunrong; Xu, Jin; Zhang, Bo; Yao, Wantong; Xu, Wenyan; Wu, Wenzhe; Xu, Yongfeng; Wang, Hao; Ni, Quanxing; Hou, Huimin; Yu, Xianjun

    2012-02-15

    Integrin αvβ3 receptor is expressed on several types of cancer cells, including pancreatic cancer cells, and plays an important role in tumor growth and metastasis. The ability to target the integrin αvβ3 receptor on cancer cells increases the efficacy of targeted therapy and reduces the side effects. The aim of this study is to develop a novel arginine-glycine-aspartic acid (RGD) peptide -conjugated albumin nanoparticle to enhance the intracellular uptake of anticancer drug into the pancreatic cancer cells through receptor-mediated endocytosis. In the cellular uptake studies, the fluorescent signal of RGD-conjugated BSANPs in BxPC3 cells was higher than that of BSANPs without RGD conjugation as determined by fluorescence spectrophotometer. We also found that BSANPs bound to BxPC3 cells in a time- and concentration-dependent manner. The uptake of RGD-conjugated BSANPs by pancreatic cancer cells was inhibited by an excess amount of free RGD peptide, indicating that the binding and/or uptake were mediated by the αvβ3 receptor. Furthermore, the nanoparticles were found to be located close to the nuclei by using laser scanning confocal microscopy. Besides, no significant in vitro cytotoxicity was observed as measured with MTT assay. Both in vitro and in vivo antitumor efficacy was improved by targeting gemcitabine-loaded nanoparticles to BxPC-3 cells using RGD peptides. Therefore, the RGD-conjugated BSANPs hold great potential as an effective drug delivery system to deliver therapeutic agents to pancreatic cancer.

  14. Cellular Density Effect on RGD Ligand Internalization in Glioblastoma for MRI Application

    PubMed Central

    Moncelet, Damien; Bouchaud, Véronique; Mellet, Philippe; Ribot, Emeline; Miraux, Sylvain; Franconi, Jean-Michel; Voisin, Pierre

    2013-01-01

    Cellular density is a parameter measured for glioma grade and invasiveness diagnosis. The characterization of the cellular density can be performed, non invasively, by magnetic resonance imaging (MRI), since, this technique displays a good resolution. Nevertheless MRI sensitivity is critical. Development of smart contrast agents appears useful to increase MRI signal to noise ratio (SNR). Tumor invasiveness is correlated with high expression of integrins that can be targeted by RGD motif. In this study, MRI contrast agents or fluorescent probes linked to RGD-peptides were used, in a glioma model, to assess the relation between RGD uptake/signal improvement/cell density and consequently tumor invasiveness. Experiments were performed in vitro with U87-MG glioma cells. Flow cytometry and microscopy experiments with RGD and iRGD-alexa488 demonstrated that cell internalization was dependent on cell density. The internalization involved a clathrin-dependent endocytosis. Cytoskeleton and particularly the microtubules were concerned. Actin filaments played a minor role. The internalization was also dependent on the glycolysis and the oxidative phosphorylations. The cellular density modulated the importance of the endocytosis pathways and of the metabolism but not the cytoskeleton contribution. The internalization of the RGD-peptide associated to gadolinium chelate increased the SNR of U87 cells. Moreover, following the cell density augmentation, the SNR increased with a low amplitude but a trend was clearly determined. In conclusion, RGD-peptide internalization appeared, in vitro, as a marker of cellular density. In perspective, the combination of these peptides with contrast agents associated to more sensitive MRI techniques could improve the MRI signal allowing the characterization of cellular density for tumor diagnosis. PMID:24386117

  15. Quantum Dimer Model: Phase Diagrams

    NASA Astrophysics Data System (ADS)

    Goldstein, Garry; Chamon, Claudio; Castelnovo, Claudio

    We present new theoretical analysis of the Quantum Dimer Model. We study dimer models on square, cubic and triangular lattices and we reproduce their phase diagrams (which were previously known only numerically). We show that there are several types of dimer liquids and solids. We present preliminary analysis of several other models including doped dimers and planar spin ice, and some results on the Kagome and hexagonal lattices.

  16. Evidence for dimerization of dimers in K+ channel assembly.

    PubMed Central

    Tu, L; Deutsch, C

    1999-01-01

    Voltage-gated K+ channels are tetrameric, but how the four subunits assemble is not known. We analyzed inactivation kinetics and peak current levels elicited for a variety of wild-type and mutant Kv1.3 subunits, expressed singly, in combination, and as tandem constructs, to show that 1) the dominant pathway involves a dimerization of dimers, and 2) dimer-dimer interaction may involve interaction sites that differ from those involved in monomer-monomer association. Moreover, using nondenaturing gel electrophoresis, we detected dimers and tetramers, but not trimers, in the translation reaction of Kv1.3 monomers. PMID:10096897

  17. Topical ocular delivery to laser-induced choroidal neovascularization by dual internalizing RGD and TAT peptide-modified nanoparticles

    PubMed Central

    Chu, Yongchao; Chen, Ning; Yu, Huajun; Mu, Hongjie; He, Bin; Hua, Hongchen; Wang, Aiping; Sun, Kaoxiang

    2017-01-01

    A nanoparticle (NP) was developed to target choroidal neovascularization (CNV) via topical ocular administration. The NPs were prepared through conjugation of internalizing arginine-glycine-aspartic acid RGD (iRGD; Ac-CCRGDKGPDC) and transactivated transcription (TAT) (RKKRRQRRRC) peptide to polymerized ethylene glycol and lactic-co-glycolic acid. The iRGD sequence can specifically bind with integrin αvβ3, while TAT facilitates penetration through the ocular barrier. 1H nuclear magnetic resonance and high-performance liquid chromatography demonstrated that up to 80% of iRGD and TAT were conjugated to poly(ethylene glycol)– poly(lactic-co-glycolic acid). The resulting particle size was 67.0±1.7 nm, and the zeta potential of the particles was −6.63±0.43 mV. The corneal permeation of iRGD and TAT NPs increased by 5.50- and 4.56-fold compared to that of bare and iRGD-modified NPs, respectively. Cellular uptake showed that the red fluorescence intensity of iRGD and TAT NPs was highest among primary NPs and iRGD- or TAT-modified NPs. CNV was fully formed 14 days after photocoagulation in Brown Norway (BN) rats as shown by optical coherence tomography and fundus fluorescein angiography analyses. Choroidal flat mounts in BN rats showed that the red fluorescence intensity of NPs followed the order of iRGD and TAT NPs > TAT-modified NPs > iRGD-modified NPs > primary NPs. iRGD and TAT dual-modified NPs thus displayed significant targeting and penetration ability both in vitro and in vivo, indicating that it is a promising drug delivery system for managing CNV via topical ocular administration. PMID:28260884

  18. Triazole RGD antagonist reverts TGFβ1-induced endothelial-to-mesenchymal transition in endothelial precursor cells.

    PubMed

    Bianchini, Francesca; Peppicelli, Silvia; Fabbrizzi, Pierangelo; Biagioni, Alessio; Mazzanti, Benedetta; Menchi, Gloria; Calorini, Lido; Pupi, Alberto; Trabocchi, Andrea

    2017-01-01

    Fibrosis is the dramatic consequence of a dysregulated reparative process in which activated fibroblasts (myofibroblasts) and Transforming Growth Factor β1 (TGFβ1) play a central role. When exposed to TGFβ1, fibroblast and epithelial cells differentiate in myofibroblasts; in addition, endothelial cells may undergo endothelial-to-mesenchymal transition (EndoMT) and actively participate to the progression of fibrosis. Recently, the role of αv integrins, which recognize the Arg-Gly-Asp (RGD) tripeptide, in the release and signal transduction activation of TGFβ1 became evident. In this study, we present a class of triazole-derived RGD antagonists that interact with αvβ3 integrin. Above different compounds, the RGD-2 specifically interferes with integrin-dependent TGFβ1 EndoMT in Endothelial Colony-Forming Cells (ECPCs) derived from circulating Endothelial Precursor Cells (ECPCs). The RGD-2 decreases the amount of membrane-associated TGFβ1, and reduces both ALK5/TGFβ1 type I receptor expression and Smad2 phosphorylation in ECPCs. We found that RGD-2 antagonist reverts EndoMT, reducing α-smooth muscle actin (α-SMA) and vimentin expression in differentiated ECPCs. Our results outline the critical role of integrin in fibrosis progression and account for the opportunity of using integrins as target for anti-fibrotic therapeutic treatment.

  19. Impact of RGD amount in dextran-based hydrogels for cell delivery.

    PubMed

    Riahi, Nesrine; Liberelle, Benoît; Henry, Olivier; De Crescenzo, Gregory

    2017-04-01

    Dextran is one of the hydrophilic polymers that is used for hydrogel preparation. As any polysaccharide, it presents a high density of hydroxyl groups, which make possible several types of derivatization and crosslinking reactions. Furthermore, dextran is an excellent candidate for hydrogel fabrication with controlled cell/scaffold interactions as it is resistant to protein adsorption and cell adhesion. RGD peptide can be grafted to the dextran in order to promote selected cell adhesion and proliferation. Altogether, we have developed a novel strategy to graft the RGD peptide sequence to dextran-based hydrogel using divinyl sulfone as a linker. The resulting RGD functionalized dextran-based hydrogels were transparent, presented a smooth surface and were easy to handle. The impact of varying RGD peptide amounts, hydrogel porosity and topology upon human umbilical vein endothelial cell (HUVEC) adhesion, proliferation and infiltration was investigated. Our results demonstrated that 0.1% of RGD-modified dextran within the gel was sufficient to support HUVEC cells adhesion to the hydrogel surface. Sodium chloride was added (i) to the original hydrogel mix in order to form a macroporous structure presenting interconnected pores and (ii) to the hydrogel surface to create small orifices essential for cells migration inside the matrix.

  20. Encapsulation of eptifibatide in RGD-modified nanoliposomes improves platelet aggregation inhibitory activity.

    PubMed

    Bardania, Hassan; Shojaosadati, Seyed Abbas; Kobarfard, Farzad; Dorkoosh, Farid; Zadeh, Marjan Esfahani; Naraki, Mahmoud; Faizi, Mehrdad

    2017-02-01

    Eptifibatide is an antiplatelet drug used for the treatment of thrombosis. However, as a result of its accumulation in non-targeted tissues and short half-life, it has a limited efficacy. In this study, RGD-modified nano-liposomes (RGD-MNL) were prepared as carriers for the targeted delivery of eptifibatide to activated platelets. The nano-liposomes were about 90 ± 10 nm in size, with an encapsulation efficiency of 37 ± 5 % and a good stability during 21 days, with a negligible change in the size of nanoliosomes. The in vitro cytotoxicity of nanoliposomes was examined using MTT assay. The results obtained from the ex vivo study showed that the antiplatelet activity of eptifibatide encapsulated nanoliposomes was higher in comparison with the free drug (81.63 vs. 46.17 % for RGD-MNL) and (66.67 vs. 46.17 % for UNL), and this increase was more significant for nanoliposomes targeted with RGD peptide (81.63 %; p < 0.05). The results indicated that RGD-MNL encapsulated eptifibatide had no significant cytotoxic effect on cells. In conclusion, the present nanoliposome formulation can be regarded as a new delivery system for protection and enhancement of the antiplatelet activity of eptifibatide.

  1. RGD-peptide conjugated inulin-ibuprofen nanoparticles for targeted delivery of Epirubicin.

    PubMed

    Zhang, Luzhong; Li, Guicai; Gao, Ming; Liu, Xin; Ji, Bing; Hua, Ruheng; Zhou, Youlang; Yang, Yumin

    2016-08-01

    Recently, chemotherapy-based polymeric nanoparticles have been extensively investigated for solid tumor treatment. Tumor targeted nanoparticles demonstrated great potential for improved accumulation in the tumor tissue, superior anticancer activity and reduced side effects. Thus, inulin-ibuprofen polymer was synthesized by esterification between inulin and ibuprofen, and RGD targeted epirubicin (EPB) loaded nanoparticles were prepared by the self-assembly of inulin-ibuprofen polymer and in situ encapsulation of EPB. RGD conjugated EPB loaded nanoparticles were characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). The EPB release from the nanoparticles showed pH-dependent profile and accelerated by the decreased pH value, which would favor the effective drug delivery in vivo. Intracellular uptake analysis suggested that RGD conjugated nanoparticles could be easily internalized by the cancer cells. In vitro cytotoxicity revealed that RGD conjugated EPB loaded nanoparticles exhibited the better antitumor efficacy compared with non-conjugated nanoparticles. More importantly, RGD conjugated EPB loaded nanoparticles showed superior anticancer effects and reduced toxicity than free EPB and non-conjugated nanoparticles by in vivo antitumor activity, EPB biodistribution and histology analysis.

  2. Cyclic RGD peptide incorporation on phage major coat proteins for improved internalization by HeLa cells.

    PubMed

    Choi, Dong Shin; Jin, Hyo-Eon; Yoo, So Young; Lee, Seung-Wuk

    2014-02-19

    Delivering therapeutic materials or imaging reagents into specific tumor tissues is critically important for development of novel cancer therapeutics and diagnostics. Genetically engineered phages possess promising structural features to develop cancer therapeutic materials. For cancer targeting purposes, we developed a novel engineered phage that expressed cyclic RGD (cRGD) peptides on the pVIII major coat protein using recombinant DNA technology. Using a type 88 phage engineering approach, which inserts a new gene to express additional major coat protein in the noncoding region of the phage genome, we incorporated an additional pVIII major coat protein with relatively bulky cRGD and assembled heterogeneous major coat proteins on the F88.4 phage surfaces. With IPTG control, we could tune different numbers of cRGD peptide displayed on the phage particles up to 140 copies. The resulting phage with cRGD on the recombinant pVIII protein exhibited enhanced internalization efficiency into HeLa cells in a ligand density and conformational structure dependent manner when comparing with the M13 phages modified with either linear RGD on pVIII or cRGD on pIII. Our cRGD peptide engineered phage could be useful for cancer therapy or diagnostic purposes after further modifying the phage with drug molecules or contrast reagents in the future.

  3. Effects of RGD immobilization on light-induced cell sheet detachment from TiO2 nanodots films.

    PubMed

    Cheng, Kui; Wang, Tiantian; Yu, Mengliu; Wan, Hongping; Lin, Jun; Weng, Wenjian; Wang, Huiming

    2016-06-01

    Light-induced cell detachment is reported to be a safe and effective cell sheet harvest method. In the present study, the effects of arginine-glycine-aspartic acid (RGD) immobilization on cell growth, cell sheet construction and cell harvest through light illumination are investigated. RGD was first immobilized on TiO2 nanodots films through simple physical adsorption, and then mouse pre-osteoblastic MC3T3-E1 cells were seeded on the films. It was found that RGD immobilization promoted cell adhesion and proliferation. It was also observed that cells cultured on RGD immobilized films showed relatively high level of pan-cadherin. Cells harvested with ultraviolet illumination (365 nm) showed good viability on both RGD immobilized and unmodified TiO2 nanodot films. Single cell detachment assay showed that cells detached more quickly on RGD immobilized TiO2 nanodot films. That could be ascribed to the RGD release after UV365 illumination. The current study demonstrated that RGD immobilization could effectively improve both the cellular responses and light-induced cell harvest.

  4. Bio-compatibility of ion beam-modified and RGD-grafted polyethylene

    NASA Astrophysics Data System (ADS)

    Ročková-Hlaváčková, K.; Švorčík, V.; Bačáková, L.; Dvořánková, B.; Heitz, J.; Hnatowicz, V.

    2004-09-01

    Polyethylene (PE) was implanted with 15 keV Ar + and Kr + ions to the fluences from 3 × 10 12-1 × 10 15 cm -2 and subsequently grafted with amino acid sequence Arg-Gly-Asp (RGD), i.e. a minimum adhesion motif recognized by integrin receptors on cells. The structural changes of PE were studied using goniometric technique, UV-VIS, LIF spectroscopy and by measuring specimen electrical resistance. The adhesion and proliferation of mouse embryonic fibroblasts 3T3 on the modified PE were studied under in vitro conditions. Addition of RGD sequence onto double bonds created by the ion irradiation on polymeric chain was observed. The adhesion and proliferation of the 3T3 cells is increased by ion implantation and additionally also by RGD grafting.

  5. Improved tumor-targeting MRI contrast agents: Gd(DOTA) conjugates of a cycloalkane-based RGD peptide

    SciTech Connect

    Park, Ji-Ae; Lee, Yong Jin; Ko, In Ok; Kim, Tae-Jeong; Chang, Yongmin; Lim, Sang Moo; Kim, Kyeong Min; Kim, Jung Young

    2014-12-12

    Highlights: • Development of improved tumor-targeting MRI contrast agents. • To increase the targeting ability of RGD, we developed cycloalkane-based RGD peptides. • Gd(DOTA) conjugates of cycloalkane-based RGD peptide show improved tumor signal enhancement in vivo MR images. - Abstract: Two new MRI contrast agents, Gd-DOTA-c(RGD-ACP-K) (1) and Gd-DOTA-c(RGD-ACH-K) (2), which were designed by incorporating aminocyclopentane (ACP)- or aminocyclohexane (ACH)-carboxylic acid into Gd-DOTA (gadolinium-tetraazacyclo dodecanetetraacetic acid) and cyclic RGDK peptides, were synthesized and evaluated for tumor-targeting ability in vitro and in vivo. Binding affinity studies showed that both 1 and 2 exhibited higher affinity for integrin receptors than cyclic RGDyK peptides, which were used as a reference. These complexes showed high relaxivity and good stability in human serum and have the potential to improve target-specific signal enhancement in vivo MR images.

  6. RGD peptide-modified multifunctional dendrimer platform for drug encapsulation and targeted inhibition of cancer cells.

    PubMed

    He, Xuedan; Alves, Carla S; Oliveira, Nilsa; Rodrigues, João; Zhu, Jingyi; Bányai, István; Tomás, Helena; Shi, Xiangyang

    2015-01-01

    Development of multifunctional nanoscale drug-delivery systems for targeted cancer therapy still remains a great challenge. Here, we report the synthesis of cyclic arginine-glycine-aspartic acid (RGD) peptide-conjugated generation 5 (G5) poly(amidoamine) dendrimers for anticancer drug encapsulation and targeted therapy of cancer cells overexpressing αvβ3 integrins. In this study, amine-terminated G5 dendrimers were used as a platform to be sequentially modified with fluorescein isothiocyanate (FI) via a thiourea linkage and RGD peptide via a polyethylene glycol (PEG) spacer, followed by acetylation of the remaining dendrimer terminal amines. The developed multifunctional dendrimer platform (G5.NHAc-FI-PEG-RGD) was then used to encapsulate an anticancer drug doxorubicin (DOX). We show that approximately six DOX molecules are able to be encapsulated within each dendrimer platform. The formed complexes are water-soluble, stable, and able to release DOX in a sustained manner. One- and two-dimensional NMR techniques were applied to investigate the interaction between dendrimers and DOX, and the impact of the environmental pH on the release rate of DOX from the dendrimer/DOX complexes was also explored. Furthermore, cell biological studies demonstrate that the encapsulation of DOX within the G5.NHAc-FI-PEG-RGD dendrimers does not compromise the anticancer activity of DOX and that the therapeutic efficacy of the dendrimer/DOX complexes is solely related to the encapsulated DOX drug. Importantly, thanks to the role played by RGD-mediated targeting, the developed dendrimer/drug complexes are able to specifically target αvβ3 integrin-overexpressing cancer cells and display specific therapeutic efficacy to the target cells. The developed RGD peptide-targeted multifunctional dendrimers may thus be used as a versatile platform for targeted therapy of different types of αvβ3 integrin-overexpressing cancer cells.

  7. The coxsackievirus A9 RGD motif is not essential for virus viability.

    PubMed Central

    Hughes, P J; Horsnell, C; Hyypiä, T; Stanway, G

    1995-01-01

    An RGD (arginine-glycine-aspartic acid) motif in coxsackievirus A9 has been implicated in internalization through an interaction with the integrin alpha v beta 3. We have produced a number of virus mutants, lacking the motif, which have a small-plaque phenotype in LLC-Mk2 and A-Vero cells and are phenotypically normal in RD cells. Substitution of flanking amino acids also affected plaque size. The results suggest that interaction between the RGD motif and alpha v beta 3 is not critical for virus viability in the cell lines tested and therefore that alternative regions of the CAV-9 capsid are involved in internalization. PMID:7494317

  8. Dynamical dimer-dimer correlation functions from exact diagonalization

    SciTech Connect

    Werner, Ralph

    2001-05-01

    A regularization method is presented to deduce dynamic correlation functions from exact diagonalization calculations. It is applied to dimer-dimer correlation functions in quantum spin chains relevant for the description of spin-Peierls systems. Exact results for the XY model are presented. The analysis draws into doubt that the dimer-dimer correlation functions show the same scale invariance as spin-spin correlation functions. The results are applied to describe the quasielastic scattering in CuGeO{sub 3} and the hardening of the Peierls-active phonons.

  9. The acrylonitrile dimer ion

    NASA Astrophysics Data System (ADS)

    Ervasti, Henri K.; Jobst, Karl J.; Burgers, Peter C.; Ruttink, Paul J. Ae; Terlouw, Johan K.

    2007-04-01

    Large energy barriers prohibit the rearrangement of solitary acrylonitrile ions, CH2CHCN+, into their more stable hydrogen-shift isomers CH2CCNH+ or CHCH-CNH+. This prompted us to examine if these isomerizations occur by self-catalysis in acrylonitrile dimer ions. Such ions, generated by chemical ionization experiments of acrylonitrile with an excess of carbon dioxide, undergo five dissociations in the [mu]s time frame, as witnessed by peaks at m/z 53, 54, 79, 80 and 105 in their metastable ion mass spectrum. Collision experiments on these product ions, deuterium labeling, and a detailed computational analysis using the CBS-QB3 model chemistry lead to the following conclusions: (i) the m/z 54 ions are ions CH2CHCNH+ generated by self-protonation in ion-dipole stabilized hydrogen-bridged dimer ions [CH2CHCN...H-C(CN)CH2]+ and [CH2CHCN...H-C(H)C(H)CN]+; the proton shifts in these ions are associated with a small reverse barrier; (ii) dissociation of the H-bridged ions into CH2CCNH+ or CHCH-CNH+ by self-catalysis is energetically feasible but kinetically improbable: experiment shows that the m/z 53 ions are CH2CHCN+ ions, generated by back dissociation; (iii) the peaks at m/z 79, 80 and 105 correspond with the losses of HCN, C2H2 and H, respectively. The calculations indicate that these ions are generated from dimer ions that have adopted the (much more stable) covalently bound "head-to-tail" structure [CH2CHCN-C(H2)C(H)CN]+; experiments indicate that the m/z 79 (C5H5N) and m/z 105 (C6H6N2) ions have linear structures but the m/z 80 (C4H4N2) ions consist of ionized pyrimidine in admixture with its stable pyrimidine-2-ylidene isomer. Acrylonitrile is a confirmed species in interstellar space and our study provides experimental and computational evidence that its dimer radical cation yields the ionized prebiotic pyrimidine molecule.

  10. D Dimer in acute care

    PubMed Central

    Sathe, Prachee M.; Patwa, Urvil D.

    2014-01-01

    Pulmonary embolism, Deep Vein Thrombosis (DVT) and Disseminated intravascular coagulation (DIC) are important sources of mortality and morbidity in intensive care unit (ICU). And every time D-dimer remains the the commonest investigation. Many times D-dimer is erroneously considered as a diagnostic test in above mentioned conditions. Its interpretation requires cautions. To circumvent this source of error it is necessary to understand D-dimer test and its significance in various disorder. This article review some basic details of D-dimer, condition associated with its increased level and some prognostic value in intracranial hemorrhage and gastrointestinal (GI) bleed. PMID:25337485

  11. Helicoidal multi-lamellar features of RGD-functionalized silk biomaterials for corneal tissue engineering

    PubMed Central

    Gil, Eun Seok; Mandal, Biman B.; Park, Sang-Hyug; Marchant, Jeffrey K.; Omenetto, Fiorenzo G.; Kaplan, David L.

    2010-01-01

    RGD-coupled silk protein-biomaterial lamellar systems were prepared and studied with human cornea fibroblasts (hCFs) to match functional requirements. A strategy for corneal tissue engineering was pursued to replicate the structural hierarchy of human corneal stroma within thin stacks of lamellae-like tissues, in this case constructed from scaffolds constructed with RGD-coupled, patterned, porous, mechanically robust and transparent silk films. The influence of RGD-coupling on the orientation, proliferation, ECM organization, and gene expression of hCFs was assessed. RGD surface modification enhanced cell attachment, proliferation, alignment and expression of both collagens (type I and V) and proteoglycans (decorin and biglycan). Confocal and histological images of the lamellar systems revealed that the bio-functionalized silk human cornea 3D constructs exhibited integrated corneal stroma tissue with helicoidal multi-lamellar alignment of collagen-rich and proteoglycan-rich extracellular matrix, with transparency of the construct. This biomimetic approach to replicate corneal stromal tissue structural hierarchy and architecture demonstrates a useful strategy for engineering human cornea. Further, this approach can be exploited for other tissue systems due to the pervasive nature of such helicoids in most human tissues. PMID:20801503

  12. Green tea polyphenol tailors cell adhesivity of RGD displaying surfaces: multicomponent models monitored optically

    NASA Astrophysics Data System (ADS)

    Peter, Beatrix; Farkas, Eniko; Forgacs, Eniko; Saftics, Andras; Kovacs, Boglarka; Kurunczi, Sandor; Szekacs, Inna; Csampai, Antal; Bosze, Szilvia; Horvath, Robert

    2017-02-01

    The interaction of the anti-adhesive coating, poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) and its Arg-Gly-Asp (RGD) functionalized form, PLL-g-PEG-RGD, with the green tea polyphenol, epigallocatechin-gallate (EGCg) was in situ monitored. After, the kinetics of cellular adhesion on the EGCg exposed coatings were recorded in real-time. The employed plate-based waveguide biosensor is applicable to monitor small molecule binding and sensitive to sub-nanometer scale changes in cell membrane position and cell mass distribution; while detecting the signals of thousands of adhering cells. The combination of this remarkable sensitivity and throughput opens up new avenues in testing complicated models of cell-surface interactions. The systematic studies revealed that, despite the reported excellent antifouling properties of the coatings, EGCg strongly interacted with them, and affected their cell adhesivity in a concentration dependent manner. Moreover, the differences between the effects of the fresh and oxidized EGCg solutions were first demonstrated. Using a semiempirical quantumchemical method we showed that EGCg binds to the PEG chains of PLL-g-PEG-RGD and effectively blocks the RGD sites by hydrogen bonds. The calculations supported the experimental finding that the binding is stronger for the oxidative products. Our work lead to a new model of polyphenol action on cell adhesion ligand accessibility and matrix rigidity.

  13. Green tea polyphenol tailors cell adhesivity of RGD displaying surfaces: multicomponent models monitored optically

    PubMed Central

    Peter, Beatrix; Farkas, Eniko; Forgacs, Eniko; Saftics, Andras; Kovacs, Boglarka; Kurunczi, Sandor; Szekacs, Inna; Csampai, Antal; Bosze, Szilvia; Horvath, Robert

    2017-01-01

    The interaction of the anti-adhesive coating, poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) and its Arg-Gly-Asp (RGD) functionalized form, PLL-g-PEG-RGD, with the green tea polyphenol, epigallocatechin-gallate (EGCg) was in situ monitored. After, the kinetics of cellular adhesion on the EGCg exposed coatings were recorded in real-time. The employed plate-based waveguide biosensor is applicable to monitor small molecule binding and sensitive to sub-nanometer scale changes in cell membrane position and cell mass distribution; while detecting the signals of thousands of adhering cells. The combination of this remarkable sensitivity and throughput opens up new avenues in testing complicated models of cell-surface interactions. The systematic studies revealed that, despite the reported excellent antifouling properties of the coatings, EGCg strongly interacted with them, and affected their cell adhesivity in a concentration dependent manner. Moreover, the differences between the effects of the fresh and oxidized EGCg solutions were first demonstrated. Using a semiempirical quantumchemical method we showed that EGCg binds to the PEG chains of PLL-g-PEG-RGD and effectively blocks the RGD sites by hydrogen bonds. The calculations supported the experimental finding that the binding is stronger for the oxidative products. Our work lead to a new model of polyphenol action on cell adhesion ligand accessibility and matrix rigidity. PMID:28186133

  14. The Disease Portals, disease-gene annotation and the RGD disease ontology at the Rat Genome Database.

    PubMed

    Hayman, G Thomas; Laulederkind, Stanley J F; Smith, Jennifer R; Wang, Shur-Jen; Petri, Victoria; Nigam, Rajni; Tutaj, Marek; De Pons, Jeff; Dwinell, Melinda R; Shimoyama, Mary

    2016-01-01

    The Rat Genome Database (RGD;http://rgd.mcw.edu/) provides critical datasets and software tools to a diverse community of rat and non-rat researchers worldwide. To meet the needs of the many users whose research is disease oriented, RGD has created a series of Disease Portals and has prioritized its curation efforts on the datasets important to understanding the mechanisms of various diseases. Gene-disease relationships for three species, rat, human and mouse, are annotated to capture biomarkers, genetic associations, molecular mechanisms and therapeutic targets. To generate gene-disease annotations more effectively and in greater detail, RGD initially adopted the MEDIC disease vocabulary from the Comparative Toxicogenomics Database and adapted it for use by expanding this framework with the addition of over 1000 terms to create the RGD Disease Ontology (RDO). The RDO provides the foundation for, at present, 10 comprehensive disease area-related dataset and analysis platforms at RGD, the Disease Portals. Two major disease areas are the focus of data acquisition and curation efforts each year, leading to the release of the related Disease Portals. Collaborative efforts to realize a more robust disease ontology are underway. Database URL:http://rgd.mcw.edu.

  15. The effect of incorporating RGD adhesive peptide in polyethylene glycol diacrylate hydrogel on osteogenesis of bone marrow stromal cells.

    PubMed

    Yang, Fan; Williams, Christopher G; Wang, Dong-An; Lee, Hyukjin; Manson, Paul N; Elisseeff, Jennifer

    2005-10-01

    Advances in tissue engineering require biofunctional scaffolds that can not only provide cells with structural support, but also interact with cells in a biological manner. To achieve this goal, a frequently used cell adhesion peptide Arg-Gly-Asp (RGD) was covalently incorporated into poly(ethylene glycol) diacrylate (PEODA) hydrogel and its dosage effect (0.025, 1.25 and 2.5 mm) on osteogenesis of marrow stromal cells in a three-dimensional environment was examined. Expression of bone-related markers, osteocalcin (OCN) and Alkaline phosphatase (ALP), increased significantly as the RGD concentration increased. Compared with no RGD, 2.5 mm RGD group showed a 1344% increase in ALP production and a 277% increase in OCN accumulation in the medium. RGD helped MSCs maintain cbfa-1 expression when shifted from a two-dimensional environment to a three-dimensional environment. Soluble RGD was found to completely block the mineralization of marrow stromal cells, as manifested by quantitative calcium assay, phosphorus elemental analysis and Von Kossa staining. In conclusion, we have demonstrated that RGD-conjugated PEODA hydrogel promotes the osteogenesis of MSCs in a dosage-dependent manner, with 2.5 mm being optimal concentration.

  16. cRGD-Modified Benzimidazole-based pH-Responsive Nanoparticles for Enhanced Tumor Targeted Doxorubicin Delivery.

    PubMed

    Liu, Jinjian; Liu, Qian; Yang, Cuihong; Sun, Yu; Zhang, Yumin; Huang, Pingsheng; Zhou, Junhui; Liu, Qiang; Chu, Liping; Huang, Fan; Deng, Liandong; Dong, Anjie; Liu, Jianfeng

    2016-05-04

    Finding a smart cancer drug delivery carrier with long blood circulation, enhanced cancer targeting, and quick drug release in tumors is critical for efficient cancer chemotherapy. Herein, we design a cRGD-polycarboxybetaine methacrylate-b-polybenzimidazole methacrylate (cRGD-PCB-b-PBBMZ) copolymer to self-assemble into smart drug-loaded nanoparticles (cRGD-PCM NPs) which can target αvβ3 integrin overexpressed cancer tissue by cRGD peptide unit and release drug quickly in cancer cells by protonation of benzimidazole groups. The outer PCB layer can resist protein adhesion, and there are only about 10% of proteins in mouse serum adhered to the surface of PCM NPs. With the pKa value of 5.08 of the benzimidazole units, DOX can be released from NPs in pH 5.0 PBS. cRGD-PCM NPs can bring more DOX into HepG2 cells than nontargeting PCM NPs, and there has high DOX release rate in HepG2 cells because of the protonation of benzimidazole groups in endosome and lysosome. MTT assay verifies that higher cellular uptake of DOX causes higher cytotoxicity. Furthermore, the results of ex vivo imaging studies confirm that cRGD-PCM/DOX NPs can successfully deliver DOX into tumor tissue from the injection site. Therefore, the multifunctional cRGD-PCM NPs show great potential as novel nanocarriers for targeting cancer chemotherapy.

  17. The Influence of RGD-Bearing Hydrogels on the Re-expression of Contractile Vascular Smooth Muscle Cell Phenotype

    PubMed Central

    Beamish, Jeffrey A.; Fu, Alexander; Choi, Ae-jin; Haq, Nada; Kottke-Marchant, Kandice; Marchant, Roger E.

    2009-01-01

    This study reports on the ability of poly(ethylene glycol) diacrylate (PEGDA) hydrogel scaffolds with pendant integrin-binding GRGDSP peptides (RGD-gels) to support the re-differentiation of cultured vascular smooth muscle cells (SMCs) toward a contractile phenotype. Human coronary SMCs were seeded on RGD-gels, hydrogels with other extracellular matrix derived peptides, fibronectin (FN) and laminin (LN). Differentiation was induced on RGD-gels with low serum medium containing soluble heparin, and the differentiation status was monitored by mRNA expression, protein expression, and intracellular protein organization of the contractile smooth muscle markers, smooth muscle α-actin, calponin and SM-22α. RGD-gels supported a rapid induction (2.7- to 25-fold up-regulation) of SMC marker gene mRNA, with expression levels that were equivalent to FN and LN controls. Marker protein levels mirrored the changes in mRNA expression, with levels on RGD-gels indistinguishable from FN and LN controls. Furthermore, these markers co-localized in stress fibers within SMCs on RGD-gels suggesting the recapitulation of a contractile apparatus within the cells. These results indicate that SMCs cultured on RGD-bearing hydrogels can re-differentiate toward a contractile phenotype suggesting this material is an excellent candidate for further development as a bioactive scaffold that regulates SMC phenotype. PMID:19481795

  18. The Disease Portals, disease–gene annotation and the RGD disease ontology at the Rat Genome Database

    PubMed Central

    Hayman, G. Thomas; Laulederkind, Stanley J. F.; Smith, Jennifer R.; Wang, Shur-Jen; Petri, Victoria; Nigam, Rajni; Tutaj, Marek; De Pons, Jeff; Dwinell, Melinda R.; Shimoyama, Mary

    2016-01-01

    The Rat Genome Database (RGD; http://rgd.mcw.edu/) provides critical datasets and software tools to a diverse community of rat and non-rat researchers worldwide. To meet the needs of the many users whose research is disease oriented, RGD has created a series of Disease Portals and has prioritized its curation efforts on the datasets important to understanding the mechanisms of various diseases. Gene-disease relationships for three species, rat, human and mouse, are annotated to capture biomarkers, genetic associations, molecular mechanisms and therapeutic targets. To generate gene–disease annotations more effectively and in greater detail, RGD initially adopted the MEDIC disease vocabulary from the Comparative Toxicogenomics Database and adapted it for use by expanding this framework with the addition of over 1000 terms to create the RGD Disease Ontology (RDO). The RDO provides the foundation for, at present, 10 comprehensive disease area-related dataset and analysis platforms at RGD, the Disease Portals. Two major disease areas are the focus of data acquisition and curation efforts each year, leading to the release of the related Disease Portals. Collaborative efforts to realize a more robust disease ontology are underway. Database URL: http://rgd.mcw.edu PMID:27009807

  19. Density-tunable conjugation of cyclic RGD ligands with polyion complex vesicles for the neovascular imaging of orthotopic glioblastomas.

    PubMed

    Kawamura, Wataru; Miura, Yutaka; Kokuryo, Daisuke; Toh, Kazuko; Yamada, Naoki; Nomoto, Takahiro; Matsumoto, Yu; Sueyoshi, Daiki; Liu, Xueying; Aoki, Ichio; Kano, Mitsunobu R; Nishiyama, Nobuhiro; Saga, Tsuneo; Kishimura, Akihiro; Kataoka, Kazunori

    2015-06-01

    Introduction of ligands into 100 nm scaled hollow capsules has great potential for diagnostic and therapeutic applications in drug delivery systems. Polyethylene glycol-conjugated (PEGylated) polyion complex vesicles (PICsomes) are promising hollow nano-capsules that can survive for long periods in the blood circulation and can be used to deliver water-soluble macromolecules to target tissues. In this study, cyclic RGD (cRGD) peptide, which is specifically recognized by αVβ3 and αvβ5 integrins that are expressed at high levels in the neovascular system, was conjugated onto the distal end of PEG strands on PICsomes for active neovascular targeting. Density-tunable cRGD-conjugation was achieved using PICsomes with definite fraction of end-functionalized PEG, to substitute 20, 40, and 100% of PEG distal end of the PICsomes to cRGD moieties. Compared with control-PICsomes without cRGD, cRGD-PICsomes exhibited increased uptake into human umbilical vein endothelial cells. Intravital confocal laser scanning microscopy revealed that the 40%-cRGD-PICsomes accumulated mainly in the tumor neovasculature and remained in the perivascular region even after 24 h. Furthermore, we prepared superparamagnetic iron oxide (SPIO)-loaded cRGD-PICsomes for magnetic resonance imaging (MRI) and successfully visualized the neovasculature in an orthotopic glioblastoma model, which suggests that SPIO-loaded cRGD-PICsomes might be useful as a MRI contrast reagent for imaging of the tumor microenvironment, including neovascular regions that overexpress αVβ3 integrins.

  20. cRGD-installed polymeric micelles loading platinum anticancer drugs enable cooperative treatment against lymph node metastasis.

    PubMed

    Makino, Jun; Cabral, Horacio; Miura, Yutaka; Matsumoto, Yu; Wang, Ming; Kinoh, Hiroaki; Mochida, Yuki; Nishiyama, Nobuhiro; Kataoka, Kazunori

    2015-12-28

    Lymph node metastasis (LNM) is correlated with decreased survival, indicating high tumor malignancy and being a potential source for subsequent fatal metastases. Targeted therapies inhibiting the formation of LNM, while eliminating established metastatic foci, could provide synergistic effects by reducing the incidence and growth of metastasis. Based on the inhibitory activity of cRGD peptide against the development of metastasis, and the LNM targeting ability of systemically injected drug-loaded polymeric micelles, herein, we studied the capability of cRGD-installed polymeric micelles incorporating the platinum anticancer drug (1,2-diaminocylohexane)platinum(II) (DACHPt) for cooperatively inhibiting the formation and progression of LNM. As cRGD-installed DACHPt-loaded micelles (cRGD-DACHPt/m) presented similar size, drug loading and surface charge to non-conjugated micelles (MeO-DACHPt/m), the differences in the biological performance of the micelles were endorsed to the effect of the ligand. In a syngeneic melanoma model, both MeO-DACHPt/m and cRGD-DACHPt/m showed comparable antitumor activity against the primary tumors and the established metastatic foci in lymph nodes. However, cRGD-DACHPt/m significantly enhanced the efficacy against LNM draining from primary tumors through the effective inhibition of the spreading of cancer cells. This improved inhibition was associated with the ability of cRGD-DACHPt/m to reduce the migration of melanoma cells, which was higher than that of MeO-DACHPt/m, free cRGD and their combination. These results support our strategy of using cRGD-installed micelles for attaining cooperative therapies against LNM exploiting the inhibitory function of the peptide and the cytotoxic effect of the micelles.

  1. Density-tunable conjugation of cyclic RGD ligands with polyion complex vesicles for the neovascular imaging of orthotopic glioblastomas

    NASA Astrophysics Data System (ADS)

    Kawamura, Wataru; Miura, Yutaka; Kokuryo, Daisuke; Toh, Kazuko; Yamada, Naoki; Nomoto, Takahiro; Matsumoto, Yu; Sueyoshi, Daiki; Liu, Xueying; Aoki, Ichio; Kano, Mitsunobu R.; Nishiyama, Nobuhiro; Saga, Tsuneo; Kishimura, Akihiro; Kataoka, Kazunori

    2015-06-01

    Introduction of ligands into 100 nm scaled hollow capsules has great potential for diagnostic and therapeutic applications in drug delivery systems. Polyethylene glycol-conjugated (PEGylated) polyion complex vesicles (PICsomes) are promising hollow nano-capsules that can survive for long periods in the blood circulation and can be used to deliver water-soluble macromolecules to target tissues. In this study, cyclic RGD (cRGD) peptide, which is specifically recognized by αVβ3 and αvβ5 integrins that are expressed at high levels in the neovascular system, was conjugated onto the distal end of PEG strands on PICsomes for active neovascular targeting. Density-tunable cRGD-conjugation was achieved using PICsomes with definite fraction of end-functionalized PEG, to substitute 20, 40, and 100% of PEG distal end of the PICsomes to cRGD moieties. Compared with control-PICsomes without cRGD, cRGD-PICsomes exhibited increased uptake into human umbilical vein endothelial cells. Intravital confocal laser scanning microscopy revealed that the 40%-cRGD-PICsomes accumulated mainly in the tumor neovasculature and remained in the perivascular region even after 24 h. Furthermore, we prepared superparamagnetic iron oxide (SPIO)-loaded cRGD-PICsomes for magnetic resonance imaging (MRI) and successfully visualized the neovasculature in an orthotopic glioblastoma model, which suggests that SPIO-loaded cRGD-PICsomes might be useful as a MRI contrast reagent for imaging of the tumor microenvironment, including neovascular regions that overexpress αVβ3 integrins.

  2. Density-tunable conjugation of cyclic RGD ligands with polyion complex vesicles for the neovascular imaging of orthotopic glioblastomas

    PubMed Central

    Kawamura, Wataru; Miura, Yutaka; Kokuryo, Daisuke; Toh, Kazuko; Yamada, Naoki; Nomoto, Takahiro; Matsumoto, Yu; Sueyoshi, Daiki; Liu, Xueying; Aoki, Ichio; Kano, Mitsunobu R; Nishiyama, Nobuhiro; Saga, Tsuneo; Kishimura, Akihiro; Kataoka, Kazunori

    2015-01-01

    Introduction of ligands into 100 nm scaled hollow capsules has great potential for diagnostic and therapeutic applications in drug delivery systems. Polyethylene glycol-conjugated (PEGylated) polyion complex vesicles (PICsomes) are promising hollow nano-capsules that can survive for long periods in the blood circulation and can be used to deliver water-soluble macromolecules to target tissues. In this study, cyclic RGD (cRGD) peptide, which is specifically recognized by αVβ3 and αvβ5 integrins that are expressed at high levels in the neovascular system, was conjugated onto the distal end of PEG strands on PICsomes for active neovascular targeting. Density-tunable cRGD-conjugation was achieved using PICsomes with definite fraction of end-functionalized PEG, to substitute 20, 40, and 100% of PEG distal end of the PICsomes to cRGD moieties. Compared with control-PICsomes without cRGD, cRGD-PICsomes exhibited increased uptake into human umbilical vein endothelial cells. Intravital confocal laser scanning microscopy revealed that the 40%-cRGD-PICsomes accumulated mainly in the tumor neovasculature and remained in the perivascular region even after 24 h. Furthermore, we prepared superparamagnetic iron oxide (SPIO)-loaded cRGD-PICsomes for magnetic resonance imaging (MRI) and successfully visualized the neovasculature in an orthotopic glioblastoma model, which suggests that SPIO-loaded cRGD-PICsomes might be useful as a MRI contrast reagent for imaging of the tumor microenvironment, including neovascular regions that overexpress αVβ3 integrins. PMID:27877805

  3. Bioabsorbable Bypass Grafts Biofunctionalised with RGD Have Enhanced Biophysical Properties and Endothelialisation Tested In vivo

    PubMed Central

    Antonova, Larisa V.; Seifalian, Alexander M.; Kutikhin, Anton G.; Sevostyanova, Victoria V.; Krivkina, Evgeniya O.; Mironov, Andrey V.; Burago, Andrey Y.; Velikanova, Elena A.; Matveeva, Vera G.; Glushkova, Tatiana V.; Sergeeva, Evgeniya A.; Vasyukov, Georgiy Y.; Kudryavtseva, Yuliya A.; Barbarash, Olga L.; Barbarash, Leonid S.

    2016-01-01

    Small diameter arterial bypass grafts are considered as unmet clinical need since the current grafts have poor patency of 25% within 5 years. We have developed a 3D scaffold manufactured from natural and synthetic biodegradable polymers, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(𝜀-caprolactone) (PCL), respectively. Further to improve the biophysical properties as well as endothelialisation, the grafts were covalently conjugated with arginine-glycine-aspartic acid (RGD) bioactive peptides. The biophysical properties as well as endothelialisation of PHBV/PCL and PCL 2 mm diameter bypass grafts were assessed with and without biofunctionalisation with RGD peptides in vitro and in vivo. Morphology of the grafts was assessed by scanning electron microscopy, whereas physico-mechanical properties were evaluated using a physiological circulating system equipped with a state of art ultrasound vascular wall tracking system. Endothelialisation of the grafts in vitro and in vivo were assessed using a cell viability assay and rat abdominal aorta replacement model, respectively. The biofunctionalisation with RGD bioactive peptides decreased mean fiber diameter and mean pore area in PHBV/PCL grafts; however, this was not the case for PCL grafts. Both PHBV/PCL and PCL grafts with RGD peptides had lower durability compared to those without; these durability values were similar to those of internal mammary artery. Modification of PHBV/PCL and PCL grafts with RGD peptides increased endothelial cell viability in vitro by a factor of eight and enhanced the formation of an endothelial cell monolayer in vivo 1 month postimplantation. In conclusion, PHBV/PCL small-caliber graft can be a suitable 3D scaffold for the development of a tissue engineering arterial bypass graft. PMID:27252652

  4. Iodine-125-labeled cRGD-gold nanoparticles as tumor-targeted radiosensitizer and imaging agent

    NASA Astrophysics Data System (ADS)

    Su, Ning; Dang, Yajie; Liang, Guangli; Liu, Guizhi

    2015-04-01

    Research interests on radiosensitive property of gold nanoparticles (GNPs) are rapidly raised because of the extensively proved in vitro effectiveness and clinical necessity. However, the issue of targeted accumulation of GNPs in tumor tissues hindered the transference to in vivo applications. In this study, hybrid nano-sized cyclic Arg-Gly-Asp-conjugated GNPs (cRGD-GNPs) integrated with radioactive iodine-125 was fabricated as tumor-targeted radiosensitizer. Therapeutic effects, including acute apoptosis (2 days post treatment) and long-term influence (up to 21 days), were investigated on NCI-H446 tumor-bearing mice via Tc-99 m-Annexin V SPECT and volume measurements, respectively. Apoptosis and volume loss were consistent in showing that tumor growth was effectively suppressed via the treatment of 125I-cRGD-GNP sensitized radiotherapy (RT), a more significantly radiosensitive effect than the treatment of non-targeted GNPs with RT, RT treatment alone, and no treatment. SPECT/CT images showed that the uptake of cRGD-GNPs by tumor tissues reached the peak target/non-target value of 4.76 at around 2 h post injection, and dynamic radioactivity monitoring showed that 125I-cRGD-GNPs maintained about 2.5% of injected dosage at 55 h post injection. For long-term influence, a significant radiosensitized RT-induced volume loss was observed. Hence, cyclic RGD conjugation makes the GNP-based radiosensitizer tumor targeting, offering a new modality for enhancing radiotherapeutic efficacy. Additionally, the introduction of I-125 serves as both a therapeutic factor and a radiotracer for in vivo tracking of GNPs.

  5. RGD-peptide modified alginate by a chemoenzymatic strategy for tissue engineering applications.

    PubMed

    Sandvig, Ioanna; Karstensen, Kristin; Rokstad, Anne Mari; Aachmann, Finn Lillelund; Formo, Kjetil; Sandvig, Axel; Skjåk-Bræk, Gudmund; Strand, Berit Løkensgard

    2015-03-01

    One of the main challenges in tissue engineering and regenerative medicine is the ability to maintain optimal cell function and survival post-transplantation. Biomaterials such as alginates are commonly used for immunoisolation, while they may also provide structural support to the cell transplants by mimicking the extracellular matrix. In this study, arginine-glycine-aspartate (RGD)-peptide-coupled alginates of tailored composition were produced by adopting a unique chemoenzymatic strategy for substituting the nongelling mannuronic acid on the alginate. Alginates with and without RGD were produced with high and low content of G. Using carbodiimide chemistry 0.1-0.2% of the sugar units were substituted by peptide. Furthermore, the characterization by (1)H-nuclear magnetic resonance (NMR) revealed by-products from the coupling reaction that partly could be removed by coal filtration. Olfactory ensheathing cells (OECs) and myoblasts were grown in two-dimensional (2D) and 3D cultures of RGD-peptide modified or unmodified alginates obtained by the chemoenzymatically strategy and compared to native alginate. Both OECs and myoblasts adhered to the RGD-peptide modified alginates in 2D cultures, forming bipolar protrusions. OEC encapsulation resulted in cell survival for up to 9 days, thus demonstrating the potential for short-term 3D culture. Myoblasts showed long-term survival in 3D cultures, that is, up to 41 days post encapsulation. The RGD modifications did not result in marked changes in cell viability in 3D cultures. We demonstrate herein a unique technique for tailoring peptide substituted alginates with a precise and flexible composition, conserving the gel forming properties relevant for the use of alginate in tissue engineering.

  6. Final report on the amended safety assessment of diisopropyl dimer dilinoleate, dicetearyl dimer dilinoleate, diisostearyl dimer dilinoleate, dioctyl dimer dilinoleate, dioctyldodecyl dimer dilinoleate, and ditridecyl dimer dilinoleate.

    PubMed

    Fiume, Monice Zondlo

    2003-01-01

    Diisopropyl Dimer Dilinoleate, Dicetearyl Dimer Dilinoleate, Diisostearyl Dimer Dilinoleate, Dioctyl Dimer Dilinoleate, Dioctyldodecyl Dimer Dilinoleate, and Ditridecyl Dimer Dilinoleate are diesters of their respective alcohols and dilinoleic acid. They function as skin-conditioning agents in a variety of cosmetic products at concentrations around 10%, but may be used at concentrations up to 53% in lipsticks. These ingredients do not absorb radiation in the ultraviolet (UV) UVA or UVB range and the only impurities expected are <0.5% dilinoleic acid, <0.1% isopropyl alcohol or <1% isostearyl alcohol, and/or small amounts of dilinoleic acid and cetearyl alcohol or octyldodecanol, depending on which diester is used. The potential skin penetration of these ingredients was evaluated using an estimate of the octanol/water partition coefficient (logP of 17.7) based on the structure of Diisopropyl Dimer Dilinoleate. This is consistent with the insolubility of these ingredients in water. Safety test data on dilinoleic acid (no adverse effects) were considered relevant because dilinoleic acid is a component of these diesters and a likely breakdown product. The acute oral and dermal LD(50) values for rats of Diisopropyl, Diisostearyl, and Dioctyldodecyl Dimer Dilinoleate were >5.0 g/kg. In a subchronic feeding study, macrophage aggregation was seen in the mesenteric lymph node at the lowest dose level (0.1% in the diet). These ingredients did not produce skin or ocular irritation in animal tests, nor were they comedogenic. Ames testing, clastogenesis in human lymphocytes in culture, and L5178Y mouse lymphoma cell forward mutations were all negative, indicating no dilinoleic acid genotoxicity. No carcinogenicity or reproductive/developmental toxicity data were available; however, structural alerts that would suggest a mutagenic or carcinogenic risk are absent. Significant reproductive/developmental toxicity or other systemic toxicity is not expected with these ingredients

  7. Synthesis of Novel c(AmpRGD)-Sunitinib Dual Conjugates as Molecular Tools Targeting the αvβ3 Integrin/VEGFR2 Couple and Impairing Tumor-Associated Angiogenesis.

    PubMed

    Sartori, Andrea; Portioli, Elisabetta; Battistini, Lucia; Calorini, Lido; Pupi, Alberto; Vacondio, Federica; Arosio, Daniela; Bianchini, Francesca; Zanardi, Franca

    2017-01-12

    On the basis of a previously discovered anti-αVβ3 integrin peptidomimetic (c(AmpRGD)) and the clinically approved antiangiogenic kinase inhibitor sunitinib, three novel dual conjugates were synthesized (compounds 1-3), featuring the covalent and robust linkage between these two active modules. In all conjugates, the ligand binding competence toward αVβ3 (using both isolated receptors and αVβ3-overexpressing endothelial progenitor EP cells) and the kinase inhibitory activity (toward both isolated kinases and EPCs) remained almost untouched and comparable to the activity of the single active units. Compounds 1-3 showed interesting antiangiogenesis properties in an in vitro tubulogenic assay; furthermore, dimeric-RGD conjugate 3 strongly inhibited in vivo angiogenesis in Matrigel plug assays in FVB mice. These results offer proof-of-concept of how the covalent conjugation of two angiogenesis-related small modules may result in novel and stable molecules, which impair tumor-related angiogenesis with equal or even superior ability as compared to the single modules or their simple combinations.

  8. The Effect of Superparamagnetic Iron Oxide with iRGD Peptide on the Labeling of Pancreatic Cancer Cells In Vitro: A Preliminary Study

    PubMed Central

    Zuo, Hou Dong; Yao, Wei Wu; Chen, Tian Wu; Zhu, Jiang; Zhang, Juan Juan; Pu, Yu; Liu, Gang; Zhang, Xiao Ming

    2014-01-01

    The iRGD peptide loaded with iron oxide nanoparticles for tumor targeting and tissue penetration was developed for targeted tumor therapy and ultrasensitive MR imaging. Binding of iRGD, a tumor homing peptide, is mediated by integrins, which are widely expressed on the surface of cells. Several types of small molecular drugs and nanoparticles can be transfected into cells with the help of iRGD peptide. Thus, we postulate that SPIO nanoparticles, which have good biocompatibility, can also be transfected into cells using iRGD. Despite the many kinds of cell labeling studies that have been performed with SPIO nanoparticles and RGD peptide or its analogues, only a few have applied SPIO nanoparticles with iRGD peptide in pancreatic cancer cells. This paper reports our preliminary findings regarding the effect of iRGD peptide (CRGDK/RGPD/EC) combined with SPIO on the labeling of pancreatic cancer cells. The results suggest that SPIO with iRGD peptide can enhance the positive labeling rate of cells and the uptake of SPIO. Optimal functionalization was achieved with the appropriate concentration or concentration range of SPIO and iRGD peptide. This study describes a simple and economical protocol to label panc-1 cells using SPIO in combination with iRGD peptide and may provide a useful method to improve the sensitivity of pancreatic cancer imaging. PMID:24977163

  9. The effect of superparamagnetic iron oxide with iRGD peptide on the labeling of pancreatic cancer cells in vitro: a preliminary study.

    PubMed

    Zuo, Hou Dong; Yao, Wei Wu; Chen, Tian Wu; Zhu, Jiang; Zhang, Juan Juan; Pu, Yu; Liu, Gang; Zhang, Xiao Ming

    2014-01-01

    The iRGD peptide loaded with iron oxide nanoparticles for tumor targeting and tissue penetration was developed for targeted tumor therapy and ultrasensitive MR imaging. Binding of iRGD, a tumor homing peptide, is mediated by integrins, which are widely expressed on the surface of cells. Several types of small molecular drugs and nanoparticles can be transfected into cells with the help of iRGD peptide. Thus, we postulate that SPIO nanoparticles, which have good biocompatibility, can also be transfected into cells using iRGD. Despite the many kinds of cell labeling studies that have been performed with SPIO nanoparticles and RGD peptide or its analogues, only a few have applied SPIO nanoparticles with iRGD peptide in pancreatic cancer cells. This paper reports our preliminary findings regarding the effect of iRGD peptide (CRGDK/RGPD/EC) combined with SPIO on the labeling of pancreatic cancer cells. The results suggest that SPIO with iRGD peptide can enhance the positive labeling rate of cells and the uptake of SPIO. Optimal functionalization was achieved with the appropriate concentration or concentration range of SPIO and iRGD peptide. This study describes a simple and economical protocol to label panc-1 cells using SPIO in combination with iRGD peptide and may provide a useful method to improve the sensitivity of pancreatic cancer imaging.

  10. Snake venom disintegrins: novel dimeric disintegrins and structural diversification by disulphide bond engineering.

    PubMed Central

    Calvete, Juan J; Moreno-Murciano, M Paz; Theakston, R David G; Kisiel, Dariusz G; Marcinkiewicz, Cezary

    2003-01-01

    We report the isolation and amino acid sequences of six novel dimeric disintegrins from the venoms of Vipera lebetina obtusa (VLO), V. berus (VB), V. ammodytes (VA), Echis ocellatus (EO) and Echis multisquamatus (EMS). Disintegrins VLO4, VB7, VA6 and EO4 displayed the RGD motif and inhibited the adhesion of K562 cells, expressing the integrin alpha5beta1 to immobilized fibronectin. A second group of dimeric disintegrins (VLO5 and EO5) had MLD and VGD motifs in their subunits and blocked the adhesion of the alpha4beta1 integrin to vascular cell adhesion molecule 1 with high selectivity. On the other hand, disintegrin EMS11 inhibited both alpha5beta1 and alpha4beta1 integrins with almost the same degree of specificity. Comparison of the amino acid sequences of the dimeric disintegrins with those of other disintegrins by multiple-sequence alignment and phylogenetic analysis, in conjunction with current biochemical and genetic data, supports the view that the different disintegrin subfamilies evolved from a common ADAM (a disintegrin and metalloproteinase-like) scaffold and that structural diversification occurred through disulphide bond engineering. PMID:12667142

  11. Ligand Conformation Dictates Membrane and Endosomal Trafficking of Arginine-Glycine-Aspartate (RGD)-Functionalized Mesoporous Silica Nanoparticles

    SciTech Connect

    Fang, I-Ju; Slowing, Igor I; Wu, Kevin C.W.; Lin, Victor S.Y.; Trewyn, Brian

    2012-05-15

    Recent breakthrough research on mesoporous silica nanoparticle (MSN) materials has illustrated their significant potential in biological applications due to their excellent drug delivery and endocytotic behavior. We set out to determine if MSN, covalently functionalized with conformation specific bioactive molecules (either linear or cyclic RGD ligands), behave towards mammalian cells in a similar manner as the free ligands. We discovered that RGD immobilized on the MSN surface did not influence the integrity of the porous matrix and improved the endocytosis efficiency of the MSN materials. Through competition experiments with free RGD ligands, we also discovered a conformation specific receptor–integrin association. The interaction between RGD immobilized on the MSN surface and integrins plays an important role in endosome trafficking, specifically dictating the kinetics of endosomal escape. Thus, covalent functionalization of biomolecules on MSN assists in the design of a system for controlling the interface with cancer cells.

  12. Highly Water-soluble, Near-infrared Emissive BODIPY Polymeric Dye Bearing RGD Peptide Residues for Cancer Imaging

    PubMed Central

    Zhu, Shilei; Zhang, Jingtuo; Janjanam, Jagadeesh; Bi, Jianheng; Vegesna, Giri; Tiwari, Ashutosh; Luo, Fen-Tair; Wei, Jianjun

    2012-01-01

    Near-infrared emissive BODIPY polymeric dye bearing cancer-homing cyclic arginine-glycine-aspartic acid (RGD) peptide residues (polymer B) was prepared by post-polymerization functionalization of BODIPY polymeric dye bearing bromo groups through tetra(ethylene glycol tethered spacers (polymer A) with thiol-functionalized RGD cancer-homing peptide through thioether bonds under a mild basic condition. Polymer B possesses excellent water solubility, good photostability, biocompatibility and resistance to nonspecific interactions to normal endothelial cells, and can efficiently detect breast tumor cells through specific cooperative binding of cancer-homing RGD peptides to αVβ3 integrins of cancer cells while its parent polymer Awith outRGD residues fails to target cancer cells. PMID:23245906

  13. Proteolytic degradation of the RGD-binding and non-RGD-binding conformers of human platelet integrin glycoprotein IIb/IIIa: clues for identification of regions involved in the receptor's activation.

    PubMed Central

    Calvete, J J; Mann, K; Schäfer, W; Fernandez-Lafuente, R; Guisán, J M

    1994-01-01

    The human integrin glycoprotein (GP)IIb/IIIa plays a central role in haemostasis as an inducible receptor for fibrinogen and other RGD-containing adhesive proteins at the platelet plasma membrane. Expression of the fibrinogen receptor on platelet activation involves conformational changes in the quaternary structure of GPIIb/IIIa. Little is known, however, about the nature of this conformational transition. Given that isolated GPIIb/IIIa contains a mixture of RGD-binding and non-RGD-binding heterodimers, we used limited proteolysis as a tool for investigating the structural differences between the two conformers. Comparison of their fragmentation patterns shows that, whereas in the non-RGD-binding form of GPIIb/IIIa the N-terminal half of the heavy chain of GPIIb (GPIIbH) and the central region of GPIIIa are cleaved by endoproteinase Arg-C, these domains associate tightly with one another in the RGD-binding GPIIb/IIIa and are thus protected from proteolysis. In addition, the C-terminal half of GPIIb becomes more susceptible to degradation in the non-RGD-binding GPIIb/IIIa conformer. Our interpretation, in the context of available structural and functional data, is that a major relative reorientation of the GPIIbH and GPIIIa extracellular domains takes place along the subunit interface during the conformational transition of the platelet integrin. Images Figure 1 PMID:8129707

  14. Preclinical Evaluation of Sequential Combination of Oncolytic Adenovirus Delta-24-RGD and Phosphatidylserine-Targeting Antibody in Pancreatic Ductal Adenocarcinoma.

    PubMed

    Dai, Bingbing; Roife, David; Kang, Ya'an; Gumin, Joy; Rios Perez, Mayrim V; Li, Xinqun; Pratt, Michael; Brekken, Rolf A; Fueyo-Margareto, Juan; Lang, Frederick F; Fleming, Jason B

    2017-04-01

    Delta-24-RGD (DNX-2401) is a conditional replication-competent oncolytic virus engineered to preferentially replicate in and lyse tumor cells with abnormality of p16/RB/E2F pathway. In a phase I clinical trial, Delta-24-RGD has shown favorable safety profile and promising clinical efficacy in brain tumor, which prompted us to evaluate its anticancer activity in pancreatic ductal adenocarcinoma (PDAC), which also has high frequency of homozygous deletion and promoter methylation of CDKN2A encoding the p16 protein. Our results demonstrate that Delta-24-RGD can induce dramatic cytotoxicity in a subset of PDAC cell lines with high cyclin D1 expression. Induction of autophagy and apoptosis by Delta-24-RGD in sensitive PDAC cells was confirmed with LC3B-GFP autophagy reporter and acridine orange staining as well as Western blotting analysis of LC3B-II expression. Notably, we found that Delta-24-RGD induced phosphatidylserine exposure in infected cells independent of cells' sensitivity to Delta-24-RGD, which renders a rationale for combination of Delta-24-RGD viral therapy and phosphatidylserine targeting antibody for PDAC. In a mouse PDAC model derived from a liver metastatic pancreatic cancer cell line, Delta-24-RGD significantly inhibited tumor growth compared with control (P < 0.001), and combination of phosphatidylserine targeting antibody 1N11 further enhanced its anticancer activity (P < 0.01) possibly through inducing synergistic anticancer immune responses. Given that these 2 agents are currently in clinical evaluation, our study warrants further clinical evaluation of this novel combination strategy in pancreatic cancer therapy. Mol Cancer Ther; 16(4); 662-70. ©2016 AACR.

  15. Graphene oxide-stimulated myogenic differentiation of C2C12 cells on PLGA/RGD peptide nanofiber matrices

    NASA Astrophysics Data System (ADS)

    Shin, Y. C.; Lee, J. H.; Kim, M. J.; Hong, S. W.; Oh, J.-W.; Kim, C.-S.; Kim, B.; Hyun, J. K.; Kim, Y.-J.; Han, D.-W.

    2015-07-01

    During the last decade, much attention has been paid to graphene-based nanomaterials because they are considered as potential candidates for biomedical applications such as scaffolds for tissue engineering and substrates for the differentiation of stem cells. Until now, electrospun matrices composed of various biodegradable copolymers have been extensively developed for tissue engineering and regeneration; however, their use in combination with graphene oxide (GO) is novel and challenging. In this study, nanofiber matrices composed of poly(lactic-co-glycolic acid, PLGA) and M13 phage with RGD peptide displayed on its surface (RGD peptide-M13 phage) were prepared as extracellular matrix (ECM)-mimicking substrates. RGD peptide is a tripeptide (Arg-Gly-Asp) found on ECM proteins that promotes various cellular behaviors. The physicochemical properties of PLGA and RGD peptide-M13 phage (PLGA/RGD peptide) nanofiber matrices were characterized by atomic force microscopy, Fourier-transform infrared spectroscopy and thermogravimetric analysis. In addition, the growth of C2C12 mouse myoblasts on the PLGA/RGD peptide matrices was examined by measuring the metabolic activity. Moreover, the differentiation of C2C12 mouse myoblasts on the matrices when treated with GO was evaluated. The cellular behaviors, including growth and differentiation of C2C12 mouse myoblasts, were substantially enhanced on the PLGA/RGD peptide nanofiber matrices when treated with GO. Overall, these findings suggest that the PLGA/RGD peptide nanofiber matrices can be used in combination with GO as a novel strategy for skeletal tissue regeneration.

  16. High affinity RGD-binding sites at the plasma membrane of Arabidopsis thaliana links the cell wall.

    PubMed

    Canut, H; Carrasco, A; Galaud, J P; Cassan, C; Bouyssou, H; Vita, N; Ferrara, P; Pont-Lezica, R

    1998-10-01

    The heptapeptide Tyr-Gly-Arg-Gly-Asp-Ser-Pro containing the sequence Arg-Gly-Asp (RGD--the essential structure recognised by animal cells in substrate adhesion molecules) was tested on epidermal cells of onion and cultured cells of Arabidopsis upon plasmolysis. Dramatic changes were observed on both types of cells following treatment: on onion cells, Hechtian strands linking the cell wall to the membrane were lost, while Arabidopsis cells changed from concave to convex plasmolysis. A control heptapeptide Tyr-Gly-Asp-Gly-Arg-Ser-Pro had no effect on the shape of plasmolysed cells. Protoplasts isolated from Arabidopsis cells agglutinate in the presence of ProNectinF, a genetically engineered protein of 72 kDa containing 13 RGD sequences: several protoplasts may adhere to a single molecule of ProNectinF. The addition of the RGD-heptapeptide disrupted the adhesion between the protoplasts. Purified plasma membrane from Arabidopsis cells exhibits specific binding sites for the iodinated RGD-heptapeptide. The binding is saturable, reversible, and two types of high affinity sites (Kd1 approximately 1 nM, and Kd2 approximately 40 nM) can be discerned. Competitive inhibition by several structurally related peptides and proteins noted the specific requirement for the RGD sequence. Thus, the RGD-binding activity of Arabidopsis fulfils the adhesion features of integrins, i.e. peptide specificity, subcellular location, and involvement in plasma membrane-cell wall attachments.

  17. RGD peptide-displaying M13 bacteriophage/PLGA nanofibers as cell-adhesive matrices for smooth muscle cells

    NASA Astrophysics Data System (ADS)

    Shin, Yong Cheol; Lee, Jong Ho; Jin, Oh Seong; Lee, Eun Ji; Jin, Lin Hua; Kim, Chang-Seok; Hong, Suck Won; Han, Dong-Wook; Kim, Chuntae; Oh, Jin-Woo

    2015-01-01

    Extracellular matrices (ECMs) are network structures that play an essential role in regulating cellular growth and differentiation. In this study, novel nanofibrous matrices were fabricated by electrospinning M13 bacteriophage and poly(lactic- co-glycolic acid) (PLGA) and were shown to be structurally and functionally similar to natural ECMs. A genetically-engineered M13 bacteriophage was constructed to display Arg-Gly-Asp (RGD) peptides on its surface. The physicochemical properties of RGD peptide-displaying M13 bacteriophage (RGD-M13 phage)/PLGA nanofibers were characterized by using scanning electron microscopy and Fourier-transform infrared spectroscopy. We used immunofluorescence staining to confirm that M13 bacteriophages were homogenously distributed in RGD-M13 phage/PLGA matrices. Furthermore, RGD-M13 phage/PLGA nanofibrous matrices, having excellent biocompatibility, can enhance the behaviors of vascular smooth muscle cells. This result suggests that RGD-M13 phage/PLGA nanofibrous matrices have potentials to serve as tissue engineering scaffolds.

  18. An iRGD Based Strategy to Study Electrochemically the Species Inside a Cell

    PubMed Central

    Ning, Limin; Li, Xiaoxi; Ding, Xiaorong; Yin, Yongmei; Li, Genxi

    2012-01-01

    This paper reports a method for electrical communication between the inner part of cells and an electrode with the help of iRGD peptide. Due to the enhancement of the cell penetration caused by iRGD peptide, DNA molecules, previously modified on a gold electrode surface, can be easily transfected into the cells. At the same time, doxorubicin, an anticancer drug, can also be transfected into cells with high penetration. Consequently, doxorubicin binds to DNA chains through electrostatic interaction, and the redox reaction is transferred out of the cell across the cell membrane. As a result, this work may provide a novel way to get information from inside of cells. PMID:22949871

  19. FITC-conjugated cyclic RGD peptides as fluorescent probes for staining integrin αvβ3/αvβ5 in tumor tissues.

    PubMed

    Zheng, Yumin; Ji, Shundong; Czerwinski, Andrzej; Valenzuela, Francisco; Pennington, Michael; Liu, Shuang

    2014-11-19

    This study sought to evaluate FITC-conjugated cyclic RGD peptides (FITC-RGD2, FITC-3P-RGD2, and FITC-Galacto-RGD2) as fluorescent probes for in vitro assays of integrin αvβ3/αvβ5 expression in tumor tissues. FITC-RGD2, FITC-3P-RGD2, and FITC-Galacto-RGD2 were prepared, and their integrin αvβ3/αvβ5 binding affinity was determined using the displacement assay against (125)I-echistatin bound to U87MG glioma cells. IC50 values of FITC-Galacto-RGD2, FITC-3P-RGD2, and FITC-RGD2 were calculated to be 28 ± 8, 32 ± 7, and 89 ± 17 nM, respectively. The integrin αvβ3/αvβ5 binding affinity followed a general trend: FITC-Galacto-RGD2 ∼ FITC-3P-RGD2 > FITC-RGD2. The xenografted tumor-bearing models were established by subcutaneous injection of 5 × 10(6) tumor cells into shoulder flank (U87MG, A549, HT29, and PC-3) or mammary fat pad (MDA-MB-435) of each athymic nude mouse. Three to six weeks after inoculation, the tumor size was 0.1-0.3 g. Tumors were harvested for integrin αvβ3/αvβ5 staining, as well as hematoxylin and eosin (H&E) staining. Six human carcinoma tissues (colon cancer, pancreatic cancer, lung adenocarcinoma, squamous cell lung cancer, gastric cancer, and esophageal cancer) were obtained from recently diagnosed cancer patients. Human carcinoma slides were deparaffinized in xylene, rehydrated with ethanol, and then used for integrin αvβ3/αvβ5 staining, as well as H&E staining. It was found that the tumor staining procedures with FITC-conjugated cyclic RGD peptides were much simpler than those with the fluorescence-labeled integrin αvβ3 antibodies. Since FITC-RGD2, FITC-3P-RGD2, and FITC-Galacto-RGD2 were able to co-localize with the fluorescence-labeled integrin β3 antibody, their tumor localization and tumor cell binding are integrin αvβ3-specific. Quantification of the fluorescent intensity in five xenografted tumors (U87MG, MDA-MB-435, A549, HT29, and PC-3) and six human carcinoma tissues revealed an excellent linear relationship

  20. Application of RGD-containing peptides as imaging probes for alphavbeta3 expression.

    PubMed

    Dijkgraaf, Ingrid; Beer, Ambros J; Wester, Hans-Jurgen

    2009-01-01

    Integrin alphavbeta3 plays a pivotale role in tumor angiogenesis and is a receptor for the extracellular matrix proteins with the exposed arginine-glysine-aspartic acid (RGD) tripeptide sequence (e.g. vitronectin, fibronectin). Alphavbeta3 is overexpressed on activated endothelial cells during tumor-induced angiogenesis, whereas it is absent on quiescent endothelial cells and normal tissues. Furthermore, alphavbeta3 is expressed on various tumor cell lines. Due to this restricted expression of alphavbeta3 in tumors, alphavbeta3 is considered a suitable receptor for tumor targeting. In the past decade, several RGD-containing peptide antagonists have been evaluated for monitoring alphavbeta3 expression using SPECT, PET, MRI, OI and US. Molecular imaging tracers for this integrin receptor could be used to noninvasively visualize alphavbeta3 expression in tumors. Noninvasive determination of alphavbeta3 expression potentially can be used to monitor treatment response to antiangiogenic drugs or even to select patients likely to respond to treatment with antiangiogenic drugs. In this review a brief overview on the currently used RGD-containing peptides as imaging probes for noninvasive visualization of alphavbeta3 expression using PET, SPECT, MRI, OI and US is given.

  1. Novel Bifunctional Cyclic Chelator for 89Zr Labeling–Radiolabeling and Targeting Properties of RGD Conjugates

    PubMed Central

    2015-01-01

    Within the last years 89Zr has attracted considerable attention as long-lived radionuclide for positron emission tomography (PET) applications. So far desferrioxamine B (DFO) has been mainly used as bifunctional chelating system. Fusarinine C (FSC), having complexing properties comparable to DFO, was expected to be an alternative with potentially higher stability due to its cyclic structure. In this study, as proof of principle, various FSC-RGD conjugates targeting αvß3 integrins were synthesized using different conjugation strategies and labeled with 89Zr. In vitro stability, biodistribution, and microPET/CT imaging were evaluated using [89Zr]FSC-RGD conjugates or [89Zr]triacetylfusarinine C (TAFC). Quantitative 89Zr labeling was achieved within 90 min at room temperature. The distribution coefficients of the different radioligands indicate hydrophilic character. Compared to [89Zr]DFO, [89Zr]FSC derivatives showed excellent in vitro stability and resistance against transchelation in phosphate buffered saline (PBS), ethylenediaminetetraacetic acid solution (EDTA), and human serum for up to 7 days. Cell binding studies and biodistribution as well as microPET/CT imaging experiments showed efficient receptor-specific targeting of [89Zr]FSC-RGD conjugates. No bone uptake was observed analyzing PET images indicating high in vivo stability. These findings indicate that FSC is a highly promising chelator for the development of 89Zr-based PET imaging agents. PMID:25941834

  2. A peptide isolated from phage display libraries is a structural and functional mimic of an RGD-binding site on integrins

    PubMed Central

    1995-01-01

    Many integrins recognize short RGD-containing amino acid sequences and such peptide sequences can be identified from phage libraries by panning with an integrin. Here, in a reverse strategy, we have used such libraries to isolate minimal receptor sequences that bind to fibronectin and RGD-containing fibronectin fragments in affinity panning. A predominant cyclic motif, *CWDDG/LWLC*, was obtained (the asterisks denote a potential disulfide bond). Studies using the purified phage and the corresponding synthetic cyclic peptides showed that *CWDDGWLC*-expressing phage binds specifically to fibronectin and to fibronectin fragments containing the RGD sequence. The binding did not require divalent cations and was inhibited by both RGD and *CWDDGWLC*-containing synthetic peptides. Conversely, RGD-expressing phage attached specifically to immobilized *CWDDGWLC*-peptide and the binding could be blocked by the respective synthetic peptides in solution. Moreover, fibronectin bound to a *CWDDGWLC*-peptide affinity column, and could be eluted with an RGD-containing peptide. The *CWDDGWLC*-peptide inhibited RGD-dependent cell attachment to fibronectin and vitronectin, but not to collagen. A region of the beta subunit of RGD-binding integrins that has been previously demonstrated to be involved in ligand binding includes a polypeptide stretch, KDDLW (in beta 3) similar to WDDG/LWL. Synthetic peptides corresponding to this region in beta 3 were found to bind RGD-displaying phage and conversion of its two aspartic residues into alanines greatly reduced the RGD binding. Polyclonal antibodies raised against the *CWDDGWLC*- peptide recognized beta 1 and beta 3 in immunoblots. These data indicate that the *CWDDGWLC*-peptide is a functional mimic of ligand binding sites of RGD-directed integrins, and that the structurally similar site in the integrin beta subunit is a binding site for RGD. PMID:7657703

  3. Extra-domain B in Oncofetal Fibronectin Structurally Promotes Fibrillar Head-to-tail Dimerization of Extracellular Matrix Protein*

    PubMed Central

    Schiefner, André; Gebauer, Michaela; Skerra, Arne

    2012-01-01

    The type III extra-domain B (ED-B) is specifically spliced into fibronectin (Fn) during embryogenesis and neoangiogenesis, including many cancers. The x-ray structure of the recombinant four-domain fragment FnIII7B89 reveals a tightly associated, extended head-to-tail dimer, which is stabilized via pair-wise shape and charge complementarity. A tendency toward ED-B-dependent dimer formation in solution was supported by size exclusion chromatography and analytical ultracentrifugation. When amending the model with the known three-dimensional structure of the FnIII10 domain, its RGD loop as well as the adhesion synergy region in FnIII9–10 become displayed on the same face of the dimer; this should allow simultaneous binding of at least two integrins and, thus, receptor clustering on the cell surface and intracellular signaling. Insertion of ED-B appears to stabilize overall head-to-tail dimerization of two separate Fn chains, which, together with alternating homodimer formation via disulfide bridges at the C-terminal Fn tail, should lead to the known macromolecular fibril formation. PMID:22442152

  4. The synergistic effect of folate and RGD dual ligand of nanographene oxide on tumor targeting and photothermal therapy in vivo

    NASA Astrophysics Data System (ADS)

    Jang, Cheol; Lee, Jong Hyun; Sahu, Abhishek; Tae, Giyoong

    2015-11-01

    Effective delivery of nanoparticles to the target site is necessary for successful biomedical applications. Inefficient targeting is a major concern for nanomedicines in cancer therapy. Conjugation of multiple targeting ligands to the nanoparticle surface might further enhance the targeting efficiency by a co-operative effect of individual ligands. In this study, a dual ligand targeting nanographene oxide (nGO) was developed by non-covalent interaction with folate and cRGD functionalized pluronic, which allowed precise control of ligand number on the nGO surface and ensured stability under physiological conditions. The tumor targeting abilities of single and dual ligand decorated nGOs were evaluated in vitro by using KB cells, over-expressing folate and integrin αvβ3 receptors. In vitro cellular uptake analysis by flow cytometry and confocal laser scanning microscopy showed enhanced uptake of dual ligand modified nGO compared to any of the single ligand modified nGOs. The cellular uptake of dual targeted cRGD-FA-nGO was increased by 1.9 and 2.4 folds compared to single targeted cRGD-nGO or FA-nGO, respectively. The in vivo biodistribution experiment in a mouse xenograft model also confirmed the synergistic targeting effect of cRGD and folate dual functionalized nGO. A significantly higher tumor accumulation of cRGD-FA-nGO was observed compared to cRGD-nGO or FA-nGO. The higher tumor accumulation of dual targeted nGO resulted in complete ablation of tumor tissue through an enhanced photothermal effect by NIR laser irradiation. Therefore, co-functionalization of a nanoparticle by cRGD and folate is a potentially useful way to enhance the tumor targeting efficacy.Effective delivery of nanoparticles to the target site is necessary for successful biomedical applications. Inefficient targeting is a major concern for nanomedicines in cancer therapy. Conjugation of multiple targeting ligands to the nanoparticle surface might further enhance the targeting efficiency by a

  5. RGD-modified liposomes enhance efficiency of aclacinomycin A delivery: evaluation of their effect in lung cancer.

    PubMed

    Feng, Chan; Li, Xiaoyan; Dong, Chunyan; Zhang, Xuemei; Zhang, Xie; Gao, Yong

    2015-01-01

    In this study, long-circulating Arg-Gly-Asp (RGD)-modified aclacinomycin A (ACM) liposomes were prepared by thin film hydration method. Their morphology, particle size, encapsulation efficiency, and in vitro release were investigated. The RGD-ACM liposomes was about 160 nm in size and had the visual appearance of a yellowish suspension. The zeta potential was -22.2 mV and the encapsulation efficiency was more than 93%. The drug-release behavior of the RGD-ACM liposomes showed a biphasic pattern, with an initial burst release and followed by sustained release at a constant rate. After being dissolved in phosphate-buffered saline (pH 7.4) and kept at 4°C for one month, the liposomes did not aggregate and still had the appearance of a milky white colloidal solution. In a pharmacokinetic study, rats treated with RGD-ACM liposomes showed slightly higher plasma concentrations than those treated with ACM liposomes. Maximum plasma concentrations of RGD-ACM liposomes and ACM liposomes were 4,532 and 3,425 ng/mL, respectively. RGD-ACM liposomes had a higher AUC0-∞ (1.54-fold), mean residence time (2.09-fold), and elimination half-life (1.2-fold) when compared with ACM liposomes. In an in vivo study in mice, both types of liposomes inhibited growth of human lung adenocarcinoma (A549) cells and markedly decreased tumor size when compared with the control group. There were no obvious pathological tissue changes in any of the treatment groups. Our results indicate that RGD-modified ACM liposomes have a better antitumor effect in vivo than their unmodified counterparts.

  6. Dimer crystallization of chiral proteoids.

    PubMed

    Wang, Po-Yuan; Mason, Thomas G

    2017-03-08

    Proteins can self-assemble into a variety of exquisitely organized structures through hierarchical reaction pathways. To examine how different core shapes of proteins and entropy combine to influence self-assembly, we create systems of lithographically fabricated proteomimetic colloids, or 'proteoids', and explore how Brownian monolayers of mobile proteoids, which have hard interactions, self-assemble as they are slowly crowded. Remarkably, chiral C-shaped proteoids having circular heads on only one side form enantiopure lock-and-key chiral dimers; these dimers have corrugated, shape-complementary perimeters, so they, in turn, form lock-and-key arrangements into chiral dimer crystals. Time-lapse video microscopy reveals the expulsion of monomers from the growing dimer crystals through tautomerization translocation reactions which expedite the crystallization kinetics. By lithographically mutating proteoids, we also tune the types and structures of the resulting dimer crystals. Thus, rational design of sub-particle features in hard-core colloidal shapes can be used to sterically select desired self-assembly pathways without introducing any site-specific attractions, thereby generating a striking degree of hierarchical self-ordering, reminiscent of protein crystallization.

  7. Haldane relation for interacting dimers

    NASA Astrophysics Data System (ADS)

    Giuliani, Alessandro; Mastropietro, Vieri; Lucio Toninelli, Fabio

    2017-03-01

    We consider a model of weakly interacting close-packed dimers on the two-dimensional square lattice. In a previous paper, we computed both the multi-point dimer correlations, which display non-trivial critical exponents, continuously varying with the interaction strength; and the height fluctuations, which, after proper coarse graining and rescaling, converge to a massless Gaussian field with a suitable interaction-dependent pre-factor (‘amplitude’). In this paper, we prove the identity between the critical exponent of the two-point dimer correlation and the amplitude of this massless Gaussian field. This identity is the restatement, in the context of interacting dimers, of one of the Haldane universality relations, part of his Luttinger-liquid conjecture, originally formulated in the context of one-dimensional interacting Fermi systems. Its validity is a strong confirmation of the effective massless Gaussian field description of the interacting dimer model, which was proposed on the basis of formal bosonization arguments. We also conjecture that a certain discrete curve defined at the lattice level via the Temperley bijection converges in the scaling limit to an SLE κ process, with κ depending non-trivially on the interaction and related in a simple way to the amplitude of the limiting Gaussian field.

  8. The antitumor activity of a doxorubicin loaded, iRGD-modified sterically-stabilized liposome on B16-F10 melanoma cells: in vitro and in vivo evaluation

    PubMed Central

    Yu, Ke-Fu; Zhang, Wei-Qiang; Luo, Li-Min; Song, Ping; Li, Dan; Du, Ruo; Ren, Wei; Huang, Dan; Lu, Wan-Liang; Zhang, Xuan; Zhang, Qiang

    2013-01-01

    Considering the fact that iRGD (tumor-homing peptide) demonstrates tumor-targeting and tumor-penetrating activity, and that B16-F10 (murine melanoma) cells overexpress both αv integrin receptor and neuropilin-1 (NRP-1), the purpose of this study was to prepare a novel doxorubicin (DOX)-loaded, iRGD-modified, sterically-stabilized liposome (SSL) (iRGD-SSL-DOX) in order to evaluate its antitumor activity on B16-F10 melanoma cells in vitro and in vivo. The iRGD-SSL-DOX was prepared using a thin-film hydration method. The characteristics of iRGD-SSL-DOX were evaluated. The in vitro leakage of DOX from iRGD-SSL-DOX was tested. The in vitro tumor-targeting and tumor-penetrating characteristics of iRGD-modified liposomes on B16-F10 cells were investigated. The in vivo tumor-targeting and tumor-penetrating activities of iRGD-modified liposomes were performed in B16-F10 tumor-bearing nude mice. The antitumor effect of iRGD-SSL-DOX was evaluated in B16-F10 tumor-bearing C57BL/6 mice in vivo. The average particle size of the iRGD-SSL-DOX was found to be 91 nm with a polydispersity index (PDI) of 0.16. The entrapment efficiency of iRGD-SSL-DOX was 98.36%. The leakage of DOX from iRGD-SSL-DOX at the 24-hour time point was only 7.5%. The results obtained from the in vitro flow cytometry and confocal microscopy, as well as in vivo biodistribution and confocal immunofluorescence microscopy experiments, indicate that the tumor-targeting and tumor-penetrating activity of the iRGD-modified SSL was higher than that of unmodified SSL. In vivo antitumor activity results showed that the antitumor effect of iRGD-SSL-DOX against melanoma tumors was higher than that of SSL-DOX in B16-F10 tumor-bearing mice. In conclusion, the iRGD-SSL-DOX is a tumor-targeting and tumor-penetrating peptide modified liposome which has significant antitumor activity against melanoma tumors. PMID:23885174

  9. Adventures in holographic dimer models

    NASA Astrophysics Data System (ADS)

    Kachru, Shamit; Karch, Andreas; Yaida, Sho

    2011-03-01

    We abstract the essential features of holographic dimer models, and develop several new applications of these models. Firstly, semi-holographically coupling free band fermions to holographic dimers, we uncover novel phase transitions between conventional Fermi liquids and non-Fermi liquids, accompanied by a change in the structure of the Fermi surface. Secondly, we make dimer vibrations propagate through the whole crystal by way of double trace deformations, obtaining nontrivial band structure. In a simple toy model, the topology of the band structure experiences an interesting reorganization as we vary the strength of the double trace deformations. Finally, we develop tools that would allow one to build, in a bottom-up fashion, a holographic avatar of the Hubbard model.

  10. iRGD tumor-penetrating peptide-modified oncolytic adenovirus shows enhanced tumor transduction, intratumoral dissemination and antitumor efficacy.

    PubMed

    Puig-Saus, C; Rojas, L A; Laborda, E; Figueras, A; Alba, R; Fillat, C; Alemany, R

    2014-08-01

    Endovenously administered oncolytic viruses extravasate and penetrate poorly into tumors. iRGD is a cyclic peptide that enhances tumor penetration when conjugated or coadministered with different types of molecules such as drugs, nanoparticles or phages. iRGD-mediated tumor penetration occurs in three steps: binding to αv-integrins on tumor vasculature or tumor cells, exposure by proteolysis of a C-terminal motif that binds to neuropilin-1 (NRP-1) and cell internalization. We have genetically inserted the iRGD peptide in the fiber C terminus of ICOVIR15K, an oncolytic tumor-retargeted adenovirus to increase its tumor penetration. In vitro, NRP-1 interaction improved binding and internalization of the virus in different cancer cells overexpressing integrins and NRP-1. However, such NRP-1-mediated internalization did not affect transduction or cytotoxicity. In vivo, iRGD did not change the normal organ transduction pattern, with liver and spleen as main targeted organs. In tumors, however, iRGD enhanced transduction and early adenovirus dissemination through the tumor mass leading to an improved antitumor efficacy.

  11. IL-6 Antibody and RGD Peptide Conjugated Poly(amidoamine) Dendrimer for Targeted Drug Delivery of HeLa Cells.

    PubMed

    Mekuria, Shewaye Lakew; Debele, Tilahun Ayane; Chou, Hsiao-Ying; Tsai, Hsieh-Chih

    2016-01-14

    In this study, PAMAM dendrimer (G4.5) was conjugated with two targeting moieties, IL-6 antibody and RGD peptide (G4.5-IL6 and G4.5-RGD conjugates). Doxorubicin anticancer drug was physically loaded onto G4.5-IL6 and G4.5-RGD with the encapsulation efficiency of 51.3 and 30.1% respectively. The cellular internalization and uptake efficiency of G4.5-IL6/DOX and G4.5-RGD/DOX complexes was observed and compared by confocal microscopy and flow cytometry using HeLa cells, respectively. The lower IC50 value of G4.5-IL6/DOX in comparison to G4.5-RGD/DOX is indication that higher drug loading and faster drug release rate corresponded with greater cytotoxicity. The cytotoxic effect was further verified by increment in late apoptotic/necrotic cells due to delivery of drug through receptor-mediated endocytosis. On the basis of these results, G4.5-IL6 is a better suited carrier for targeted drug delivery of DOX to cervical cancer cells.

  12. VE-cadherin RGD motifs promote metastasis and constitute a potential therapeutic target in melanoma and breast cancers

    PubMed Central

    Bartolomé, Rubén A.; Torres, Sofía; de Val, Soledad Isern; Escudero-Paniagua, Beatriz; Calviño, Eva; Teixidó, Joaquín; Casal, J. Ignacio

    2017-01-01

    We have investigated the role of vascular-endothelial (VE)-cadherin in melanoma and breast cancer metastasis. We found that VE-cadherin is expressed in highly aggressive melanoma and breast cancer cell lines. Remarkably, inactivation of VE-cadherin triggered a significant loss of malignant traits (proliferation, adhesion, invasion and transendothelial migration) in melanoma and breast cancer cells. These effects, except transendothelial migration, were induced by the VE-cadherin RGD motifs. Co-immunoprecipitation experiments demonstrated an interaction between VE-cadherin and α2β1 integrin, with the RGD motifs found to directly affect β1 integrin activation. VE-cadherin-mediated integrin signaling occurred through specific activation of SRC, ERK and JNK, including AKT in melanoma. Knocking down VE-cadherin suppressed lung colonization capacity of melanoma or breast cancer cells inoculated in mice, while pre-incubation with VE-cadherin RGD peptides promoted lung metastasis for both cancer types. Finally, an in silico study revealed the association of high VE-cadherin expression with poor survival in a subset of melanoma patients and breast cancer patients showing low CD34 expression. These findings support a general role for VE-cadherin and other RGD cadherins as critical regulators of lung and liver metastasis in multiple solid tumours. These results pave the way for cadherin-specific RGD targeted therapies to control disseminated metastasis in multiple cancers. PMID:27966446

  13. No-carrier-added nucleophilic 18F-labelling in an electrochemical cell exemplified by the routine production of [18F]altanserin.

    PubMed

    Hamacher, K; Coenen, H H

    2006-09-01

    A new type of electrochemical cell with anodic deposition of no-carrier-added [(18)F]fluoride and variable reaction volume has been developed. The reactor is designed for small reaction volumes and non-thermal drying of [(18)F]fluoride. The implementation of this reactor into a complete remotely controlled synthesis device is described for the routine production of [(18)F]altanserin. A radiochemical yield of 23+/-5% was obtained via cryptate-mediated nucleophilic (18)F-fluorination. Batches of up to 6 GBq [(18)F]altanserin, suitable for human application, with a molar activity of >500 GBq/micromol were obtained within 75 min.

  14. Design and Investigation of a [(18)F]-Labeled Benzamide Derivative as a High Affinity Dual Sigma Receptor Subtype Radioligand for Prostate Tumor Imaging.

    PubMed

    Yang, Dongzhi; Comeau, Anthony; Bowen, Wayne D; Mach, Robert H; Ross, Brian D; Hong, Hao; Van Dort, Marcian E

    2017-03-06

    High overexpression of sigma (σ) receptors (σ1 and σ2 subtypes) in a variety of human solid tumors has prompted the development of σ receptor-targeting radioligands, as imaging agents for tumor detection. A majority of these radioligands to date target the σ2 receptor, a potential marker of tumor proliferative status. The identification of approximately equal proportions of both σ receptor subtypes in prostate tumors suggests that a high affinity, dual σ receptor-targeting radioligand could potentially provide enhanced tumor targeting efficacy in prostate cancer. To accomplish this goal, we designed a series of ligands which bind to both σ receptor subtypes with high affinity. Ligand 3a in this series, displaying optimal dual σ receptor subtype affinity (σ1, 6.3 nM; σ2, 10.2 nM) was radiolabeled with fluorine-18 ((18)F) to give [(18)F]3a and evaluated as a σ receptor-targeting radioligand in the mouse PC-3 prostate tumor model. Cellular assays with PC-3 cells demonstrated that a major proportion of [(18)F]3a was localized to cell surface σ receptors, while ∼10% of [(18)F]3a was internalized within cells after incubation for 3.5 h. Serial PET imaging in mice bearing PC-3 tumors revealed that uptake of [(18)F]3a was 1.6 ± 0.8, 4.4 ± 0.3, and 3.6 ± 0.6% ID/g (% injection dose per gram) in σ receptor-positive prostate tumors at 15 min, 1.5 h, and 3.5 h postinjection, respectively (n = 3) resulting in clear tumor visualization. Blocking studies conducted with haloperidol (a nonselective inhibitor for both σ receptor subtypes) confirmed that the uptake of [(18)F]3a was σ receptor-mediated. Histology analysis confirmed similar expression of σ1 and σ2 in PC-3 tumors which was significantly greater than its expression in normal organs/tissues such as liver, kidney, and muscle. Metabolite studies revealed that >50% of radioactivity in PC-3 tumors at 30 min postinjection represented intact [(18)F]3a. Prominent σ receptor-specific uptake of [(18)F]3a in prostate tumors and its subsequent clear visualization with PET imaging indicate potential utility for the diagnosis of prostate carcinoma.

  15. PET Imaging of Extracellular pH in Tumors with 64Cu- and 18F-Labeled pHLIP Peptides: A Structure–Activity Optimization Study

    PubMed Central

    2016-01-01

    pH (low) insertion peptides (pHLIP peptides) target acidic extracellular environments in vivo due to pH-dependent cellular membrane insertion. Two variants (Var3 and Var7) and wild-type (WT) pHLIP peptides have shown promise for in vivo imaging of breast cancer. Two positron emitting radionuclides (64Cu and 18F) were used to label the NOTA- and NO2A-derivatized Var3, Var7, and WT peptides for in vivo biodistribution studies in 4T1 orthotopic tumor-bearing BALB/c mice. All of the constructs were radiolabeled with 64Cu or [18F]-AlF in good yield. The in vivo biodistribution of the 12 constructs in 4T1 orthotopic allografted female BALB/c mice indicated that NO2A-cysVar3, radiolabeled with either 18F (4T1 uptake; 8.9 ± 1.7%ID/g at 4 h p.i.) or 64Cu (4T1 uptake; 8.2 ± 0.9%ID/g at 4 h p.i. and 19.2 ± 1.8% ID/g at 24 h p.i.), shows the most promise for clinical translation. Additional studies to investigate other tumor models (melanoma, prostate, and brain tumor models) indicated the universality of tumor targeting of these tracers. From this study, future clinical translation will focus on 18F- or 64Cu-labeled NO2A-cysVar3. PMID:27396694

  16. Specific, reversible binding of [18F]benperidol to baboon D2 receptors: PET evaluation of an improved 18F-labeled ligand.

    PubMed

    Moerlein, S M; Perlmutter, J S; Welch, M J

    1995-08-01

    [18F]Benperidol ([18F]BP), a positron-emitting analogue of the dopaminergic D2 antagonist benperidol, was evaluated as a radiopharmaceutical for use with positron emission tomography (PET). PET imaging of baboons after i.v. injection of [18F]BP indicated that the radiofluorinated ligand rapidly localized in vivo within dopaminergic receptor-rich cerebral tissues, and that selective disposition was retained for over 2 h. Pretreatment of an animal with unlabeled receptor-specific antagonists prior to injection of [18F]BP confirmed that the radioligand bound specifically to central D2 receptors in vivo, and not to S2 or D1 receptors. [18F]BP bound to D2 receptors in a reversible manner; unlabeled eticlopride displaced D2 receptor-bound [18F]BP in vivo. The radioligand was metabolized in the periphery to polar metabolites which are not expected to cross the blood-brain barrier. [18F]BP has advantages over other tracers as a radiopharmaceutical for PET study of central D2 receptor activity, and can be applied for noninvasive evaluation of the interaction of unlabeled drugs with central D2 receptor sites.

  17. Modulation of integrin-binding selectivity by mutation within the RGD-loop of snake venom proteins: a novel drug development approach.

    PubMed

    Lu, X; Lu, D; Scully, M F; Kakkar, V V

    2003-06-01

    Integrins are a family of heterodimeric class I transmembrane receptors, many of which bind to the RGD sequence in adhesive proteins and mediate the adhesive interactions of a variety of cells. The RGD motif has also been found in snake venom proteins that specifically inhibit integrin binding function and serve as potent integrin antagonists. The majority of these proteins interact with beta1 and beta3 associated integrins and their potency is at least 500-2000 times higher than short RGD peptides. Structural and functional studies suggest that the inhibitory potency of these proteins lies in subtle positional requirements of the tripeptide RGD that is harboured in a defined flexible loop. The integrin-binding specificity and selectivity of each of the proteins is controlled by amino acid residues in this loop in close vicinity to the RGD-motif. The review includes an overview of the structure and function of snake-venom integrin antagonists. The ability of these proteins to control platelet aggregation, cell adhesion and ligand binding is compared to that of short linear, cyclic RGD-peptides and RGD-containing proteins and the influence of modulation of amino acid residues flanking the RGD motif is also considered. The review is intended to provide insight into the development of novel inhibitors as drugs.

  18. Dimerization of Cell-Adhesion Molecules Can Increase Their Binding Strength.

    PubMed

    Huang, Wenmao; Qin, Meng; Li, Ying; Cao, Yi; Wang, Wei

    2017-02-14

    Cell-adhesion molecules (CAMs) often exist as homodimers under physiological conditions. However, owing to steric hindrance, simultaneous binding of two ligands to the homodimers at the same location can hardly be satisfied, and the molecular mechanism underlying this natural design is still unknown. Here, we present a theoretical model to understand the rupture behavior of cell-adhesion bonds formed by multiple binding ligands with a single receptor. We found that the dissociation forces for the cell-adhesion bond could be greatly enhanced in comparison with the monomer case through a ligand rebinding and exchange mechanism. We also confirmed this prediction by measuring dimeric cRGD (cyclic Arg-Gly-Asp) unbinding from integrin (αvβ3) using atomic force microscopy-based single-molecule force spectroscopy. Our finding addresses the mechanism of increasing the binding strength of cell-adhesion bonds through dimerization at the single-molecule level, representing a key step toward the understanding of complicated cell-adhesion behaviors. Moreover, our results also highlight a wealth of opportunities to design mechanically stronger bioconjunctions for drug delivery, biolabeling, and surface modification.

  19. Development of a novel cyclic RGD peptide for multiple targeting approaches of liposomes to tumor region.

    PubMed

    Amin, Mohamadreza; Mansourian, Mercedeh; Koning, Gerben A; Badiee, Ali; Jaafari, Mahmoud Reza; ten Hagen, Timo L M

    2015-12-28

    Liposomes containing cytotoxic agents and targeted with Arg-Gly-Asp based peptides have frequently been used against αvβ3 integrin on tumor neovasculature. However, like many other ligand modified liposomes these preparations suffered from enhanced uptake by the reticulo endothelial system (RES) and off-targeted interaction with integrin receptors vastly expressed in normal organs causing poor biodistribution and toxic effects. Here we mainly focus on development of a RGD-modified liposomal delivery system to enhance both targeting selectivity and tumor uptake. First, sterically stabilized liposomal doxorubicin (SSLD) prepared and decorated with cRGDfK and RGDyC peptides differ in their physical properties. Stability assessments as well as in vitro and in vivo studies revealed that increasing the peptide hydrophobicity promotes the therapeutic efficacy of RGD-SSLD in a C-26 tumor model due to decreased recognition by RES and opsonization and limited off-targeted interactions. Then a novel N-methylated RGD peptide was designed and its capability in targeting integrin presenting cells was comprehensively assessed both in vitro and in vivo. RGDf[N-methyl]C promotes the liposome internalization by HUVEC via integrin mediated endocytosis. Intravital microscopy in window chamber bearing mice illustrated the capability of RGDf[N-methyl]C-liposomes in targeting both tumor vasculature and tumor cells in murine B16F0 and human BLM tumor models. Quantitative biodistribution in mice bearing B16F0 tumor revealed its high affinity to tumor with no considerable affinity to normal organs. Treatment by high dose of RGDf[N-methyl]C-SSLD was found more effective than non-targeted SSLD and no toxic side effect was observed. In conclusion, the RGDf[N-methyl]C-liposome was found promising in targeting tumor vasculature as well as other cells inside the tumor.

  20. DFT computational study of the RGD peptide interaction with the rutile TiO2 (110) surface

    NASA Astrophysics Data System (ADS)

    Muir, J. M. R.; Costa, D.; Idriss, H.

    2014-06-01

    Planewave DFT calculations including ab initio molecular dynamics (AIMD) were used to model the adsorption of a biologically relevant peptide sequence, arginine-glycine-aspartic acid (RGD), upon a rutile TiO2 (110) surface. It was found that binding is solely through the aspartic acid end of the RGD. The carboxy groups bind through dissociative bridging and molecular forms, similar to formic acid. The energy of adsorption is much smaller (0.5-0.77 eV) than seen for formic acid and the molecular adsorption is the strongest adsorption mode. Neutral adsorption is favoured over zwitterionic adsorption and adsorption through the carboxy group of the aspartic acid side chain rather than the terminal carboxy group is favoured due to a configuration allowing an additional surface-carbonyl bond. The RGD backbone is not significantly disrupted upon adsorption.

  1. Chitosan microsphere scaffold tethered with RGD-conjugated poly(methacrylic acid) brushes as effective carriers for the endothelial cells.

    PubMed

    Yang, Zhenyi; Yuan, Shaojun; Liang, Bin; Liu, Yang; Choong, Cleo; Pehkonen, Simo O

    2014-09-01

    Endothelial cell-matrix interactions play a vital role in promoting vascularization of engineered tissues. The current study reports a facile and controllable method to develop a RGD peptide-functionalized chitosan microsphere scaffolds for rapid cell expansion of human umbilical vein endothelial cells (HUVECs). Functional poly(methacrylic acid) (PMAA) brushes are grafted from the chitosan microsphere surfaces via surface-initiated ATRP. Subsequent conjugation of RGD peptides on the pendent carboxyl groups of PMAA side chain is accomplished by carbodiimide chemistry to facilitate biocompatibility of the 3D CS scaffolding system. In vitro cell-loading assay of HUVECs exhibits a significant improvment of cell adhesion, spreading, and proliferation on the RGD peptide-immobilized CS microsphere surfaces.

  2. Computational study of the RGD-peptide interactions with perovskite-type BFO-(1 1 1) membranes under aqueous conditions

    NASA Astrophysics Data System (ADS)

    Li, Hai-long; Bian, Liang; Hou, Wen-ping; Dong, Fa-Qin; Song, Mian-Xin; Zhang, Xiao-yan; Wang, Li-sheng

    2016-07-01

    We elucidated a number of facets regarding arginine-glycine-aspartate (RGD)-bismuth ferrite (BFO)-(1 1 1) membrane interactions and reactivity that have previously remained unexplored on a molecular level. Results demonstrate the intra-molecular interaction facilitates a ;horseshoe; structure of RGD adsorbed onto the BFO-(1 1 1) membrane, through the electrostatic (Asp-cation-Fe) and water-bridge (Osbnd H2O and H2Osbnd NH2) interactions. The effect of structural and electron-transfer interactions is attributed to the cation-valences, indicating that the divalent cations are electron-acceptors and the monovalent cations as electron-donors. Notably, the strongly bound Ca2+ ion exerts a ;gluing; effect on the Asp-side-chain, indicating a tightly packed RGD-BFO configuration. Thus, modulating the biological response of BFO-(1 1 1) membrane will allow us to design more appropriate interfaces for implantable diagnostic and therapeutic perovskite-type micro-devices.

  3. Kinetics of DNA tile dimerization.

    PubMed

    Jiang, Shuoxing; Yan, Hao; Liu, Yan

    2014-06-24

    Investigating how individual molecular components interact with one another within DNA nanoarchitectures, both in terms of their spatial and temporal interactions, is fundamentally important for a better understanding of their physical behaviors. This will provide researchers with valuable insight for designing more complex higher-order structures that can be assembled more efficiently. In this report, we examined several spatial factors that affect the kinetics of bivalent, double-helical (DH) tile dimerization, including the orientation and number of sticky ends (SEs), the flexibility of the double helical domains, and the size of the tiles. The rate constants we obtained confirm our hypothesis that increased nucleation opportunities and well-aligned SEs accelerate tile-tile dimerization. Increased flexibility in the tiles causes slower dimerization rates, an effect that can be reversed by introducing restrictions to the tile flexibility. The higher dimerization rates of more rigid tiles results from the opposing effects of higher activation energies and higher pre-exponential factors from the Arrhenius equation, where the pre-exponential factor dominates. We believe that the results presented here will assist in improved implementation of DNA tile based algorithmic self-assembly, DNA based molecular robotics, and other specific nucleic acid systems, and will provide guidance to design and assembly processes to improve overall yield and efficiency.

  4. Kinetics of DNA Tile Dimerization

    PubMed Central

    2015-01-01

    Investigating how individual molecular components interact with one another within DNA nanoarchitectures, both in terms of their spatial and temporal interactions, is fundamentally important for a better understanding of their physical behaviors. This will provide researchers with valuable insight for designing more complex higher-order structures that can be assembled more efficiently. In this report, we examined several spatial factors that affect the kinetics of bivalent, double-helical (DH) tile dimerization, including the orientation and number of sticky ends (SEs), the flexibility of the double helical domains, and the size of the tiles. The rate constants we obtained confirm our hypothesis that increased nucleation opportunities and well-aligned SEs accelerate tile–tile dimerization. Increased flexibility in the tiles causes slower dimerization rates, an effect that can be reversed by introducing restrictions to the tile flexibility. The higher dimerization rates of more rigid tiles results from the opposing effects of higher activation energies and higher pre-exponential factors from the Arrhenius equation, where the pre-exponential factor dominates. We believe that the results presented here will assist in improved implementation of DNA tile based algorithmic self-assembly, DNA based molecular robotics, and other specific nucleic acid systems, and will provide guidance to design and assembly processes to improve overall yield and efficiency. PMID:24794259

  5. Enhanced anticancer efficacy of paclitaxel through multistage tumor-targeting liposomes modified with RGD and KLA peptides

    PubMed Central

    Sun, Jiawei; Jiang, Lei; Lin, Yi; Gerhard, Ethan Michael; Jiang, Xuehua; Li, Li; Yang, Jian; Gu, Zhongwei

    2017-01-01

    Mitochondria serve as both “energy factories” and “suicide weapon stores” of cells. Targeted delivery of cytotoxic drugs to the mitochondria of tumor cells and tumor vascular cells is a promising strategy to improve the efficacy of chemotherapy. Here, multistage tumor-targeting liposomes containing two targeted peptide-modified lipids, cRGD-PEG2000-DSPE and KLA-PEG2000-DSPE, were developed for encapsulation of the anticancer drug paclitaxel (PTX, RGD-KLA/PTX-Lips). Compared with Taxol (free PTX), RGD/PTX-Lips and KLA/PTX-Lips, the half-maximal inhibitory concentration (IC50) value of RGD-KLA/PTX-Lips in vitro was 1.9-, 36.7- and 22.7-fold lower with 4T1 cells, respectively, because of higher levels of cellular uptake. Similar results were also observed with human umbilical vascular endothelial cells (HUVECs). An apoptosis assay showed that the total apoptotic ratio of RGD-KLA/PTX-Lips was the highest because of the mitochondria-targeted drug delivery and the activation of mitochondrial apoptosis pathways, as evidenced by visible mitochondrial localization, decreased mitochondrial membrane potential, release of cytochrome c and increased activities of caspase-9 and caspase-3. The strongest tumor growth inhibition (TGI; 80.6%) and antiangiogenesis effects without systemic toxicity were also observed in RGD-KLA/PTX-Lip-treated 4T1 tumor xenograft BALB/c mice. In conclusion, these multistage tumor-targeting liposomes represent a promising anticancer drug delivery system (DDS) capable of maximizing anticancer therapeutic efficacy and minimizing systemic toxicity. PMID:28280323

  6. Dual-functionalized liposomal delivery system for solid tumors based on RGD and a pH-responsive antimicrobial peptide

    PubMed Central

    Zhang, Qianyu; Lu, Libao; Zhang, Li; Shi, Kairong; Cun, Xingli; Yang, Yuting; Liu, Yayuan; Gao, Huile; He, Qin

    2016-01-01

    [D]-H6L9, as a pH-responsive anti-microbial peptide (AMP), has been evidenced by us to be an excellent choice in tumor microenvironment-responsive delivery as it could render liposomes responsive to the acidified tumor microenvironment. However, [D]-H6L9-modified liposomes could not actively target to tumor area. Therefore, integrin αvβ3-targeted peptide RGD was co-modified with [D]-H6L9 onto liposomes [(R + D)-Lip] for improved tumor delivery efficiency. Under pH 6.3, (R + D)-Lip could be taken up by C26 cells and C26 tumor spheroids (integrin αvβ3-positive) with significantly improved efficiency compared with other groups, which was contributed by both RGD and [D]-H6L9, while RGD did not increase the cellular uptake performance on MCF-7 cells (integrin αvβ3-negative). Results showed that RGD could decrease cellular uptake of (R + D)-Lip while [D]-H6L9 could increase it, implying the role of both RGD and [D]-H6L9 in cellular internalization of (R + D)-Lip. On the other hand, (R + D)-Lip could escape the entrapment of lysosomes. PTX-loaded (R + D)-Lip could further increase the cellular toxicity against C26 cells compared with liposomes modified only with RGD and [D]-H6L9 respectively, and achieve remarkable tumor inhibition effect on C26 tumor models. PMID:26842655

  7. Characterization of mAb dimers reveals predominant dimer forms common in therapeutic mAbs

    PubMed Central

    Plath, Friederike; Ringler, Philippe; Graff-Meyer, Alexandra; Stahlberg, Henning; Lauer, Matthias E.; Rufer, Arne C.; Graewert, Melissa A.; Svergun, Dmitri; Gellermann, Gerald; Finkler, Christof; Stracke, Jan O.; Koulov, Atanas; Schnaible, Volker

    2016-01-01

    ABSTRACT The formation of undesired high molecular weight species such as dimers is an important quality attribute for therapeutic monoclonal antibody formulations. Therefore, the thorough understanding of mAb dimerization and the detailed characterization mAb dimers is of great interest for future pharmaceutical development of therapeutic antibodies. In this work, we focused on the analyses of different mAb dimers regarding size, surface properties, chemical identity, overall structure and localization of possible dimerization sites. Dimer fractions of different mAbs were isolated to a satisfactory purity from bulk material and revealed 2 predominant overall structures, namely elongated and compact dimer forms. The elongated dimers displayed one dimerization site involving the tip of the Fab domain. Depending on the stress applied, these elongated dimers are connected either covalently or non-covalently. In contrast, the compact dimers exhibited non-covalent association. Several interaction points were detected for the compact dimers involving the hinge region or the base of the Fab domain. These results indicate that mAb dimer fractions are rather complex and may contain more than one kind of dimer. Nevertheless, the overall appearance of mAb dimers suggests the existence of 2 predominant dimeric structures, elongated and compact, which are commonly present in preparations of therapeutic mAbs. PMID:27031922

  8. Water dimer equilibrium constant of saturated vapor

    NASA Astrophysics Data System (ADS)

    Malomuzh, N. P.; Mahlaichuk, V. N.; Khrapatyi, S. V.

    2014-08-01

    The value and temperature dependence of the dimerization constant for saturated water vapor are determined. A general expression that links the second virial coefficient and the dimerization constant is obtained. It is shown that the attraction between water monomers and dimers is fundamental, especially at T > 350 K. The range of application for the obtained results is determined.

  9. Surface investigation on biomimetic materials to control cell adhesion: the case of RGD conjugation on PCL.

    PubMed

    Causa, Filippo; Battista, Edmondo; Della Moglie, Raffaella; Guarnieri, Daniela; Iannone, Maria; Netti, Paolo A

    2010-06-15

    The cell recognition of bioactive ligands immobilized on polymeric surfaces is strongly dependent on ligand presentation at the cell/material interface. While small peptide sequences such as Arg-Gly-Asp (RGD) are being widely used to obtain biomimetic interfaces, surface characteristics after immobilization as well as presentation of such ligands to cell receptors deserve more detailed investigation. Here, we immobilized an RGD-based sequence on poly(epsilon-caprolactone) (PCL), a largely widespread polymeric material used in biomedical applications, after polymer aminolysis. The surface characteristics along with the efficacy of the functionalization was monitored by surface analysis (FTIR-ATR, contact angle measurements, surface free energy determination) and spectrophotometric assays specially adapted for the analytical quantification of functional groups and/or peptides at the interface. Particular attention was paid to the evaluation of a number, morphology, and penetration depth of immobilized functional groups and/or peptides engrafted on polymeric substrates. In particular, a typical morphology in peptide distribution was evidenced on the surface raised from polymer crystallites, while a significant penetration depth of the engrafted molecules was revealed. NIH3T3 fibroblast adhesion studies verified the correct presentation of the ligand with enhanced cell attachment after peptide conjugation. Such work proposes a morphological and analytical approach in surface characterization to study the surface treatment and the distribution of ligands immobilized on polymeric substrates.

  10. Electronic Structure, Dielectric Response, and Surface Charge Distribution of RGD (1FUV) Peptide

    NASA Astrophysics Data System (ADS)

    Adhikari, Puja; Wen, Amy M.; French, Roger H.; Parsegian, V. Adrian; Steinmetz, Nicole F.; Podgornik, Rudolf; Ching, Wai-Yim

    2014-07-01

    Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor.

  11. The RGD integrin binding site in human L1-CAM is important for nuclear signaling

    SciTech Connect

    Gast, Daniela; Riedle, Svenja; Kiefel, Helena; Mueerkoester, Susanne Sebens; Schaefer, Heiner; Schaefer, Michael K.E.; Altevogt, Peter

    2008-08-01

    L1 cell adhesion molecule (L1-CAM) is a transmembrane cell adhesion molecule initially defined as a promigratory molecule in the developing nervous system. L1 is also overexpressed in a variety of human carcinomas and is associated with bad prognosis. In carcinoma cell lines L1 augments cell motility and metastasis, tumor growth in nude mice and induces expression of L1-dependent genes. It is not known whether L1-signaling requires ligand binding. The RGD motif in the sixth Ig domain of L1 is a binding site for integrins. In the present study we analyzed the role of RGDs in L1-signaling using site-directed mutagenesis combined with antibody blocking studies. We observed that L1-RGE expressing HEK293 cells showed reduced cell-cell binding, cell motility, invasiveness and tumor growth in NOD/SCID mice. The RGE-mutation impaired L1-dependent gene regulation and antibodies to {alpha}v{beta}5 integrin had similar effects. Mutant L1 was unable to translocate to the nucleus. Our findings highlight the importance of the RGD site in L1 for human tumors and suggest that nuclear signaling of L1 is dependent on integrins.

  12. Electronic structure, dielectric response, and surface charge distribution of RGD (1FUV) peptide.

    PubMed

    Adhikari, Puja; Wen, Amy M; French, Roger H; Parsegian, V Adrian; Steinmetz, Nicole F; Podgornik, Rudolf; Ching, Wai-Yim

    2014-07-08

    Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor.

  13. Fiber optic D dimer biosensor

    DOEpatents

    Glass, R.S.; Grant, S.A.

    1999-08-17

    A fiber optic sensor for D dimer (a fibrinolytic product) can be used in vivo (e.g., in catheter-based procedures) for the diagnosis and treatment of stroke-related conditions in humans. Stroke is the third leading cause of death in the United States. It has been estimated that strokes and stroke-related disorders cost Americans between $15-30 billion annually. Relatively recently, new medical procedures have been developed for the treatment of stroke. These endovascular procedures rely upon the use of microcatheters. These procedures could be facilitated with this sensor for D dimer integrated with a microcatheter for the diagnosis of clot type, and as an indicator of the effectiveness, or end-point of thrombolytic therapy. 4 figs.

  14. Fiber optic D dimer biosensor

    DOEpatents

    Glass, Robert S.; Grant, Sheila A.

    1999-01-01

    A fiber optic sensor for D dimer (a fibrinolytic product) can be used in vivo (e.g., in catheter-based procedures) for the diagnosis and treatment of stroke-related conditions in humans. Stroke is the third leading cause of death in the United States. It has been estimated that strokes and stroke-related disorders cost Americans between $15-30 billion annually. Relatively recently, new medical procedures have been developed for the treatment of stroke. These endovascular procedures rely upon the use of microcatheters. These procedures could be facilitated with this sensor for D dimer integrated with a microcatheter for the diagnosis of clot type, and as an indicator of the effectiveness, or end-point of thrombolytic therapy.

  15. Mechanism of FGF receptor dimerization and activation

    NASA Astrophysics Data System (ADS)

    Sarabipour, Sarvenaz; Hristova, Kalina

    2016-01-01

    Fibroblast growth factors (fgfs) are widely believed to activate their receptors by mediating receptor dimerization. Here we show, however, that the FGF receptors form dimers in the absence of ligand, and that these unliganded dimers are phosphorylated. We further show that ligand binding triggers structural changes in the FGFR dimers, which increase FGFR phosphorylation. The observed effects due to the ligands fgf1 and fgf2 are very different. The fgf2-bound dimer structure ensures the smallest separation between the transmembrane (TM) domains and the highest possible phosphorylation, a conclusion that is supported by a strong correlation between TM helix separation in the dimer and kinase phosphorylation. The pathogenic A391E mutation in FGFR3 TM domain emulates the action of fgf2, trapping the FGFR3 dimer in its most active state. This study establishes the existence of multiple active ligand-bound states, and uncovers a novel molecular mechanism through which FGFR-linked pathologies can arise.

  16. MAGP2 controls Notch via interactions with RGD binding integrins: Identification of a novel ECM-integrin-Notch signaling axis.

    PubMed

    Deford, Peter; Brown, Kasey; Richards, Rae Lee; King, Aric; Newburn, Kristin; Westover, Katherine; Albig, Allan R

    2016-02-01

    Canonical Notch signaling involves Notch receptor activation via interaction with cell surface bound Notch ligand. Recent findings also indicate that Notch signaling may be modulated by cross-talk with other signaling mechanisms. The ECM protein MAGP2 was previously shown to regulate Notch in a cell type dependent manner, although the molecular details of this interaction have not been dissected. Here, we report that MAGP2 cell type specific control of Notch is independent of individual Notch receptor-ligand combinations but dependent on interaction with RGD binding integrins. Overexpressed MAGP2 was found to suppress transcriptional activity from the Notch responsive Hes1 promoter activity in endothelial cells, while overexpression of a RGD→RGE MAGP2 mutant increased Notch signaling in the same cell type. This effect was not unique to MAGP2 since the RGD domain of the ECM protein EGFL7 was also found to be an important modulator of Hes1 promoter activity. Independently of MAGP2 or EGFL7, inhibition of RGD-binding integrins with soluble RGD peptides also increased accumulation of active N1ICD fragments and Notch responsive promoter activity independently of changes in Notch1, Jag1, or Dll4 expression. Finally, β1 or β3 integrin blocking antibodies also enhanced Notch signaling. Collectively, these results answer the question of how MAGP2 controls cell type dependent Notch signaling, but more importantly uncover a new mechanism to understand how extracellular matrices and cellular environments impact Notch signaling.

  17. RGD peptides and monoclonal antibodies, antagonists of alpha(v)-integrin, enter the cells by independent endocytic pathways.

    PubMed

    Castel, S; Pagan, R; Mitjans, F; Piulats, J; Goodman, S; Jonczyk, A; Huber, F; Vilaró, S; Reina, M

    2001-12-01

    Cyclic synthetic peptides containing the arginine-glycine-aspartate motif (cRGD) and monoclonal antibodies (mAbs) targeted for individual integrins have been developed as potential therapeutic drugs for the treatment of several diseases. We showed that a cRGD peptide targeted for alpha(v)beta(3) was internalized in alpha(v)-integrin expressing and nonexpressing melanoma cells by an integrin independent fluid-phase endocytosis pathway that does not alter the number of functional integrin receptors at the cell surface. In contrast, a blocking mAb directed to alpha(v) was internalized by an integrin-dependent endocytosis pathway that reduced the number of functional integrin receptors at the cell surface. We prove that melanoma cells pretreated with the mAb do not readhere to the substrate, whereas cells pretreated with cRGD peptide retain their readhesion capacity. Given the growing importance of RGD peptides, knowledge of these cellular mechanisms is required to improve the development of antiangiogenic and anti-inflammatory drugs.

  18. Installing multifunctionality on titanium with RGD-decorated polyurethane-polyurea roxithromycin loaded nanoparticles: toward new osseointegrative therapies.

    PubMed

    Rocas, Pau; Hoyos-Nogués, Mireia; Rocas, Josep; Manero, José M; Gil, Javier; Albericio, Fernando; Mas-Moruno, Carlos

    2015-09-16

    A novel class of polyurethane-polyurea nanoparticles (PUUa NPs) to install multifunctionality on biomaterials is presented. Biofunctionalization of titanium with roxithromycin loaded RGD-decorated PUUa NPs results in an outstanding improvement of osteoblast adhesion and strong suppression of bacterial attachment. This strategy represents a powerful approach to enhance the osseointegration of implant materials.

  19. The effect of RGD fluorosurfactant polymer modification of ePTFE on endothelial cell adhesion, growth, and function

    PubMed Central

    Larsen, Coby C.; Kligman, Faina; Kottke-Marchant, Kandice; Marchant, Roger E.

    2007-01-01

    We have synthesized and characterized a novel peptide fluorosurfactant polymer (PFSP) modification that facilitates the adhesion and growth of endothelial cells on ePTFE vascular graft material. This PFSP consists of a poly(vinyl amine) (PVAm) backbone with integrin binding Arg-Gly-Asp (RGD) peptides and perfluorocarbon pendant branches for adsorption and stable adhesion to underlying ePTFE. Aqueous PFSP solution was used to modify the surface of fluorocarbon substrates. Following subconfluent seeding, endothelial cell (EC) adhesion and growth on PFSP was assessed by determining cell population at different time points. Spectroscopic results indicated successful synthesis of PFSP. PFSP modification of ePTFE reduced the receding water contact angle measurement from 120° to 6°, indicating successful surface modification. Quantification of cell population demonstrated reduced EC attachment efficiency but increased growth rate on RGD PFSP compared with fibronectin (FN). Actin staining revealed a well-developed cytoskeleton for ECs on RGD PFSP indicative of stable adhesion. Uptake of acetylated low-density lipoprotein and positive staining for VE-Cadherin confirm EC phenotype for adherent cells. Production of prostacyclin, a potent antiplatelet agent, was equivalent between ECs on FN and RGD PFSP surfaces. Our results indicate successful synthesis and surface modification with PFSP; this is a simple, quantitative, and effective approach to modifying ePTFE to encourage endothelial cell attachment, growth, and function. PMID:16762410

  20. Gold Nanorods Conjugated with Doxorubicin and cRGD for Combined Anticancer Drug Delivery and PET Imaging

    PubMed Central

    Xiao, Yuling; Hong, Hao; Matson, Vyara Z.; Javadi, Alireza; Xu, Wenjin; Yang, Yunan; Zhang, Yin; Engle, Jonathan W.; Nickles, Robert J.; Cai, Weibo; Steeber, Douglas A.; Gong, Shaoqin

    2012-01-01

    A multifunctional gold nanorod (GNR)-based nanoplatform for targeted anticancer drug delivery and positron emission tomography (PET) imaging of tumors was developed and characterized. An anti-cancer drug (i.e., doxorubicin (DOX)) was covalently conjugated onto PEGylated (PEG: polyethylene glycol) GNR nanocarriers via a hydrazone bond to achieve pH-sensitive controlled drug release. Tumor-targeting ligands (i.e., the cyclo(Arg-Gly-Asp-D-Phe-Cys) peptides, cRGD) and 64Cu-chelators (i.e., 1,4,7-triazacyclononane-N, N', N''-triacetic acid (NOTA)) were conjugated onto the distal ends of the PEG arms to achieve active tumor-targeting and PET imaging, respectively. Based on flow cytometry analysis, cRGD-conjugated nanocarriers (i.e., GNR-DOX-cRGD) exhibited a higher cellular uptake and cytotoxicity than non-targeted ones (i.e., GNR-DOX) in vitro. However, GNR-DOX-cRGD and GNR-DOX nanocarriers had similar in vivo biodistribution according to in vivo PET imaging and biodistribution studies. Due to the unique optical properties of GNRs, this multifunctional GNR-based nanoplatform can potentially be optimized for combined cancer therapies (chemotherapy and photothermal therapy) and multimodality imaging (PET, optical, X-ray computed tomography (CT), etc.). PMID:22916075

  1. RGD Peptide Cell-Surface Display Enhances the Targeting and Therapeutic Efficacy of Attenuated Salmonella-mediated Cancer Therapy.

    PubMed

    Park, Seung-Hwan; Zheng, Jin Hai; Nguyen, Vu Hong; Jiang, Sheng-Nan; Kim, Dong-Yeon; Szardenings, Michael; Min, Jung Hyun; Hong, Yeongjin; Choy, Hyon E; Min, Jung-Joon

    2016-01-01

    Bacteria-based anticancer therapies aim to overcome the limitations of current cancer therapy by actively targeting and efficiently removing cancer. To achieve this goal, new approaches that target and maintain bacterial drugs at sufficient concentrations during the therapeutic window are essential. Here, we examined the tumor tropism of attenuated Salmonella typhimurium displaying the RGD peptide sequence (ACDCRGDCFCG) on the external loop of outer membrane protein A (OmpA). RGD-displaying Salmonella strongly bound to cancer cells overexpressing αvβ3, but weakly bound to αvβ3-negative cancer cells, suggesting the feasibility of displaying a preferential homing peptide on the bacterial surface. In vivo studies revealed that RGD-displaying Salmonellae showed strong targeting efficiency, resulting in the regression in αvβ3-overexpressing cancer xenografts, and prolonged survival of mouse models of human breast cancer (MDA-MB-231) and human melanoma (MDA-MB-435). Thus, surface engineering of Salmonellae to display RGD peptides increases both their targeting efficiency and therapeutic effect.

  2. RGD-modifided oncolytic adenovirus exhibited potent cytotoxic effect on CAR-negative bladder cancer-initiating cells.

    PubMed

    Yang, Y; Xu, H; Shen, J; Yang, Y; Wu, S; Xiao, J; Xu, Y; Liu, X-Y; Chu, L

    2015-05-14

    Cancer-initiating cell (CIC) is critical in cancer development, maintenance and recurrence. The reverse expression pattern of coxsackie and adenovirus receptor (CAR) and αν integrin in bladder cancer decreases the infection efficiency of adenovirus. We constructed Arg-Gly-Asp (RGD)-modified oncolytic adenovirus, carrying EGFP or TNF-related apoptosis-inducing ligand (TRAIL) gene (Onco(Ad).RGD-hTERT-EGFP/TRAIL), and applied them to CAR-negative bladder cancer T24 cells and cancer-initiating T24 sphere cells. Onco(Ad).RGD-hTERT-EGFP had enhanced infection ability and cytotoxic effect on T24 cells and T24 sphere cells, but little cytoxicity on normal urothelial SV-HUC-1 cells compared with the unmodified virus Onco(Ad).hTERT-EGFP. Notably, Onco(Ad).RGD-hTERT-TRAIL induced apoptosis in T24 cells and T24 sphere cells. Furthermore, it completely inhibited xenograft initiation established by the oncolytic adenovirus-pretreated T24 sphere cells, and significantly suppressed tumor growth by intratumoral injection. These results provided a promising therapeutic strategy for CAR-negative bladder cancer through targeting CICs.

  3. Degradable and biocompatible nanoparticles decorated with cyclic RGD peptide for efficient drug delivery to hepatoma cells in vitro.

    PubMed

    Loyer, Pascal; Bedhouche, Wahib; Huang, Zhi Wei; Cammas-Marion, Sandrine

    2013-10-01

    Amphiphilic derivatives of poly(benzyl malate) were synthesized and characterized with the aim of being used as degradable and biocompatible building blocks for the design of functional nanoparticles (NPs). An anti-cancer model drug, doxorubicin, has been successfully encapsulated into the prepared NPs and its release profile has been evaluated in water and in culture medium. NPs bearing biotin molecules were prepared either for site-specific drug delivery via the targeting of biotin receptors overexpressed on the surface of several cancer cells, or for grafting biotinylated cyclic RGD peptide onto their surface using the strong and highly specific interactions between biotin and the streptavidin protein. We have shown that this binding did not affect dramatically the physico-chemical properties of the corresponding NPs. Cyclic RGD grafted fluorescent NPs were more efficiently uptaken by the HepaRG hepatoma cells than biotinylated fluorescent NPs. Furthermore, the targeting of HepaRG hepatoma cells with NPs bearing cyclic RGD was very efficient and much weaker for HeLa and HT29 cell lines confirming that cyclic RGD is a suitable targeting agent for liver cells. Our results also provide a new mean for rapid screening of short hepatotropic peptides in order to design NPs showing specific liver targeting properties.

  4. Transferred-NOE NMR experiments on intact human platelets: receptor-bound conformation of RGD-peptide mimics.

    PubMed

    Potenza, Donatella; Belvisi, Laura

    2008-01-21

    The aim of this work is to show that transferred-NOE provides useful and detailed information on membrane-bound receptor-ligand interactions in living cells. Here, we study the interaction between intact human platelets and some ligands containing the RGD sequence. Conformational properties of the free and bound pentapeptides are reported.

  5. The effect of RGD fluorosurfactant polymer modification of ePTFE on endothelial cell adhesion, growth, and function.

    PubMed

    Larsen, Coby C; Kligman, Faina; Kottke-Marchant, Kandice; Marchant, Roger E

    2006-10-01

    We have synthesized and characterized a novel peptide fluorosurfactant polymer (PFSP) modification that facilitates the adhesion and growth of endothelial cells on expanded polytetrafluoroetheylene (ePTFE) vascular graft material. This PFSP consists of a poly(vinyl amine) (PVAm) backbone with integrin binding Arg-Gly-Asp (RGD) peptides and perfluorocarbon pendant branches for adsorption and stable adhesion to underlying ePTFE. Aqueous PFSP solution was used to modify the surface of fluorocarbon substrates. Following subconfluent seeding, endothelial cell (EC) adhesion and growth on PFSP was assessed by determining cell population at different time points. Spectroscopic results indicated successful synthesis of PFSP. PFSP modification of ePTFE reduced the receding water contact angle measurement from 120 degrees to 6 degrees , indicating successful surface modification. Quantification of cell population demonstrated reduced EC attachment efficiency but increased growth rate on RGD PFSP compared with fibronectin (FN). Actin staining revealed a well-developed cytoskeleton for ECs on RGD PFSP indicative of stable adhesion. Uptake of acetylated low-density lipoprotein and positive staining for VE-Cadherin confirm EC phenotype for adherent cells. Production of prostacyclin, a potent antiplatelet agent, was equivalent between ECs on FN and RGD PFSP surfaces. Our results indicate successful synthesis and surface modification with PFSP; this is a simple, quantitative, and effective approach to modifying ePTFE to encourage endothelial cell attachment, growth, and function.

  6. Comparison of new bone formation, implant integration, and biocompatibility between RGD-hydroxyapatite and pure hydroxyapatite coating for cementless joint prostheses--an experimental study in rabbits.

    PubMed

    Bitschnau, Achim; Alt, Volker; Böhner, Felicitas; Heerich, Katharina Elisabeth; Margesin, Erika; Hartmann, Sonja; Sewing, Andreas; Meyer, Christof; Wenisch, Sabine; Schnettler, Reinhard

    2009-01-01

    This is the first work to report on additional Arginin-Glycin-Aspartat (RGD) coating on precoated hydroxyapatite (HA) surfaces regarding new bone formation, implant bone contact, and biocompatibility compared to pure HA coating and uncoated stainless K-wires. There were 39 rabbits in total with 6 animals for the RGD-HA and HA group for the 4 week time period and 9 animals for each of the 3 implant groups for the 12 week observation. A 2.0 K-wire either with RGD-HA or with pure HA coating or uncoated was placed into the intramedullary canal of the tibia. After 4 and 12 weeks, the tibiae were harvested and three different areas of the tibia were assessed for quantitative and qualitative histology for new bone formation, direct implant bone contact, and formation of multinucleated giant cells. Both RGD-HA and pure HA coating showed statistically higher new bone formation and implant bone contact after 12 weeks than the uncoated K-wire. There were no significant differences between the RGD-HA and the pure HA coating in new bone formation and direct implant bone contact after 4 and 12 weeks. The number of multinucleated giant did not differ significantly between the RGD-HA and HA group after both time points. Overall, no significant effects of an additional RGD coating on HA surfaces were detected in this model after 12 weeks.

  7. Noninvasive monitoring of early antiangiogenic therapy response in human nasopharyngeal carcinoma xenograft model using MRI with RGD-conjugated ultrasmall superparamagnetic iron oxide nanoparticles

    PubMed Central

    Cui, Yanfen; Zhang, Caiyuan; Luo, Ran; Liu, Huanhuan; Zhang, Zhongyang; Xu, Tianyong; Zhang, Yong; Wang, Dengbin

    2016-01-01

    Purpose Arginine-glycine-aspartic acid (RGD)-based nanoprobes allow specific imaging of integrin αvβ3, a protein overexpressed during angiogenesis. Therefore, this study applied a novel RGD-coupled, polyacrylic acid (PAA)-coated ultrasmall superparamagnetic iron oxide (USPIO) (referred to as RGD-PAA-USPIO) in order to detect tumor angiogenesis and assess the early response to antiangiogenic treatment in human nasopharyngeal carcinoma (NPC) xenograft model by magnetic resonance imaging (MRI). Materials and methods The binding specificity of RGD-PAA-USPIO with human umbilical vein endothelial cells (HUVECs) was confirmed by Prussian blue staining and transmission electron microscopy in vitro. The tumor targeting of RGD-PAA-USPIO was evaluated in the NPC xenograft model. Later, mice bearing NPC underwent MRI at baseline and after 4 and 14 days of consecutive treatment with Endostar or phosphate-buffered saline (n=10 per group). Results The specific uptake of the RGD-PAA-USPIO nanoparticles was mainly dependent on the interaction between RGD and integrin αvβ3 of HUVECs. The tumor targeting of RGD-PAA-USPIO was observed in the NPC xenograft model. Moreover, the T2 relaxation time of mice in the Endostar-treated group decreased significantly compared with those in the control group both on days 4 and 14, consistent with the immunofluorescence results of CD31 and CD61 (P<0.05). Conclusion This study demonstrated that the magnetic resonance molecular nanoprobes, RGD-PAA-USPIOs, allow noninvasive in vivo imaging of tumor angiogenesis and assessment of the early response to antiangiogenic treatment in NPC xenograft model, favoring its potential clinical translation. PMID:27895477

  8. Inhibitory Effects of PEI-RGD/125I-(αV) ASODN on Growth and Invasion of HepG2 Cells

    PubMed Central

    Cai, Haidong; Qiao, Yu; Sun, Ming; Yuan, Xueyu; Luo, Qiong; Yang, Yuehua; Yuan, Shidong; Lv, Zhongwei

    2015-01-01

    Background To investigate the in vitro inhibitory effects of PEI-RGD/125I-(αV)ASODN (PEI, polyethylenimine; RGD, Arg-Gly-Asp; ASODN, antisense oligodeoxynucleotide) on the growth and invasion of HepG2 cells. Material/Methods ASODN of the integrin αV-subunit was marked with 125I and underwent complexation with PEI-RGD, a PEI derivative. Next, PEI-RGD/125I-(αV) ASODN was introduced into HepG2 cells via receptor-mediated transfection, and its inhibition rate on HepG2 cell growth was tested using the methyl thiazolyl tetrazolium (MTT) method. The effects of PEI-RGD/125I-(αV) ASODN on HepG2 cell invasion ability were evaluated using the Boyden chamber assay. Results 1) The 125I marking rate of (αV) ASODN was 73.78±4.09%, and the radiochemical purity was 96.68±1.38% (greater than 90% even after a 48-h incubation period at 37°C), indicating high stability. 2) The cytotoxicity assays showed that the cell inhibition rates did not differ significantly between the PEI-RGD/125I-(αV)ASODN group and the PEI-RGD/(αV) ASODN group, but they were both significantly higher than in the other groups and were positively correlated (r=0.879) with the dosage within a certain range. 3) The invasion assays showed that the inhibition rate was significantly greater in the PEI-RGD/125I-(αV) ASODN group compared to the other groups. Conclusions PEI-RGD/125I-(αV) ASODN can efficiently inhibit the growth and proliferation of HepG2 cells and can also weaken their invasive ability. PMID:26258995

  9. Development of a strategy to functionalize a dextrin-based hydrogel for animal cell cultures using a starch-binding module fused to RGD sequence

    PubMed Central

    Moreira, Susana M; Andrade, Fábia K; Domingues, Lucíla; Gama, Miguel

    2008-01-01

    Background Several approaches can be used to functionalize biomaterials, such as hydrogels, for biomedical applications. One of the molecules often used to improve cells adhesion is the peptide Arg-Gly-Asp (RGD). The RGD sequence, present in several proteins from the extra-cellular matrix (ECM), is a ligand for integrin-mediated cell adhesion; this sequence was recognized as a major functional group responsible for cellular adhesion. In this work a bi-functional recombinant protein, containing a starch binding module (SBM) and RGD sequence was used to functionalize a dextrin-based hydrogel. The SBM, which belongs to an α-amylase from Bacillus sp. TS-23, has starch (and dextrin, depolymerized starch) affinity, acting as a binding molecule to adsorb the RGD sequence to the hydrogel surface. Results The recombinant proteins SBM and RGD-SBM were cloned, expressed, purified and tested in in vitro assays. The evaluation of cell attachment, spreading and proliferation on the dextrin-based hydrogel surface activated with recombinant proteins were performed using mouse embryo fibroblasts 3T3. A polystyrene cell culture plate was used as control. The results showed that the RGD-SBM recombinant protein improved, by more than 30%, the adhesion of fibroblasts to dextrin-based hydrogel. In fact, cell spreading on the hydrogel surface was observed only in the presence of the RGD-SBM. Conclusion The fusion protein RGD-SBM provides an efficient way to functionalize the dextrin-based hydrogel. Many proteins in nature that hold a RGD sequence are not cell adhesive, probably due to the conformation/accessibility of the peptide. We therefore emphasise the successful expression of a bi-functional protein with potential for different applications. PMID:18854017

  10. cRGD-directed, NIR-responsive and robust AuNR/PEG-PCL hybrid nanoparticles for targeted chemotherapy of glioblastoma in vivo.

    PubMed

    Zhong, Yinan; Wang, Chao; Cheng, Ru; Cheng, Liang; Meng, Fenghua; Liu, Zhuang; Zhong, Zhiyuan

    2014-12-10

    cRGD-directed, NIR-responsive and robust AuNR/PEG-PCL hybrid nanoparticles (cRGD-HNs) were designed and developed for targeted chemotherapy of human glioma xenografts in mice. As expected, cRGD-HNs had excellent colloidal stability. The in vitro release studies showed that drug release from DOX-loaded cRGD-HNs (cRGD-HN-DOX) was minimal under physiological conditions but markedly accelerated upon NIR irradiation at a low power density of 0.2 W/cm2, due to photothermally induced phase transition of PCL regime. MTT assays showed that the antitumor activity of cRGD-HN-DOX in αvβ3 integrin over-expressed human glioblastoma U87MG cells was greatly boosted by mild NIR irradiation, which was significantly more potent than non-targeting HN-DOX counterpart under otherwise the same conditions and was comparable or superior to free DOX, supporting receptor-mediated endocytosis mechanism. The in vivo pharmacokinetics studies showed that cRGD-HN-DOX had much longer circulation time than free DOX. The in vivo imaging and biodistribution studies revealed that cRGD-HN-DOX could actively target human U87MG glioma xenograft in nude mice. The therapeutic studies in human U87MG glioma xenografts exhibited that cRGD-HN-DOX in combination with NIR irradiation completely inhibited tumor growth and possessed much lower side effects than free DOX. The Kaplan-Meier survival curves showed that all mice treated with cRGD-HN-DOX plus NIR irradiation survived over an experimental period of 48 days while control groups treated with PBS, cRGD-HN-DOX, cRGD-HNs with NIR irradiation, free DOX, or HN-DOX with NIR irradiation (non-targeting control) had short life spans of 15-40 days. Ligand-directed AuNR/PEG-PCL hybrid nanoparticles with evident tumor-targetability as well as superior spatiotemporal and rate control over drug release have emerged as an appealing platform for cancer chemotherapy in vivo.

  11. D-Dimer elevation and adverse outcomes.

    PubMed

    Halaby, Rim; Popma, Christopher J; Cohen, Ander; Chi, Gerald; Zacarkim, Marcelo Rodrigues; Romero, Gonzalo; Goldhaber, Samuel Z; Hull, Russell; Hernandez, Adrian; Mentz, Robert; Harrington, Robert; Lip, Gregory; Peacock, Frank; Welker, James; Martin-Loeches, Ignacio; Daaboul, Yazan; Korjian, Serge; Gibson, C Michael

    2015-01-01

    D-Dimer is a biomarker of fibrin formation and degradation. While a D-dimer within normal limits is used to rule out the diagnosis of deep venous thrombosis and pulmonary embolism among patients with a low clinical probability of venous thromboembolism (VTE), the prognostic association of an elevated D-dimer with adverse outcomes has received far less emphasis. An elevated D-dimer is independently associated with an increased risk for incident VTE, recurrent VTE, and mortality. An elevated D-dimer is an independent correlate of increased mortality and subsequent VTE across a broad variety of disease states. Therefore, medically ill subjects in whom the D-dimer is elevated constitute a high risk subgroup in which the prospective evaluation of the efficacy and safety of antithrombotic therapy is warranted.

  12. Solitary waves in dimer binary collision model

    NASA Astrophysics Data System (ADS)

    Ahsan, Zaid; Jayaprakash, K. R.

    2017-01-01

    Solitary wave propagation in nonlinear diatomic (dimer) chains is a very interesting topic of research in the study of nonlinear lattices. Such waves were recently found to be supported by the essentially nonlinear granular lattice and Toda lattice. An interesting aspect of this discovery is attributed to the realization of a spectrum of the mass ratio (the only system parameter governing the dynamics) that supports the propagation of such waves corresponding to the considered interaction potential. The objective of this exposition is to explore solitary wave propagation in the dimer binary collision (BC) model. Interestingly, the dimer BC model supports solitary wave propagation at a discrete spectrum of mass ratios similar to those observed in granular and Toda dimers. Further, we report a qualitative and one-to-one correspondence between the spectrum of the mass ratio corresponding to the dimer BC model and those corresponding to granular and Toda dimer chains.

  13. Dimerization of Human Growth Hormone by Zinc

    NASA Astrophysics Data System (ADS)

    Cunningham, Brian C.; Mulkerrin, Michael G.; Wells, James A.

    1991-08-01

    Size-exclusion chromatography and sedimentation equilibrium studies demonstrated that zinc ion (Zn2+) induced the dimerization of human growth hormone (hGH). Scatchard analysis of 65Zn2+ binding to hGH showed that two Zn2+ ions associate per dimer of hGH in a cooperative fashion. Cobalt (II) can substitute for Zn2+ in the hormone dimer and gives a visible spectrum characteristic of cobalt coordinated in a tetrahedral fashion by oxygen- and nitrogen-containing ligands. Replacement of potential Zn2+ ligands (His18, His21, and Glu174) in hGH with alanine weakened both Zn2+ binding and hGH dimer formation. The Zn2+-hGH dimer was more stable than monomeric hGH to denaturation in guanidine-HCl. Formation of a Zn2+-hGH dimeric complex may be important for storage of hGH in secretory granules.

  14. MS-Monitored Conjugation of Poly(ethylene glycol) Monomethacrylate to RGD Peptides

    PubMed Central

    Bol’shakov, Oleg I.; Akala, Emmanuel O.

    2014-01-01

    Development of biologically active polymers is an active area of research due to their applications in varied and diverse fields of biomedical research: cell adhesion, tissue proliferation, and drug delivery. Recent advances in chemical modification allow fine-tuning of the properties of biomedical polymers to improve their applications: blood circulation half-life, stimuli-responsive degradation, site-specific targeting, drug loading, etc. In this article, convergent synthesis of polymerizable macromonomers bearing a site-specific ligand (RGD peptide) using a low molecular weight MA-poly(ethylene glycols) (PEGs) is presented. The method affords macromonomers useful as the starting materials to produce biomedical polymers. We found matrix assisted laser desorption/ionization mass spectromerty convenient in monitoring the conjugation process via step-by-step following of PEG modification. PMID:24976670

  15. Monomer-dimer problem on some networks

    NASA Astrophysics Data System (ADS)

    Wu, Ruijuan; Yan, Weigen

    2016-09-01

    Zhang et al. (2012) obtained the exact formula for the number of all possible monomer-dimer arrangements and the asymptotic growth constant on a scale-free small-world network. In this note, we generalize this result and obtain the exact solution on the monomer-dimer model on many networks. Particularly, we prove that these networks have the same asymptotic growth constant of the number of monomer-dimer arrangements.

  16. Thermalization of a dimerized antiferromagnetic spin chain.

    PubMed

    Konstantinidis, N P

    2016-01-20

    Thermalization is investigated for the one-dimensional anisotropic antiferromagnetic Heisenberg model with dimerized nearest-neighbor interactions that break integrability. For this purpose the time evolution of local operator expectation values after an interacting quench is calculated directly with the Chebyshev polynomial expansion, and the deviation of the diagonal from the canonical thermal ensemble value is calculated for increasing system size for these operators. The spatial and spin symmetries of the Hamiltonian are taken into account to divide it into symmetry subsectors. The rate of thermalization is found to weaken with the dimerization parameter as the Hamiltonian evolves between two integrable limits, the non-dimerized and the fully dimerized where the chain breaks up into isolated dimers. This conclusion is supported by the distribution of the local operator off-diagonal elements between the eigenstates of the Hamiltonian with respect to their energy difference, which determines the strength of temporal fluctuations. The off-diagonal elements have a low-energy peak for small dimerization which facilitates thermalization, and originates in the reduction of spatial symmetry with respect to the non-dimerized limit. For increasing dimerization their distribution changes and develops a single low-energy maximum that relates to the fully dimerized limit and slows down thermalization.

  17. Tumor-penetration and antitumor efficacy of cetuximab are enhanced by co-administered iRGD in a murine model of human NSCLC

    PubMed Central

    Zhang, Yang; Yang, Jie; Ding, Manhua; Li, Liantao; Lu, Zheng; Zhang, Qing; Zheng, Junnian

    2016-01-01

    Lung cancer is the leading cause of cancer-associated mortality, worldwide. For this reason, novel therapies are required for the treatment of this devastating disease. Cetuximab is a monoclonal antibody against epidermal growth factor receptor (EGFR), which is overexpressed in a variety of solid tumors, including non-small cell lung cancer (NSCLC). The therapeutic efficacy of cetuximab for NSCLC is limited to use as a monotherapy or in combination with chemotherapy. The objective of the present study was to develop a novel strategy to enhance the therapeutic efficacy of cetuximab for NSCLC by a co-administration with the tumor-penetrating internalizing RGD peptide (iRGD). Human NSCLC subcutaneous xenograft models established with the A549 cell line in nude mice were treated with 30 mg/kg cetuximab, 4 mg/kg iRGD, cetuximab plus iRGD or phosphate-buffered saline. The tumor-penetration, in vivo therapeutic efficacy and involved mechanism were evaluated. The present study showed that the A549 xenograft model is sensitive to the co-administration of cetuximab and iRGD. Treatment with cetuximab plus iRGD resulted in a significant increase in the tumor-penetration of cetuximab and tumor reduction compared with cetuximab monotherapy. In conclusion, iRGD enhances the effects of co-administered cetuximab in an NSCLC model. The combined application of cetuximab and iRGD may be a novel strategy to enhance the clinical therapeutic efficacy of cetuximab for the treatment of NSCLC. PMID:27899989

  18. Targeted systemic delivery of siRNA to cervical cancer model using cyclic RGD-installed unimer polyion complex-assembled gold nanoparticles.

    PubMed

    Yi, Yu; Kim, Hyun Jin; Mi, Peng; Zheng, Meng; Takemoto, Hiroyasu; Toh, Kazuko; Kim, Beob Soo; Hayashi, Kotaro; Naito, Mitsuru; Matsumoto, Yu; Miyata, Kanjiro; Kataoka, Kazunori

    2016-12-28

    For systemic delivery of small interfering RNA (siRNA) to solid tumors, we developed an actively-targeted unimer polyion complex-assembled gold nanoparticle (uPIC-AuNP) by a two-step assembling process. First is the monodispersed uPIC formation from the single molecules of therapeutic siRNA and the block catiomer, cyclic RGD (cRGD) peptide-installed poly(ethylene glycol)-block-poly(l-lysine) modified with lipoic acid (LA) at the ω-end (cRGD-PEG-PLL-LA). Second is the surface decoration of a 20nm-sized AuNP with uPICs. The cRGD-installed uPIC-AuNPs (cRGD-uPIC-AuNP) provided the targetability for selective binding to the cancer and cancer-related endothelial cellular surface, while regulating their size <50nm with a quite narrow distribution. The targeting efficacy of the cRGD-uPIC-AuNP was confirmed by in vitro cellular uptake in cultured cervical cancer (HeLa) cells and in vivo tumor accumulation in a subcutaneous HeLa model after systemic administration, compared with a non-targeted control uPIC-AuNP. Due to the targetability of the ligand, the cRGD-uPIC-AuNP achieved the significantly enhanced gene silencing ability in the subcutaneous HeLa tumor. Ultimately, the systemic delivery of siRNA targeted for papilloma virus-derived E6 oncogene by cRGD-uPIC-AuNP significantly inhibited the growth of subcutaneous HeLa tumor. This research demonstrates that the bottom-up construction of nanocarriers using monodispersed building blocks can be employed as delivery platforms for RNA interference-based cancer therapy.

  19. Intestinal anti-inflammatory effects of RGD-functionalized silk fibroin nanoparticles in trinitrobenzenesulfonic acid-induced experimental colitis in rats

    PubMed Central

    Rodriguez-Nogales, Alba; Algieri, Francesca; De Matteis, Laura; Lozano-Perez, A. Abel; Garrido-Mesa, Jose; Vezza, Teresa; de la Fuente, J M.; Cenis, Jose Luis; Gálvez, Julio; Rodriguez-Cabezas, Maria Elena

    2016-01-01

    Background Current treatment of inflammatory bowel disease is based on the use of immunosuppressants or anti-inflammatory drugs, which are characterized by important side effects that can limit their use. Previous research has been performed by administering these drugs as nanoparticles that target the ulcerated intestinal regions and increase their bioavailability. It has been reported that silk fibroin can act as a drug carrier and shows anti-inflammatory properties. Purpose This study was designed to enhance the interaction of the silk fibroin nanoparticles (SFNs) with the injured intestinal tissue by functionalizing them with the peptide motif RGD (arginine–glycine–aspartic acid) and to evaluate the intestinal anti-inflammatory properties of these RGD-functionalized silk fibroin nanoparticles (RGD-SFNs) in the trinitrobenzenesulfonic acid (TNBS) model of rat colitis. Materials and methods SFNs were prepared by nanoprecipitation in methanol, and the linear RGD peptide was linked to SFNs using glutaraldehyde as the crosslinker. The SFNs (1 mg/rat) and RGD-SFNs (1 mg/rat) were administered intrarectally to TNBS-induced colitic rats for 7 days. Results The SFN treatments ameliorated the colonic damage, reduced neutrophil infiltration, and improved the compromised oxidative status of the colon. However, only the rats treated with RGD-SFNs showed a significant reduction in the expression of different pro-inflammatory cytokines (interleukin [IL]-1β, IL-6, and IL-12) and inducible nitric oxide synthase in comparison with the TNBS control group. Moreover, the expression of both cytokine-induced neutrophil chemoattractant-1 and monocyte chemotactic protein-1 was significantly diminished by the RGD-SFN treatment. However, both treatments improved the intestinal wall integrity by increasing the gene expression of some of its markers (trefoil factor-3 and mucins). Conclusion SFNs displayed intestinal anti-inflammatory properties in the TNBS model of colitis in rats

  20. A Novel Strategy to Improve the Therapeutic Efficacy of Gemcitabine for Non-Small Cell Lung Cancer by the Tumor-Penetrating Peptide iRGD

    PubMed Central

    Li, Ke; Wang, Haiyu; Li, Huizhong; Zheng, Junnian

    2015-01-01

    Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, comprising approximately 75–80% of all lung cancers. Gemcitabine is an approved chemotherapy drug for NSCLC. The objective of this study was to develop a novel strategy to improve the therapeutic efficacy of Gemcitabine for NSCLC by the co-administered iRGD peptide. We showed that the rates of positive expression of αvβ3, αvβ5 and NRP-1 in the A549 cell line were 68.5%, 35.3% and 94.5%, respectively. The amount of Evans Blue accumulated in the tumor of Evans Blue+iRGD group was 2.5 times that of Evans Blue group. The rates of growth inhibition of the tumors of the iRGD group, the Gemcitabine group and the Gemcitabine+iRGD group were 8%, 59.8% and 86.9%, respectively. The results of mechanism studies showed that PCNA expression in the Gemcitabine+iRGD group decreased 71.5% compared with that in Gemcitabine group. The rate of apoptosis in the Gemcitabine+iRGD group was 2.2 time that of the Gemcitabine group. Therefore, the tumor-penetrating Peptide iRGD can enhance the tumor-penetrating ability and therapeutic efficacy of Gemcitabine in the A549 xenograft. The combined application of Gemcitabine with iRGD may be a novel strategy to enhance the clinical therapeutic efficacy of Gemcitabine in patients with NSCLC. PMID:26066322

  1. [68Ga]FSC-(RGD)3 a trimeric RGD peptide for imaging αvβ3 integrin expression based on a novel siderophore derived chelating scaffold—synthesis and evaluation

    PubMed Central

    Knetsch, Peter A.; Zhai, Chuangyan; Rangger, Christine; Blatzer, Michael; Haas, Hubertus; Kaeopookum, Piriya; Haubner, Roland; Decristoforo, Clemens

    2015-01-01

    Over the last years Gallium-68 (68Ga) has received tremendous attention for labeling of radiopharmaceuticals for positron emission tomography (PET). 68Ga labeling of biomolecules is currently based on bifunctional chelators containing aminocarboxylates (mainly DOTA and NOTA). We have recently shown that cyclic peptide siderophores have very good complexing properties for 68Ga resulting in high specific activities and excellent metabolic stabilities, in particular triacetylfusarinine-C (TAFC). We postulated, that, starting from its deacetylated form (Fusarinine-C (FSC)) trimeric bioconjugates are directly accessible to develop novel targeting peptide based 68Ga labeled radiopharmaceuticals. As proof of principle we report on the synthesis and 68Ga-radiolabeling of a trimeric FSC-RGD conjugate, [68Ga]FSC-(RGD)3, targeting αvβ3 integrin, which is highly expressed during tumor-induced angiogenesis. Synthesis of the RGD peptide was carried out applying solid phase peptide synthesis (SPPS), followed by the coupling to the siderophore [Fe]FSC via in situ activation using HATU/HOAt and DIPEA. Subsequent demetalation allowed radiolabeling of FSC-(RGD)3 with 68Ga. The radiolabeling procedure was optimized regarding peptide amount, reaction time, temperature as well buffer systems. For in vitro evaluation partition coefficient, protein binding, serum stability, αvβ3 integrin binding affinity, and tumor cell uptake were determined. For in vitro tests as well as for the biodistribution studies αvβ3 positive human melanoma M21 and αvβ3 negative M21-L cells were used. [68Ga]FSC-(RGD)3 was prepared with high radiochemical yield (> 98%). Distribution coefficient was − 3.6 revealing a hydrophilic character, and an IC50 value of 1.8 ± 0.6 nM was determined indicating a high binding affinity for αvβ3 integrin. [68Ga]FSC-(RGD)3 was stable in PBS (pH 7.4), FeCl3- and DTPA-solution as well as in fresh human serum at 37 °C for 2 hours. Biodistribution assay confirmed

  2. [(68)Ga]FSC-(RGD)3 a trimeric RGD peptide for imaging αvβ3 integrin expression based on a novel siderophore derived chelating scaffold-synthesis and evaluation.

    PubMed

    Knetsch, Peter A; Zhai, Chuangyan; Rangger, Christine; Blatzer, Michael; Haas, Hubertus; Kaeopookum, Piriya; Haubner, Roland; Decristoforo, Clemens

    2015-02-01

    Over the last years Gallium-68 ((68)Ga) has received tremendous attention for labeling of radiopharmaceuticals for positron emission tomography (PET). (68)Ga labeling of biomolecules is currently based on bifunctional chelators containing aminocarboxylates (mainly DOTA and NOTA). We have recently shown that cyclic peptide siderophores have very good complexing properties for (68)Ga resulting in high specific activities and excellent metabolic stabilities, in particular triacetylfusarinine-C (TAFC). We postulated, that, starting from its deacetylated form (Fusarinine-C (FSC)) trimeric bioconjugates are directly accessible to develop novel targeting peptide based (68)Ga labeled radiopharmaceuticals. As proof of principle we report on the synthesis and (68)Ga-radiolabeling of a trimeric FSC-RGD conjugate, [(68)Ga]FSC-(RGD)3, targeting αvβ3 integrin, which is highly expressed during tumor-induced angiogenesis. Synthesis of the RGD peptide was carried out applying solid phase peptide synthesis (SPPS), followed by the coupling to the siderophore [Fe]FSC via in situ activation using HATU/HOAt and DIPEA. Subsequent demetalation allowed radiolabeling of FSC-(RGD)3 with (68)Ga. The radiolabeling procedure was optimized regarding peptide amount, reaction time, temperature as well buffer systems. For in vitro evaluation partition coefficient, protein binding, serum stability, αvβ3 integrin binding affinity, and tumor cell uptake were determined. For in vitro tests as well as for the biodistribution studies αvβ3 positive human melanoma M21 and αvβ3 negative M21-L cells were used. [(68)Ga]FSC-(RGD)3 was prepared with high radiochemical yield (>98%). Distribution coefficient was -3.6 revealing a hydrophilic character, and an IC50 value of 1.8±0.6 nM was determined indicating a high binding affinity for αvβ3 integrin. [(68)Ga]FSC-(RGD)3 was stable in PBS (pH7.4), FeCl3- and DTPA-solution as well as in fresh human serum at 37°C for 2hours. Biodistribution assay

  3. Recombinant expression of mutants of the Frankenstein disintegrin, RTS-ocellatusin. Evidence for the independent origin of RGD and KTS/RTS disintegrins.

    PubMed

    Sanz-Soler, Raquel; Lorente, Carolina; Company, Beatriz; Sanz, Libia; Juárez, Paula; Pérez, Alicia; Zhang, Yun; Jin, Yang; Chen, Runqiang; Eble, Johannes A; Calvete, Juan J; Bolás, Gema

    2012-09-15

    The requirements to transform a short disintegrin of the RGD clade into an RTS disintegrin, were investigated through the generation of recombinant mutants of ocellatusin in which the RGD tripeptide was substituted for RTS in different positions along the integrin-specificity loop. Any attempt to create an active integrin α(1)β(1) inhibitory motif within the specificity loop of ocellatusin was unsuccessful. Replacing the whole RGD-loop of ocellatusin by the RTS-loop of jerdostatin was neither sufficient for confering α(1)β(1) binding specificity to this ocellatusin-RTS Frankenstein(2) mutant. Factors other than the integrin-binding loop sequence per se are thus required to transform a disintegrin scaffold from the RGD clade into another scaffold from the RTS/KTS clade. Moreover, our results provide evidences, that the RTS/KTS short disintegrins have potentially been recruited into the venom gland of Eurasian vipers independently from the canonical neofunctionalization pathway of the RGD disintegrins. PCR-amplifications of jerdostatin-like sequences from a number of taxa across reptiles, including snakes (Crotalinae, Viperinae, and Elapidae taxa) and lizards (Lacertidae and Iguanidae) clearly showed that genes coding for RTS/KTS disintegrins existed long before the split of Lacertidae and Iguania, thus predating the recruitment of the SVMP precursors of disintegrins, providing strong support for the view of an independent evolutionary history of the RTS/KTS and the RGD clades of short disintegrins.

  4. RGD-conjugated silica-coated gold nanorods on the surface of carbon nanotubes for targeted photoacoustic imaging of gastric cancer

    NASA Astrophysics Data System (ADS)

    Wang, Can; Bao, Chenchen; Liang, Shujing; Fu, Hualin; Wang, Kan; Deng, Min; Liao, Qiande; Cui, Daxiang

    2014-05-01

    Herein, we reported for the first time that RGD-conjugated silica-coated gold nanorods on the surface of multiwalled carbon nanotubes were successfully used for targeted photoacoustic imaging of in vivo gastric cancer cells. A simple strategy was used to attach covalently silica-coated gold nanorods (sGNRs) onto the surface of multiwalled carbon nanotubes (MWNTs) to fabricate a hybrid nanostructure. The cross-linked reaction occurred through the combination of carboxyl groups on the MWNTs and the amino group on the surface of sGNRs modified with a silane coupling agent. RGD peptides were conjugated with the sGNR/MWNT nanostructure; resultant RGD-conjugated sGNR/MWNT probes were investigated for their influences on viability of MGC803 and GES-1 cells. The nude mice models loaded with gastric cancer cells were prepared, the RGD-conjugated sGNR/MWNT probes were injected into gastric cancer-bearing nude mice models via the tail vein, and the nude mice were observed by an optoacoustic imaging system. Results showed that RGD-conjugated sGNR/MWNT probes showed good water solubility and low cellular toxicity, could target in vivo gastric cancer cells, and obtained strong photoacoustic imaging in the nude model. RGD-conjugated sGNR/MWNT probes will own great potential in applications such as targeted photoacoustic imaging and photothermal therapy in the near future.

  5. Interpenetrating polymer networks containing gelatin modified with PEGylated RGD and soluble KGF: synthesis, characterization, and application in in vivo critical dermal wound.

    PubMed

    Waldeck, Heather; Chung, Amy S; Kao, Weiyuan John

    2007-09-15

    The purpose of this study was to evaluate the biocompatibility and the efficacy in wound healing of a gelatin-based interpenetrating polymer network (IPN) containing poly(ethylene glycol) (PEG)-ylated RGD and soluble KGF-1 (RGD-IPN+KGF). IPNs were applied to full-thickness wounds on a rat model. Wound healing was assessed through histological grading of the host response and percent area contraction at 2 days, 1 week, 2 weeks, and 3 weeks. A control IPN containing unmodified gelatin (unmod-IPN) and a conventional clinical bandage were applied to similar wounds and also evaluated. During the first week of healing, the unmod-IPN and conventional dressing wound showed a greater amount of contraction than that of RGD-IPN+KGF. However, by 3 weeks the extent of wound contraction was comparable between treatments. The RGD-IPN+KGF treated wound demonstrated lower macrophage and fibroblast densities at 3 weeks as compared to unmod-IPN treated wounds. RGD-IPN+KGF acted as a tissue scaffold while preventing the entry of foreign bodies, advantages not seen with the conventional dressing. The extent of cellularity and extracellular matrix organization was higher for wounds healed with RGD-IPN+KGF than those healed with unmod-IPN. These results indicate that both soluble and immobilized bioactive factors can be incorporated into our IPN platform to enhance the rate and the quality of dermal wound healing.

  6. RGD-conjugated silica-coated gold nanorods on the surface of carbon nanotubes for targeted photoacoustic imaging of gastric cancer.

    PubMed

    Wang, Can; Bao, Chenchen; Liang, Shujing; Fu, Hualin; Wang, Kan; Deng, Min; Liao, Qiande; Cui, Daxiang

    2014-01-01

    Herein, we reported for the first time that RGD-conjugated silica-coated gold nanorods on the surface of multiwalled carbon nanotubes were successfully used for targeted photoacoustic imaging of in vivo gastric cancer cells. A simple strategy was used to attach covalently silica-coated gold nanorods (sGNRs) onto the surface of multiwalled carbon nanotubes (MWNTs) to fabricate a hybrid nanostructure. The cross-linked reaction occurred through the combination of carboxyl groups on the MWNTs and the amino group on the surface of sGNRs modified with a silane coupling agent. RGD peptides were conjugated with the sGNR/MWNT nanostructure; resultant RGD-conjugated sGNR/MWNT probes were investigated for their influences on viability of MGC803 and GES-1 cells. The nude mice models loaded with gastric cancer cells were prepared, the RGD-conjugated sGNR/MWNT probes were injected into gastric cancer-bearing nude mice models via the tail vein, and the nude mice were observed by an optoacoustic imaging system. Results showed that RGD-conjugated sGNR/MWNT probes showed good water solubility and low cellular toxicity, could target in vivo gastric cancer cells, and obtained strong photoacoustic imaging in the nude model. RGD-conjugated sGNR/MWNT probes will own great potential in applications such as targeted photoacoustic imaging and photothermal therapy in the near future.

  7. Cyclic RGD peptide-modified liposomal drug delivery system for targeted oral apatinib administration: enhanced cellular uptake and improved therapeutic effects

    PubMed Central

    Song, Zhiwang; Lin, Yun; Zhang, Xia; Feng, Chan; Lu, Yonglin; Gao, Yong; Dong, Chunyan

    2017-01-01

    Apatinib is an oral tyrosine kinase inhibitor, which selectively targets vascular endothelial growth factor receptor 2 and has the potential to treat many tumors therapeutically. Cyclic arginylglycylaspartic acid (cRGD)- and polyethylene glycol (PEG)-modified liposomes (cRGD-Lipo-PEG) were constructed to act as a targeted delivery system for the delivery of apatinib to the human colonic cancer cell line, HCT116. These cRGD-modified liposomes specifically recognized integrin αvβ3 and exhibited greater uptake efficiency with respect to delivering liposomes into HCT116 cells when compared to nontargeted liposomes (Lipo-PEG), as well as greater death of tumor cells and apoptosis. The mechanism by which cRGD-Lipo-PEG targets cells was elucidated further with competition assays. To determine the anticancer efficacy in vivo, nude mice were implanted with HCT116 xenografts and treated with apatinib-loaded liposomes or free apatinib intravenously or via intragastric administration. The active and passive targeting of cRGD-Lipo-PEG led to significant tumor treatment targeting ability, better inhibition of tumor growth, and less toxicity when compared with treatments using uncombined apatinib. The results presented strongly support the case for cRGD-Lipo-PEG representing a targeted delivery system for apatinib in the treatment of colonic cancer. PMID:28331317

  8. Potassium Hexacyanoferrate (III)-Catalyzed Dimerization of Hydroxystilbene: Biomimetic Synthesis of Indane Stilbene Dimers.

    PubMed

    Xie, Jing-Shan; Wen, Jin; Wang, Xian-Fen; Zhang, Jian-Qiao; Zhang, Ji-Fa; Kang, Yu-Long; Hui, You-Wei; Zheng, Wen-Sheng; Yao, Chun-Suo

    2015-12-18

    Using potassium hexacyanoferrate (III)-sodium acetate as oxidant, the oxidative coupling reaction of isorhapontigenin and resveratrol in aqueous acetone resulted in the isolation of three new indane dimers 4, 6, and 7, together with six known stilbene dimers. Indane dimer 5 was obtained for the first time by direct transformation from isorhapontigenin. The structures and relative configurations of the dimers were elucidated using spectral analysis, and their possible formation mechanisms were discussed. The results indicate that this reaction could be used as a convenient method for the semi-synthesis of indane dimers because of the mild conditions and simple reaction products.

  9. Electronic transitions of palladium dimer

    SciTech Connect

    Qian, Yue; Ng, Y. W.; Chen, Zhihua; Cheung, A. S.-C.

    2013-11-21

    The laser induced fluorescence spectrum of palladium dimer (Pd{sub 2}) in the visible region between 480 and 700 nm has been observed and analyzed. The gas-phase Pd{sub 2} molecule was produced by laser ablation of palladium metal rod. Eleven vibrational bands were observed and assigned to the [17.1] {sup 3}II{sub g} - X{sup 3}Σ{sub u}{sup +} transition system. The bond length (r{sub o}) and vibrational frequency (ΔG{sub 1/2}) of the ground X{sup 3}Σ{sub u}{sup +} state were determined to be 2.47(4) Å and 211.4(5) cm{sup −1}, respectively. A molecular orbital energy level diagram was used to understand the observed ground and excited electronic states. This is the first gas-phase experimental investigation of the electronic transitions of Pd{sub 2}.

  10. Antitumor effect of iRGD-modified liposomes containing conjugated linoleic acid–paclitaxel (CLA-PTX) on B16-F10 melanoma

    PubMed Central

    Du, Ruo; Zhong, Ting; Zhang, Wei-Qiang; Song, Ping; Song, Wen-Ding; Zhao, Yang; Wang, Chao; Tang, Yi-Qun; Zhang, Xuan; Zhang, Qiang

    2014-01-01

    In the present study, we prepared a novel delivery system of iRGD (CRGDK/RGPD/EC)-modified sterically stabilized liposomes (SSLs) containing conjugated linoleic acid–paclitaxel (CLA-PTX). The anti-tumor effect of iRGD-SSL-CLA-PTX was investigated on B16-F10 melanoma in vitro and in vivo. The in vitro targeting effect of iRGD-modified SSLs was investigated in a real-time confocal microscopic analysis experiment. An endocytosis-inhibition assay was used to evaluate the endocytosis pathways of the iRGD-modified SSLs. In addition, the in vitro cellular uptake and in vitro cytotoxicity of iRGD-SSL-CLA-PTX were evaluated in B16-F10 melanoma cells. In vivo biodistribution and in vivo antitumor effects of iRGD-SSL-CLA-PTX were investigated in B16-F10 tumor-bearing mice. The induction of apoptosis by iRGD-SSL-CLA-PTX was evaluated in tumor-tissue sections. Real-time confocal microscopic analysis results indicated that the iRGD-modified SSLs internalized into B16-F10 cells faster than SSLs. The identified endocytosis pathway of iRGD-modified SSLs indicated that energy- and lipid raft-mediated endocytosis played a key role in the liposomes’ cellular uptake. The results of the cellular uptake experiment indicated that the increased cellular uptake of CLA-PTX in the iRGD-SSL-CLA-PTX-treated group was 1.9-, 2.4-, or 2.1-fold compared with that in the CLA-PTX group after a 2-, 4-, or 6-hour incubation, respectively. In the biodistribution test, the CLA-PTX level in tumor tissues from iRGD-SSL-CLA-PTX-treated mice at 1 hour (1.84±0.17 μg/g) and 4 hours (1.17±0.28 μg/g) was 2.3- and 2.0-fold higher than that of CLA-PTX solution at 1 hour (0.79±0.06 μg/g) and 4 hours (0.58±0.04 μg/g). The value of the area under the curve for the first 24 hours in the tumors of iRGD-SSL-CLA-PTX-treated mice was significantly higher than that in the SSL-CLA-PTX and CLA-PTX solution-treated groups (P<0.01). The in vivo antitumor results indicated that iRGD-SSL-CLA-PTX significantly

  11. Antitumor effect of iRGD-modified liposomes containing conjugated linoleic acid-paclitaxel (CLA-PTX) on B16-F10 melanoma.

    PubMed

    Du, Ruo; Zhong, Ting; Zhang, Wei-Qiang; Song, Ping; Song, Wen-Ding; Zhao, Yang; Wang, Chao; Tang, Yi-Qun; Zhang, Xuan; Zhang, Qiang

    2014-01-01

    In the present study, we prepared a novel delivery system of iRGD (CRGDK/RGPD/EC)-modified sterically stabilized liposomes (SSLs) containing conjugated linoleic acid-paclitaxel (CLA-PTX). The anti-tumor effect of iRGD-SSL-CLA-PTX was investigated on B16-F10 melanoma in vitro and in vivo. The in vitro targeting effect of iRGD-modified SSLs was investigated in a real-time confocal microscopic analysis experiment. An endocytosis-inhibition assay was used to evaluate the endocytosis pathways of the iRGD-modified SSLs. In addition, the in vitro cellular uptake and in vitro cytotoxicity of iRGD-SSL-CLA-PTX were evaluated in B16-F10 melanoma cells. In vivo biodistribution and in vivo antitumor effects of iRGD-SSL-CLA-PTX were investigated in B16-F10 tumor-bearing mice. The induction of apoptosis by iRGD-SSL-CLA-PTX was evaluated in tumor-tissue sections. Real-time confocal microscopic analysis results indicated that the iRGD-modified SSLs internalized into B16-F10 cells faster than SSLs. The identified endocytosis pathway of iRGD-modified SSLs indicated that energy- and lipid raft-mediated endocytosis played a key role in the liposomes' cellular uptake. The results of the cellular uptake experiment indicated that the increased cellular uptake of CLA-PTX in the iRGD-SSL-CLA-PTX-treated group was 1.9-, 2.4-, or 2.1-fold compared with that in the CLA-PTX group after a 2-, 4-, or 6-hour incubation, respectively. In the biodistribution test, the CLA-PTX level in tumor tissues from iRGD-SSL-CLA-PTX-treated mice at 1 hour (1.84±0.17 μg/g) and 4 hours (1.17±0.28 μg/g) was 2.3- and 2.0-fold higher than that of CLA-PTX solution at 1 hour (0.79±0.06 μg/g) and 4 hours (0.58±0.04 μg/g). The value of the area under the curve for the first 24 hours in the tumors of iRGD-SSL-CLA-PTX-treated mice was significantly higher than that in the SSL-CLA-PTX and CLA-PTX solution-treated groups (P<0.01). The in vivo antitumor results indicated that iRGD-SSL-CLA-PTX significantly inhibited

  12. Structural characterization of dimeric murine aminoacylase III.

    PubMed

    Ryazantsev, Sergey; Abuladze, Natalia; Newman, Debra; Bondar, Galyna; Kurtz, Ira; Pushkin, Alexander

    2007-05-01

    Aminoacylase III (AAIII) plays an important role in deacetylation of acetylated amino acids and N-acetylated S-cysteine conjugates of halogenated alkenes and alkanes. AAIII, recently cloned from mouse kidney and partially characterized, is a mixture of tetramers and dimers. In the present work, AAIII dimers were purified and shown to be enzymatically active. Limited trypsinolysis showed two domains of approximately 9 and 25 kDa. The three-dimensional structure of the dimer was studied by electron microscopy of negative stained samples and by single-particle reconstruction. A 16A resolution model of the AAIII dimer was created. It has an unusual, cage-like, structure. A realistic AAIII tetramer model was built from two dimers.

  13. Antiadhesive polymer brush coating functionalized with antimicrobial and RGD peptides to reduce biofilm formation and enhance tissue integration.

    PubMed

    Muszanska, Agnieszka K; Rochford, Edward T J; Gruszka, Agnieszka; Bastian, Andreas A; Busscher, Henk J; Norde, Willem; van der Mei, Henny C; Herrmann, Andreas

    2014-06-09

    This paper describes the synthesis and characterization of polymer-peptide conjugates to be used as infection-resistant coating for biomaterial implants and devices. Antiadhesive polymer brushes composed of block copolymer Pluronic F-127 (PF127) were functionalized with antimicrobial peptides (AMP), able to kill bacteria on contact, and arginine-glycine-aspartate (RGD) peptides to promote the adhesion and spreading of host tissue cells. The antiadhesive and antibacterial properties of the coating were investigated with three bacterial strains: Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. The ability of the coating to support mammalian cell growth was determined using human fibroblast cells. Coatings composed of the appropriate ratio of the functional components: PF127, PF127 modified with AMP, and PF127 modified with RGD showed good antiadhesive and bactericidal properties without hampering tissue compatibility.

  14. Accuracy of RGD approximation for computing light scattering properties of diffusing and motile bacteria. [Rayleigh-Gans-Debye

    NASA Technical Reports Server (NTRS)

    Kottarchyk, M.; Chen, S.-H.; Asano, S.

    1979-01-01

    The study tests the accuracy of the Rayleigh-Gans-Debye (RGD) approximation against a rigorous scattering theory calculation for a simplified model of E. coli (about 1 micron in size) - a solid spheroid. A general procedure is formulated whereby the scattered field amplitude correlation function, for both polarized and depolarized contributions, can be computed for a collection of particles. An explicit formula is presented for the scattered intensity, both polarized and depolarized, for a collection of randomly diffusing or moving particles. Two specific cases for the intermediate scattering functions are considered: diffusing particles and freely moving particles with a Maxwellian speed distribution. The formalism is applied to microorganisms suspended in a liquid medium. Sensitivity studies revealed that for values of the relative index of refraction greater than 1.03, RGD could be in serious error in computing the intensity as well as correlation functions.

  15. Universal four-Boson states in ultracold molecular gases: resonant effects in dimer-dimer collisions.

    PubMed

    D'Incao, J P; von Stecher, J; Greene, Chris H

    2009-07-17

    We study the manifestations of universal four-body physics in ultracold dimer-dimer collisions. We show that resonant features associated with three-body Efimov physics and dimer-dimer scattering lengths are universally related. The emergence of universal four-boson states allows for the tunability of the dimer-dimer interaction, thus enabling the future study of ultracold molecular gases with both attractive and repulsive interactions. Moreover, our study of the interconversion between dimers and Efimov trimers shows that B2+B2-->B3+B rearrangement reactions can provide an efficient trimer formation mechanism. Our analysis of the temperature dependence of this reaction provides an interpretation of the available experimental data and sheds light on the possible experimental realization of rearrangement processes in ultracold gases.

  16. Monocyte activation in response to polyethylene glycol hydrogels grafted with RGD and PHSRN separated by interpositional spacers of various lengths.

    PubMed

    Schmidt, David Richard; Kao, Weiyuan John

    2007-12-01

    Polyethylene glycol (PEG) is often cited as a "stealth" polymer, capable of resisting both protein adsorption and cell adhesion. By extension, PEG would then be expected to limit the host response. Monocyte-derived macrophages play an integral role in inflammation, and thus their response to a material can potentially dictate the overall host response to a biomaterial. In the present study, monocyte responses following interaction with a photopolymerized PEG hydrogel were compared with those from standard tissue culture polystyrene (TCPS). Additionally, the effect of the spacing between RGD and PHSRN, the corresponding synergy sequence on fibronectin (FN), was evaluated using peptides with differing spacer lengths grafted to the PEG hydrogel. Monocyte adherent density on the PEG-only hydrogel was comparable with that of TCPS; however, the secretion of the proinflammatory molecules interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and granulocyte-macrophage colony stimulating factor (GM-CSF) increased dramatically following monocyte interaction with PEG-only hydrogels as compared with TCPS. The matrix metalloproteinase-2 (MMP-2) concentration was similar for all surfaces, while both the matrix metalloproteinase-9 (MMP-9) and FN concentrations were above the range of the assay for all substrates. Cell density was higher on the PHSRNG(13)RGD grafted substrate as compared with PHSRNG(6)RGD, but neither sequence increased cell density versus RGD alone. Although protein concentration did sometimes vary with different peptides, this variation was minimal in comparison with the surface effects between TCPS and the PEG-only hydrogel. This study explores the roles of PEG and FN-derived peptides on monocyte activation.

  17. RGD peptide-modified dendrimer-entrapped gold nanoparticles enable highly efficient and specific gene delivery to stem cells.

    PubMed

    Kong, Lingdan; Alves, Carla S; Hou, Wenxiu; Qiu, Jieru; Möhwald, Helmuth; Tomás, Helena; Shi, Xiangyang

    2015-03-04

    We report the use of arginine-glycine-aspartic (Arg-Gly-Asp, RGD) peptide-modified dendrimer-entrapped gold nanoparticles (Au DENPs) for highly efficient and specific gene delivery to stem cells. In this study, generation 5 poly(amidoamine) dendrimers modified with RGD via a poly(ethylene glycol) (PEG) spacer and with PEG monomethyl ether were used as templates to entrap gold nanoparticles (AuNPs). The native and the RGD-modified PEGylated dendrimers and the respective well characterized Au DENPs were used as vectors to transfect human mesenchymal stem cells (hMSCs) with plasmid DNA (pDNA) carrying both the enhanced green fluorescent protein and the luciferase (pEGFPLuc) reporter genes, as well as pDNA encoding the human bone morphogenetic protein-2 (hBMP-2) gene. We show that all vectors are capable of transfecting the hMSCs with both pDNAs. Gene transfection using pEGFPLuc was demonstrated by quantitative Luc activity assay and qualitative evaluation by fluorescence microscopy. For the transfection with hBMP-2, the gene delivery efficiency was evaluated by monitoring the hBMP-2 concentration and the level of osteogenic differentiation of the hMSCs via alkaline phosphatase activity, osteocalcin secretion, calcium deposition, and von Kossa staining assays. Our results reveal that the stem cell gene delivery efficiency is largely dependent on the composition and the surface functionality of the dendrimer-based vectors. The coexistence of RGD and AuNPs rendered the designed dendrimeric vector with specific stem cell binding ability likely via binding of integrin receptor on the cell surface and improved three-dimensional conformation of dendrimers, which is beneficial for highly efficient and specific stem cell gene delivery applications.

  18. Tumor targeting with RGD peptide ligands-design of new molecular conjugates for imaging and therapy of cancers.

    PubMed

    Garanger, Elisabeth; Boturyn, Didier; Dumy, Pascal

    2007-09-01

    Development of molecular devices endowed with tumor-targeting functions and carrying cytotoxic components should enable the specific delivery of chemotherapeutics to malignant tissues, thus increasing their local efficacy while limiting their peripheral toxicity. Such molecular vectors can pave the way for the development of new classes of therapeutics, fighting against protagonists of neoplastic development. In line with this concept, peptide ligands containing the Arginine-Glycine-Aspartate (RGD) triad, which display a strong affinity and selectivity to the alpha(V)beta(3) integrin, have been developed to target the tumor-associated cells expressing the alpha (V)beta (3) receptors. Among the validated ligands, the leader compound is the cyclic pentapeptide c[-RGDf(NMe)V-] (Cilengitide) developed by kessler et al. (J. Med. Chem., 1999, 42, 3033-3040). This compound has entered phase II clinical trials as an anti-angiogenic agent. Further studies have been directed to develop molecular conjugates of the parent c[-RGDfK-] with conventional chemotherapeutics or with labels for non-invasive imaging technologies. More recently, multimeric RGD containing compounds have been exploited to improve the targeting potential as well as cell-membrane breaching, through receptor-mediated endocytosis. The latter have been constructed on various scaffolds (polylysines or polyglutamates, liposomes, nanoparticles...). Our group has developed a chemical system combining all these properties where multivalent RGD targeting functions are associated with functional molecules through a cyclopeptide template. The latter represents a relevant non-viral vector for tumor targeting, imaging and therapy. This review describes the considerations for the design of the diverse RGD ligands developed so far and reports an overview of the main applications of these structures in cancer research.

  19. Membrane-associated Ras dimers are isoform-specific: K-Ras dimers differ from H-Ras dimers.

    PubMed

    Jang, Hyunbum; Muratcioglu, Serena; Gursoy, Attila; Keskin, Ozlem; Nussinov, Ruth

    2016-06-15

    Are the dimer structures of active Ras isoforms similar? This question is significant since Ras can activate its effectors as a monomer; however, as a dimer, it promotes Raf's activation and MAPK (mitogen-activated protein kinase) cell signalling. In the present study, we model possible catalytic domain dimer interfaces of membrane-anchored GTP-bound K-Ras4B and H-Ras, and compare their conformations. The active helical dimers formed by the allosteric lobe are isoform-specific: K-Ras4B-GTP favours the α3 and α4 interface; H-Ras-GTP favours α4 and α5. Both isoforms also populate a stable β-sheet dimer interface formed by the effector lobe; a less stable β-sandwich interface is sustained by salt bridges of the β-sheet side chains. Raf's high-affinity β-sheet interaction is promoted by the active helical interface. Collectively, Ras isoforms' dimer conformations are not uniform; instead, the isoform-specific dimers reflect the favoured interactions of the HVRs (hypervariable regions) with cell membrane microdomains, biasing the effector-binding site orientations, thus isoform binding selectivity.

  20. Toward the development of a novel non-RGD cyclic peptide drug conjugate for treatment of human metastatic melanoma

    PubMed Central

    Redko, Boris; Tuchinsky, Helena; Segal, Tamar; Tobi, Dror; Luboshits, Galia; Ashur-Fabian, Osnat; Pinhasov, Albert; Gerlitz, Gabi; Gellerman, Gary

    2017-01-01

    The newly discovered short (9 amino acid) non-RGD S-S bridged cyclic peptide ALOS-4 (H-cycl(Cys-Ser-Ser-Ala-Gly-Ser-Leu-Phe-Cys)-OH), which binds to integrin αvβ3 is investigated as peptide carrier for targeted drug delivery against human metastatic melanoma. ALOS4 binds specifically the αvβ3 overexpressing human metastatic melanoma WM-266-4 cell line both in vitro and in ex vivo assays. Coupling ALOS4 to the topoisomerase I inhibitor Camptothecin (ALOS4-CPT) increases the cytotoxicity of CPT against human metastatic melanoma cells while reduces dramatically the cytotoxicity against non-cancerous cells as measured by the levels of γH2A.X, active caspase 3 and cell viability. Moreover, conjugating ALOS4 to CPT even increases the chemo-stability of CPT under physiological pH. Bioinformatic analysis using Rosetta platform revealed potential docking sites of ALOS4 on the αvβ3 integrin which are distinct from the RGD binding sites. We propose to use this specific non-RGD cyclic peptide as the therapeutic carrier for conjugation of drugs in order to improve efficacy and reduce toxicity of currently available treatments of human malignant melanoma. PMID:27768593

  1. Introducing RGD peptides on PHBV films through PEG-containing cross-linkers to improve the biocompatibility.

    PubMed

    Wang, Yan-Yan; Lü, Lan-Xin; Shi, Jun-Cai; Wang, Hai-Feng; Xiao, Zhong-Dang; Huang, Ning-Ping

    2011-03-14

    Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biodegradable polyester, has been a good candidate of biomaterial employed in tissue engineering. However, the PHBV film is hydrophobic and has no recognition sites for cell attachment. In this study, PHBV films are activated by ammonia plasma treatment to produce amino groups on the surface, followed by sequential reactions with a heterobifunctional cross-linker containing a segment of poly(ethylene glycol) (PEG) and further with RGD-containing peptides. XPS analyses of modified surfaces after each reaction step reveal that the RGD-containing peptides have been covalently grafted onto PHBV films. The result of cell viability assay indicates that the RGD-modified PHBV films exhibit a distinctly improved cellular compatibility. Moreover, according to the results of serum adsorption tests by optical waveguide lightmode spectroscopy (OWLS) and fibrinogen adsorption tests by enzyme-linked immunosorbent assay (ELISA) on unmodified and modified PHBV surfaces, the introduced PEG chains can significantly decrease the nonspecific adsorption of proteins from serum and fibrinogen from plasma, thus decreasing the risk of thrombus formation and improving the blood compatibility of implanted materials.

  2. Aqueous synthesized near-infrared-emitting quantum dots for RGD-based in vivo active tumour targeting

    NASA Astrophysics Data System (ADS)

    Lu, Yimei; Zhong, Yiling; Wang, Jie; Su, Yuanyuan; Peng, Fei; Zhou, Yanfeng; Jiang, Xiangxu; He, Yao

    2013-04-01

    Over the past two decades, fluorescent quantum dots (QDs) have been highly attractive for a myriad of bioapplications due to their unique optical properties. For bioimaging applications, QD-based in vivo specific tumour targeting is vitally important in the biological and biomedical fields. Aqueous synthesized QDs (aqQDs) exhibit excellent aqueous dispersibility without requiring any post-treatment and have small hydrodynamic diameters (generally <5 nm), which are highly useful for bioimaging applications. We herein present the first example of in vivo active tumour targeting using water-dispersed near-infrared-emitting aqQDs modified with Arg-Gly-Asp (RGD) peptides. In vitro and in vivo studies (e.g., tumour cell labelling, histological analysis, and active tumour targeting) demonstrate that the prepared RGD-decorated aqQDs exhibit highly bio-specific properties, enabling sensitive and specific targeting of tumour sites in both cells and living animals. Our results suggest that the new class of RGD-decorated aqQDs are highly promising as fluorescent bioprobes for a wide range of biological applications.

  3. Vibrationally resolved emission of thiophosgene dimer

    NASA Astrophysics Data System (ADS)

    Berrios, Eduardo; Hui, Ho Yee; Gruebele, Martin

    2010-09-01

    During a study of thiophosgene electronic spectra, Fujiwara and co-workers observed a broad electronic transition peaked at 37 000 cm -1, attributed to thiophosgene dimer. Our dispersed fluorescence spectra of a thiophosgene molecular beam excited at 36 000 cm -1 reveal several vibrational modes too low in frequency for thiophosgene. We assign them to modes of thiophosgene dimer or their combination bands. MP2 calculations support the vibrational assignment. TD-DFT, CASSCF, and coupled cluster calculations suggest that the bright electronic state of thiophosgene dimer is the B 2u symmetry fifth excited singlet state. Two additional transitions are assigned to a thiophosgene synthesis impurity, trichloromethanesulfenyl chloride.

  4. Quantum dimer model for the pseudogap metal

    PubMed Central

    Punk, Matthias; Allais, Andrea; Sachdev, Subir

    2015-01-01

    We propose a quantum dimer model for the metallic state of the hole-doped cuprates at low hole density, p. The Hilbert space is spanned by spinless, neutral, bosonic dimers and spin S=1/2, charge +e fermionic dimers. The model realizes a “fractionalized Fermi liquid” with no symmetry breaking and small hole pocket Fermi surfaces enclosing a total area determined by p. Exact diagonalization, on lattices of sizes up to 8×8, shows anisotropic quasiparticle residue around the pocket Fermi surfaces. We discuss the relationship to experiments. PMID:26195771

  5. Quantum dimer model for the pseudogap metal.

    PubMed

    Punk, Matthias; Allais, Andrea; Sachdev, Subir

    2015-08-04

    We propose a quantum dimer model for the metallic state of the hole-doped cuprates at low hole density, p. The Hilbert space is spanned by spinless, neutral, bosonic dimers and spin S = 1/2, charge +e fermionic dimers. The model realizes a "fractionalized Fermi liquid" with no symmetry breaking and small hole pocket Fermi surfaces enclosing a total area determined by p. Exact diagonalization, on lattices of sizes up to 8 × 8, shows anisotropic quasiparticle residue around the pocket Fermi surfaces. We discuss the relationship to experiments.

  6. RNAi-mediated gene knockdown and anti-angiogenic therapy of RCCs using a cyclic RGD-modified liposomal-siRNA system.

    PubMed

    Sakurai, Yu; Hatakeyama, Hiroto; Sato, Yusuke; Hyodo, Mamoru; Akita, Hidetaka; Ohga, Noritaka; Hida, Kyoko; Harashima, Hideyoshi

    2014-01-10

    Angiogenesis is one of crucial processes associated with tumor growth and development, and consequently a prime target for cancer therapy. Although tumor endothelial cells (TECs) play a key role in pathological angiogenesis, investigating phenotypical changes in neovessels when a gene expression in TEC is suppressed is a difficult task. Small interfering RNA (siRNA) represents a potential agent due to its ability to silence a gene of interest. We previously developed a system for in vivo siRNA delivery to cancer cells that involves a liposomal-delivery system, a MEND that contains a unique pH-sensitive cationic lipid, YSK05 (YSK-MEND). In the present study, we report on the development of a system that permits the delivery of siRNA to TECs by combining the YSK-MEND and a ligand that is specific to TECs. Cyclo(Arg-Gly-Asp-D-Phe-Lys) (cRGD) is a well-known ligand to αVβ3 integrin, which is selectively expressed at high levels in TECs. We incorporated cRGD into the YSK-MEND (RGD-MEND) to achieve an efficient gene silencing in TECs. Quantitative RT-PCR and the 5' rapid amplification of cDNA ends PCR indicated that the intravenous injection of RGD-MEND at a dose of 4.0mg/kg induced a significant RNAi-mediated gene reduction in TEC but not in endothelial cells of other organs. Finally, we evaluated the therapeutic potency of the RGD-MEND encapsulating siRNA against vascular endothelial growth factor receptor 2. A substantial delay in tumor growth was observed after three sequential RGD-MEND injections on alternate days. In conclusion, the RGD-MEND represents a new approach for the characterization of TECs and for us in anti-angiogenic therapy.

  7. RGD Surface Functionalization of the Hydrophilic Acrylic Intraocular Lens Material to Control Posterior Capsular Opacification

    PubMed Central

    Huang, Yi-Shiang; Bertrand, Virginie; Bozukova, Dimitriya; Pagnoulle, Christophe; Labrugère, Christine; De Pauw, Edwin; De Pauw-Gillet, Marie-Claire; Durrieu, Marie-Christine

    2014-01-01

    Posterior Capsular Opacification (PCO) is the capsule fibrosis developed on implanted IntraOcular Lens (IOL) by the de-differentiation of Lens Epithelial Cells (LECs) undergoing Epithelial Mesenchymal Transition (EMT). Literature has shown that the incidence of PCO is multifactorial including the patient's age or disease, surgical technique, and IOL design and material. Reports comparing hydrophilic and hydrophobic acrylic IOLs have shown that the former has more severe PCO. On the other hand, we have previously demonstrated that the adhesion of LECs is favored on hydrophobic compared to hydrophilic materials. By combining these two facts and contemporary knowledge in PCO development via the EMT pathway, we propose a biomimetically inspired strategy to promote LEC adhesion without de-differentiation to reduce the risk of PCO development. By surface grafting of a cell adhesion molecule (RGD peptide) onto the conventional hydrophilic acrylic IOL material, the surface-functionalized IOL can be used to reconstitute a capsule-LEC-IOL sandwich structure, which has been considered to prevent PCO formation in literature. Our results show that the innovative biomaterial improves LEC adhesion, while also exhibiting similar optical (light transmittance, optical bench) and mechanical (haptic compression force, IOL injection force) properties compared to the starting material. In addition, compared to the hydrophobic IOL material, our bioactive biomaterial exhibits similar abilities in LEC adhesion, morphology maintenance, and EMT biomarker expression, which is the crucial pathway to induce PCO. The in vitro assays suggest that this biomaterial has the potential to reduce the risk factor of PCO development. PMID:25501012

  8. Intravascularly Administered RGD-Displaying Measles Viruses Bind to and Infect Neovessel Endothelial Cells In Vivo

    PubMed Central

    Ong, Hooi Tin; Trejo, Theodore R; Pham, Linh D; Oberg, Ann L; Russell, Stephen J; Peng, Kah-Whye

    2009-01-01

    Systemically administered vectors must cross the endothelial lining of tumor blood vessels to access cancer cells. Vectors that interact with markers on the lumenal surface of these endothelial cells might have enhanced tumor localization. Here, we generated oncolytic measles viruses (MVs) displaying αvβ3 integrin-binding peptides, cyclic arginine-glycine-aspartate (RGD) or echistatin, on the measles hemagglutinin protein. Both viruses had expanded tropisms, and efficiently entered target cells via binding to integrins, but also retained their native tropisms for CD46 and signaling lymphocyte activation molecule (SLAM). When fluorescently labeled and injected intravascularly into chick chorioallantoic membranes (CAMs), in contrast to unmodified viruses, the integrin-binding viral particles bound to the lumenal surface of the developing chick neovessels and infected the CAM vascular endothelial cells. In a mouse model of VEGF-induced angiogenesis in the ear pinna, the integrin-binding viruses, but not the parental virus, infected cells at sites of new blood vessel formation. When given intravenously to mice bearing tumor xenografts, the integrin-binding virus infected endothelial cells of tumor neovessels in addition to tumor parenchyma. To our knowledge, this is the first report demonstrating that oncolytic MVs can be engineered to target the lumenal endothelial surface of newly formed blood vessels when administered intravenously in living animals. PMID:19277014

  9. A Comprehensive Evaluation of the Activity and Selectivity Profile of Ligands for RGD-binding Integrins

    PubMed Central

    Kapp, Tobias G.; Rechenmacher, Florian; Neubauer, Stefanie; Maltsev, Oleg V.; Cavalcanti-Adam, Elisabetta A.; Zarka, Revital; Reuning, Ute; Notni, Johannes; Wester, Hans-Jürgen; Mas-Moruno, Carlos; Spatz, Joachim; Geiger, Benjamin; Kessler, Horst

    2017-01-01

    Integrins, a diverse class of heterodimeric cell surface receptors, are key regulators of cell structure and behaviour, affecting cell morphology, proliferation, survival and differentiation. Consequently, mutations in specific integrins, or their deregulated expression, are associated with a variety of diseases. In the last decades, many integrin-specific ligands have been developed and used for modulation of integrin function in medical as well as biophysical studies. The IC50-values reported for these ligands strongly vary and are measured using different cell-based and cell-free systems. A systematic comparison of these values is of high importance for selecting the optimal ligands for given applications. In this study, we evaluate a wide range of ligands for their binding affinity towards the RGD-binding integrins αvβ3, αvβ5, αvβ6, αvβ8, α5β1, αIIbβ3, using homogenous ELISA-like solid phase binding assay. PMID:28074920

  10. Generalized Fibonacci Numbers and Dimer Statistics

    NASA Astrophysics Data System (ADS)

    Lu, W. T.; Wu, F. Y.

    2003-04-01

    We establish new product identities involving the q-analogue of the Fibonacci numbers. We show that the identities lead to alternate expressions of generating functions for close-packed dimers on non-orientable surfaces.

  11. Generalized Fibonacci Numbers and Dimer Statistics

    NASA Astrophysics Data System (ADS)

    Lu, W. T.; Wu, F. Y.

    We establish new product identities involving the q-analogue of the Fibonacci numbers. We show that the identities lead to alternate expressions of generating functions for close-packed dimers on non-orientable surfaces.

  12. Pfaffian Correlation Functions of Planar Dimer Covers

    NASA Astrophysics Data System (ADS)

    Aizenman, Michael; Valcázar, Manuel Laínz; Warzel, Simone

    2017-01-01

    The Pfaffian structure of the boundary monomer correlation functions in the dimer-covering planar graph models is rederived through a combinatorial/topological argument. These functions are then extended into a larger family of order-disorder correlation functions which are shown to exhibit Pfaffian structure throughout the bulk. Key tools involve combinatorial switching symmetries which are identified through the loop-gas representation of the double dimer model, and topological implications of planarity.

  13. The two-state dimer receptor model: a general model for receptor dimers.

    PubMed

    Franco, Rafael; Casadó, Vicent; Mallol, Josefa; Ferrada, Carla; Ferré, Sergi; Fuxe, Kjell; Cortés, Antoni; Ciruela, Francisco; Lluis, Carmen; Canela, Enric I

    2006-06-01

    Nonlinear Scatchard plots are often found for agonist binding to G-protein-coupled receptors. Because there is clear evidence of receptor dimerization, these nonlinear Scatchard plots can reflect cooperativity on agonist binding to the two binding sites in the dimer. According to this, the "two-state dimer receptor model" has been recently derived. In this article, the performance of the model has been analyzed in fitting data of agonist binding to A(1) adenosine receptors, which are an example of receptor displaying concave downward Scatchard plots. Analysis of agonist/antagonist competition data for dopamine D(1) receptors using the two-state dimer receptor model has also been performed. Although fitting to the two-state dimer receptor model was similar to the fitting to the "two-independent-site receptor model", the former is simpler, and a discrimination test selects the two-state dimer receptor model as the best. This model was also very robust in fitting data of estrogen binding to the estrogen receptor, for which Scatchard plots are concave upward. On the one hand, the model would predict the already demonstrated existence of estrogen receptor dimers. On the other hand, the model would predict that concave upward Scatchard plots reflect positive cooperativity, which can be neither predicted nor explained by assuming the existence of two different affinity states. In summary, the two-state dimer receptor model is good for fitting data of binding to dimeric receptors displaying either linear, concave upward, or concave downward Scatchard plots.

  14. Role of Rydberg states in the photostability of heterocyclic dimers: the case of pyrazole dimer.

    PubMed

    Zilberg, Shmuel; Haas, Yehuda

    2012-11-26

    A new route for the nonradiative decay of photoexcited, H-bonded, nitrogen-containing, heterocyclic dimers is offered and exemplified by a study of the pyrazole dimer. In some of these systems the N(3s) Rydberg state is the lowest excited singlet state. This state is formed by direct light absorption or by nonradiative transition from the allowed ππ* state. An isomer of this Rydberg state is formed by H atom transfer to the other component of the dimer. The newly formed H-bonded radical pair is composed of two radicals (a H-adduct of pyrazole, a heterocyclic analogue of the NH(4) radical) and the pyrazolium π-radical. It is calculated to have a shallow local minimum and is the lowest point on the PES of the H-pyrazole/pyrazolium radical pair. This species can cross back to the ground state of the original dimer through a relatively small energy gap and compete with the H-atom loss channel, known for the monomer. In both Rydberg dimers, an electron occupies a Rydberg orbital centered mostly on one of the two components of the dimer. This Rydberg Center Shift (RCS) mechanism, proposed earlier (Zilberg, S.; Kahan, A.; Haas, Y. Phys. Chem. Chem. Phys. 2012, 14, 8836), leads to deactivation of the electronically excited dimer while keeping it intact. It, thus, may explain the high photostability of the pyrazole dimer as well as other heterocyclic dimers.

  15. 21 CFR 176.120 - Alkyl ketene dimers.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Alkyl ketene dimers. 176.120 Section 176.120 Food... Use Only as Components of Paper and Paperboard § 176.120 Alkyl ketene dimers. Alkyl ketene dimers may... section. (a) The alkyl ketene dimers are manufactured by the dehydrohalogenation of the acyl...

  16. 21 CFR 176.120 - Alkyl ketene dimers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Alkyl ketene dimers. 176.120 Section 176.120 Food... Use Only as Components of Paper and Paperboard § 176.120 Alkyl ketene dimers. Alkyl ketene dimers may... section. (a) The alkyl ketene dimers are manufactured by the dehydrohalogenation of the acyl...

  17. Ayadualin, a novel RGD peptide with dual antihemostatic activities from the sand fly Lutzomyia ayacuchensis, a vector of Andean-type cutaneous leishmaniasis.

    PubMed

    Kato, Hirotomo; Gomez, Eduardo A; Fujita, Megumi; Ishimaru, Yuka; Uezato, Hiroshi; Mimori, Tatsuyuki; Iwata, Hiroyuki; Hashiguchi, Yoshihisa

    2015-05-01

    Sequence analysis of the Lutzomyia (Lu.) ayacuchensis salivary gland cDNA library identified a short peptide containing an RGD (Arg-Gly-Asp) sequence flanked by two cysteine residues in the C-terminal end as the most abundant transcript. In the present study, a recombinant protein of the RGD-containing peptide, designated ayadualin, was expressed in Escherichia coli and its activity was characterized. Ayadualin inhibited both collagen and ADP-induced platelet aggregations by interfering with the binding of integrin αIIbβ3 to fibrinogen. The RGD sequence and cysteine residues located on both sides of the RGD sequence were essential for the inhibitory action. Moreover, ayadualin efficiently inhibited the intrinsic blood coagulation pathway irrespective of the RGD sequence. Measuring the enzymatic activity of coagulation factors using chromogenic substrates revealed that ayadualin efficiently inhibited factor XIIa (FXIIa) activity in a dose-dependent manner. In addition, pre-incubation of ayadualin with FXII inhibited FXIIa activity, while activated FXIIa was not affected by ayadualin, indicating that ayadualin inhibits the activation of FXII, but not enzymatic activity of FXIIa. These results indicated that ayadualin plays an important role in the blood feeding of Lu. ayacuchensis by inhibiting host hemostasis via dual mechanisms.

  18. Multilayered polyion complexes with dissolvable silica layer covered by controlling densities of cRGD-conjugated PEG chains for cancer-targeted siRNA delivery.

    PubMed

    Naito, Mitsuru; Azuma, Ryota; Takemoto, Hiroyasu; Hori, Mao; Yoshinaga, Naoto; Osawa, Shigehito; Kamegawa, Rimpei; Kim, Hyun Jin; Ishii, Takehiko; Nishiyama, Nobuhiro; Miyata, Kanjiro; Kataoka, Kazunori

    2017-03-12

    Surface functionalization of nanoparticles is a crucial factor for nanoparticle-mediated drug and nucleic acid delivery. Particularly, the density of targeting ligands on nanoparticle significantly affects the affinity of nanoparticles to specific cellular surface (or receptor) through the multivalent binding effect. Herein, multilayered polyion complexes (mPICs) are prepared to possess varying densities of cyclic RGD peptide (cRGD) ligands for cancer-targeted small interfering RNA (siRNA) delivery. A template PIC is first prepared by mixing siRNAs with homo catiomers of N-substituted polyaspartamide bearing tetraethylenepentamine (PAsp(TEP)) in aqueous solution, followed by silica-coating through silicate condensation reaction. Then, silica-coated PICs (sPICs) are further covered with block catiomers of PAsp(TEP) and poly(ethylene glycol) (PEG) equipped with cRGD ligand. Successful preparation of targeted mPICs is confirmed from the changes in size and ζ-potential and the elemental analysis by transmission electron microscopy. Notably, the number of cRGD ligands per mPIC is regulated by altering the silicate concentration upon preparation of sPICs, which is confirmed by fluorescence correlation spectroscopy using fluorescent-labeled block catiomers. Ultimately, the targeted mPICs with a higher number of cRGD ligands demonstrate more efficient cellular uptake in cultured cancer cells, leading to enhanced gene silencing activity.

  19. Bone regeneration potential of stem cells derived from periodontal ligament or gingival tissue sources encapsulated in RGD-modified alginate scaffold.

    PubMed

    Moshaverinia, Alireza; Chen, Chider; Xu, Xingtian; Akiyama, Kentaro; Ansari, Sahar; Zadeh, Homayoun H; Shi, Songtao

    2014-02-01

    Mesenchymal stem cells (MSCs) provide an advantageous alternative therapeutic option for bone regeneration in comparison to current treatment modalities. However, delivering MSCs to the defect site while maintaining a high MSC survival rate is still a critical challenge in MSC-mediated bone regeneration. Here, we tested the bone regeneration capacity of periodontal ligament stem cells (PDLSCs) and gingival mesenchymal stem cells (GMSCs) encapsulated in a novel RGD- (arginine-glycine-aspartic acid tripeptide) coupled alginate microencapsulation system in vitro and in vivo. Five-millimeter-diameter critical-size calvarial defects were created in immunocompromised mice and PDLSCs and GMSCs encapsulated in RGD-modified alginate microspheres were transplanted into the defect sites. New bone formation was assessed using microcomputed tomography and histological analyses 8 weeks after transplantation. Results confirmed that our microencapsulation system significantly enhanced MSC viability and osteogenic differentiation in vitro compared with non-RGD-containing alginate hydrogel microspheres with larger diameters. Results confirmed that PDLSCs were able to repair the calvarial defects by promoting the formation of mineralized tissue, while GMSCs showed significantly lower osteogenic differentiation capability. Further, results revealed that RGD-coupled alginate scaffold facilitated the differentiation of oral MSCs toward an osteoblast lineage in vitro and in vivo, as assessed by expression of osteogenic markers Runx2, ALP, and osteocalcin. In conclusion, these results for the first time demonstrated that MSCs derived from orofacial tissue encapsulated in RGD-modified alginate scaffold show promise for craniofacial bone regeneration. This treatment modality has many potential dental and orthopedic applications.

  20. Dual targeting strategy of magnetic nanoparticle-loaded and RGD peptide-activated stimuli-sensitive polymeric micelles for delivery of paclitaxel

    NASA Astrophysics Data System (ADS)

    Lin, Meng Meng; Kang, Yoon Joong; Sohn, Youngjoo; Kim, Do Kyung

    2015-06-01

    A double targeting strategy of anti-neoplastic agent paclitaxel (PTX) was developed by incorporating magnetic nanoparticles and RGD peptide for enhanced cell cytotoxicity effect at lower dosage. A dual targeting mechanism including magnetic targeting and RGD ligand-specific targeting enhanced the overall cytotoxicity and reduced the effective dosage of PTX to achieve enhanced and sustained release of PTX in vitro. We addressed the issues of water-insolubility of oleic acid (OA)-stabilized SPIONs and low incorporation efficiency of hydrophobic PTX with SPION nanocarriers by using an amphiphilic polymer poly[( N-isopropylacrylamide-r-acrylamide)-b- l-lactic acid] (PNAL) as micelle-forming materials. A targeting moiety, GGGGRGD peptide, a RGD sequence-containing peptide with a short linker, is attached to the surface of PNAL-SPIONs via a homo-crosslinker. Confocal microscopy image analysis revealed that the cellular uptake was increased from (1.5 ± 0.5 % (PNAL) to 11.7 ± 0.8 % (RGD-PNAL-SPIONs) at 6 h incubation, once both RGD peptide and magnetic force attraction were incorporated into the carriers. Such multi-targeting nanocarriers showed promising potential in cancer-oriented diagnosis and therapy.

  1. Synthesis and characterization of acrylic terpolymers with RGD peptides for biomedical applications.

    PubMed

    Fussell, Garland W; Cooper, Stuart L

    2004-07-01

    The goal of this research was to design a biomaterial, using acrylic terpolymers, which could support endothelial cells and function in small diameter vascular graft applications. Hexyl methacrylate (HMA) and octyl methacrylate (OMA) were used as comonomers to produce a material with a low glass transition temperature (T(g)). Methacrylic acid (MAA) was used to provide ionic character, and methyl methacrylate (MMA) was selected because of its wide usage in biomedical applications. Cation neutralization was employed to modify the mechanical properties. RGD-based peptide sequences were attached to promote endothelial cell adhesion, because vascular grafts seeded with endothelial cells have fewer problems with thrombosis. The two methods used to incorporate peptide sequences were a chain transfer reaction during polymerization, and a coupling reaction attaching the peptides to carboxyl groups on the polymer after polymerization. The compositions that produced T(g)s of approximately 0 degrees C were 75 mol% OMA and 92 mol% HMA. The Young's modulus of the HMA copolymer was approximately 0.37 MPa, well below the desired value of 0.9 MPa. Likewise, the Young's modulus of approximately 0.50 MPa for the OMA copolymer was also below the desired value. After partial neutralization with sodium cations, the Young's moduli increased to approximately 0.93 and 0.99 MPa, respectively. The chain transfer reaction lowered the molecular weights and mechanical properties of the copolymers, while the coupling reaction method had little effect on these properties. The chain transfer method appears to be a promising one-step method to produce polymers with a wide range of peptide concentrations.

  2. Covalent bonding of YIGSR and RGD to PEDOT/PSS/MWCNT-COOH composite material to improve the neural interface.

    PubMed

    Wang, Kun; Tang, Rong-Yu; Zhao, Xiao-Bo; Li, Jun-Jie; Lang, Yi-Ran; Jiang, Xiao-Xia; Sun, Hong-Ji; Lin, Qiu-Xia; Wang, Chang-Yong

    2015-11-28

    The development of coating materials for neural interfaces has been a pursued to improve the electrical, mechanical and biological performances. For these goals, a bioactive coating was developed in this work featuring a poly(3,4-ethylenedioxythiophene) (PEDOT)/carbon nanotube (CNT) composite and covalently bonded YIGSR and RGD. Its biological effect and electrical characteristics were assessed in vivo on microwire arrays (MWA). The coated electrodes exhibited a significantly higher charge storage capacity (CSC) and lower electrochemical impedance at 1 kHz which are desired to improve the stimulating and recording performances, respectively. Acute neural recording experiments revealed that coated MWA possess a higher signal/noise ratio capturing spikes undetected by uncoated electrodes. Moreover, coated MWA possessed more active sites and single units, and the noise floor of coated electrodes was lower than that of uncoated electrodes. There is little information in the literature concerning the chronic performance of bioactively modified neural interfaces in vivo. Therefore in this work, chronic in vivo tests were conducted and the PEDOT/PSS/MWCNT-polypeptide coated arrays exhibited excellent performances with the highest mean maximal amplitude from day 4 to day 12 during which the acute response severely compromised the performance of the electrodes. In brief, we developed a simple method of covalently bonding YIGSR and RGD to a PEDOT/PSS/MWCNT-COOH composite improving both the biocompatibility and electrical performance of the neural interface. Our findings suggest that YIGSR and RGD modified PEDOT/PSS/MWCNT is a promising bioactivated composite coating for neural recording and stimulating.

  3. Covalent bonding of YIGSR and RGD to PEDOT/PSS/MWCNT-COOH composite material to improve the neural interface

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Tang, Rong-Yu; Zhao, Xiao-Bo; Li, Jun-Jie; Lang, Yi-Ran; Jiang, Xiao-Xia; Sun, Hong-Ji; Lin, Qiu-Xia; Wang, Chang-Yong

    2015-11-01

    The development of coating materials for neural interfaces has been a pursued to improve the electrical, mechanical and biological performances. For these goals, a bioactive coating was developed in this work featuring a poly(3,4-ethylenedioxythiophene) (PEDOT)/carbon nanotube (CNT) composite and covalently bonded YIGSR and RGD. Its biological effect and electrical characteristics were assessed in vivo on microwire arrays (MWA). The coated electrodes exhibited a significantly higher charge storage capacity (CSC) and lower electrochemical impedance at 1 kHz which are desired to improve the stimulating and recording performances, respectively. Acute neural recording experiments revealed that coated MWA possess a higher signal/noise ratio capturing spikes undetected by uncoated electrodes. Moreover, coated MWA possessed more active sites and single units, and the noise floor of coated electrodes was lower than that of uncoated electrodes. There is little information in the literature concerning the chronic performance of bioactively modified neural interfaces in vivo. Therefore in this work, chronic in vivo tests were conducted and the PEDOT/PSS/MWCNT-polypeptide coated arrays exhibited excellent performances with the highest mean maximal amplitude from day 4 to day 12 during which the acute response severely compromised the performance of the electrodes. In brief, we developed a simple method of covalently bonding YIGSR and RGD to a PEDOT/PSS/MWCNT-COOH composite improving both the biocompatibility and electrical performance of the neural interface. Our findings suggest that YIGSR and RGD modified PEDOT/PSS/MWCNT is a promising bioactivated composite coating for neural recording and stimulating.

  4. RGD-conjugated mesoporous silica-encapsulated gold nanorods enhance the sensitization of triple-negative breast cancer to megavoltage radiation therapy

    PubMed Central

    Zhao, Ning; Yang, Zhangru; Li, Bingxin; Meng, Jin; Shi, Zeliang; Li, Ping; Fu, Shen

    2016-01-01

    Multifunctional nanoprobes have great potential as effective radiosensitizers and drug carriers. RGD-modified gold nanorods could increase the uptake of nanoparticles via receptor-mediated endocytosis in integrin alphaV beta3-overexpressing breast cancer cells, which could enhance the effects of radiation on tumor cells, leading to further radiosensitization. The purpose of our study was to demonstrate that RGD-conjugated mesoporous silica-encapsulated gold nanorods significantly enhanced the sensitization of triple-negative breast cancer to megavoltage energy. The results indicated that RGD-conjugated mesoporous silica-encapsulated gold nanorod multifunctional nanoprobes could achieve radiosensitization in vitro and in vivo, which suggests the potential translation of this nanotechnology to clinical applications in tumor-targeting and selective therapy. PMID:27822038

  5. 2.0 A crystal structure of a four-domain segment of human fibronectin encompassing the RGD loop and synergy region.

    PubMed

    Leahy, D J; Aukhil, I; Erickson, H P

    1996-01-12

    We have determined the 2.0 A crystal structure of a fragment of human fibronectin encompassing the seventh through the RGD-containing tenth type III repeats (FN7-10). The structure reveals an extended rod-like molecule with a long axis of approximately 140 A and highly variable relationships between adjacent domains. An unusually small rotation between domains 9 and 10 creates a distinctive binding site, in which the RGD loop from domain 10 and the "synergy" region from domain 9 are on the same face of FN7-10 and thus easily accessible to a single integrin molecule. The cell-binding RGD loop is well-ordered in this structure and extends approximately 10 A away from the FN7-10 core.

  6. RGD-conjugated mesoporous silica-encapsulated gold nanorods enhance the sensitization of triple-negative breast cancer to megavoltage radiation therapy.

    PubMed

    Zhao, Ning; Yang, Zhangru; Li, Bingxin; Meng, Jin; Shi, Zeliang; Li, Ping; Fu, Shen

    Multifunctional nanoprobes have great potential as effective radiosensitizers and drug carriers. RGD-modified gold nanorods could increase the uptake of nanoparticles via receptor-mediated endocytosis in integrin alphaV beta3-overexpressing breast cancer cells, which could enhance the effects of radiation on tumor cells, leading to further radiosensitization. The purpose of our study was to demonstrate that RGD-conjugated mesoporous silica-encapsulated gold nanorods significantly enhanced the sensitization of triple-negative breast cancer to megavoltage energy. The results indicated that RGD-conjugated mesoporous silica-encapsulated gold nanorod multifunctional nanoprobes could achieve radiosensitization in vitro and in vivo, which suggests the potential translation of this nanotechnology to clinical applications in tumor-targeting and selective therapy.

  7. Integrin Engagement by the Helical RGD Motif of the Helicobacter pylori CagL Protein Is Regulated by pH-induced Displacement of a Neighboring Helix*

    PubMed Central

    Bonsor, Daniel A.; Pham, Kieu T.; Beadenkopf, Robert; Diederichs, Kay; Haas, Rainer; Beckett, Dorothy; Fischer, Wolfgang; Sundberg, Eric J.

    2015-01-01

    Arginine-aspartate-glycine (RGD) motifs are recognized by integrins to bridge cells to one another and the extracellular matrix. RGD motifs typically reside in exposed loop conformations. X-ray crystal structures of the Helicobacter pylori protein CagL revealed that RGD motifs can also exist in helical regions of proteins. Interactions between CagL and host gastric epithelial cell via integrins are required for the translocation of the bacterial oncoprotein CagA. Here, we have investigated the molecular basis of the CagL-host cell interactions using structural, biophysical, and functional analyses. We solved an x-ray crystal structure of CagL that revealed conformational changes induced by low pH not present in previous structures. Using analytical ultracentrifugation, we found that pH-induced conformational changes in CagL occur in solution and not just in the crystalline environment. By designing numerous CagL mutants based on all available crystal structures, we probed the functional roles of CagL conformational changes on cell surface integrin engagement. Together, our data indicate that the helical RGD motif in CagL is buried by a neighboring helix at low pH to inhibit CagL binding to integrin, whereas at neutral pH the neighboring helix is displaced to allow integrin access to the CagL RGD motif. This novel molecular mechanism of regulating integrin-RGD motif interactions by changes in the chemical environment provides new insight to H. pylori-mediated oncogenesis. PMID:25837254

  8. Ocular Localization and Transduction by Adenoviral Vectors Are Serotype-Dependent and Can Be Modified by Inclusion of RGD Fiber Modifications

    PubMed Central

    Ueyama, Kazuhiro; Mori, Keisuke; Shoji, Takuhei; Omata, Hidekazu; Gehlbach, Peter L.; Brough, Douglas E.; Wei, Lisa L.; Yoneya, Shin

    2014-01-01

    Purpose To evaluate localization and transgene expression from adenoviral vector of serotypes 5, 35, and 28, ± an RGD motif in the fiber following intravitreal or subretinal administration. Methods Ocular transduction by adenoviral vector serotypes ± RGD was studied in the eyes of mice receiving an intravitreous or subretinal injection. Each serotype expressed a CMV-GFP expression cassette and histological sections of eyes were examined. Transgene expression levels were examined using luciferase (Luc) regulated by the CMV promoter. Results GFP localization studies revealed that serotypes 5 and 28 given intravitreously transduced corneal endothelial, trabecular, and iris cells. Intravitreous delivery of the unmodified Ad35 serotype transduced only trabecular meshwork cells, but, the modification of the RGD motif into the fiber of the Ad35 viral vector base expanded transduction to corneal endothelial and iris cells. Incorporation of the RGD motif into the fiber knob with deletion of RGD from the penton base did not affect the transduction ability of the Ad5 vector base. Subretinal studies showed that RGD in the Ad5 knob shifted transduction from RPE cells to photoreceptor cells. Using a CMV-Luc expression cassette, intravitreous delivery of all the tested vectors, such as Ad5-, Ad35- and Ad28- resulted in an initial rapid induction of luciferase activity that thereafter declined. Subretinal administration of vectors showed a marked difference in transgene activity. Ad35-Luc gene expression peaked at 7 days and remained elevated for 6 months. Ad28-Luc expression was high after 1 day and remained sustained for one month. Conclusions Different adenoviral vector serotypes ± modifications transduce different cells within the eye. Transgene expression can be brief or extended and is serotype and delivery route dependent. Thus, adenoviral vectors provide a versatile platform for the delivery of therapeutic agents for ocular diseases. PMID:25232844

  9. Cell-Adhesive Matrices Composed of RGD Peptide-Displaying M13 Bacteriophage/Poly(lactic-co-glycolic acid) Nanofibers Beneficial to Myoblast Differentiation.

    PubMed

    Shin, Yong Cheol; Lee, Jong Ho; Jin, Linhua; Kim, Min Jeong; Kim, Chuntae; Hong, Suck Won; Oh, Jin Woo; Han, Dong-Wook

    2015-10-01

    Recently, there has been considerable effort to develop suitable scaffolds for tissue engineering applications. Cell adhesion is a prerequisite for cells to survive. In nature, the extracellular matrix (ECM) plays this role. Therefore, an ideal scaffold should be structurally similar to the natural ECM and have biocompatibility and biodegradability. In addition, the scaffold should have biofunctionality, which provides the potent ability to enhance the cellular behaviors, such as adhesion, proliferation and differentiation. This study concentrates on fabricating cell-adhesive matrices composed of RGD peptide-displaying M13 bacteriophage (RGD-M13 phage) and poly(lactic-co-glycolic acid, PLGA) nanofibers. Long rod-shaped M13 bacteriophages are non-toxic and can express many desired proteins on their surface. A genetically engineered M13 phage was constructed to display RGD peptides on its surface. PLGA is a biodegradable polymer with excellent biocompatibility and suitable physicochemical property for adhesive matrices. In this study, RGD-M13 phage/PLGA hybrid nanofiber matrices were fabricated by electrospinning. The physicochemical properties of these matrices were characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and contact angle measurement. In addition, the cellular behaviors, such as the initial attachment, proliferation and differentiation, were analyzed by a CCK-8 assay and immunofluorescence staining to evaluate the potential application of these matrices to tissue engineering scaffolds. The RGD-M13 phage/PLGA nanofiber matrices could enhance the cellular behaviors and promote the differentiation of C2C12 myoblasts. These results suggest that the RGD-M13 phage/PLGA nanofiber matrices are beneficial to myoblast differentiation and can serve as effective tissue engineering scaffolds.

  10. Integrin engagement by the helical RGD motif of the Helicobacter pylori CagL protein is regulated by pH-induced displacement of a neighboring helix.

    PubMed

    Bonsor, Daniel A; Pham, Kieu T; Beadenkopf, Robert; Diederichs, Kay; Haas, Rainer; Beckett, Dorothy; Fischer, Wolfgang; Sundberg, Eric J

    2015-05-15

    Arginine-aspartate-glycine (RGD) motifs are recognized by integrins to bridge cells to one another and the extracellular matrix. RGD motifs typically reside in exposed loop conformations. X-ray crystal structures of the Helicobacter pylori protein CagL revealed that RGD motifs can also exist in helical regions of proteins. Interactions between CagL and host gastric epithelial cell via integrins are required for the translocation of the bacterial oncoprotein CagA. Here, we have investigated the molecular basis of the CagL-host cell interactions using structural, biophysical, and functional analyses. We solved an x-ray crystal structure of CagL that revealed conformational changes induced by low pH not present in previous structures. Using analytical ultracentrifugation, we found that pH-induced conformational changes in CagL occur in solution and not just in the crystalline environment. By designing numerous CagL mutants based on all available crystal structures, we probed the functional roles of CagL conformational changes on cell surface integrin engagement. Together, our data indicate that the helical RGD motif in CagL is buried by a neighboring helix at low pH to inhibit CagL binding to integrin, whereas at neutral pH the neighboring helix is displaced to allow integrin access to the CagL RGD motif. This novel molecular mechanism of regulating integrin-RGD motif interactions by changes in the chemical environment provides new insight to H. pylori-mediated oncogenesis.

  11. Genome-wide DNA polymorphism in the indica rice varieties RGD-7S and Taifeng B as revealed by whole genome re-sequencing.

    PubMed

    Fu, Chong-Yun; Liu, Wu-Ge; Liu, Di-Lin; Li, Ji-Hua; Zhu, Man-Shan; Liao, Yi-Long; Liu, Zhen-Rong; Zeng, Xue-Qin; Wang, Feng

    2016-03-01

    Next-generation sequencing technologies provide opportunities to further understand genetic variation, even within closely related cultivars. We performed whole genome resequencing of two elite indica rice varieties, RGD-7S and Taifeng B, whose F1 progeny showed hybrid weakness and hybrid vigor when grown in the early- and late-cropping seasons, respectively. Approximately 150 million 100-bp pair-end reads were generated, which covered ∼86% of the rice (Oryza sativa L. japonica 'Nipponbare') reference genome. A total of 2,758,740 polymorphic sites including 2,408,845 SNPs and 349,895 InDels were detected in RGD-7S and Taifeng B, respectively. Applying stringent parameters, we identified 961,791 SNPs and 46,640 InDels between RGD-7S and Taifeng B (RGD-7S/Taifeng B). The density of DNA polymorphisms was 256.8 SNPs and 12.5 InDels per 100 kb for RGD-7S/Taifeng B. Copy number variations (CNVs) were also investigated. In RGD-7S, 1989 of 2727 CNVs were overlapped in 218 genes, and 1231 of 2010 CNVs were annotated in 175 genes in Taifeng B. In addition, we verified a subset of InDels in the interval of hybrid weakness genes, Hw3 and Hw4, and obtained some polymorphic InDel markers, which will provide a sound foundation for cloning hybrid weakness genes. Analysis of genomic variations will also contribute to understanding the genetic basis of hybrid weakness and heterosis.

  12. Multiply charged monopoles in cubic dimer model

    NASA Astrophysics Data System (ADS)

    Ganesh Jaya, Sreejith; Powell, Stephen

    2015-03-01

    The classical cubic dimer model is a 3D statistical mechanical system whose degrees of freedom are dimers that occupy the edges between nearest neighbour vertices of a cubic lattice. Dimer occupancies are subject to the local constraint that every vertex is associated with exactly one dimer. In the presence of an aligning interaction, it is known that the system exhibits an unconventional continuous thermal phase transition from a symmetry broken columnar phase to a Coulomb-phase. The transition is in the NCCP1 universality class, which also describes the Neel-VBS transition in the JQ model and the S =1/2 Heisenberg model with suppression of hedgehog defects. Using Monte-Carlo simulations of a pair of defects in a background of fluctuating dimers, we calculate the scaling exponents for fugacities of monopole defects of charge Q = 2 and 3 at this critical point. Our estimates suggest that Q = 3 monopoles are relevant and could therefore drive the JQ model away from the NCCP1 critical point on a hexagonal lattice.

  13. A dimeric state for PRC2

    PubMed Central

    Davidovich, Chen; Goodrich, Karen J.; Gooding, Anne R.; Cech, Thomas R.

    2014-01-01

    Polycomb repressive complex-2 (PRC2) is a histone methyltransferase required for epigenetic silencing during development and cancer. Long non-coding RNAs (lncRNAs) can recruit PRC2 to chromatin. Previous studies identified PRC2 subunits in a complex with the apparent molecular weight of a dimer, which might be accounted for by the incorporation of additional protein subunits or RNA rather than PRC2 dimerization. Here we show that reconstituted human PRC2 is in fact a dimer, using multiple independent approaches including analytical size exclusion chromatography (SEC), SEC combined with multi-angle light scattering and co-immunoprecipitation of differentially tagged subunits. Even though it contains at least two RNA-binding subunits, each PRC2 dimer binds only one RNA molecule. Yet, multiple PRC2 dimers bind a single RNA molecule cooperatively. These observations suggest a model in which the first RNA binding event promotes the recruitment of multiple PRC2 complexes to chromatin, thereby nucleating repression. PMID:24992961

  14. The diamagnetic susceptibility of the tubulin dimer.

    PubMed

    Bras, Wim; Torbet, James; Diakun, Gregory P; Rikken, Geert L J A; Diaz, J Fernando

    2014-01-01

    An approximate value of the diamagnetic anisotropy of the tubulin dimer, Δχ dimer, has been determined assuming axial symmetry and that only the α -helices and β -sheets contribute to the anisotropy. Two approaches have been utilized: (a) using the value for the Δχ α for an α -helical peptide bond given by Pauling (1979) and (b) using the previously determined anisotropy of fibrinogen as a calibration standard. The Δχ dimer ≈ 4 × 10(-27) JT(-2) obtained from these measurements are similar to within 20%. Although Cotton-Mouton measurements alone cannot be used to estimate Δχ directly, the value we measured, CMdimer = (1.41 ± 0.03) × 10(-8) T(-2)cm(2)mg(-1), is consistent with the above estimate for Δχ dimer. The method utilized for the determination of the tubulin dimer diamagnetic susceptibility is applicable to other proteins and macromolecular assemblies as well.

  15. Linking in domain-swapped protein dimers

    PubMed Central

    Baiesi, Marco; Orlandini, Enzo; Trovato, Antonio; Seno, Flavio

    2016-01-01

    The presence of knots has been observed in a small fraction of single-domain proteins and related to their thermodynamic and kinetic properties. The exchanging of identical structural elements, typical of domain-swapped proteins, makes such dimers suitable candidates to validate the possibility that mutual entanglement between chains may play a similar role for protein complexes. We suggest that such entanglement is captured by the linking number. This represents, for two closed curves, the number of times that each curve winds around the other. We show that closing the curves is not necessary, as a novel parameter G′, termed Gaussian entanglement, is strongly correlated with the linking number. Based on 110 non redundant domain-swapped dimers, our analysis evidences a high fraction of chains with a significant intertwining, that is with |G′| > 1. We report that Nature promotes configurations with negative mutual entanglement and surprisingly, it seems to suppress intertwining in long protein dimers. Supported by numerical simulations of dimer dissociation, our results provide a novel topology-based classification of protein-swapped dimers together with some preliminary evidence of its impact on their physical and biological properties. PMID:27659606

  16. Partition-DFT on the water dimer.

    PubMed

    Gómez, Sara; Nafziger, Jonathan; Restrepo, Albeiro; Wasserman, Adam

    2017-02-21

    As is well known, the ground-state symmetry group of the water dimer switches from its equilibrium Cs-character to C2h-character as the distance between the two oxygen atoms of the dimer decreases below RO-O∼2.5 Å. For a range of RO-O between 1 and 5 Å, and for both symmetries, we apply Partition Density Functional Theory (PDFT) to find the unique monomer densities that sum to the correct dimer densities while minimizing the sum of the monomer energies. We calculate the work involved in deforming the isolated monomer densities and find that it is slightly larger for the Cs geometry for all RO-O. We discuss how the PDFT densities and the corresponding partition potentials support the orbital-interaction picture of hydrogen-bond formation.

  17. Slab photonic crystals with dimer colloid bases

    SciTech Connect

    Riley, Erin K.; Liddell Watson, Chekesha M.

    2014-06-14

    The photonic band gap properties for centered rectangular monolayers of asymmetric dimers are reported. Colloids in suspension have been organized into the phase under confinement. The theoretical model is inspired by the range of asymmetric dimers synthesized via seeded emulsion polymerization and explores, in particular, the band structures as a function of degree of lobe symmetry and degree of lobe fusion. These parameters are varied incrementally from spheres to lobe-tangent dimers over morphologies yielding physically realizable particles. The work addresses the relative scarcity of theoretical studies on photonic crystal slabs with vertical variation that is consistent with colloidal self-assembly. Odd, even and polarization independent gaps in the guided modes are determined for direct slab structures. A wide range of lobe symmetry and degree of lobe fusion combinations having Brillouin zones with moderate to high isotropy support gaps between odd mode band indices 3-4 and even mode band indices 1-2 and 2-3.

  18. Integrable oscillator type and Schrödinger type dimers

    NASA Astrophysics Data System (ADS)

    Khare, Avinash; Saxena, Avadh

    2017-02-01

    A PT-symmetric dimer is a two-site nonlinear oscillator dimer or a two-site nonlinear Schrödinger dimer where one site loses and the other site gains energy at the same rate. We present a wide class of integrable oscillator type dimers whose Hamiltonian is of arbitrary even order. Further, we also present a wide class of integrable nonlinear Schrödinger type dimers where again the Hamiltonian is of arbitrary even order. Finally, we consider a recently discussed complex dimer model and point out a few integrable cases in that model.

  19. Graded-index optical dimer formed by optical force.

    PubMed

    Akbarzadeh, Alireza; Koschny, Thomas; Kafesaki, Maria; Economou, Eleftherios N; Soukoulis, Costas M

    2016-05-30

    We propose an optical dimer formed from two spherical lenses bound by the pressure that light exerts on matter. With the help of the method of force tracing, we find the required graded-index profiles of the lenses for the existence of the dimer. We study the dynamics of the opto-mechanical interaction of lenses under the illumination of collimated light beams and quantitatively validate the performance of proposed dimer. We also examine the stability of dimer due to the lateral misalignments and we show how restoring forces bring the dimer into lateral equilibrium. The dimer can be employed in various practical applications such as optical manipulation, sensing and imaging.

  20. Rubidium dimer destruction by a diode laser

    SciTech Connect

    Ban, T.; Aumiler, D.; Pichler, G.

    2005-02-01

    We observed rubidium dimer destruction by excitation of rubidium vapor with diode laser light tuned across the Rb D{sub 2} resonance line in a 2400 GHz tuning interval. The destruction was measured for rubidium atom concentrations in the (1-9)x10{sup 16} cm{sup -3} range, pump beam power up to 43 mW, and with a 5 Torr of the helium buffer gas. We discuss the physical mechanisms involved and specify the molecular pathways which may effectively lead to the observed dimer destruction.

  1. The Effects of TiO2 Nanodot Films with RGD Immobilization on Light-Induced Cell Sheet Technology

    PubMed Central

    Yu, Meng-Liu; Yu, Meng-Fei; Zhu, Li-Qin; Wang, Tian-Tian; Zhou, Yi; Wang, Hui-Ming

    2015-01-01

    Cell sheet technology is a new strategy in tissue engineering which could be possible to implant into the body without a scaffold. In order to get an integrated cell sheet, a light-induced method via UV365 is used for cell sheet detachment from culture dishes. In this study, we investigated the possibility of cell detachment and growth efficiency on TiO2 nanodot films with RGD immobilization on light-induced cell sheet technology. Mouse calvaria-derived, preosteoblastic (MC3T3-E1) cells were cultured on TiO2 nanodot films with (TR) or without (TN) RGD immobilization. After cells were cultured with or without 5.5 mW/cm2 UV365 illumination, cell morphology, cell viability, osteogenesis related RNA and protein expression, and cell detachment ability were compared, respectively. Light-induced cell detachment was possible when cells were cultured on TR samples. Also, cells cultured on TR samples showed better cell viability, alongside higher protein and RNA expression than on TN samples. This study provides a new biomaterial for light-induced cell/cell sheet harvesting. PMID:26417596

  2. RGD-conjugated two-photon absorbing near-IR emitting fluorescent probes for tumor vascular imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Belfield, Kevin D.; Yue, Xiling; Morales, Alma R.; Githaiga, Grace W.; Woodward, Adam W.; Tang, Simon; Sawada, Junko; Komatsu, Masanobu; Liu, Xuan

    2016-03-01

    Observation of the activation and inhibition of angiogenesis processes is important in the progression of cancer. Application of targeting peptides, such as a small peptide that contains adjacent L-arginine (R), glycine (G) and L-aspartic acid (D) residues can afford high selectivity and deep penetration in vessel imaging. To facilitate deep tissue vasculature imaging, probes that can be excited via two-photon absorption (2PA) in the near-infrared (NIR) and subsequently emit in the NIR are essential. In this study, the enhancement of tissue image quality with RGD conjugates was investigated with new NIR-emitting pyranyl fluorophore derivatives in two-photon fluorescence microscopy. Linear and nonlinear photophysical properties of the new probes were comprehensively characterized; significantly the probes exhibited good 2PA over a broad spectral range from 700-1100 nm. Cell and tissue images were then acquired and examined, revealing deep penetration and high contrast with the new pyranyl RGD-conjugates up to 350 μm in tumor tissue.

  3. RGD-conjugated rod-like viral nanoparticles on 2D scaffold improved bone differentiation of mesenchymal stem cells

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Pongkwan, Sitasuwan; Lee, L.; Li, Kai; Nguyen, Huong

    2014-05-01

    Viral nanoparticles have uniform and well-defined nano-structures and can be produced in large quantities. Several plant viral nanoparticles have been tested in biomedical applications due to the lack of mammalian cell infectivity. We are particularly interested in using Tobacco mosaic virus (TMV), which has been demonstrated to enhance bone tissue regeneration, as a tuneable nanoscale building block for biomaterials development. Unmodified TMV particles have been shown to accelerate osteogenic differentiation of adult stem cells by synergistically upregulating BMP2 and IBSP expression with dexamethasone. However, the lack of affinity to mammalian cell surface resulted in low initial cell adhesion. In this study, to increase cell binding capacity of TMV based material the chemical functionalization of TMV with arginine-glycine-aspartic acid (RGD) peptide was explored. An azide-derivatized RGD peptide was “clicked” to tyrosine residues on TMV outer surface via an efficient copper(I) catalysed azide-alkyne cycloaddition reaction. The ligand spacing is calculated to be 2-4 nm, which could offer a polyvalent ligand clustering effect for enhanced cell receptor signalling, further promoting the proliferation and osteogenic differentiation of bone marrow derived mesenchymal stem cells.

  4. Quaternary Zn-Ag-In-Se quantum dots for biomedical optical imaging of RGD-modified micelles.

    PubMed

    Deng, Dawei; Qu, Lingzhi; Zhang, Jian; Ma, Yuxiang; Gu, Yueqing

    2013-11-13

    Exploring the synthesis of new biocompatible quantum dots (QDs) helps in overcoming the intrinsic toxicity of the existing QDs composed of highly toxic heavy metals (e.g., Cd, Hg, Pb, etc.) and is particularly interesting for the future practical application of QDs in biomedical imaging. Hence, in this report, a new one-pot approach to oil-soluble (highly toxic heavy metal-free) highly luminescent quaternary Zn-Ag-In-Se (ZAISe) QDs was designed. Their photoluminescence (PL) emission could be systematically tuned from 660 to 800 nm by controlling the Ag/Zn feed ratio, and their highest PL quantum yield is close to 50% after detailed optimization. Next, by using biodegradable RGD peptide (arginine-glycine-aspartic acid)-modified N-succinyl-N'-octyl-chitosan (RGD-SOC) micelles as a water transfer agent, the versatility of these quaternary ZAISe QDs for multiscale bioimaging of micelles (namely, in vitro and in vivo evaluating the tumor targeting of drug carriers) was further explored, as a promising alternative for Cd- and Pb-based QDs.

  5. Modeling the Interaction between Integrin-Binding Peptide (RGD) and Rutile Surface: The Effect of Na+ on Peptide Adsorption

    SciTech Connect

    Wu, Chunya; Skelton, Adam; Chen, Mingjun; Vlcek, Lukas; Cummings, Peter T

    2011-01-01

    The dynamics of a single tripeptide Arg-Gly-Asp (RGD) adsorbing onto negatively charged hydroxylated rutile (110) surface in aqueous solution was studied using molecular dynamics (MD) simulations. The results indicate that the adsorbed Na{sup +} ions play an important role in determining the binding geometry of RGD. With an initial 'horseshoe' configuration, the charged side groups (COO{sup -} and NH{sub 2}) of the peptide are able to interact with the surface through direct hydrogen bonds (H bonds) in the very early stage of adsorption. The Na{sup +} ions approach the positively charged Arg side chain, competing with the Arg side chain for adsorption to the negatively charged hydroxyl oxygen. In coordination with the structural adjustment of the peptide, the Arg residue is driven to detach from the rutile surface. In contrast, the Na+ ions in close proximity to the negatively charged Asp side chain contribute to the binding of the COO{sup -} group on the surface, helping the carboxyl oxygen not involved in COO{sup -}-surface H bonds to orientate toward the hydroxyl hydrogens. Once both carboxyl oxygens form enough H bonds with the hydroxyl hydrogens, the redundant ions move toward a more favorable adsorption site.

  6. RGD-conjugated Two-photon Absorbing Near-IR Emitting Fluorescent Probes for Tumor Vasculature Imaging

    PubMed Central

    Yue, Xiling; Morales, Alma R.; Githaiga, Grace W.; Woodward, Adam W.; Tang, Simon; Sawada, Junko; Komatsu, Masanobu; Liu, Xuan; Belfield, Kevin D.

    2015-01-01

    Observation of the activation and inhibition of angiogenesis processes is important in the progression of cancer. Application of targeting peptides, such as a small peptide that contains adjacent L-arginine (R), glycine (G) and L-aspartic acid (D) residues can afford high selectivity and deep penetration in vessel imaging. To facilitate deep tissue vasculature imaging, probes that can be excited via two-photon absorption (2PA) in the near-infrared (NIR) and subsequently emit in the NIR are essential. In this study, the enhancement of tissue image quality with RGD conjugates was investigated with new NIR-emitting pyranyl fluorophore derivatives in two-photon fluorescence microscopy. Linear and nonlinear photophysical properties of the new probes were comprehensively characterized; significantly the probes exhibited good 2PA over a broad spectral range from 700–1100 nm. Cell and tissue images were then acquired and examined, revealing deep penetration and high contrast with the new pyranyl RGD-conjugates up to 350 μm in tumor tissue. PMID:26351137

  7. Radiolabeled Cyclic RGD Peptides as Radiotracers for Imaging Tumors and Thrombosis by SPECT

    PubMed Central

    Zhou, Yang; Chakraborty, Sudipta; Liu, Shuang

    2011-01-01

    The integrin family is a group of transmembrane glycoprotein comprised of 19 α- and 8 β-subunits that are expressed in 25 different α/β heterodimeric combinations on the cell surface. Integrins play critical roles in many physiological processes, including cell attachment, proliferation, bone remodeling, and wound healing. Integrins also contribute to pathological events such as thrombosis, atherosclerosis, tumor invasion, angiogenesis and metastasis, infection by pathogenic microorganisms, and immune dysfunction. Among 25 members of the integrin family, the αvβ3 is studied most extensively for its role of tumor growth, progression and angiogenesis. In contrast, the αIIbβ3 is expressed exclusively on platelets, facilitates the intercellular bidirectional signaling (“inside-out” and “outside-in”) and allows the aggregation of platelets during vascular injury. The αIIbβ3 plays an important role in thrombosis by its activation and binding to fibrinogen especially in arterial thrombosis due to the high blood flow rate. In the resting state, the αIIbβ3 on platelets does not bind to fibrinogen; on activation, the conformation of platelet is altered and the binding sites of αIIbβ3 are exposed for fibrinogen to crosslink platelets. Over the last two decades, integrins have been proposed as the molecular targets for diagnosis and therapy of cancer, thrombosis and other diseases. Several excellent review articles have appeared recently to cover a broad range of topics related to the integrin-targeted radiotracers and their nuclear medicine applications in tumor imaging by single photon emission computed tomography (SPECT) or a positron-emitting radionuclide for positron emission tomography (PET). This review will focus on recent developments of αvβ3-targeted radiotracers for imaging tumors and the use of αIIbβ3-targeted radiotracers for thrombosis imaging, and discuss different approaches to maximize the targeting capability of cyclic RGD peptides

  8. Adsorption of dimeric surfactants in lamellar silicates

    NASA Astrophysics Data System (ADS)

    Balcerzak, Mateusz; Pietralik, Zuzanna; Domka, Ludwik; Skrzypczak, Andrzej; Kozak, Maciej

    2015-12-01

    The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay - hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1‧-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d001) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH2 and CH3 groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  9. A new lignan dimer from Mallotus philippensis.

    PubMed

    Mai, Nguyen Thi; Cuong, Nguyen Xuan; Thao, Nguyen Phuong; Nam, Nguyen Hoai; Khoi, Nguyen Huu; Minh, Chau Van; Heyden, Yvan Vander; Thuan, Ngo Thi; Tuyen, Nguyen Van; Quetin-Leclercq, Joëlle; Kiem, Phan Van

    2010-03-01

    A new lignan dimer, bilariciresinol (1), was isolated from the leaves of Mallotus philippensis, along with platanoside (2), isovitexin (3), dihydromyricetin (4), bergenin (5), 4-O-galloylbergenin (6), and pachysandiol A (7). Their structures were elucidated by spectroscopic experiments including 1D and 2D NMR and FTICR-MS.

  10. Functional Asymmetry in Kinesin and Dynein Dimers

    PubMed Central

    Rank, Katherine C.; Rayment, Ivan

    2012-01-01

    Active transport along the microtubule lattice is a complex process that involves both the Kinesin and Dynein superfamily of motors. Transportation requires sophisticated regulation much of which occurs through the motor’s tail domain. However, a significant portion of this regulation also occurs through structural changes that arise in the motor and the microtubule upon binding. The most obvious structural change being the manifestation of asymmetry. To a first approximation in solution, kinesin dimers exhibit two-fold symmetry, and microtubules, helical symmetry. The higher symmetries of both the kinesin dimers and microtubule lattice are lost on formation of the kinesin-microtubule complex. Loss of symmetry has functional consequences such as an asymmetric hand-over-hand mechanism in plus-end directed kinesins, asymmetric microtubule binding in the Kinesin-14 family, spatially biased stepping in dynein, and cooperative binding of additional motors to the microtubule. This review focuses on how the consequences of asymmetry affect regulation of motor heads within a dimer, dimers within an ensemble of motors, and suggests how these asymmetries may affect regulation of active transport within the cell. PMID:23066835

  11. Amplitude enhancement by a gold dimer

    NASA Astrophysics Data System (ADS)

    Hong, Xin; Wang, Jingxin; Jin, Zheng

    2016-10-01

    The unique optical properties such as brightness, non-bleaching, good bio-compatibility make gold particles ideal label candidates for molecular probes. Due to the strongly enhanced field, aggregation of gold nanoparticles finds themselves plenty of applications in bio-imaging. But limited by its small cross-section associated with nanometer sized particle, it is a big challenge to employ it in a single molecular detection. The field enhancement results from the effect of plasmonic coupling between two closely attached gold nanoparticle under the right excitation condition. With the aim to apply the gold dimer probe to find the molecules in our recently established optical detection method, we compared of the amplitude enhancement by the dimer relative to a single particle. The amplitude distribution under a highly focused illumination objective was calculated, whose results suggest that at the optimized excitation condition, the local field can be enhanced 190 fold. In consequence, experimental detection was carried out. Gold dimers were linked together by the hybridization of two single chain DNAs. Dimer and single particle probes were mixed together in one detection. Overwhelming contrast between these two kinds of probes were clearly exhibited in the experimental detection image. This method can provide a way to a high specific detection in early diagnosis.

  12. Conjugation with RGD Peptides and Incorporation of Vascular Endothelial Growth Factor Are Equally Efficient for Biofunctionalization of Tissue-Engineered Vascular Grafts

    PubMed Central

    Antonova, Larisa V.; Seifalian, Alexander M.; Kutikhin, Anton G.; Sevostyanova, Victoria V.; Matveeva, Vera G.; Velikanova, Elena A.; Mironov, Andrey V.; Shabaev, Amin R.; Glushkova, Tatiana V.; Senokosova, Evgeniya A.; Vasyukov, Georgiy Yu.; Krivkina, Evgeniya O.; Burago, Andrey Yu.; Kudryavtseva, Yuliya A.; Barbarash, Olga L.; Barbarash, Leonid S.

    2016-01-01

    The blend of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(ε-caprolactone) (PCL) has recently been considered promising for vascular tissue engineering. However, it was shown that PHBV/PCL grafts require biofunctionalization to achieve high primary patency rate. Here we compared immobilization of arginine–glycine–aspartic acid (RGD)-containing peptides and the incorporation of vascular endothelial growth factor (VEGF) as two widely established biofunctionalization approaches. Electrospun PHBV/PCL small-diameter grafts with either RGD peptides or VEGF, as well as unmodified grafts were implanted into rat abdominal aortas for 1, 3, 6, and 12 months following histological and immunofluorescence assessment. We detected CD31+/CD34+/vWF+ cells 1 and 3 months postimplantation at the luminal surface of PHBV/PCL/RGD and PHBV/PCL/VEGF, but not in unmodified grafts, with the further observation of CD31+CD34−vWF+ phenotype. These cells were considered as endothelial and produced a collagen-positive layer resembling a basement membrane. Detection of CD31+/CD34+ cells at the early stages with subsequent loss of CD34 indicated cell adhesion from the bloodstream. Therefore, either conjugation with RGD peptides or the incorporation of VEGF promoted the formation of a functional endothelial cell layer. Furthermore, both modifications increased primary patency rate three-fold. In conclusion, both of these biofunctionalization approaches can be considered as equally efficient for the modification of tissue-engineered vascular grafts. PMID:27854352

  13. Cloning and sequence analysis of human breast epithelial antigen BA46 reveals an RGD cell adhesion sequence presented on an epidermal growth factor-like domain.

    PubMed

    Couto, J R; Taylor, M R; Godwin, S G; Ceriani, R L; Peterson, J A

    1996-04-01

    The BA46 antigen of the human milk fat globule (HMFG) membrane is expressed in human breast carcinomas and has been used successfully as a target for experimental breast cancer radioimmunotherapy. To characterize this antigen further, we obtained the entire cDNA sequence and focused on its possible role in cell adhesion. The derived protein sequence of BA46 encodes a 387-residue precursor composed of a putative signal peptide, an amino-terminal epidermal growth factor (EGF)-like domain containing the cell adhesion tripeptide arginine-glycine-aspartic acid (RGD), and human factor V and factor VIII C1/C2-like domains. The EGF-like domain of BA46 is similar to the calcium-binding EGF-like domains of several coagulation factors, but the BA46 domain lacks a residue required for calcium binding and the coagulation factor domains do not include an RGD sequence. Assuming that all EGF-like domains fold into a similar structure, the RGD-containing sequence in BA46 is inserted between two antiparallel beta strands. This positioning suggests a novel function for the EGF-like domain as a scaffold for RGD presentation.

  14. The integrin alpha 9 beta 1 mediates cell attachment to a non-RGD site in the third fibronectin type III repeat of tenascin.

    PubMed

    Yokosaki, Y; Palmer, E L; Prieto, A L; Crossin, K L; Bourdon, M A; Pytela, R; Sheppard, D

    1994-10-28

    We have previously reported the sequence of the integrin alpha 9 subunit, a partner of the beta 1 subunit that is expressed in basal keratinocytes, hepatocytes, airway epithelial cells, and smooth and skeletal muscle. In the present study, we have stably expressed alpha 9 beta 1 on the surface of the human embryonic kidney cell line 293 and the human colon carcinoma cell line SW480 and used these transfected cells lines to identify ligand(s) for this integrin. Transfected cells did not appear to utilize alpha 9 beta 1 for attachment to the extracellular matrix proteins fibronectin, laminin, vitronectin, fibrinogen, thrombospondin, or type I or IV collagen. However, in contrast to mock transfectants, both 293 cells and SW480 cells expressing alpha 9 beta 1 adhered to intact chicken tenascin. By utilizing a variety of recombinant fragments of tenascin, we were able to localize the binding site for alpha 9 beta 1 to the third type III repeat. This repeat contains the arginine-glycine-aspartic acid (RGD) tripeptide that has been shown to serve as a binding site in tenascin for alpha v-integrins. However, the RGD site does not appear to be the binding site for alpha 9 beta 1, as the attachment of alpha 9 transfectants to this fragment was not inhibited by RGD peptide, nor by changing the RGD site to RAD or RAA.

  15. Indirect coating of RGD peptides using a poly-L-lysine spacer enhances jaw periosteal cell adhesion, proliferation, and differentiation into osteogenic tissue.

    PubMed

    Ardjomandi, N; Klein, C; Kohler, K; Maurer, A; Kalbacher, H; Niederländer, J; Reinert, S; Alexander, D

    2012-08-01

    The aim of our study was to generate a biofunctionalized, three-dimensional (3D) biomaterial to enhance jaw periosteal cell (JPC) adhesion and differentiation into osteogenic tissue. Therefore, open-cell polylactic acid (OPLA) scaffolds were coated covalently with different RGD peptides (a conserved recognition sequence of the most ECM proteins--arginine-glycine-asparagine) and different coating variants. The linear and cyclic RGD peptides were either applied directly or indirectly via a poly-L-lysine (PLL) spacer. JPCs were analyzed on coated constructs in 2D and 3D cultures and showed enhanced rates for indirectly coated scaffolds using the PLL spacer. By gene expression, we detected significantly increased levels of osteogenic marker genes, such as alkaline phosphatase, RUNX2, and AMELY in JPCs seeded onto PLL/linear RGD constructs compared to the otherwise-coated constructs. An analysis of the JPC mineralization capacity revealed the highest amounts of calcium-phosphate precipitates in cells growing within the PLL/linear scaffolds. Additionally, the JPC adhesion behavior on OPLA scaffolds seems to be mediated by ITGB3, ITGB1, and ITGAV, as shown by blocking assays. We concluded that coating of OPLA constructs with linear RGD peptides via PLL represents a suitable approach for functionalizing the polymer surface and enhancing adhesion, proliferation, and mineralization of JPCs.

  16. Localized light-induced protein dimerization in living cells using a photocaged dimerizer

    PubMed Central

    Ballister, Edward R.; Aonbangkhen, Chanat; Mayo, Alyssa M.; Lampson, Michael A.; Chenoweth, David M.

    2015-01-01

    Regulated protein localization is critical for many cellular processes. Several techniques have been developed for experimental control over protein localization, including chemically induced and light-induced dimerization, which both provide temporal control. Light-induced dimerization offers the distinct advantage of spatial precision within subcellular length scales. A number of elegant systems have been reported that utilize natural light-sensitive proteins to induce dimerization via direct protein–protein binding interactions, but the application of these systems at cellular locations beyond the plasma membrane has been limited. Here we present a new technique to rapidly and reversibly control protein localization in living cells with subcellular spatial resolution using a cell-permeable, photoactivatable chemical inducer of dimerization. We demonstrate light-induced recruitment of a cytosolic protein to individual centromeres, kinetochores, mitochondria and centrosomes in human cells, indicating that our system is widely applicable to many cellular locations. PMID:25400104

  17. Dimerization of visual pigments in vivo

    PubMed Central

    Zhang, Tao; Cao, Li-Hui; Kumar, Sandeep; Enemchukwu, Nduka O.; Zhang, Ning; Lambert, Alyssia; Zhao, Xuchen; Jones, Alex; Wang, Shixian; Dennis, Emily M.; Fnu, Amrita; Ham, Sam; Rainier, Jon; Yau, King-Wai; Fu, Yingbin

    2016-01-01

    It is a deeply engrained notion that the visual pigment rhodopsin signals light as a monomer, even though many G protein-coupled receptors are now known to exist and function as dimers. Nonetheless, recent studies (albeit all in vitro) have suggested that rhodopsin and its chromophore-free apoprotein, R-opsin, may indeed exist as a homodimer in rod disk membranes. Given the overwhelmingly strong historical context, the crucial remaining question, therefore, is whether pigment dimerization truly exists naturally and what function this dimerization may serve. We addressed this question in vivo with a unique mouse line (S-opsin+Lrat−/−) expressing, transgenically, short-wavelength–sensitive cone opsin (S-opsin) in rods and also lacking chromophore to exploit the fact that cone opsins, but not R-opsin, require chromophore for proper folding and trafficking to the photoreceptor’s outer segment. In R-opsin’s absence, S-opsin in these transgenic rods without chromophore was mislocalized; in R-opsin’s presence, however, S-opsin trafficked normally to the rod outer segment and produced functional S-pigment upon subsequent chromophore restoration. Introducing a competing R-opsin transmembrane helix H1 or helix H8 peptide, but not helix H4 or helix H5 peptide, into these transgenic rods caused mislocalization of R-opsin and S-opsin to the perinuclear endoplasmic reticulum. Importantly, a similar peptide-competition effect was observed even in WT rods. Our work provides convincing evidence for visual pigment dimerization in vivo under physiological conditions and for its role in pigment maturation and targeting. Our work raises new questions regarding a potential mechanistic role of dimerization in rhodopsin signaling. PMID:27462111

  18. Dimer monomer transition and dimer re-formation play important role for ATM cellular function during DNA repair.

    PubMed

    Du, Fengxia; Zhang, Minjie; Li, Xiaohua; Yang, Caiyun; Meng, Hao; Wang, Dong; Chang, Shuang; Xu, Ye; Price, Brendan; Sun, Yingli

    2014-10-03

    The ATM protein kinase, is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks, mediates responses to ionizing radiation in mammalian cells. Here we show that ATM is held inactive in unirradiated cells as a dimer and phosphorylates the opposite strand of the dimer in response to DNA damage. Cellular irradiation induces rapid intermolecular autophosphorylation of serine 1981 that causes dimer dissociation and initiates cellular ATM kinase activity. ATM cannot phosphorylate the substrates when it could not undergo dimer monomer transition. After DNA repair, the active monomer will undergo dephosphorylation to form dimer again and dephosphorylation is critical for dimer re-formation. Our work reveals novel function of ATM dimer monomer transition and explains why ATM dimer monomer transition plays such important role for ATM cellular activity during DNA repair.

  19. Bone Regeneration Potential of Stem Cells Derived from Periodontal Ligament or Gingival Tissue Sources Encapsulated in RGD-Modified Alginate Scaffold

    PubMed Central

    Chen, Chider; Xu, Xingtian; Akiyama, Kentaro; Ansari, Sahar; Zadeh, Homayoun H.; Shi, Songtao

    2014-01-01

    Mesenchymal stem cells (MSCs) provide an advantageous alternative therapeutic option for bone regeneration in comparison to current treatment modalities. However, delivering MSCs to the defect site while maintaining a high MSC survival rate is still a critical challenge in MSC-mediated bone regeneration. Here, we tested the bone regeneration capacity of periodontal ligament stem cells (PDLSCs) and gingival mesenchymal stem cells (GMSCs) encapsulated in a novel RGD- (arginine-glycine-aspartic acid tripeptide) coupled alginate microencapsulation system in vitro and in vivo. Five-millimeter-diameter critical-size calvarial defects were created in immunocompromised mice and PDLSCs and GMSCs encapsulated in RGD-modified alginate microspheres were transplanted into the defect sites. New bone formation was assessed using microcomputed tomography and histological analyses 8 weeks after transplantation. Results confirmed that our microencapsulation system significantly enhanced MSC viability and osteogenic differentiation in vitro compared with non-RGD-containing alginate hydrogel microspheres with larger diameters. Results confirmed that PDLSCs were able to repair the calvarial defects by promoting the formation of mineralized tissue, while GMSCs showed significantly lower osteogenic differentiation capability. Further, results revealed that RGD-coupled alginate scaffold facilitated the differentiation of oral MSCs toward an osteoblast lineage in vitro and in vivo, as assessed by expression of osteogenic markers Runx2, ALP, and osteocalcin. In conclusion, these results for the first time demonstrated that MSCs derived from orofacial tissue encapsulated in RGD-modified alginate scaffold show promise for craniofacial bone regeneration. This treatment modality has many potential dental and orthopedic applications. PMID:24070211

  20. Pharmacophore refinement of gpIIb/IIIa antagonists based on comparative studies of antiadhesive cyclic and acyclic RGD peptides

    NASA Astrophysics Data System (ADS)

    Müller, Gerhard; Gurrath, Marion; Kessler, Horst

    1994-12-01

    Structurally guided design approaches to low-molecular-weight platelet aggregation antagonists addressing the platelet-associated heterodimeric cell surface receptor gpIIb/IIIa rely on comparative studies of an ensemble of conformationally and biologically characterized compounds, since no high-resolution structure of the receptor system is available. We report a classical indirect and comparative pharmacophore refinement approach based on a series of small cyclic Arg-Gly-Asp (RGD) peptides as gpIIb/IIIa-fibrinogen interaction antagonists. These peptides have previously been investigated as potent and selective tumor cell adhesion inhibitors. The definition of geometrical descriptors classifying the RGD peptide conformations and their subsequent analysis over selected RGD- and RXD-containing protein structures allows for a correlation of distinct structural features for platelet aggregation inhibition. An almost parallel alignment of the Arg and Asp side chains was identified by a vector analysis as being present in all active cyclic hexa-and pentapeptides. This orientation is induced mainly by the constraint of backbone cyclization and is not of any covalent tripeptide-inherent origin, which was rationalized by a 500 ps high-energy MD simulation of a sequentially related linear model peptide. The incorporation of the recognition tripeptide Arg-Gly-Asp into the cyclic peptide templates acted as a filter mechanism, restricting the otherwise free torsional relation of both side chains to a parallel orientation. Based on the derived results, several detailed features of the receptor binding site could be deduced in terms of receptor complementarity. These findings should govern the design of next-generation compounds with enhanced activities. Furthermore, the complementary stereochemical characteristics of the substrate can be used as boundary conditions for pseudoreceptor modelling studies that are capable of reconstructing a hypothetical binding pocket

  1. Robust Therapeutic Efficacy of Matrix Metalloproteinase-2-Cleavable Fas-1-RGD Peptide Complex in Chronic Inflammatory Arthritis

    PubMed Central

    Sa, Keum Hee; Sung, Shijin; Park, Jae Yong; Jo, Dong-Gyu; Park, Jae Hyung; Kim, In San; Kang, Young Mo

    2016-01-01

    Objective Therapeutic agents that are transformable via introducing cleavable linkage by locally enriched MMP-2 within inflamed synovium would enhance therapeutic efficacy on chronic inflammatory arthritis. Transforming growth factor-β-inducible gene-h3 (βig-h3), which consists of four fas-1 domains and an Arg-Gly-Asp (RGD) motif, intensifies inflammatory processes by facilitating adhesion and migration of fibroblast-like synoviocyte in the pathogenesis of rheumatoid arthritis (RA). The aim of this study was to investigate whether a MMP-2-cleavable peptide complex consisting of a fas-1 domain and an RGD peptide blocks the interaction between βig-h3 and resident cells and leads to the amelioration of inflammatory arthritis. Methods We designed βig-h3-derivatives, including the fourth fas-1 domain truncated for H1 and H2 sequences of mouse (MFK00) and MMP-2-cleavable peptide complex (MFK902). MMP-2 selectivity was examined by treatment with a series of proteases. MFK902 efficacy was determined by the adhesion and migration assay with NIH3T3 cells in vitro and collagen-induced arthritis (CIA) model using male DBA/1J mice in vivo. The mice were treated intraperitoneally with MFK902 at different dosages. Results MFK902 was specifically cleaved by active MMP-2 in a concentration-dependent manner, and βig-h3-mediated adhesion and migration were more effectively inhibited by MFK902, compared with RGD or MFK00 peptides. The arthritis activity of murine CIA, measured by clinical arthritis index and incidence of arthritic paws, was significantly ameliorated after treatment with all dosages of MFK902 (1, 10, and 30 mg/kg). MFK902 ameliorated histopathologic deterioration and reduced the expression of inflammatory mediators simultaneously with improvement of clinical features. In addition, a favorable safety profile of MFK902 was demonstrated in vivo. Conclusion The present study revealed that MMP-2-cleavable peptide complex based on βig-h3 structure is a potent and safe

  2. On the Pyrazine and Pyrazine-Pyrimidine Dimers.

    DTIC Science & Technology

    1986-06-01

    Lennard - Jones -hydrogen-bonding (LJ-HB) potential energy calculations. The pyrazine isotopic hetero- and homo-dimers possess nearly identical spectra with the exception that the perpendicular dimer features are displaced to the red by approx. 11 cm. Exchange or exciton interactions in this system are vanishingly small (less than 1/cm). The geometrics suggested by the isotopically substituted pyrazine dimer spectra are the same as those found for the pyrazine-h sub 4 homo-dimer: a parallel planar hydrogen bonded and a perpendicular dimer. The pyrazine-h sub 4 and pyrazine-h

  3. Pyrimidine dimer formation and repair in human skin

    SciTech Connect

    Sutherland, B.M.; Harber, L.C.; Kochevar, I.E.

    1980-09-01

    Cyclobutyl pyrimidine dimers have been detected in the DNA of human skin following in vivo irradiation with suberythermal doses of ultraviolet (UV) radiation from FS-20 sun lamp fluorescent tubes. Dimers were assayed by treatment of extracted DNA with Micrococus luteus UV-specific endonuclease, alkaline agarose electrophoresis, and ethidum bromide staining. This technique, in contrast to conventional dimer assays, can be used with nonradioactive DNA and is optimal at low UV light doses. These data suggest that some dimer disappearance by excision repair occurs within 20 min of UV irradiation and that photoreactivation of dimers can make a contribution to the total repair process.

  4. Calcium-dependent Dimerization of Human Soluble Calcium Activated Nucleotidase: Characterization of the Dimer Interface

    SciTech Connect

    Yang,M.; Horii, K.; Herr, A.; Kirley, T.

    2006-01-01

    Mammals express a protein homologous to soluble nucleotidases used by blood-sucking insects to inhibit host blood clotting. These vertebrate nucleotidases may play a role in protein glycosylation. The activity of this enzyme family is strictly dependent on calcium, which induces a conformational change in the secreted, soluble human nucleotidase. The crystal structure of this human enzyme was recently solved; however, the mechanism of calcium activation and the basis for the calcium-induced changes remain unclear. In this study, using analytical ultracentrifugation and chemical cross-linking, we show that calcium or strontium induce noncovalent dimerization of the soluble human enzyme. The location and nature of the dimer interface was elucidated using a combination of site-directed mutagenesis and chemical cross-linking, coupled with crystallographic analyses. Replacement of Ile{sup 170}, Ser{sup 172}, and Ser{sup 226} with cysteine residues resulted in calcium-dependent, sulfhydryl-specific intermolecular cross-linking, which was not observed after cysteine introduction at other surface locations. Analysis of a super-active mutant, E130Y, revealed that this mutant dimerized more readily than the wild-type enzyme. The crystal structure of the E130Y mutant revealed that the mutated residue is found in the dimer interface. In addition, expression of the full-length nucleotidase revealed that this membrane-bound form can also dimerize and that these dimers are stabilized by spontaneous oxidative cross-linking of Cys{sup 30}, located between the single transmembrane helix and the start of the soluble sequence. Thus, calcium-mediated dimerization may also represent a mechanism for regulation of the activity of this nucleotidase in the physiological setting of the endoplasmic reticulum or Golgi.

  5. Shear- vs. nanotopography-guided control of growth of endothelial cells on RGD-nanoparticle-nanowell arrays

    PubMed Central

    2013-01-01

    Endothelialization of therapeutic cardiovascular implants is essential for their intravascular hemocompatibility. We previously described a novel nanowell-RGD-nanoparticle ensemble, which when applied to surfaces led to enhanced endothelialization and retention under static conditions and low flow rates. In the present study we extend our work to determine the interrelated effects of flow rate and the orientation of ensemble-decorated surface arrays on the growth, adhesion and morphology of endothelial cells. Human umbilical vascular endothelial cells (HUVECs) were grown on array surfaces with either 1 μm × 5 μm spacing (“parallel to flow”) and 5 μm × 1 μm spacing (“perpendicular to flow”) and were exposed to a range of shear stress of (0 to 4.7 ± 0.2 dyn·cm-2 ), utilizing a pulsatile flow chamber. Under physiological flow (4.7 ± 0.2 dyn·cm-2), RGD-nanoparticle-nanowell array patterning significantly enhanced cell adhesion and spreading compared with control surfaces and with static conditions. Furthermore, improved adhesion coincided with higher alignment to surface patterning, intimating the importance of interaction and response to the array surface as a means of resisting flow detachment. Under sub-physiological condition (1.7 ± 0.3 dyn·cm-2; corresponding to early angiogenesis), nanowell-nanoparticle patterning did not provide enhanced cell growth and adhesion compared with control surfaces. However, it revealed increased alignment along the direction of flow, rather than the direction of the pattern, thus potentially indicating a threshold for cell guidance and related retention. These results could provide a cue for controlling cell growth and alignment under varying physiological conditions. PMID:23607894

  6. Efficient, dual-stimuli responsive cytosolic gene delivery using a RGD modified disulfide-linked polyethylenimine functionalized gold nanorod.

    PubMed

    Wang, Feihu; Shen, Yuanyuan; Zhang, Wenjun; Li, Min; Wang, Yun; Zhou, Dejian; Guo, Shengrong

    2014-12-28

    Controlled-release systems capable of responding to external stimuli and/or unique internal environments have received great interests in site-specific gene and/or drug delivery. In this work, a functionalized gene nanocarrier for dual-stimuli triggered cytosolic gene delivery is developed and showing high gene delivery efficacy with low cytotoxicity. The nanocarrier is prepared by conjugating gold nanorod (GNR) with multiple disulfide cross-linked short PEIs to harness the advantageous properties of GNR based near infrared (NIR) laser induced photothermal heating and intracellular stimuli-triggered degradability of disulfide cross-linked short PEIs (DSPEI). The DSPEI is further grafted with a poly(ethylene glycol) (PEG) section to afford high carrier stability in cell cultures and a terminal RGD peptide for specific targeting of cancer cells. The nanocarrier is found to effectively condense plasmid DNA to form a highly stable GNR-DSPEI-PEG-RGD/DNA complex with tumor cell-targeting ability that can be efficiently uptaken by cancer cells. Moreover, the loaded genes can be effectively released from the complex triggered by the high intracellular glutathione content and/or by photothermal effect of NIR irradiation at 808 nm. Interestingly, the GNRs-based complex can easily escape from intracellular endo-/lyso-somal compartments and release the gene load into the cytosol upon exposure to NIR irradiation, resulting in significantly improved gene transfection efficiency. Our new gene carrier exhibits high gene transfection efficiency, comparable to or even better than that of high MW PEIs, but with a much lower cytotoxicity. Additionally, neither the GNR-based carrier nor the laser treatment shows any significant evidence of cytotoxicity. This work demonstrates a promising strategy for intracellular stimuli triggered, photothermal controllable gene delivery system, which can be further applied to many other nanomedicine fields.

  7. Excitonic interaction in the fluorene dimer

    NASA Astrophysics Data System (ADS)

    Wessel, John; Beck, Steven; Highstrete, Clark

    1994-12-01

    The fluorene van der Waals dimer exhibits a complex origin spectrum. This region has been studied by resonance two-photon ionization and by fluorescence excitation spectroscopies. The spectra can be interpreted on the basis of intermediate strength exciton coupling, in which the electronic interaction is comparable to the van der Waals vibrational energies. The spectra are reasonably well described by two distorted adiabatic potential surfaces, which correspond to the two excitonic components of the origin system. A single Franck-Condon active intermolecular mode provides a reasonable description of the system, however the potentials have significant cubic and quartic contributions. Non-Born-Oppenheimer nuclear momentum coupling is present and intermodal (IVR) interactions are observed, even for intermolecular modes as low as v=1. The results are remarkably different from prior observations of excitonic structure in other systems, providing a detailed picture of coupling between electronic and intermolecular motion in a van der Waals dimer.

  8. Electronic Transitions of Palladium and Vanadium Dimer

    NASA Astrophysics Data System (ADS)

    Qian, Yue; Ng, Y. W.; Cheung, A. S.-C.

    2013-06-01

    The laser induced fluorescence (LIF) spectrum of palladium dimer (Pd_{2}) in the visible region between 480 and 700 nm has been studied. Five vibrational bands were recorded and analyzed; they are assigned to a ^{3} Π _{g} - X^{3} Σ _{u} ^{+} system. The vibrational frequency of the ground X^{3} Σ _{u} ^{+} state has been determined to be 211.4 cm^{-1}. This is the first experimental observation of the LIF spectrum of Pd_{2}. In addition, the LIF spectrum of vanadium dimer (V_{2}) has also been studied; several new transition band systems were observed in the wavelength between 480 and 530 nm. The analysis of the spectra recorded for these two molecules will be presented.

  9. Minimization of a Protein–DNA Dimerizer

    PubMed Central

    Stafford, Ryan L.; Arndt, Hans-Dieter; Brezinski, Mary L.; Ansari, Aseem Z.; Dervan, Peter B.

    2011-01-01

    A protein–DNA dimerizer constructed from a DNA-binding polyamide and the peptide FYPWMKG facilitates the binding of a natural transcription factor Exd to an adjacent DNA site. The Exd binding domain can be reduced to a dipeptide WM attached to the polyamide through an ε-aminohexanoic acid linker with retention of protein–DNA dimerizer activity. Screening a library of analogues indicated that the tryptophan indole moiety is more important than methionine’s side chain or the N-terminal acetamide. Remarkably, switching the stereochemistry of the tryptophan residue (l to d) stabilizes the dimerizer•Exd•DNA ternary complex at 37 °C. These observations provide design principles for artificial transcription factors that may function in concert with the cellular regulatory circuitry. PMID:17290996

  10. Fibrillar dimer formation of islet amyloid polypeptides

    NASA Astrophysics Data System (ADS)

    Chiu, Chi-cheng; de Pablo, Juan J.

    2015-09-01

    Amyloid deposits of human islet amyloid polypeptide (hIAPP), a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 - 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 - 29 are involved in an intermediate that exhibits transient β-sheets, consistent with recent experimental and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.

  11. Fibrillar dimer formation of islet amyloid polypeptides

    SciTech Connect

    Chiu, Chi -cheng; de Pablo, Juan J.

    2015-05-08

    Amyloid deposits of human islet amyloid polypeptide (hIAPP), a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 – 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 – 29 are involved in an intermediate that exhibits transient β-sheets, consistent with recent experimental and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.

  12. Theoretical studies of transition metal dimers

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Bauschlicher, Charles W., Jr.

    1985-01-01

    The CASSCF approach was used to perform the MCSCF calculations for a number of transition metal dimers, including the Sc2, Ti2, Cr2, Cu2, TiV, Y2, Nb2, and Mo2 molecules; in addition, CASSCF/CI calculations were carried out for Sc2, Ti2, Cu2, and Y2. The CASSCF procedure is shown to provide a consistent set of calculations for these molecules, from which trends and a simple qualitative picture of the electronic structure may be derived. In particular, the calculations confirmed the ground states of the Sc2 and the TiV, and led to predictions for other molecules in this series. In addition to specific predictions, the study provides a simple qualitative picture of the bonding in these dimers.

  13. Palmitoylated APP Forms Dimers, Cleaved by BACE1.

    PubMed

    Bhattacharyya, Raja; Fenn, Rebecca H; Barren, Cory; Tanzi, Rudolph E; Kovacs, Dora M

    2016-01-01

    A major rate-limiting step for Aβ generation and deposition in Alzheimer's disease brains is BACE1-mediated cleavage (β-cleavage) of the amyloid precursor protein (APP). We previously reported that APP undergoes palmitoylation at two cysteine residues (Cys186 and Cys187) in the E1-ectodomain. 8-10% of total APP is palmitoylated in vitro and in vivo. Palmitoylated APP (palAPP) shows greater preference for β-cleavage than total APP in detergent resistant lipid rafts. Protein palmitoylation is known to promote protein dimerization. Since dimerization of APP at its E1-ectodomain results in elevated BACE1-mediated cleavage of APP, we have now investigated whether palmitoylation of APP affects its dimerization and whether this leads to elevated β-cleavage of the protein. Here we report that over 90% of palAPP is dimerized while only ~20% of total APP forms dimers. PalAPP-dimers are predominantly cis-oriented while total APP dimerizes in both cis- and trans-orientation. PalAPP forms dimers 4.5-times more efficiently than total APP. Overexpression of the palmitoylating enzymes DHHC7 and DHHC21 that increase palAPP levels and Aβ release, also increased APP dimerization in cells. Conversely, inhibition of APP palmitoylation by pharmacological inhibitors reduced APP-dimerization in coimmunoprecipitation and FLIM/FRET assays. Finally, in vitro BACE1-activity assays demonstrate that palmitoylation-dependent dimerization of APP promotes β-cleavage of APP in lipid-rich detergent resistant cell membranes (DRMs), when compared to total APP. Most importantly, generation of sAPPβ-sAPPβ dimers is dependent on APP-palmitoylation while total sAPPβ generation is not. Since BACE1 shows preference for palAPP dimers over total APP, palAPP dimers may serve as novel targets for effective β-cleavage inhibitors of APP as opposed to BACE1 inhibitors.

  14. Palmitoylated APP Forms Dimers, Cleaved by BACE1

    PubMed Central

    Fenn, Rebecca H.; Barren, Cory; Tanzi, Rudolph E.; Kovacs, Dora M.

    2016-01-01

    A major rate-limiting step for Aβ generation and deposition in Alzheimer’s disease brains is BACE1-mediated cleavage (β-cleavage) of the amyloid precursor protein (APP). We previously reported that APP undergoes palmitoylation at two cysteine residues (Cys186 and Cys187) in the E1-ectodomain. 8–10% of total APP is palmitoylated in vitro and in vivo. Palmitoylated APP (palAPP) shows greater preference for β-cleavage than total APP in detergent resistant lipid rafts. Protein palmitoylation is known to promote protein dimerization. Since dimerization of APP at its E1-ectodomain results in elevated BACE1-mediated cleavage of APP, we have now investigated whether palmitoylation of APP affects its dimerization and whether this leads to elevated β-cleavage of the protein. Here we report that over 90% of palAPP is dimerized while only ~20% of total APP forms dimers. PalAPP-dimers are predominantly cis-oriented while total APP dimerizes in both cis- and trans-orientation. PalAPP forms dimers 4.5-times more efficiently than total APP. Overexpression of the palmitoylating enzymes DHHC7 and DHHC21 that increase palAPP levels and Aβ release, also increased APP dimerization in cells. Conversely, inhibition of APP palmitoylation by pharmacological inhibitors reduced APP-dimerization in coimmunoprecipitation and FLIM/FRET assays. Finally, in vitro BACE1-activity assays demonstrate that palmitoylation-dependent dimerization of APP promotes β-cleavage of APP in lipid-rich detergent resistant cell membranes (DRMs), when compared to total APP. Most importantly, generation of sAPPβ-sAPPβ dimers is dependent on APP-palmitoylation while total sAPPβ generation is not. Since BACE1 shows preference for palAPP dimers over total APP, palAPP dimers may serve as novel targets for effective β-cleavage inhibitors of APP as opposed to BACE1 inhibitors. PMID:27875558

  15. rLj-RGD3, a Novel Recombinant Toxin Protein from Lampetra japonica, Protects against Cerebral Reperfusion Injury Following Middle Cerebral Artery Occlusion Involving the Integrin-PI3K/Akt Pathway in Rats

    PubMed Central

    Jiang, Junshu; Wang, Shengnan; Jia, Qilan; Wang, Yue; Li, Weiping; Zhou, Qin; Lv, Li; Li, Qingwei

    2016-01-01

    Background The RGD-toxin protein Lj-RGD3 is a naturally occurring 118 amino acid peptide that can be obtained from the salivary gland of the Lampetra japonica fish. This unique peptide contains 3 RGD (Arg-Gly-Asp) motifs in its primary structure. Lj-RGD3 is available in recombinant form (rLj-RGD3) and can be produced in large quantities using DNA recombination techniques. The pharmacology of the three RGD motif-containing peptides has not been studied. This study investigated the protective effects of rLj-RGD3, a novel polypeptide, against ischemia/reperfusion-induced damage to the brain caused by middle cerebral artery occlusion (MCAO) in a rat stroke model. We also explored the mechanism by which rLj-RGD3 acts by measuring protein and mRNA expression levels, with an emphasis on the FAK and integrin-PI3K/Akt anti-apoptosis pathways. Methods rLj-RGD3 was obtained from the buccal secretions of Lampetra japonica using gene recombination technology. Sprague Dawley (SD) rats were randomly divided into the following seven groups: a sham group; a vehicle-treated (VT) group; 100.0 μg·kg-1, 50.0 μg·kg-1 and 25.0 μg·kg-1 dose rLj-RGD3 groups; and two positive controls, including 1.5 mg·kg-1 Edaravone (ED) and 100.0 μg·kg-1 Eptifibatide (EP). MCAO was induced using a model consisting of 2 h of ischemia and 24 h of reperfusion. Behavioral changes were observed in the normal and operation groups after focal cerebral ischemia/reperfusion was applied. In addition, behavioral scores were evaluated at 4 and 24 h after reperfusion. Brain infarct volumes were determined based on 2,3,5-triphenyltetrazolium chloride (TTC) staining. Pathological changes in brain tissues were observed using hematoxylin and eosin (H&E) staining. Moreover, neuronal apoptosis was detected using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) assays. We determined the expression levels of focal adhesion kinase (FAK), phosphatidyl inositol 3-kinase (PI3K

  16. Dimer monomer transition and dimer re-formation play important role for ATM cellular function during DNA repair

    SciTech Connect

    Du, Fengxia; Zhang, Minjie; Li, Xiaohua; Yang, Caiyun; Meng, Hao; Wang, Dong; Chang, Shuang; Xu, Ye; Price, Brendan; Sun, Yingli

    2014-10-03

    Highlights: • ATM phosphorylates the opposite strand of the dimer in response to DNA damage. • The PETPVFRLT box of ATM plays a key role in its dimer dissociation in DNA repair. • The dephosphorylation of ATM is critical for dimer re-formation after DNA repair. - Abstract: The ATM protein kinase, is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks, mediates responses to ionizing radiation in mammalian cells. Here we show that ATM is held inactive in unirradiated cells as a dimer and phosphorylates the opposite strand of the dimer in response to DNA damage. Cellular irradiation induces rapid intermolecular autophosphorylation of serine 1981 that causes dimer dissociation and initiates cellular ATM kinase activity. ATM cannot phosphorylate the substrates when it could not undergo dimer monomer transition. After DNA repair, the active monomer will undergo dephosphorylation to form dimer again and dephosphorylation is critical for dimer re-formation. Our work reveals novel function of ATM dimer monomer transition and explains why ATM dimer monomer transition plays such important role for ATM cellular activity during DNA repair.

  17. Surface-subsurface model for a dimer-dimer catalytic reaction: a Monte Carlo simulation study

    NASA Astrophysics Data System (ADS)

    Khan, K. M.; Albano, E. V.

    2002-02-01

    The surface-subsurface model for a dimer-dimer reaction of the type A2 + 2B2→2AB2 has been studied through Monte Carlo simulation via a model based on the lattice gas non-thermal Langmuir-Hinshelwood mechanism, which involves the precursor motion of the B2 molecule. The motion of precursors is considered on the surface as well as in the subsurface. The most interesting feature of this model is that it yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions. The phase diagram is qualitatively similar to the well known Ziff, Gulari and Barshad (ZGB) model. The width of the window depends upon the mobility of precursors. The continuous transition disappears when the mobility of the surface precursors is extended to the third-nearest neighbourhood. The dependence of production rate on partial pressure of B2 dimer is predicted by simple mathematical equations in our model.

  18. Analysis of SecA Dimerization in Solution

    PubMed Central

    2015-01-01

    The Sec pathway mediates translocation of protein across the inner membrane of bacteria. SecA is a motor protein that drives translocation of preprotein through the SecYEG channel. SecA reversibly dimerizes under physiological conditions, but different dimer interfaces have been observed in SecA crystal structures. Here, we have used biophysical approaches to address the nature of the SecA dimer that exists in solution. We have taken advantage of the extreme salt sensitivity of SecA dimerization to compare the rates of hydrogen–deuterium exchange of the monomer and dimer and have analyzed the effects of single-alanine substitutions on dimerization affinity. Our results support the antiparallel dimer arrangement observed in one of the crystal structures of Bacillus subtilis SecA. Additional residues lying within the preprotein binding domain and the C-terminus are also protected from exchange upon dimerization, indicating linkage to a conformational transition of the preprotein binding domain from an open to a closed state. In agreement with this interpretation, normal mode analysis demonstrates that the SecA dimer interface influences the global dynamics of SecA such that dimerization stabilizes the closed conformation. PMID:24786965

  19. Antiangiogenic gene therapy of experimental pancreatic tumor by sFlt-1 plasmid DNA carried by RGD-modified crosslinked polyplex micelles.

    PubMed

    Vachutinsky, Yelena; Oba, Makoto; Miyata, Kanjiro; Hiki, Shigehiro; Kano, Mitsunobu R; Nishiyama, Nobuhiro; Koyama, Hiroyuki; Miyazono, Kohei; Kataoka, Kazunori

    2011-01-05

    Disulfide crosslinked polyplex micelles with RGD peptides were formed through ion complexation of thiolated c(RGDfK)-poly(ethylene glycol)-block-poly(L-lysine) (c(RGDfK)-PEG-P(Lys-SH)) and plasmid DNA encoding sFlt-1 and tested for their therapeutic effect in BxPC3 pancreatic adenocarcinoma tumor bearing mice. These micelles, systemically injected, demonstrated significant inhibition of tumor growth up to day 18, as a result of the antiangiogenic effect that was confirmed by vascular density measurements. Significant therapeutic activity of the 15% crosslinked micelle (c(RGDfK)-PEG-P(Lys-SH15)) was achieved by combined effect of increased tumor accumulation, interaction with endothelial cells and enhanced intracellular uptake through receptor-mediated endocytosis. These results suggest that RGD targeted crosslinked polyplex micelles can be effective plasmid DNA carriers for antiangiogenic gene therapy.

  20. Modulation of ceramide synthase activity via dimerization.

    PubMed

    Laviad, Elad L; Kelly, Samuel; Merrill, Alfred H; Futerman, Anthony H

    2012-06-15

    Ceramide, the backbone of all sphingolipids, is synthesized by a family of ceramide synthases (CerS) that each use acyl-CoAs of defined chain length for N-acylation of the sphingoid long chain base. CerS mRNA expression and enzymatic activity do not always correlate with the sphingolipid acyl chain composition of a particular tissue, suggesting post-translational mechanism(s) of regulation of CerS activity. We now demonstrate that CerS activity can be modulated by dimer formation. Under suitable conditions, high M(r) CerS complexes can be detected by Western blotting, and various CerS co-immunoprecipitate. CerS5 activity is inhibited in a dominant-negative fashion by co-expression with catalytically inactive CerS5, and CerS2 activity is enhanced by co-expression with a catalytically active form of CerS5 or CerS6. In a constitutive heterodimer comprising CerS5 and CerS2, the activity of CerS2 depends on the catalytic activity of CerS5. Finally, CerS dimers are formed upon rapid stimulation of ceramide synthesis by curcumin. Together, these data demonstrate that ceramide synthesis can be regulated by the formation of CerS dimers and suggest a novel way to generate the acyl chain composition of ceramide (and downstream sphingolipids), which may depend on the interaction of CerS with each other.

  1. Caffeine dimerization: effects of sugar, salts, and water structure.

    PubMed

    Shimizu, Seishi

    2015-10-01

    Sugars and salts strongly affect the dimerization of caffeine in water. Such a change of dimerization, considered to be crucial for bitter taste suppression, has long been rationalized by the change of "water structure" induced by the additives; "kosmotropic" (water structure enhancing) salts and sugars promote dimerization, whereas "chaotropic" (water structure breaking) salts suppress dimerization. Based on statistical thermodynamics, here we challenge this consensus; we combine the rigorous Kirkwood-Buff theory of solution with the classical isodesmic model of caffeine association. Instead of the change of water structure, we show that the enhancement of caffeine dimerization is due to the exclusion of additives from caffeine, and that the weakening of dimerization is due to the binding of additives on caffeine.

  2. Metal enhanced fluorescence of Ag-nanoshell dimer

    NASA Astrophysics Data System (ADS)

    Liaw, Jiunn-Woei; Chen, Huang-Chih; Chen, Bae-Renn; Kuo, Mao-Kuen

    2014-04-01

    The plasmon modes of Ag-nanoshell dimer on metal enhanced fluorescence (MEF) are studied theoretically. The amplified excitation rate of a dimer (two identical Ag nanoshells) illuminated by a plane wave for exciting a molecule located at the gap center is calculated. Subsequently, the apparent quantum yield of the emission of the excited molecule affected by the dimer is investigated. The multiple multipole method is used for the both simulations. Finally, the enhancement factor of the dimer on the overall photoluminescence of the molecule in terms of the two parameters is evaluated. Our results show that Ag-nanoshell dimer is a dual-band photoluminescence enhancer for MEF at the bonding dipole and quadrupole modes. The former is broadband, and the latter narrowband. Both bands depend on the gap size. Moreover, the average enhancement factor of Ag-nanoshell dimer for MEF with a Stokes shift is discussed.

  3. Morphinane alkaloid dimers from Sinomenium acutum.

    PubMed

    Jin, Hui-Zi; Wang, Xiao-Ling; Wang, Hong-Bing; Wang, Yu-Bo; Lin, Li-Ping; Ding, Jian; Qin, Guo-Wei

    2008-01-01

    Two new morphinane alkaloid dimers, 2,2'-disinomenine (1) and 7',8'-dihydro-1,1'-disinomenine (2), and known 1, 1'-disinomenine (3), were isolated from ethanol extracts of stems of Sinomenium acutum. Their structures were elucidated on the basis of spectroscopic methods. The absolute configuration of alkaloids 1-3 was determined by direct comparison of their CD spectra with the known alkaloid sinomenine. The isolated alkaloids were tested for cytotoxicity against A549, P388, and HeLa cell lines, and 1 and 3 showed weak inhibition against A549 and Hela cells.

  4. Thermodynamic properties for the sodium dimer

    NASA Astrophysics Data System (ADS)

    Song, Xiao-Qin; Wang, Chao-Wen; Jia, Chun-Sheng

    2017-04-01

    We present a closed-form expression of the classical vibrational partition function for the improved Rosen-Morse potential energy model. We give explicit expressions for the vibrational mean energy, vibrational specific heat, vibrational free energy, and vibrational entropy for diatomic molecule systems. The properties of these thermodynamic functions for the Na2 dimer are discussed in detail. We find that the improved Rosen-Morse potential model is superior to the harmonic oscillator in calculating the heat capacity for the Na2 molecules.

  5. Thermodynamics of acetylene van der Waals dimerization

    NASA Technical Reports Server (NTRS)

    Colussi, A. J.; Sander, S. P.; Friedl, R. R.

    1991-01-01

    Integrated band intensities of the 620/cm absorption in (C2H2)2 are measured by FTIR spectroscopy at constant acetylene pressure between 198 and 273 K. These data, in conjunction with ab initio results for (C2H2)2, are used for the statistical evaluation of the equilibrium constant Kp(T) for acetylene-cluster dimerization. The present results are used to clarify the role of molecular clusters in chemical systems at or near equilibrium, in particular in Titan's stratosphere.

  6. Dimerization of thymol blue in solution: Theoretical evidence.

    PubMed

    Balderas-Hernández, Patricia; Vargas, Rubicelia; Rojas-Hernández, Alberto; Ramírez-Silva, Ma Teresa; Galván, Marcelo

    2007-02-28

    The possibility of dimerization of thymol blue was addressed by ab initio and force field calculations. In agreement with experimental information, a dimer forming symmetrical chemical environments for hydrogen bond formation was determined. This dimer is stable in vacuum and aqueous media and corresponds to the same protonated state proposed by the experiment. A comparison of the CVFF and MM3 force fields and ab initio results shows the suitability of CVFF to qualitatively describe this system.

  7. Synthesis and biological evaluation (in vitro and in vivo) of cyclic arginine-glycine-aspartate (RGD) peptidomimetic-paclitaxel conjugates targeting integrin αVβ3.

    PubMed

    Colombo, Raffaele; Mingozzi, Michele; Belvisi, Laura; Arosio, Daniela; Piarulli, Umberto; Carenini, Nives; Perego, Paola; Zaffaroni, Nadia; De Cesare, Michelandrea; Castiglioni, Vittoria; Scanziani, Eugenio; Gennari, Cesare

    2012-12-13

    A small library of integrin ligand-paclitaxel conjugates 10-13 was synthesized with the aim of using the tumor-homing cyclo[DKP-RGD] peptidomimetics for site-directed delivery of the cytotoxic drug. All the paclitaxel-RGD constructs 10-13 inhibited biotinylated vitronectin binding to the purified αVβ3 integrin receptor at low nanomolar concentration and showed in vitro cytotoxic activity against a panel of human tumor cell lines similar to that of paclitaxel. Among the cell lines, the cisplatin-resistant IGROV-1/Pt1 cells expressed high levels of integrin αVβ3, making them attractive to be tested in in vivo models. cyclo[DKP-f3-RGD]-PTX 11 displayed sufficient stability in physiological solution and in both human and murine plasma to be a good candidate for in vivo testing. In tumor-targeting experiments against the IGROV-1/Pt1 human ovarian carcinoma xenotransplanted in nude mice, compound 11 exhibited a superior activity compared with paclitaxel, despite the lower (about half) molar dosage used.

  8. Insights into the Binding of Cyclic RGD Peptidomimetics to α5β1 Integrin by using Live‐Cell NMR And Computational Studies

    PubMed Central

    Guzzetti, Ileana; Civera, Monica; Vasile, Francesca; Arosio, Daniela; Tringali, Cristina; Piarulli, Umberto; Gennari, Cesare; Pignataro, Luca

    2016-01-01

    Abstract The interaction of a small library of cyclic DKP–RGD peptidomimetics with α5β1 integrin has been investigated by means of an integrated experimental and computational approach. Bioaffinity NMR techniques, including saturation transfer difference (STD) and transferred NOESY, were applied to the ligands in a suspension of intact MDA‐MB‐231 breast cancer cells, in which integrin α5β1 is highly expressed. The NMR data were compared with the docking calculations of the RGD ligands in the crystal structure of the α5β1 binding site, and were integrated with competitive binding assays to the purified α5β1 integrin. Ligand binding epitopes involve protons of both the RGD moiety and the DKP scaffold, although the stereochemistry and the functionalization of the DKP scaffold as well as the macrocycle conformation determine a great variability in the interaction. The ligand showing the highest number of STD signals is also the most potent α5β1 ligand of the series, displaying a nanomolar IC 50 value. PMID:28168158

  9. Antitumor magnetic hyperthermia induced by RGD-functionalized Fe3O4 nanoparticles, in an experimental model of colorectal liver metastases

    PubMed Central

    Arriortua, Oihane K; Garaio, Eneko; Herrero de la Parte, Borja; Lezama, Luis; Plazaola, Fernando; García, Jose Angel; Aizpurua, Jesús M; Sagartzazu, Maialen; Irazola, Mireia; Etxebarria, Nestor; García-Alonso, Ignacio; Saiz-López, Alberto; Echevarria-Uraga, José Javier

    2016-01-01

    This work reports important advances in the study of magnetic nanoparticles (MNPs) related to their application in different research fields such as magnetic hyperthermia. Nanotherapy based on targeted nanoparticles could become an attractive alternative to conventional oncologic treatments as it allows a local heating in tumoral surroundings without damage to healthy tissue. RGD-peptide-conjugated MNPs have been designed to specifically target αVβ3 receptor-expressing cancer cells, being bound the RGD peptides by “click chemistry” due to its selectivity and applicability. The thermal decomposition of iron metallo-organic precursors yield homogeneous Fe3O4 nanoparticles that have been properly functionalized with RGD peptides, and the preparation of magnetic fluids has been achieved. The nanoparticles were characterized by transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), electron magnetic resonance (EMR) spectroscopy and magnetic hyperthermia. The nanoparticles present superparamagnetic behavior with very high magnetization values, which yield hyperthermia values above 500 W/g for magnetic fluids. These fluids have been administrated to rats, but instead of injecting MNP fluid directly into liver tumors, intravascular administration of MNPs in animals with induced colorectal tumors has been performed. Afterwards the animals were exposed to an alternating magnetic field in order to achieve hyperthermia. The evolution of an in vivo model has been described, resulting in a significant reduction in tumor viability. PMID:28144504

  10. VIDAS D-dimer: fast quantitative ELISA for measuring D-dimer in plasma.

    PubMed

    Pittet, J L; de Moerloose, P; Reber, G; Durand, C; Villard, C; Piga, N; Rolland, D; Comby, S; Dupuy, G

    1996-03-01

    VIDAS D-dimer (bioMérieux) is a new quantitative ELISA for D-dimer determination designed for the VIDAS automated system. The test contains single-dose, ready-to-use reagents and is completed within 35 min. Quantitative results are obtained from a calibration curve stored in the software of the system and expressed as fibrinogen equivalent units. The two-step capture/tag test relies on two complementary monoclonal anti-D-dimer antibodies, the second one being labeled with alkaline phosphatase. The upper limit of the measuring range is 1000 micrograms/L and the lower detection limit is <50 micrograms/L, which is below the lower limit of the reference interval (68-494 micrograms/L). Reproducibility (CV) within and between runs ranges from 5% to 7%. There is no interference from heparin, bilirubin, hemoglobin, fibrinogen degradation products, or plasma turbidity. Comparison with a conventional ELISA (y) gave good correlation (r= 0.91, n= 579) and comparable results (y= 1.35x - 148, S(y/x)= 750), especially for D-dimer concentrations ranging from 0 to 1000 micrograms/L (y= 1.09x - 10.6, r= 0.88, S(y/x)= 170).

  11. Rotational spectra of propargyl alcohol dimer: A dimer bound with three different types of hydrogen bonds

    SciTech Connect

    Mani, Devendra; Arunan, E.

    2014-10-28

    Pure rotational spectra of the propargyl alcohol dimer and its three deuterium isotopologues have been observed in the 4 to 13 GHz range using a pulsed-nozzle Fourier transform microwave spectrometer. For the parent dimer, a total of 51 transitions could be observed and fitted within experimental uncertainty. For two mono-substituted and one bi-substituted deuterium isotopologues, a total of 14, 17, and 19 transitions were observed, respectively. The observed rotational constants for the parent dimer [A = 2321.8335(4) MHz, B = 1150.4774(2) MHz, and C = 1124.8898(2) MHz] are close to those of the most stable structure predicted by ab initio calculations. Spectra of the three deuterated isotopologues and Kraitchman analysis positively confirm this structure. Geometrical parameters and “Atoms in Molecules” analysis on the observed structure reveal that the two propargyl alcohol units in the dimer are bound by three different types of hydrogen bonds: O–H⋯O, O–H⋯π, and C–H⋯π. To the best of our knowledge, propargyl alcohol seems to be the smallest molecule forming a homodimer with three different points of contact.

  12. Disordered clusters of Bak dimers rupture mitochondria during apoptosis

    PubMed Central

    Uren, Rachel T; O’Hely, Martin; Iyer, Sweta; Bartolo, Ray; Shi, Melissa X; Brouwer, Jason M; Alsop, Amber E; Dewson, Grant; Kluck, Ruth M

    2017-01-01

    During apoptosis, Bak and Bax undergo major conformational change and form symmetric dimers that coalesce to perforate the mitochondrial outer membrane via an unknown mechanism. We have employed cysteine labelling and linkage analysis to the full length of Bak in mitochondria. This comprehensive survey showed that in each Bak dimer the N-termini are fully solvent-exposed and mobile, the core is highly structured, and the C-termini are flexible but restrained by their contact with the membrane. Dimer-dimer interactions were more labile than the BH3:groove interaction within dimers, suggesting there is no extensive protein interface between dimers. In addition, linkage in the mobile Bak N-terminus (V61C) specifically quantified association between dimers, allowing mathematical simulations of dimer arrangement. Together, our data show that Bak dimers form disordered clusters to generate lipidic pores. These findings provide a molecular explanation for the observed structural heterogeneity of the apoptotic pore. DOI: http://dx.doi.org/10.7554/eLife.19944.001 PMID:28182867

  13. Assembly of Drosophila centromeric nucleosomes requires CID dimerization.

    PubMed

    Zhang, Weiguo; Colmenares, Serafin U; Karpen, Gary H

    2012-01-27

    Centromeres are essential chromosomal regions required for kinetochore assembly and chromosome segregation. The composition and organization of centromeric nucleosomes containing the essential histone H3 variant CENP-A (CID in Drosophila) is a fundamental, unresolved issue. Using immunoprecipitation of CID mononucleosomes and cysteine crosslinking, we demonstrate that centromeric nucleosomes contain CID dimers in vivo. Furthermore, CID dimerization and centromeric targeting require a residue implicated in formation of the four-helix bundle, which mediates intranucleosomal H3 dimerization and nucleosome integrity. Taken together, our findings suggest that CID nucleosomes are octameric in vivo and that CID dimerization is essential for correct centromere assembly.

  14. Assembly of Drosophila Centromeric Nucleosomes Requires CID Dimerization

    PubMed Central

    Zhang, Weiguo; Colmenares, Serafin U.; Karpen, Gary H.

    2012-01-01

    SUMMARY Centromeres are essential chromosomal regions required for kinetochore assembly and chromosome segregation. The composition and organization of centromeric nucleosomes containing the essential histone H3 variant CENP-A (CID in Drosophila) is a fundamental, unresolved issue. Using immunoprecipitation of CID mononucleosomes and cysteine crosslinking, we demonstrate that centromeric nucleosomes contain CID dimers in vivo. Furthermore, CID dimerization and centromeric targeting require a residue implicated in formation of the four helix bundle, which mediates intra-nucleosomal H3 dimerization and nucleosome integrity. Taken together, our findings suggest that CID nucleosomes are octameric in vivo and that CID dimerization is essential for correct centromere assembly. PMID:22209075

  15. Chemical synthesis and structural characterization of the RGD-protein decorsin: a potent inhibitor of platelet aggregation.

    PubMed Central

    Polverino de Laureto, P.; Scaramella, E.; De Filippis, V.; Marin, O.; Doni, M. G.; Fontana, A.

    1998-01-01

    Decorsin is a 39-residue RGD-protein crosslinked by three disulfide bridges isolated from the leech Macrobdella decora belonging to the family of GPIIb-IIIa antagonists and acting as a potent inhibitor of platelet aggregation. Here we report the solid-phase synthesis of decorsin using the Fmoc strategy. The crude polypeptide was purified by reverse-phase HPLC in its reduced form and allowed to refold in the presence of glutathione. The homogeneity of the synthetic oxidized decorsin was established by reverse-phase HPLC and capillary zone electrophoresis. The results of amino acid analysis after acid hydrolysis of the synthetic protein, NH2-terminal sequencing and mass determination (4,377 Da) by electrospray mass spectrometry were in full agreement with this theory. The correct pairing of the three disulfide bridges in synthetic decorsin was determined by a combined approach of both peptide mapping using proteolytic enzymes and analysis of the disulfide chirality by CD spectroscopy in the near-UV region. Synthetic decorsin inhibited human platelet aggregation with an IC50 of approximately 0.1 microM, a figure quite similar to that determined utilizing decorsin from natural source. In particular, the synthetic protein was 2,000-fold more potent than a model RGD-peptide (e.g., Arg-Gly-Asp-Ser) in inhibiting platelet aggregation. Thermal denaturation experiments of synthetic decorsin, monitored by CD spectroscopy, revealed its high thermal stability (Tm approximately 74 degrees C). The features of the oxidative refolding process of reduced decorsin, as well as the thermal stability of the oxidized species, were compared with those previously determined for the NH2-terminal core domain fragment 1-41 or 1-43 from hirudin. This fragment shows similarity in size, pairing of the three disulfides and three-dimensional structure with those of decorsin, even if very low sequence similarity. It is suggested that the less efficient oxidative folding and the enhanced thermal

  16. cRGD grafted liposomes containing inorganic nano-precipitate complexed siRNA for intracellular delivery in cancer cells.

    PubMed

    Khatri, Nirav; Baradia, Dipesh; Vhora, Imran; Rathi, Mohan; Misra, Ambikanandan

    2014-05-28

    Development of effective vector for intracellular delivery of siRNA has always been a challenge due to its hydrophilicity, net negative surface charge and sensitivity against nucleases in biological milieu. The present investigation was aimed to develop a novel non-viral liposomal carrier for siRNA delivery. Nano-precipitate of calcium phosphate was entrapped in liposomes composed of a neutral lipid (DPPC), a fusogenic lipid (DOPE), a PEGylated lipid (DSPE-mPEG2000) and cholesterol. siRNA was made permeable through liposomal bilayer and complexed to calcium phosphate precipitates inside the liposomes. siRNA entrapped liposomes were further grafted with cRGD to achieve targeting potential against cancer cells. More than 80% of siRNA was entrapped inside the liposomes having average particle size below 150nm. Cryo-transmission electron microscopy revealed the intra-liposomal calcium phosphate precipitation and unilamellar morphology of prepared liposomes. The viability of A549 lung cancer cells was significantly higher after treatment with siRNA entrapped liposomes as compared to Lipofectamine2000 complexed siRNA. Fluorescent intensity in lung carcinoma cells was significantly higher after exposure to fluorescent siRNA entrapped liposomes than with Lipofectamine2000, which were confirmed by both confocal microscopy and flow cytometry. Live imaging by confocal microscopy ascertained the targeting efficacy of cRGD grafted liposomes compared to naked siRNA and non-grafted liposomes. Developed liposomal formulation showed effective protection of siRNA against serum nucleases along with less haemolytic potential and excellent stability against electrolyte induced flocculation. At 5nM concentration gene expression of target protein was reduced up to 24.1±3.4% while Lipofectamine2000 reduced expression level up to 26.35±1.55%. In vivo toxicity in mice suggested admirable safety profile for developed lipid based delivery vector. These results advocate that prepared

  17. Pathogenic Cysteine Removal Mutations in FGFR Extracellular Domains Stabilize Receptor Dimers and Perturb the TM Dimer Structure.

    PubMed

    Sarabipour, Sarvenaz; Hristova, Kalina

    2016-10-09

    Missense mutations that introduce or remove cysteine residues in receptor tyrosine kinases are believed to cause pathologies by stabilizing the active receptor tyrosine kinase dimers. However, the magnitude of this stabilizing effect has not been measured for full-length receptors. Here, we characterize the dimer stabilities of three full-length fibroblast growth factor receptor (FGFR) mutants harboring pathogenic cysteine substitutions: the C178S FGFR1 mutant, the C342R FGFR2 mutant, and the C228R FGFR3 mutant. We find that the three mutations stabilize the FGFR dimers. We further see that the mutations alter the configuration of the FGFR transmembrane dimers. Thus, both aberrant dimerization and perturbed dimer structure likely contribute to the pathological phenotypes arising due to these mutations.

  18. Rotational Spectrum of Propargyl Alcohol Dimer

    NASA Astrophysics Data System (ADS)

    Mani, Devendra; Arunan, E.

    2013-06-01

    Propargyl alcohol is a molecule of interest to astrophysics as well as combustion studies. Rotational-tunneling spectra of propargyl alcohol monomer is well known and shows that the molecule exists in gauche form. Recently we reported microwave spectra of Ar...propargyl alcohol complex. Propargyl alcochol exists in gauche form in the complex as well. In this study we have recorded pure rotational spectra of propargyl alcohol dimer between 4-13 GHz range.A total of 47 transitions, 24 a-type, 16 b-type and 7 c-type, have been observed and fitted with semi rigid rotor asymmetric top hamiltonian. The fitted rotational constants are: A = 2321.83323(47) MHz, B = 1150.47726(24) MHz and C = 1124.89000(20) MHz. The standard deviation for the fit is 2.5 kHz. The experimental rotational constants are very close to the structure predicted by ab-initio calculations in which two gauche-propargyl alcohol moieties are in three point contact stabilized by O-H...O, O-H...pi and C-H...pi interactions. Few transitions for duterated isotopologues of the dimer have also been observed and search for the remaining transitions is in progress. Details will be presented in the talk. E. Hirota,J. Mol. Spectrosc. 26 (1968) 335-350. J.C. Pearson, B.J. Drouin, J. Mol. Spectrosc. 234 (2005) 149-156. D. Mani, E. Arunan, ChemPhysChem 14 (2013) 754-763.

  19. The role of dimerization in prion replication.

    PubMed Central

    Tompa, Peter; Tusnády, Gábor E; Friedrich, Peter; Simon, István

    2002-01-01

    The central theme in prion diseases is the conformational transition of a cellular protein from a physiologic to a pathologic (so-called scrapie) state. Currently, two alternative models exist for the mechanism of this autocatalytic process; in the template assistance model the prion is assumed to be a monomer of the scrapie conformer, whereas in the nucleated polymerization model it is thought to be an amyloid rod. A recent variation on the latter assumes disulfide reshuffling as the mechanism of polymerization. The existence of stable dimers, let alone their mechanistic role, is not taken into account in either of these models. In this paper we review evidence supporting that the dimerization of either the normal or the scrapie state, or both, has a decisive role in prion replication. The contribution of redox changes, i.e., the temporary opening and possible rearrangement of the intramolecular disulfide bridge is also considered. We present a model including these features largely ignored so far and show that it adheres satisfactorily to the observed phenomenology of prion replication. PMID:11916832

  20. Fibrillar dimer formation of islet amyloid polypeptides

    DOE PAGES

    Chiu, Chi -cheng; de Pablo, Juan J.

    2015-05-08

    Amyloid deposits of human islet amyloid polypeptide (hIAPP), a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 – 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 – 29 are involved in an intermediate that exhibits transient β-sheets, consistent with recent experimentalmore » and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.« less

  1. Biologically and mechanically driven design of an RGD-mimetic macroporous foam for adipose tissue engineering applications.

    PubMed

    Rossi, Eleonora; Gerges, Irini; Tocchio, Alessandro; Tamplenizza, Margherita; Aprile, Paola; Recordati, Camilla; Martello, Federico; Martin, Ivan; Milani, Paolo; Lenardi, Cristina

    2016-10-01

    Despite clinical treatments for adipose tissue defects, in particular breast tissue reconstruction, have certain grades of efficacy, many drawbacks are still affecting the long-term survival of new formed fat tissue. To overcome this problem, in the last decades, several scaffolding materials have been investigated in the field of adipose tissue engineering. However, a strategy able to recapitulate a suitable environment for adipose tissue reconstruction and maintenance is still missing. To address this need, we adopted a biologically and mechanically driven design to fabricate an RGD-mimetic poly(amidoamine) oligomer macroporous foam (OPAAF) for adipose tissue reconstruction. The scaffold was designed to fulfil three fundamental criteria: capability to induce cell adhesion and proliferation, support of in vivo vascularization and match of native tissue mechanical properties. Poly(amidoamine) oligomers were formed into soft scaffolds with hierarchical porosity through a combined free radical polymerization and foaming reaction. OPAAF is characterized by a high water uptake capacity, progressive degradation kinetics and ideal mechanical properties for adipose tissue reconstruction. OPAAF's ability to support cell adhesion, proliferation and adipogenesis was assessed in vitro using epithelial, fibroblast and endothelial cells (MDCK, 3T3L1 and HUVEC respectively). In addition, in vivo subcutaneous implantation in murine model highlighted OPAAF potential to support both adipogenesis and vessels infiltration. Overall, the reported results support the use of OPAAF as a scaffold for engineered adipose tissue construct.

  2. Anti-EGFR-iRGD recombinant protein conjugated silk fibroin nanoparticles for enhanced tumor targeting and antitumor efficiency

    PubMed Central

    Bian, Xinyu; Wu, Puyuan; Sha, Huizi; Qian, Hanqing; Wang, Qing; Cheng, Lei; Yang, Yang; Yang, Mi; Liu, Baorui

    2016-01-01

    In this study, we report a novel kind of targeting with paclitaxel (PTX)-loaded silk fibroin nanoparticles conjugated with iRGD–EGFR nanobody recombinant protein (anti-EGFR-iRGD). The new nanoparticles (called A-PTX-SF-NPs) were prepared using the carbodiimide-mediated coupling procedure and their characteristics were evaluated. The cellular cytotoxicity and cellular uptake of A-PTX-SF-NPs were also investigated. The results in vivo suggested that NPs conjugated with the recombinant protein exhibited more targeting and anti-neoplastic property in cells with high EGFR expression. In the in vivo antitumor efficacy assay, the A-PTX-SF-NPs group showed slower tumor growth and smaller tumor volumes than PTX-SF-NPs in a HeLa xenograft mouse model. A real-time near-infrared fluorescence imaging study showed that A-PTX-SF-NPs could target the tumor more effectively. These results suggest that the anticancer activity and tumor targeting of A-PTX-SF-NPs were superior to those of PTX-SF-NPs and may have the potential to be used for targeted delivery for tumor therapies. PMID:27313461

  3. Synergistic retention strategy of RGD active targeting and radiofrequency-enhanced permeability for intensified RF & chemotherapy synergistic tumor treatment.

    PubMed

    Zhang, Kun; Li, Pei; He, Yaping; Bo, Xiaowan; Li, Xiaolong; Li, Dandan; Chen, Hangrong; Xu, Huixiong

    2016-08-01

    Despite gaining increasing attention, chelation of multiple active targeting ligands greatly increase the formation probability of protein corona, disabling active targeting. To overcome it, a synergistic retention strategy of RGD-mediated active targeting and radiofrequency (RF) electromagnetic field-enhanced permeability has been proposed here. It is validated that such a special synergistic retention strategy can promote more poly lactic-co-glycolic acid (PLGA)-based capsules encapsulating camptothecin (CPT) and solid DL-menthol (DLM) to enter and retain in tumor in vitro and in vivo upon exposure to RF irradiation, receiving an above 8 fold enhancement in HeLa retention. Moreover, the PLGA-based capsules can respond RF field to trigger the entrapped DLM to generate solid-liquid-gas (SLG) tri-phase transformation for enhancing RF ablation and CPT release. Therefore, depending on the enhanced RF ablation and released CPT and the validated synergistic retention effect, the inhibitory outcome for tumor growth has gained an over 10-fold improvement, realizing RF ablation & chemotherapy synergistic treatment against HeLa solid tumor, which indicates a significant promise in clinical RF ablation.

  4. Anti-tumor activity of paclitaxel through dual-targeting carrier of cyclic RGD and transferrin conjugated hyperbranched copolymer nanoparticles.

    PubMed

    Xu, Qing; Liu, Yuexian; Su, Shishuai; Li, Wei; Chen, Chunying; Wu, Yan

    2012-02-01

    Targeted delivery strategies are becoming increasingly important. Herein, a novel hyperbranched amphiphilic poly[(amine-ester)-co-(D,L-lactide)]/1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine copolymer (HPAE-co-PLA/DPPE) with RGD peptide (cRGDfK) and transferrin (Tf) on the periphery was synthesized and used to prepare paclitaxel-loaded nanoparticles (NPs) for dual-targeting chemotherapy. These NPs show satisfactory size distribution, high encapsulated efficiency and a pH-dependent release profile. The intrinsic fluorescence of the hyperbranched copolymer renders the detection and tracking of NPs in vitro and in vivo conveniently. In vitro cytotoxicity studies proved that the presence of cRGDfK enhanced the cytotoxic efficiency by 10 folds in α(ν)β(3) integrin over-expressed human umbilical vein endothelial cells, while Tf improved cytotoxicity by 2 folds in Tf receptor over-expressed human cervical carcinoma cells. The drug-loaded NPs can be efficiently transported into the vascular endothelial cells and the target tumor cells. These results indicate that the cRGDfK and Tf decorated HPAE-co-PLA/DPPE could deliver chemotherapies specifically inside the cell via receptor-mediated endocytosis with greater efficacy. Therefore, such a fluorescent nanocarrier prepared from non-cytotoxic and biodegradable polymers is promising for drug delivery in tumor therapy.

  5. Fluorescence lifetime imaging to differentiate bound from unbound ICG-cRGD both in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Stegehuis, Paulien L.; Boonstra, Martin C.; de Rooij, Karien E.; Powolny, François E.; Sinisi, Riccardo; Homulle, Harald; Bruschini, Claudio; Charbon, Edoardo; van de Velde, Cornelis J. H.; Lelieveldt, Boudewijn P. F.; Vahrmeijer, Alexander L.; Dijkstra, Jouke; van de Giessen, Martijn

    2015-03-01

    Excision of the whole tumor is crucial, but remains difficult for many tumor types. Fluorescence lifetime imaging could be helpful intraoperative to differentiate normal from tumor tissue. In this study we investigated the difference in fluorescence lifetime imaging of indocyanine green coupled to cyclic RGD free in solution/serum or bound to integrins e.g. in tumors. The U87-MG glioblastoma cell line, expressing high integrin levels, was cultured to use in vitro and to induce 4 subcutaneous tumors in a-thymic mice (n=4). Lifetimes of bound and unbound probe were measured with an experimental time-domain single-photon avalanche diode array (time resolution <100ps). In vivo measurements were taken 30-60 minutes after intravenous injection, and after 24 hours. The in vitro lifetime of the fluorophores was similar at different concentrations (20, 50 and 100μM) and showed a statistically significant higher lifetime (p<0.001) of bound probe compared to unbound probe. In vivo, lifetimes of the fluorophores in tumors were significantly higher (p<0.001) than at the control site (tail) at 30-60 minutes after probe injection. Lifetimes after 24 hours confirmed tumor-specific binding (also validated by fluorescence intensity images). Based on the difference in lifetime imaging, it can be concluded that it is feasible to separate between bound and unbound probes in vivo.

  6. Salt bridge residues between I-Ak dimer of dimers alpha-chains modulate antigen presentation.

    PubMed

    Yadati, S; Nydam, T; Demian, D; Wade, T K; Gabriel, J L; Barisas, B G; Wade, W F

    1999-03-15

    Class II dimers of dimers are predicted to have functional significance in antigen presentation. The putative contact amino acids of the I-Ak class II dimer of dimers have been identified by molecular modeling based on the DR1 crystal structure (Nydam et al., Int. Immunol. 10, 1237,1998). We have previously reported the role in antigen presentation of dimer of dimers contact amino acids located in the C-terminal domains of the alpha- and beta-chains of class II. Our calculations show that residues Ealpha89 and Ralpha145 in the alpha2-domain form an inter alpha-chain salt bridge between pairs of alphabeta-heterodimers. Other residues, Qalpha92 and Nalpha115, may be involved in close association in that part of the alpha-chain. We investigated the role of these amino acids on class II expression and antigen presentation. Class II composed of an Ealpha89K substituted alpha-chain paired with a wt beta-chain exhibited inhibited antigen presentation and expression of alpha-chain serologic epitopes. In contrast, mutation of Ralpha145E had less affect on antigen presentation and did not affect I-Ak serologic epitopes. Interchanging charges of the salt bridge residues by expressing both Ralpha145E and Ealpha89K on the same chain obviated the large negative effect of the Ealpha89K mutation on antigen presentation but not on the serologic epitopes. Our results are similar for those reported for mutation of DR3's inter-chain salt bridge with the exception that double mutants did not moderate the DR3 defect. Interestingly, the amino acids differences between I-A and DR change the location of the inter-chain salt bridges. In DR1 these residues are located at positions Ealpha88 and Kalpha111; in I-Ak these residues are located at position Ealpha89 and Ralpha145. Inter alpha-chain salt bridges are thus maintained in various class II molecules by amino acids located in different parts of the alpha2-domain. This conservation of structure suggests that considerable functional

  7. A Wacky Bridge to mTORC1 Dimerization.

    PubMed

    Montagne, Jacques

    2016-01-25

    The activity of the mTORC1 protein complex depends on multiple metabolic inputs that regulate dimerization, recruitment to the lysosome, and activation. In this issue of Developmental Cell, David-Morrison et al. (2016) show that the Drosophila protein Wacky and its mammalian counterpart WAC act as adaptors in the process of mTORC1 dimerization.

  8. Integrability of PT-symmetric dimers

    NASA Astrophysics Data System (ADS)

    Pickton, J.; Susanto, H.

    2013-12-01

    The coupled discrete linear and Kerr nonlinear Schrödinger equations with gain and loss describing transport on dimers with parity-time (PT)-symmetric potentials are considered. The model is relevant among others to experiments in optical couplers and proposals on Bose-Einstein condensates in PT-symmetric double-well potentials. It is known that the models are integrable. Here, the integrability is exploited further to construct the phase portraits of the system. A pendulum equation with a linear potential and a constant force for the phase difference between the fields is obtained, which explains the presence of unbounded solutions above a critical threshold parameter. The behavior of all solutions of the system, including changes in the topological structure of the phase plane, is then discussed.

  9. Photodissociable dimer reduction products of 2-thiopyrimidine derivatives.

    PubMed

    Wrona, M; Giziewicz, J; Shugar, D

    1975-12-01

    Both 4,6-dimethyl-2-thipyrimidine and its 1-methyl derivative undergo polarographic reduction in aqueous medium, via a 1e/1H+ reduction to a free radical which rapidly dimerizes to products isolates and identified as 4,4'-bis-(4,6-dimethyl-3,4-dihydropyrimidin-2-thione) and the corresponding 1-methyl dimer. The dimers may be oxidized electrolytically to regenerate the parent monomers. Both dimers also undergo photodissociation to quantitatively regenerate the parent monomers, in high quantum yield, 0.23 and 0.35 M/Einstein. The correlation between electrochemical and photochemical reductions of 2-thiopyrimidines are discussed, as well as the significance of the dimer photodissociation reactions in relation to nucleic acid photochemistry.

  10. Palladium dimers adsorbed on graphene: A DFT study

    NASA Astrophysics Data System (ADS)

    Kaur, Gagandeep; Gupta, Shuchi; Dharamvir, Keya

    2015-05-01

    The 2D structure of graphene shows a great promise for enhanced catalytic activity when adsorbed with palladium. We performed a systematic density functional theory (DFT) study of the adsorption of palladium dimer (Pd2) on graphene using SIESTA package, in the generalized gradient approximation (GGA). The adsorption energy, geometry, and charge transfer of Pd2-graphene system are calculated. Both horizontal and vertical orientations of Pd2 on graphene are studied. Our calculations revealed that the minimum energy configuration for Pd dimer is parallel to the graphene sheet with its two atoms occupying centre of adjacent hexagonal rings of graphene sheet. Magnetic moment is induced for Pd dimer adsorbed on graphene in vertical orientation while horizontal orientation of Pd dimer on graphene do not exhibit magnetism. Insignificant energy differences among adsorption sites means that dimer mobility on the graphene sheet is high. There is imperceptible distortion of graphene sheet perpendicular to its plane. However, some lateral displacements are seen.

  11. Internal structure of nanoparticle dimers linked by DNA.

    PubMed

    Chi, Cheng; Vargas-Lara, Fernando; Tkachenko, Alexei V; Starr, Francis W; Gang, Oleg

    2012-08-28

    We construct nanoparticle dimers linked by DNA. These dimers are basic units in a possible multiscale, hierarchical assembly and serve as a model system to understand DNA-mediated interactions, especially in the nontrivial regime when the nanoparticle and DNA are comparable in their sizes. We examine the structure of nanoparticle dimers in detail by a combination of scattering experiments and molecular simulations. We find that, for a given DNA length, the interparticle separation within the dimer is controlled primarily by the number of linking DNA. We summarize our findings in a simple model that captures the interplay of the number of DNA bridges, their length, the particle's curvature, and the excluded volume effects. We demonstrate the applicability of the model to our results, without any free parameters. As a consequence, the increase of dimer separation with increasing temperature can be understood as a result of changing the number of connecting DNA.

  12. Structures of dimeric hydrolysis products of thorium.

    PubMed

    Wilson, Richard E; Skanthakumar, S; Sigmon, Ginger; Burns, Peter C; Soderholm, L

    2007-04-02

    Three unique thorium dimeric compounds have been crystallized from either direct hydrolysis of Th4+(aq)/HCl or titration of Th(OH)4(am) with Th(NO3)4(aq) and their structures determined using single-crystal X-ray diffraction. The compound [Th2(micro2-OH)2(NO3)6(H2O)6]H2O (1) is identical to that identified previously by Johansson. Two additional unreported compounds have been identified, [Th2(micro2-OH)2(NO3)4(H2O)8](NO3)2 (2) and [Th2(micro2-OH)2Cl2(H2O)12]Cl4.2H2O (3). 1 crystallizes in the monoclinic space group P21/c, with a = 6.792(2) A, b = 11.710(4) A, c = 13.778(5) A, and beta = 102.714(5) degrees and 2 crystallizes in the monoclinic space group P21/n, with a = 6.926(5) A, b = 7.207(1) A, c = 21.502(1) A, and beta = 96.380(1) degrees . The chloride-containing dimer, 3, crystallizes in triclinic P, with a = 8.080(2) A, b = 8.880(2) A, c = 9.013(2) A, alpha = 97.41(3) degrees , beta = 91.00(3), and gamma = 116.54(3) degrees . We also present high-energy X-ray scattering data demonstrating the presence of the hydroxo-bridged moiety in solution and discuss our findings in the context of known solid-state structures. The three structures demonstrate 11-, 10-, and 9-coordinate thorium, respectively, and coupled with the scattering experiments provide additional structural and chemical insight into tetravalent actinide hydrolysis.

  13. Molecular mechanisms of pyrimidine dimer excision in Saccharomyces cerevisiae: excision of dimers in cell extracts

    SciTech Connect

    Reynolds, R.J.; Love, J.D.; Friedberg, E.C.

    1981-08-01

    Cell-free extracts prepared from rad1-19, rad2-2, rad3-1, rad4-3, rad7-1, rad10-1, rad14-1, rad16-1, and cycl-1 (rad7) mutants of Saccharomyces cerevisiae all catalyze the preferential excision of thymine-containing pyrimidine dimers from ultraviolet-irradiated DNA specifically incised with M. luteus ultraviolet deoxyribonucleic acid incising activity.

  14. PEI-g-PEG-RGD/Small Interference RNA Polyplex-Mediated Silencing of Vascular Endothelial Growth Factor Receptor and Its Potential as an Anti-Angiogenic Tumor Therapeutic Strategy

    PubMed Central

    Kim, Jihoon; Kim, Sung Wan

    2011-01-01

    Tumor angiogenesis appears to be achieved by the expression of vascular endothelial growth factor (VEGF) within solid tumors that stimulate host vascular endothelial cell mitogenesis and possibly chemotaxis. VEGF's angiogenic actions are mediated through its high-affinity binding to 2 endothelium-specific receptor tyrosine kinase, Flt-1 (VEGFR1), and Flk-1/KDR (VEGFR2). RNA interference-mediated knockdown of protein expression at the messenger RNA level provides a new therapeutic strategy to overcome various diseases. To achieve high efficacy in RNA interference-mediated therapy, it is critical to develop an efficient delivering system to deliver small interference RNA (siRNA) into tissues or cells site-specifically. We previously reported an angiogenic endothelial cell-targeted polymeric gene carrier, PEI-g-PEG-RGD. This targeted carrier was developed by the conjugation of the ανβ3/ανβ5 integrin-binding RGD peptide (ACDCRGDCFC) to the cationic polymer, branched polyethylenimine, with a hydrophilic polyethylene glycol (PEG) spacer. In this study, we used PEI-g-PEG-RGD to deliver siRNA against VEGFR1 into tumor site. The physicochemical properties of PEI-g-PEG-RGD/siRNA complexes was evaluated. Further, tumor growth profile was also investigated after systemic administration of PEI-g-PEG-RGD/siRNA complexes. PMID:21375397

  15. Radiolabeled cyclic arginine-glycine-aspartic (RGD)-conjugated iron oxide nanoparticles as single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) dual-modality agents for imaging of breast cancer

    NASA Astrophysics Data System (ADS)

    Deng, Shengming; Zhang, Wei; Zhang, Bin; Hong, Ruoyu; Chen, Qing; Dong, Jiajia; Chen, Yinyiin; Chen, Zhiqiang; Wu, Yiwei

    2015-01-01

    Ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) modified with a novel cyclic arginine-glycine-aspartate (RGD) peptide were made and radiolabeled as single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) dual-modality agents for imaging of breast cancer. The probe was tested both in vitro and in vivo to determine its receptor targeting efficacy and feasibility for SPECT and MRI. The radiochemical syntheses of 125I-cRGD-USPIO were accomplished with a radiochemical purity of 96.05 ± 0.33 %. High radiochemical stability was found in fresh human serum and in phosphate-buffered saline. The average hydrodynamic size of 125I-cRGD-USPIO determined by dynamic light scattering was 51.3 nm. Results of in vitro experiments verified the specificity of the radiolabeled nanoparticles to tumor cells. Preliminary biodistribution studies of 125I-radiolabeled cRGD-USPIO in Bcap37-bearing nude mice showed that it had long circulation half-life, high tumor uptake, and high initial blood retention with moderate liver uptake. In vivo tumor targeting and uptake of the radiolabeled nanoparticles in mice model were visualized by SPECT and MRI collected at different time points. Our results strongly indicated that the 125I-cRGD-USPIO could be used as a promising bifunctional radiotracer for early clinical tumor detection with high sensitivity and high spatial resolution by SPECT and MRI.

  16. A Novel Method for Direct site-specific Radiolabeling of Peptides Using [18F]FDG

    PubMed Central

    Namavari, Mohammad; Cheng, Zhen; Zhang, Rong; De, Abhijit; Levi, Jelena; Hoerner, Joshua K.; Yaghoubi, Shahriar S.; Syud, Faisal A.; Gambhir, Sanjiv S.

    2009-01-01

    We have used the well-accepted and easily available 2-[18F]Fluoro-2-deoxyglucose ([18F]FDG) positron emission tomography (PET) tracer as a prosthetic group for synthesis of 18F-labeled peptides. We herein report the synthesis of [18F]FDG-RGD (18F labeled linear RGD) and [18F]FDG-cyclo(RGDDYK) (18F labeled cyclic RGD) as examples of the use of [18F]FDG. We have successfully prepared [18F]FDG-RGD and [18F]FDG-cyclo(RGDDYK) in 27.5% and 41% radiochemical yields (decay corrected) respectively. The receptor binding affinity study of FDG-cyclo(RGDDYK) for integrin αvβ3 , using αvβ3 positive U87MG cells confirmed a competitive displacement with 125I-echistatin as a radioligand. The IC50 value for FDG-cyclo(RGDDYK) was determined to be 0.67 ± 0.19µM. High contrast small animal PET images with relatively moderate tumor uptake were observed for [18F]FDG-RGD and [18F]FDG-cyclo(RGDDYK) as PET probes in xenografts models expressing αvβ3 integrin. In conclusion, we have successfully used [18F]FDG as a prosthetic group to prepare 18F]FDG-RGD and [18F]FDG-cyclic[RGDDYK] based on a simple one step radiosynthesis. The one step radiosynthesis methodology consists of chemoselective oxime formation between an aminooxy functionalized peptide and [18F]FDG. The results have implications for radiolabeling of other macromolecules and would lead to a very simple strategy for routine pre-clinical and clinical use. PMID:19226160

  17. Threshold electron attachment and electron impact ionization involving oxygen dimers

    NASA Astrophysics Data System (ADS)

    Kreil, J.; Ruf, M.-W.; Hotop, H.; Ettischer, I.; Buck, U.

    1998-12-01

    Using two different crossed-beams machines we have carried out the first quantitative study of threshold electron attachment and electron impact-induced ionization and fragmentation involving oxygen dimers (O 2) 2. In the electron attachment experiment we study electron transfer from state-selected Ar **(20d) Rydberg atoms to O 2 molecules and dimers in a skimmed supersonic beam at variable nozzle temperatures ( T0) and stagnation pressures ( p0). The relative dimer density is determined through measurements of Penning ionization by metastable Ne *(3s 3P2,0) atoms and used to estimate the absolute cross-section for O 2- formation in collisions of Ar **(20d) Rydberg atoms with O 2 dimers to be nearly 10 -17 m 2, almost four orders of magnitude larger than that for O 2- formation in collisions of Ar **(20d) Rydberg atoms with O 2 monomers. The fragmentation of the oxygen cluster beam is quantitatively characterized by the transverse helium beam scattering method which allows us to spatially separate different clusters. It is shown that in 70 eV electron impact of (O 2) 2 only 3.6(4)% of the dimers are detected as dimer ions (O 2) 2+. In additional experiments involving SF 6 clusters we show that SF 6 dimers fragment nearly completely upon 70 eV electron impact, yielding SF 5+ ions (probability for (SF 6)·SF 5+ production at most 0.3%).

  18. Plaquette order in a dimerized frustrated spin ladder

    NASA Astrophysics Data System (ADS)

    Shlagman, Ofer; Shimshoni, Efrat

    2014-11-01

    We study the effect of dimerization (due to, e.g., spin-Peierls instability) on the phase diagram of a frustrated antiferromagnetic spin-1/2 ladder, with weak transverse and diagonal rung coupling. Our analysis focuses on a one-dimensional version of the model (i.e., a single two-leg ladder) where we consider two forms of dimerization on the legs: columnar dimers (CDs) and staggered dimers (SDs). We examine in particular the regime of parameters (corresponding to an intermediate X X Z anisotropy) in which the leg dimerization and the rung coupling terms are equally relevant. In both the CD and SD cases, we find that the effective field theory describing the system is a self-dual sine-Gordon model, which favors ordering and the opening of a gap to excitations. The order parameter, which reflects the interplay between the leg and rung dimerization interactions, represents a crystal of 4-spin plaquettes on which longitudinal and transverse dimers are in a coherent superposition. Depending on the leg dimerization mode, these plaquettes are closed or open, however both types spontaneously break reflection symmetry across the ladder. The closed plaquettes are stable, while the open plaquette order is relatively fragile and the corresponding gap may be tuned to zero under extreme conditions. We further find that a first-order transition occurs from the plaquette order to a valence bond crystal (VBC) of dimers on the legs. This suggests that in a higher-dimensional version of this system, this variety of distinct VBC states with comparable energies leads to the formation of domains. Effectively one-dimensional gapless spinon modes on domain boundaries may account for the experimental observation of spin-liquid behavior in a physical realization of the model.

  19. An RGD spacing of 440 nm is sufficient for integrin alpha V beta 3- mediated fibroblast spreading and 140 nm for focal contact and stress fiber formation

    PubMed Central

    1991-01-01

    The synthetic peptide Gly-Arg-Gly-Asp-Tyr (GRGDY), which contains the RGD sequence of several adhesion molecules, was covalently grafted to the surface of otherwise poorly adhesive glass substrates and was used to determine the minimal number of ligand-receptor interactions required for complete spreading of human foreskin fibroblasts. Well- defined adhesion substrates were prepared with GRGDY between 10(-3) fmol/cm2 and 10(4) fmol/cm2. As the adhesion ligand surface concentration was varied, several distinct morphologies of adherent cells were observed and categorized. The population of fully spread cells at 4 h reached a maximum at 1 fmol/cm2, with no further increases up to 10(4) fmol/cm2. Although maximal cell spreading was obtained at 1 fmol/cm2, focal contacts and stress fibers failed to form at RGD surface concentrations below 10 fmol/cm2. The minimal peptide spacings obtained in this work correspond to 440 nm for spreading and 140 nm for focal contact formation, and are much larger than those reported in previous studies with adsorbed adhesion proteins, adsorbed RGD-albumin conjugates, or peptide-grafted polyacrylamide gels. Vitronectin receptor antiserum specific for integrin alpha V beta 3 blocked cell adhesion and spreading on substrates containing 100 fmol/cm2 of surface- bound GRGDY, while fibronectin receptor antiserum specific for alpha 5 beta 1 did not. Furthermore, alpha V beta 3 was observed to cluster into focal contacts in spread cells, but alpha 5 beta 1 did not. It was thus concluded that a peptide-to-peptide spacing of 440 nm was required for alpha V beta 3-mediated cellular spreading, while 140 nm was required for alpha V beta 3-mediated focal contact formation and normal stress fiber organization in human foreskin fibroblasts; these spacings represent much fewer ligands than were previously thought to be required. PMID:1714913

  20. Triple-phase 99mTc-3P-RGD2 imaging of peripheral primitive neuroectodermal tumor in the hip muscle group with bone metastasis

    PubMed Central

    Fu, Jingjing; Song, Jinhua; Zhao, Youcai; Wang, Feng; Shao, Guoqiang

    2017-01-01

    Peripheral primitive neuroectodermal tumors (pPNETs) are a group of aggressive neoplasms that are most commonly encountered in pediatric patients and may be located in the abdomen, pelvis, thoracopulmonary region and, rarely, in the head and neck region. pPNETs in adults are extremely rare. The present study reports a case of pPNET located in the hip muscles with bone metastasis. The patient was a 44-year-old woman who complained of progressive pain and swelling with a mass near the left hip. Computed tomography (CT) and enhanced CT revealed a soft tissue mass lesion in the hip muscle group measuring 4.3×4.3×4.4 cm. The lesion was ill-defined, heterogeneous, exhibiting mild post-contrast enhancement. There was a large number of bent neovessels and several branches from the left internal iliac artery and deep femoral artery on enhanced CT scan. Triple-phase dynamic imaging with integrin αvβ3-targeted 99mTc-3P-RGD2 as the radiotracer revealed increased blood perfusion and radiotracer aggregation in the large, ill-defined, heterogeneous, hypodense mass and adjacent bone. The patient was suspected of having pPNET with bone metastasis, which was confirmed by histological examination of a sample obtained by needle aspiration. Due to the high blood perfusion of primary pPNETs and high RGD uptake by the primary and metastatic lesions, chemoembolization and anti-angiogenic therapy were considered to be the optimal therapeutic choice. This also suggested that 177Lu-labeled RGD has great potential for the targeted treatment of pPNETs with multiple metastases. PMID:28357093

  1. Monofunctionalization and dimerization of nanoparticles using coordination chemistry.

    PubMed

    Dewi, Melissa R; Gschneidtner, Tina A; Elmas, Sait; Ranford, Michael; Moth-Poulsen, Kasper; Nann, Thomas

    2015-02-24

    This paper describes a strategy for controlled nanoparticle dimerization by using a solid support approach. Two types of nanoparticles have been linked by using a 5-([2,2':6',2″-terpyridine]-4'-yloxy)pentan-1-amine (terpy-amine) iron complex. The strategy includes two major steps: first, the monofunctionalization of individual nanoparticles with terpy-amine ligand molecules on a solid support, followed by release of monofunctionalized particles and subsequent dimerization. The versatility of the approach was demonstrated by dimerizing two different types of nanoparticles: spherical gold and cube-shaped iron oxide nanoparticles.

  2. Ballistic transport in one-dimensional random dimer photonic crystals

    NASA Astrophysics Data System (ADS)

    Cherid, Samira; Bentata, Samir; Zitouni, Ali; Djelti, Radouan; Aziz, Zoubir

    2014-04-01

    Using the transfer-matrix technique and the Kronig Penney model, we numerically and analytically investigate the effect of short-range correlated disorder in Random Dimer Model (RDM) on transmission properties of the light in one dimensional photonic crystals made of three different materials. Such systems consist of two different structures randomly distributed along the growth direction, with the additional constraint that one kind of these layers always appear in pairs. It is shown that the one dimensional random dimer photonic crystals support two types of extended modes. By shifting of the dimer resonance toward the host fundamental stationary resonance state, we demonstrate the existence of the ballistic response in these systems.

  3. [Dichotomizing method applied to calculating equilibrium constant of dimerization system].

    PubMed

    Cheng, Guo-zhong; Ye, Zhi-xiang

    2002-06-01

    The arbitrary trivariate algebraic equations are formed based on the combination principle. The univariata algebraic equation of equilibrium constant kappa for dimerization system is obtained through a series of algebraic transformation, and it depends on the properties of monotonic functions whether the equation is solvable or not. If the equation is solvable, equilibrium constant of dimerization system is obtained by dichotomy and its final equilibrium constant of dimerization system is determined according to the principle of error of fitting. The equilibrium constants of trisulfophthalocyanine and biosulfophthalocyanine obtained with this method are 47,973.4 and 30,271.8 respectively. The results are much better than those reported previously.

  4. Human white blood cells contain cyclobutyl pyrimidine dimer photolyase

    SciTech Connect

    Sutherland, B.M.; Bennett, P.V.

    1995-10-10

    Although enzymatic photoreactivation of cyclobutyl pyrimidine dimers in DNA is present in almost all organisms, its presence in placental mammals is controversial. We tested human white blood cells for photolyase by using three defined DNAs (suprecoiled pET-2, nonsupercoiled bacteriphage {lambda}, and a defined-sequence 287-bp oligonucleotide), two dimer-specific endonucleases (T4 endonuclease V and UV endonuclease from Micrococcus luteus), and three assay methods. We show that human white blood cells contain photolyase that can photorepair pyrimidine dimers in defined supercoiled and linear DNAs and in a 287-bp oligonucleotide and that human photolyase is active on genomic DNA in intact human cells. 44 refs., 3 figs.

  5. Scattering properties of weakly-bound dimers of Fermi atoms

    NASA Astrophysics Data System (ADS)

    Petrov, Dmitry

    2005-03-01

    We discuss the behavior of weakly bound bosonic dimers formed in a two-component Fermi gas with a large positive scattering length for the interspecies interaction. We present a theoretical approach for solving a few-body scattering problem and describe the physics of dimer-dimer elastic and inelastic scattering. We explain why these diatomic molecules, while in the highest ro-vibrational level, are characterized by remarkable collisional stability. Co-authors are Christophe Salomon, LKB, Ecole Normale Superieure, Paris, France; Georgy Shlyapnikov, LPTMS, University of South Paris, Orsay, France.

  6. Adsorption of silver dimer on graphene - A DFT study

    SciTech Connect

    Kaur, Gagandeep; Gupta, Shuchi; Rani, Pooja; Dharamvir, Keya

    2014-04-24

    We performed a systematic density functional theory (DFT) study of the adsorption of silver dimer (Ag{sub 2}) on graphene using SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) package, in the generalized gradient approximation (GGA). The adsorption energy, geometry, and charge transfer of Ag2-graphene system are calculated. The minimum energy configuration for a silver dimer is parallel to the graphene sheet with its two atoms directly above the centre of carbon-carbon bond. The negligible charge transfer between the dimer and the surface is also indicative of a weak bond. The methodology demonstrated in this paper may be applied to larger silver clusters on graphene sheet.

  7. Electric and magnetic hotspots in dielectric nanowire dimers

    NASA Astrophysics Data System (ADS)

    Mirzaei, Ali; Miroshnichenko, Andrey E.

    2015-03-01

    We study the formation of the electric and magnetic near-field hotspots in dielectric cylindrical dimers. We compare dielectric and metallic dimers by using experimental data for all materials and consider both TM and TE polarizations of light. We demonstrate that dielectric dimers allow us to simultaneously achieve pure magnetic and electric near-field hotspots for both polarizations in contrast to plasmonic structures. This offers new approaches for near-field engineering such as sensing, control of spontaneous emission, and enhanced Raman scattering.

  8. RGD-independent cell adhesion to the carboxy-terminal heparin-binding fragment of fibronectin involves heparin-dependent and -independent activities

    PubMed Central

    1990-01-01

    Cell adhesion to extracellular matrix components such as fibronectin has a complex basis, involving multiple determinants on the molecule that react with discrete cell surface macromolecules. Our previous results have demonstrated that normal and transformed cells adhere and spread on a 33-kD heparin binding fragment that originates from the carboxy-terminal end of particular isoforms (A-chains) of human fibronectin. This fragment promotes melanoma adhesion and spreading in an arginyl-glycyl-aspartyl-serine (RGDS) independent manner, suggesting that cell adhesion to this region of fibronectin is independent of the typical RGD/integrin-mediated binding. Two synthetic peptides from this region of fibronectin were recently identified that bound [3H]heparin in a solid-phase assay and promoted the adhesion and spreading of melanoma cells (McCarthy, J. B., M. K. Chelberg, D. J. Mickelson, and L. T. Furcht. 1988. Biochemistry. 27:1380-1388). The current studies further define the cell adhesion and heparin binding properties of one of these synthetic peptides. This peptide, termed peptide I, has the sequence YEKPGSP-PREVVPRPRPGV and represents residues 1906-1924 of human plasma fibronectin. In addition to promoting RGD-independent melanoma adhesion and spreading in a concentration-dependent manner, this peptide significantly inhibited cell adhesion to the 33-kD fragment or intact fibronectin. Polyclonal antibodies generated against peptide I also significantly inhibited cell adhesion to the peptide, to the 33-kD fragment, but had minimal effect on melanoma adhesion to fibronectin. Anti-peptide I antibodies also partially inhibited [3H]heparin binding to fibronectin, suggesting that peptide I represents a major heparin binding domain on the intact molecule. The cell adhesion activity of another peptide from the 33-kD fragment, termed CS1 (Humphries, M. J., A. Komoriya, S. K. Akiyama, K. Olden, and K. M. Yamada. 1987. J. Biol. Chem., 262:6886-6892) was contrasted with

  9. Computer analysis of antigenic domains and RGD-like sequences (RGWG) in the E glycoprotein of flaviviruses: an approach to vaccine development.

    PubMed

    Becker, Y

    1990-09-01

    Antigenic domains and RGD-like sequences in the E glycoprotein of the flaviviruses Japanese encephalitis virus, yellow fever virus, West Nile virus, dengue type 4 virus, and tick-borne encephalitis virus were analyzed by computer programs that provide information on the physical properties of the polypeptides. The use of computer programs for the development of vaccines based on the synthesis of antigenic peptides is discussed. Synthetic viral peptides are proposed to be used for topical application so as to interfere with the virus-cell interaction. Viral peptides with antigenic epitopes to protect against dengue virus infection without enhancing pathogenesis may also be developed on the basis of the computer analysis.

  10. Vibrations of the carbon dioxide dimer

    NASA Astrophysics Data System (ADS)

    Chen, Hua; Light, J. C.

    2000-03-01

    Fully coupled four-dimensional quantum-mechanical calculations are presented for intermolecular vibrational states of rigid carbon dioxide dimer for J=0. The Hamiltonian operator is given in collision coordinates. The Hamiltonian matrix elements are evaluated using symmetrized products of spherical harmonics for angles and a potential optimized discrete variable representation (PO-DVR) for the intermolecular distance. The lowest ten or so states of each symmetry are reported for the potential energy surface (PES) given by Bukowski et al. [J. Chem. Phys. 110, 3785 (1999)]. Due to symmetries, there is no interconversion tunneling splitting for the ground state. Our calculations show that there is no tunneling shift of the ground state within our computation precision (0.01 cm-1). Analysis of the wave functions shows that only the ground states of each symmetry are nearly harmonic. The van der Waals frequencies and symmetry adapted force constants are found and compared to available experimental values. Strong coupling between the stretching coordinates and the bending coordinates are found for vibrationally excited states. The interconversion tunneling shifts are discussed for the vibrationally excited states.

  11. Smectic Phase Formed by DNA Dimers

    NASA Astrophysics Data System (ADS)

    Salamonczyk, Miroslaw; Gleeson, James; Jakli, Antal; Sprunt, Samuel; Dhont, Jan; Stiakakis, Emmanuel

    The rapidly expanding bio market is driving the development and characterization of new multifunctional materials. In particular, nucleic acids are under intense study for gene therapy, drug delivery and other bio-safe applications [1,2,3]. DNA is well-known to form a cholesteric nematic liquid crystal in its native form; however, much recent research has focused on self-assembly and mesomorphic behavior in concentrated solutions of short DNA helices [4]. Our work focuses on DNA dimers, consisting of 48 base-pair double-stranded helices connected by a 5 to 20 base flexible single strand, and suspended in a natural buffer. Depending on temperature, concentration and length of the flexible spacer, polarizing optical microscopy and small angle x-ray scattering reveal cholesteric nematic and, remarkably, smectic liquid crystalline phases. A model for smectic phase formation in this system will be presented. 1] J.-L. Lim et al., Int. J. of. Pharm. 490 (2015) 2652] D.-H. Kim et al., Nature Biotech. 23 (2005) 2223] K. Liu et al., Chem. Eur. J. 21 (2015) 48984] M. Nakata et al., Science 318 (2007) 1276 NSF DMR 1307674.

  12. Repressor Dimerization in the Zebrafish Somitogenesis Clock

    PubMed Central

    Cinquin, Olivier

    2007-01-01

    The oscillations of the somitogenesis clock are linked to the fundamental process of vertebrate embryo segmentation, yet little is known about their generation. In zebrafish, it has been proposed that Her proteins repress the transcription of their own mRNA. However, in its simplest form, this model is incompatible with the fact that morpholino knockdown of Her proteins can impair expression of their mRNA. Simple self-repression models also do not account for the spatiotemporal pattern of gene expression, with waves of gene expression shrinking as they propagate. Here we study computationally the networks generated by the wealth of dimerization possibilities amongst transcriptional repressors in the zebrafish somitogenesis clock. These networks can reproduce knockdown phenotypes, and strongly suggest the existence of a Her1–Her7 heterodimer, so far untested experimentally. The networks are the first reported to reproduce the spatiotemporal pattern of the zebrafish somitogenesis clock; they shed new light on the role of Her13.2, the only known link between the somitogenesis clock and positional information in the paraxial mesoderm. The networks can also account for perturbations of the clock by manipulation of FGF signaling. Achieving an understanding of the interplay between clock oscillations and positional information is a crucial first step in the investigation of the segmentation mechanism. PMID:17305423

  13. Assembly of Dimer-Based Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Liddell Watson, Chekesha M.

    2011-03-01

    Recent advances in colloid synthesis to prepare monodisperse shape anisotropic particles provide the opportunity to address challenges related to structural diversity in ordered colloidal solids. In particular, computational simulations and mechanical models suggest that upon system densification nonspherical dimer colloids undergo disorder-order and order-order phase transitions to unconventional solid structures including, base-centered monoclinic crystals, degenerate aperiodic crystals, plastic crystal or rotator, etc. based on free energy minimization. The particle systems have notable analogy to molecular systems, where the shape of molecules and their packing density has been shown to critically influence structural phase behavior and lead to a rich variety of structures, both natural and synthetic. The materials engineering challenges have been in attaining sufficiently monodisperse (size uniformity) colloidal building blocks, as well as the lack of understanding and control of self-assembly processes for non-spherical colloids. This talk highlights our investigations of how particle shape programs the self-organization of colloidal structures. Methods including evaporation mediated assembly and confinement provide a platform to understand the formation of complex colloidal structures from non-spherical building blocks (silica-coated iron oxide, polystyrene, hollow silica shell). Optical property simulations for unconventional 2D and 3D structures with nonspherical particle bases will also be discussed.

  14. Ab initio calculations of nitramine dimers

    NASA Astrophysics Data System (ADS)

    Koh-Fallet, Sharon; Schweigert, Igor

    2015-06-01

    Elevated temperatures and pressures are typically thought to have opposing effects on the reaction channels of nitramine decomposition. These high temperatures promote reactions with loose transition structures (positive activation entropies and volumes), such as N-N bond homolysis. Elevated pressures promote reactions with tight transition structures (negative activation entropies and volumes), such as intramolecular and intermolecular H transfer. However, no quantitative data exists regarding the range of temperatures and pressures at which these effects become pronounced. We are pursuing ab initio calculations of the corresponding unimolecular and bimolecular transition structures with the objective of estimating the relevant thermochemical parameters and quantifying the effects of elevated temperature and pressures on the corresponding rate constants. Here, we present density functional theory and complete active space calculations of gas-phase molecular dimers of nitramines as an intermediate step toward modeling transition structures directly in the condensed phase. This work was supported by the Naval Research Laboratory via the American Society for Engineering and Education and by the Office of Naval Research, both directly and through the Naval Research Laboratory.

  15. Dimer packings with gaps and electrostatics

    PubMed Central

    Ciucu, Mihai

    2008-01-01

    Fisher and Stephenson conjectured in 1963 that the correlation function (defined by dimer packings) of two unit holes on the square lattice is rotationally invariant in the limit of large separation between the holes. We consider the same problem on the hexagonal lattice, extend it to an arbitrary finite collection of holes, and present an explicit conjectural answer. In recent work we managed to prove this conjecture in two fairly general cases. The quantity giving the answer can be regarded as the exponential of the negative of the two-dimensional electrostatic energy of a system of charges naturally associated with the holes. We further develop this analogy to electrostatics by presenting two different natural ways to define a field in our setup, and showing that both lead to the electric field, in the limit of large separations between the holes. For one of the fields, this is also stated as a limit shape theorem for random surfaces, with the continuum limit being a sum of helicoids. We conclude by explaining the relationship of our results to previous results in the physics literature on spin correlations in the Ising model.

  16. Dimer model for Tau proteins bound in microtubule bundles

    NASA Astrophysics Data System (ADS)

    Hall, Natalie; Kluber, Alexander; Hayre, N. Robert; Singh, Rajiv; Cox, Daniel

    2013-03-01

    The microtubule associated protein tau is important in nucleating and maintaining microtubule spacing and structure in neuronal axons. Modification of tau is implicated as a later stage process in Alzheimer's disease, but little is known about the structure of tau in microtubule bundles. We present preliminary work on a proposed model for tau dimers in microtubule bundles (dimers are the minimal units since there is one microtubule binding domain per tau). First, a model of tau monomer was created and its characteristics explored using implicit solvent molecular dynamics simulation. Multiple simulations yield a partially collapsed form with separate positively/negatively charged clumps, but which are a factor of two smaller than required by observed microtubule spacing. We argue that this will elongate in dimer form to lower electrostatic energy at a cost of entropic ``spring'' energy. We will present preliminary results on steered molecular dynamics runs on tau dimers to estimate the actual force constant. Supported by US NSF Grant DMR 1207624.

  17. DLTS study of the oxygen dimer formation kinetics in silicon

    NASA Astrophysics Data System (ADS)

    Yarykin, Nikolai; Weber, Jörg

    2009-12-01

    The introduction rates of radiation defects, in particular the X- and M-centers for which the oxygen dimer is a precursor, are investigated as a function of duration of the pre-irradiation heat treatment at 480∘ C in Czochralski-grown silicon both of n- and p-types. The characteristic annealing time to grow the X-center concentration in the n-type crystal is found to be about 1 h in accordance with the model which implies no significant barrier for the dimer formation. The M-center concentration in the p-type crystal is found to be nearly independent of duration of the pre-irradiation annealing after a few minutes transient period. This behavior is ascribed to the stabilization of dimer concentration due to an effective dimer trapping in these samples.

  18. Non-stripe charge order in dimerized organic conductors

    NASA Astrophysics Data System (ADS)

    Mori, Takehiko

    2016-06-01

    This paper demonstrates charge order is important in dimerized β - and κ -phase organic conductors similar to the uniform θ - and α -phase conductors. Here the magnitude of the dimerization represents the deviation from the ideal triangular lattice in analogy with the anisotropy in the θ phase. Since the ratio of the intradimer transfer integral to the interdimer transfer integral is as large as ˜2.6 , these dimerized phases lead to a dimer Mott insulator, whereas the Coulomb repulsion is closer to the triangular lattice because the ratio of the intradimer Coulomb repulsion to the interdimer Coulomb repulsion is comparatively small (˜1.7 ). Accordingly, in the static-limit calculation, non-stripe charge order with threefold periodicity appears between the uniform and the stripe phases, and the analogy with the θ phase suggests the first-order nature of the metal-insulator transition.

  19. [Antioxidant and antibacterial activities of dimeric phenol compounds].

    PubMed

    Ogata, Masahiro

    2008-08-01

    We studied the antioxidant and antibacterial activities of monomeric and dimeric phenol compounds. Dimeric compounds had higher antioxidant activities than monomeric compounds. Electron spin resonance spin-trapping experiments showed that phenol compounds with an allyl substituent on their aromatic rings directly scavenged superoxide, and that only eugenol trapped hydroxyl radicals. We developed a generation system of the hydroxyl radical without using any metals by adding L-DOPA and DMPO to PBS or MiliQ water in vitro. We found that eugenol trapped hydroxyl radicals directly and is metabolized to a dimer. On the other hand, dipropofol, a dimer of propofol, has strong antibacterial activity against Gram-positive bacteria. However, it lacks solubility in water and this property is assumed to limit its efficacy. We tried to improve the solubility and found a new solubilization method of dipropofol in water with the addition of a monosaccharide or ascorbic acid.

  20. Sodium dimers on the surface of liquid {sup 4}He

    SciTech Connect

    Ancilotto, F.; DeToffol, G.; Toigo, F.

    1995-12-01

    We have studied the structure of a sodium dimer interacting with liquid {sup 4}He. We calculated the equilibrium configuration and binding energy of a Na{sub 2} molecule solvated in a bulk liquid {sup 4}He ``bubble`` and near the liquid-vapor interface ``dimple`` by using a density-functional approach. We find that the solvated molecule is a metastable state, while the the lowest energy bound state occurs when the molecule lies flat on the surface of the liquid. The binding energy for the ``erect`` dimer is only {similar_to}1 K higher than the flat dimer, with no potential energy barrier between the two orientations, implying relatively free rotations of the molecule on the surface. The small effects of the liquid environment on the vibrational properties of the dimer are investigated.

  1. Metallothionein dimers studied by nano-spray mass spectrometry.

    PubMed

    Hathout, Yetrib; Reynolds, Kristy J; Szilagyi, Zoltan; Fenselau, Catherine

    2002-01-15

    Both transient and stable dimers of metallothionein have been characterized, based on earlier studies using NMR, circular dichroism and size-exclusion chromatography. Here additional characterization is provided by nanospray mass spectrometry. Rapid redistribution of metal ions between monomeric Cd7- and Zn7-metallothionein 2a is monitored by nanospray. An experiment in which theses two forms of the monomeric protein are separated by a dialysis membrane, which will pass metal ions but not proteins, confirms that a transient dimer must form for metal ions to be redistributed. On the other hand, size-exclusion chromatography of reconstituted Zn7- or Cd7-metallothionein revealed the presence of monomeric and dimeric species. These dimers do not equilibrate readily to form monomers and they are shown to be covalent.

  2. Design and Preparation of Nanoparticle Dimers for SERS Detection

    DTIC Science & Technology

    2012-09-10

    aptamers (aptatags) or antibodies (antitags) as the recognition elements. Preparation of 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 09-10...resulting dimeric structures incorporate aptamers (aptatags) or antibodies (antitags) as the recognition elements. Preparation of suitable sensing...signal   enhancement   is   at   its   maximum.     The   resulting   dimeric   structures   incorporate   aptamers

  3. Anomalous atmospheric absorption spectra due to water dimer

    NASA Astrophysics Data System (ADS)

    Cai, Peipei; Zhang, Hansheng; Shen, Shanxiong; Cheng, I.-Shan

    1986-11-01

    The anomalous atmospheric absorption spectra in the window wavelength region of 8-14 microns have been suggested due to the water dimer. Based on laboratory measurements, water continuum CO2 laser absorption spectra and a resonance absorption line due to the weak local wave vapor pure rotational transition have been reported. The equilibrium concentration of water dimers in the atmosphere, the electronic binding energy and the theoretical calculations for absorption attenuation have been obtained in agreement with published data.

  4. Superconductivity in the liquid-dimer valence-bond state

    SciTech Connect

    Ioffe, L.B.; Larkin, A.I. )

    1989-10-01

    Introducing an unambiguous prescription which converts singlet dimers into quasidipoles, we describe the low-energy excitations in the liquid-dimer state as fluctuations of the average dipole moment. The exchange of these fluctuations leads to a long-range interaction between holes in this state. This interaction favors the two-particle Bose condensate and destroys the order parameter of the one-particle Bose condensate even at zero temperature.

  5. Absorption cross sections of the ClO dimer

    NASA Technical Reports Server (NTRS)

    Huder, K. J.; DeMore, W. B.

    1995-01-01

    The absorption cross sections of the ClO dimer, ClOOCl, are important to the photochemistry of ozone depletion in the Antarctic. In this work, new measurements were made of the dimer cross sections at 195 K. the results yield somewhat lower values in the long wavelength region, compared to those currently recommended in the NASA data evaluation (JPL 94-26). The corresponding solar photodissociation rates in the Antarctic are reduced by about 40%.

  6. Cholesterol-dependent Conformational Plasticity in GPCR Dimers

    PubMed Central

    Prasanna, Xavier; Sengupta, Durba; Chattopadhyay, Amitabha

    2016-01-01

    The organization and function of the serotonin1A receptor, an important member of the GPCR family, have been shown to be cholesterol-dependent, although the molecular mechanism is not clear. We performed a comprehensive structural and dynamic analysis of dimerization of the serotonin1A receptor by coarse-grain molecular dynamics simulations totaling 3.6 ms to explore the molecular details of its cholesterol-dependent association. A major finding is that the plasticity and flexibility of the receptor dimers increase with increased cholesterol concentration. In particular, a dimer interface formed by transmembrane helices I-I was found to be sensitive to cholesterol. The modulation of dimer interface appears to arise from a combination of direct cholesterol occupancy and indirect membrane effects. Interestingly, the presence of cholesterol at the dimer interface is correlated with increased dimer plasticity and flexibility. These results represent an important step in characterizing the molecular interactions in GPCR organization with potential relevance to therapeutic interventions. PMID:27535203

  7. Mechanism of dimerization of the human melanocortin 1 receptor

    SciTech Connect

    Zanna, Paola T.; Sanchez-Laorden, Berta L.; Perez-Oliva, Ana B.; Turpin, Maria C.; Herraiz, Cecilia; Jimenez-Cervantes, Celia; Garcia-Borron, Jose C.

    2008-04-04

    The melanocortin 1 receptor (MC1R) is a dimeric G protein-coupled receptor expressed in melanocytes, where it regulates the amount and type of melanins produced and determines the tanning response to ultraviolet radiation. We have studied the mechanisms of MC1R dimerization. Normal dimerization of a deleted mutant lacking the seventh transmembrane fragment and the C-terminal cytosolic extension excluded coiled-coil interactions as the basis of dimerization. Conversely, the electrophoretic pattern of wild type receptor and several Cys {yields} Ala mutants showed that four disulfide bonds are established between the monomers. Disruption of any of these bonds abolished MC1R function, but only the one involving Cys35 was essential for traffic to the plasma membrane. A quadruple Cys35-267-273-275Ala mutant migrating as a monomer in SDS-PAGE in the absence of reducing agents was able to dimerize with WT, suggesting that in addition to disulfide bond formation, dimerization involves non-covalent interactions, likely of domain swap type.

  8. Mobile Monomers and Dimers in Precipitation Kinetics: a Microscopic Approach.

    PubMed

    Berim, Gersh O; Brim, Lana I; Ruckenstein, Eli

    2017-02-02

    A microscopic theory of precipitation kinetics in solution developed previously by Ruckenstein and co-workers [ Dadyburjor , D. B. ; Ruckenstein , E. J. Cryst. Growth 1977 , 40 , 279 - 290 ; Bhakta , A. ; Ruckenstein , E. J. Chem. Phys. 1995 , 103 , 7120 - 7135 ] is generalized. The processes (not considered in the original approach) of monomer-monomer agglomeration, leading to the creation of dimers, as well as absorption (emission) of dimers by solute particles due to dimer mobility are included in the theory. The theory is applied to a model system in which particles grow up to a certain largest size and then precipitate from solution. The most important change in the system kinetics due to those two processes (monomer agglomeration to form dimers and dimer absorption and emission) is tremendous slowing of the asymptotic time behavior of the concentration of particles of largest size. This can be used to obtain experimental evidence for agglomeration of monomers and dimer mobility in the kinetics of real systems. The effect of trimer absorption (emission) is estimated, and it is shown that it is negligible in many situations.

  9. Determining equilibrium constants for dimerization reactions from molecular dynamics simulations.

    PubMed

    De Jong, Djurre H; Schäfer, Lars V; De Vries, Alex H; Marrink, Siewert J; Berendsen, Herman J C; Grubmüller, Helmut

    2011-07-15

    With today's available computer power, free energy calculations from equilibrium molecular dynamics simulations "via counting" become feasible for an increasing number of reactions. An example is the dimerization reaction of transmembrane alpha-helices. If an extended simulation of the two helices covers sufficiently many dimerization and dissociation events, their binding free energy is readily derived from the fraction of time during which the two helices are observed in dimeric form. Exactly how the correct value for the free energy is to be calculated, however, is unclear, and indeed several different and contradictory approaches have been used. In particular, results obtained via Boltzmann statistics differ from those determined via the law of mass action. Here, we develop a theory that resolves this discrepancy. We show that for simulation systems containing two molecules, the dimerization free energy is given by a formula of the form ΔG ∝ ln(P(1) /P(0) ). Our theory is also applicable to high concentrations that typically have to be used in molecular dynamics simulations to keep the simulation system small, where the textbook dilute approximations fail. It also covers simulations with an arbitrary number of monomers and dimers and provides rigorous error estimates. Comparison with test simulations of a simple Lennard Jones system with various particle numbers as well as with reference free energy values obtained from radial distribution functions show full agreement for both binding free energies and dimerization statistics.

  10. Photodissociation pathways and lifetimes of protonated peptides and their dimers

    SciTech Connect

    Aravind, G.; Klaerke, B.; Rajput, J.; Toker, Y.; Andersen, L. H.; Bochenkova, A. V.; Antoine, R.; Racaud, A.; Dugourd, P.; Lemoine, J.

    2012-01-07

    Photodissociation lifetimes and fragment channels of gas-phase, protonated YA{sub n} (n = 1,2) peptides and their dimers were measured with 266 nm photons. The protonated monomers were found to have a fast dissociation channel with an exponential lifetime of {approx}200 ns while the protonated dimers show an additional slow dissociation component with a lifetime of {approx}2 {mu}s. Laser power dependence measurements enabled us to ascribe the fast channel in the monomer and the slow channel in the dimer to a one-photon process, whereas the fast dimer channel is from a two-photon process. The slow (1 photon) dissociation channel in the dimer was found to result in cleavage of the H-bonds after energy transfer through these H-bonds. In general, the dissociation of these protonated peptides is non-prompt and the decay time was found to increase with the size of the peptides. Quantum RRKM calculations of the microcanonical rate constants also confirmed a statistical nature of the photodissociation processes in the dipeptide monomers and dimers. The classical RRKM expression gives a rate constant as an analytical function of the number of active vibrational modes in the system, estimated separately on the basis of the equipartition theorem. It demonstrates encouraging results in predicting fragmentation lifetimes of protonated peptides. Finally, we present the first experimental evidence for a photo-induced conversion of tyrosine-containing peptides into monocyclic aromatic hydrocarbon along with a formamide molecule both found in space.

  11. Conformational stability of dimeric proteins: quantitative studies by equilibrium denaturation.

    PubMed Central

    Neet, K. E.; Timm, D. E.

    1994-01-01

    The conformational stability of dimeric globular proteins can be measured by equilibrium denaturation studies in solvents such as guanidine hydrochloride or urea. Many dimeric proteins denature with a 2-state equilibrium transition, whereas others have stable intermediates in the process. For those proteins showing a single transition of native dimer to denatured monomer, the conformational stabilities, delta Gu (H2O), range from 10 to 27 kcal/mol, which is significantly greater than the conformational stability found for monomeric proteins. The relative contribution of quaternary interactions to the overall stability of the dimer can be estimated by comparing delta Gu (H2O) from equilibrium denaturation studies to the free energy associated with simple dissociation in the absence of denaturant. In many cases the large stabilization energy of dimers is primarily due to the intersubunit interactions and thus gives a rationale for the formation of oligomers. The magnitude of the conformational stability is related to the size of the polypeptide in the subunit and depends upon the type of structure in the subunit interface. The practical use, interpretation, and utility of estimation of conformational stability of dimers by equilibrium denaturation methods are discussed. PMID:7756976

  12. Magneto-association near an atom-dimer resonance

    NASA Astrophysics Data System (ADS)

    Luo, D.; Nguyen, J. H. V.; Hulet, R. G.

    2015-05-01

    Over the past decade the universal scaling of Efimov trimers has been explored in various atomic species by measuring the three-body loss coefficient. An enhancement of the three-body loss at the atom-dimer resonance has been observed, but remains unexplained. It has been attributed to an ``avanlanche mechanism'' based on resonant atom-dimer scattering, yet the effectiveness of the hypothesis is under scrutiny. We present a new piece to the puzzle. In our work, Feshbach dimers and Efimov trimers are formed near the atom-dimer resonance by RF-association, from a Bose-Einstein condensate of 7Li atoms. The molecular binding energies are tunable by the broad Feshbach resonance of the atoms in the | 1 , 1 > state. We observe that the dimer formation rate is significantly enhanced at the atom-dimer resonance. The origin of this enhanement is unclear, but it may be closely related to the enhancement of the three-body loss rate. Work supported by the NSF, ARO, and the Welch Foundation.

  13. Mass Analyzed Threshold Ionization of Lutetium Dimer

    NASA Astrophysics Data System (ADS)

    Wu, Lu; Roudjane, Mourad; Liu, Yang; Yang, Dong-Sheng

    2013-06-01

    Lu_2 is produced in a pulsed laser-vaporization metal-cluster source and studied by mass-analyzed threshold ionization (MATI) spectroscopy. The MATI spectrum displays several long progressions from the transitions between various vibrational levels of the neutral and ion electronic states. From the spectrum, the upper limit of the ionization energy of the dimer is determined to be 43996 cm^{-1}, and the vibrational frequencies are measured to be 121 cm^{-1} in the neutral state and 90 cm^{-1} in the ion state. By combining with ab initio calculations at CASPT2 level, the ground state of Lu_2 is identified as ^3Σ_g^-. The ^3Σ_g^- state has an electron configuration of 6sσ_g^25dπ_u^15dπ_u^16sσ_u^2, which is formed by the interactions of two Lu atoms in the ^2D(5d6s^2) ground state. Ionization of the neutral state removes a 5dπ_u bonding electron and yields a ion state with a considerably longer bond distance. Lu_2 has a very different bonding feature from La_2, for which a ^1Σ_g^+ ground state was previously identified with an electron configuration of 5dπ_u^46sσ_g^2 formed by the interactions of two La atoms in the ^4F(5d^26s) excited state. Yang Liu, Lu Wu, Chang-Hua Zhang, Serge A. Krasnokutski, and Dong-Sheng Yang, J. Chem. Phys. 135, 034309 (2011).

  14. UVA Generates Pyrimidine Dimers in DNA Directly

    PubMed Central

    Jiang, Yong; Rabbi, Mahir; Kim, Minkyu; Ke, Changhong; Lee, Whasil; Clark, Robert L.; Mieczkowski, Piotr A.; Marszalek, Piotr E.

    2009-01-01

    There is increasing evidence that UVA radiation, which makes up ∼95% of the solar UV light reaching the Earth's surface and is also commonly used for cosmetic purposes, is genotoxic. However, in contrast to UVC and UVB, the mechanisms by which UVA produces various DNA lesions are still unclear. In addition, the relative amounts of various types of UVA lesions and their mutagenic significance are also a subject of debate. Here, we exploit atomic force microscopy (AFM) imaging of individual DNA molecules, alone and in complexes with a suite of DNA repair enzymes and antibodies, to directly quantify UVA damage and reexamine its basic mechanisms at a single-molecule level. By combining the activity of endonuclease IV and T4 endonuclease V on highly purified and UVA-irradiated pUC18 plasmids, we show by direct AFM imaging that UVA produces a significant amount of abasic sites and cyclobutane pyrimidine dimers (CPDs). However, we find that only ∼60% of the T4 endonuclease V-sensitive sites, which are commonly counted as CPDs, are true CPDs; the other 40% are abasic sites. Most importantly, our results obtained by AFM imaging of highly purified native and synthetic DNA using T4 endonuclease V, photolyase, and anti-CPD antibodies strongly suggest that CPDs are produced by UVA directly. Thus, our observations contradict the predominant view that as-yet-unidentified photosensitizers are required to transfer the energy of UVA to DNA to produce CPDs. Our results may help to resolve the long-standing controversy about the origin of UVA-produced CPDs in DNA. PMID:19186150

  15. Active-target T1-weighted MR Imaging of Tiny Hepatic Tumor via RGD Modified Ultra-small Fe3O4 Nanoprobes

    PubMed Central

    Jia, Zhengyang; Song, Lina; Zang, Fengchao; Song, Jiacheng; Zhang, Wei; Yan, Changzhi; Xie, Jun; Ma, Zhanlong; Ma, Ming; Teng, Gaojun; Gu, Ning; Zhang, Yu

    2016-01-01

    Developing ultrasensitive contrast agents for the early detection of malignant tumors in liver is highly demanded. Constructing hepatic tumors specific targeting probes could provide more sensitive imaging information but still faces great challenges. Here we report a novel approach for the synthesis of ultra-small Fe3O4 nanoparticles conjugated with c(RGDyK) and their applications as active-target T1-weighted magnetic resonance imaging (MRI) contrast agent (T1-Fe3O4) for imaging tiny hepatic tumors in vivo. RGD-modified T1-Fe3O4 nanoprobes exhibited high r1 of 7.74 mM-1s-1 and ultralow r2/r1 of 2.8 at 3 T, reflecting their excellent T1 contrast effect at clinically relevant magnetic field. High targeting specificity together with favorable biocompatibility and strong ability to resist against non-specific uptake were evaluated through in vitro studies. Owing to the outstanding properties of tumor angiogenesis targeting with little phagocytosis in liver parenchyma, hepatic tumor as small as 2.2 mm was successfully detected via the T1 contrast enhancement of RGD-modified T1-Fe3O4. It is emphasized that this is the first report on active-target T1 imaging of hepatic tumors, which could not only significantly improve diagnostic sensitivity, but also provide post therapeutic assessments for patients with liver cancer. PMID:27570550

  16. RGD-grafted poly-L-lysine-graft-(polyethylene glycol) copolymers block non-specific protein adsorption while promoting cell adhesion.

    PubMed

    VandeVondele, Stephanie; Vörös, Janos; Hubbell, Jeffrey A

    2003-06-30

    A novel class of surface-active copolymers is described, designed to protect surfaces from nonspecific protein adsorption while still inducing specific cell attachment and spreading. A graft copolymer was synthesized, containing poly-(L-lysine) (PLL) as the backbone and substrate binding and poly(ethylene glycol) (PEG) as protein adsorption-resistant pendant side chains. A fraction of the grafted PEG was pendantly functionalized by covalent conjugation to the peptide motif RGD to induce cell binding. The graft copolymer spontaneously adsorbs from dilute aqueous solution onto negatively charged surfaces. The performance of RGD-modified PLL-g-PEG copolymers was analyzed in protein adsorption and cell culture assays. These coatings efficiently blocked the adsorption of serum proteins to Nb(2)O(5) and tissue culture polystyrene while specifically supporting attachment and spreading of human dermal fibroblasts. This surface functionalization technology is expected to be valuable in both the biomaterial and biosensor fields, because different signals can easily be combined, and sterilization and application are straightforward and cost-effective.

  17. The effect of hydrophilic chain length and iRGD on drug delivery from poly(ε-caprolactone)-poly(N-vinylpyrrolidone) nanoparticles.

    PubMed

    Zhu, Zhenshu; Xie, Chen; Liu, Qin; Zhen, Xu; Zheng, Xianchuang; Wu, Wei; Li, Rutian; Ding, Yin; Jiang, Xiqun; Liu, Baorui

    2011-12-01

    Poly(ε-caprolactone)-b-Poly(N-vinylpyrrolidone) (PCL-b-PVP) copolymers with different PVP block length were synthesized by xanthate-mediated reverse addition fragment transfer polymerization (RAFT) and the xanthate chain transfer agent on chain end was readily translated to hydroxy or aldehyde for conjugating various functional moieties, such as fluorescent dye, biotin hydrazine and tumor homing peptide iRGD. Thus, PCL-PVP nanoparticles were prepared by these functionalized PCL-b-PVP copolymers. Furthermore, paclitaxel-loaded PCL-PVP nanoparticles with satisfactory drug loading content (15%) and encapsulation efficiency (>90%) were obtained and used in vitro and in vivo antitumor examination. It was demonstrated that the length of PVP block had a significant influence on cytotoxicity, anti-BSA adsorption, circulation time, stealth behavior, biodistribution and antitumor activity for the nanoparticles. iRGD on PCL-PVP nanoparticle surface facilitated the nanoparticles to accumulate in tumor site and enhanced their penetration in tumor tissues, both of which improved the efficacy of paclitaxel-loaded nanoparticles in impeding tumor growth and prolonging the life time of H22 tumor-bearing mice.

  18. Functionalization of the PEG Corona of Nanoparticles by Clip Photochemistry in Water: Application to the Grafting of RGD Ligands on PEGylated USPIO Imaging Agent.

    PubMed

    Pourcelle, Vincent; Laurent, Sophie; Welle, Alexandre; Vriamont, Nicolas; Stanicki, Dimitri; Vander Elst, Luce; Muller, Robert N; Marchand-Brynaert, Jacqueline

    2015-05-20

    The fast development of nanomedicines requires more and more reliable chemical tools in order to accurately design materials and control the surface properties of the nano-objects used in biomedical applications. In this study we describe a smooth and simple photografting technique, i.e., the clip photochemistry, that allows the introduction of molecules of interest in inert polymers or on stealth nanoparticles directly in aqueous solution. First we developed the methodology on polyethylene glycol (PEG) and looked for critical parameters of the process (irradiation times, concentrations, washings) by using several molecular probes and adapted analytical techniques ((19)F qNMR, EA, LSC). We found that the clip photochemistry in water is a robust and efficient method to functionalize PEG. Second we applied it on PEGylated USPIO (USPIO-PEG) magnetic resonance imaging agent and succeeded in introducing RGD peptide and homemade peptidomimetics on their PEG segments. The magnetic abilities of the conjugated nanoparticles were unchanged by the derivatization process as evidenced by their relaxometric properties and their NMRD profile. When tested on Jurkat lymphocyte T Cells, which express αvβ3 integrins, the USPIO conjugated with RGD ligands leads to an increase of the transverse relaxation rate (R2) by a factor 10 to 14 as compared to USPIO-PEG. Consequently, it makes them good candidates for targeted imaging technology in cancer therapy.

  19. RGD Peptides-Conjugated Pluronic Triblock Copolymers Encapsulated with AP-2α Expression Plasmid for Targeting Gastric Cancer Therapy in Vitro and in Vivo.

    PubMed

    Wang, Wei; Liu, Zhimin; Sun, Peng; Fang, Cheng; Fang, Hongwei; Wang, Yueming; Ji, Jiajia; Chen, Jun

    2015-07-17

    Gastric cancer, a high-risk malignancy, is a genetic disease developing from a cooperation of multiple gene mutations and a multistep process. Gene therapy is a novel treatment method for treating gastric cancer. Here, we developed a novel Arg-Gly-Asp (RGD) peptides conjugated copolymers nanoparticles-based gene delivery system in order to actively targeting inhibit the growth of gastric cancer cells. These transcription factor (AP-2α) expression plasmids were also encapsulated into pluronic triblock copolymers nanoparticles which was constituted of poly(ethylene glycol)-block-poly(propylene glycol)- block-poly(ethylene glycol) (PEO-block-PPO-block-PEO, P123). The size, morphology and composition of prepared nanocomposites were further characterized by nuclear magnetic resonance (NMR), transmission electron microscopy (TEM) and dynamic light scattering (DLS). In MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide) analysis, these nanocomposites have minor effects on the proliferation of GES-1 cells but significantly decreased the viability of MGC-803, suggesting they own low cytotoxicity but good antitumor activity. The following in vivo evaluation experiments confirmed that these nanocomposites could prevent the growth of gastric cancer cells in the tumor xenograft mice model. In conclusion, these unique RGD peptides conjugated P123 encapsulated AP-2α nanocomposites could selectively and continually kill gastric cancer cells by over-expression of AP-2α in vitro and in vivo; this exhibits huge promising applications in clinical gastric cancer therapy.

  20. PEGylation enhances tumor targeting of plasmid DNA by an artificial cationized protein with repeated RGD sequences, Pronectin.

    PubMed

    Hosseinkhani, Hossein; Tabata, Yasuhiko

    2004-05-31

    The objective of this study is to investigate feasibility of a non-viral gene carrier with repeated RGD sequences (Pronectin F+) in tumor targeting for gene expression. The Pronectin F+ was cationized by introducing spermine (Sm) to the hydroxyl groups to allow to polyionically complex with plasmid DNA. The cationized Pronectin F+ prepared was additionally modified with poly(ethylene glycol) (PEG) molecules which have active ester and methoxy groups at the terminal, to form various PEG-introduced cationized Pronectin F+. The cationized Pronectin F+ with or without PEGylation at different extents was mixed with a plasmid DNA of LacZ to form respective cationized Pronectin F+-plasmid DNA complexes. The plasmid DNA was electrophoretically complexed with cationized Pronectin F+ and PEG-introduced cationized Pronectin F+, irrespective of the PEGylation extent, although the higher N/P ratio of complexes was needed for complexation with the latter Pronectin F+. The molecular size and zeta potential measurements revealed that the plasmid DNA was reduced in size to about 250 nm and the charge was changed to be positive by the complexation with cationized Pronectin F+. For the complexation with PEG-introduced cationized Pronectin F+, the charge of complex became neutral being almost 0 mV with the increasing PEGylation extents, while the molecular size was similar to that of cationized Pronectin F+. When cationized Pronectin F+-plasmid DNA complexes with or without PEGylation were intravenously injected to mice carrying a subcutaneous Meth-AR-1 fibrosarcoma mass, the PEG-introduced cationized Pronectin F+-plasmid DNA complex specifically enhanced the level of gene expression in the tumor, to a significantly high extent compared with the cationized Pronectin F+-plasmid DNA complexes and free plasmid DNA. The enhanced level of gene expression depended on the percentage of PEG introduced, the N/P ratio, and the plasmid DNA dose. A fluorescent microscopic study revealed that the

  1. Cyclic RGD conjugated poly(ethylene glycol)-co-poly(lactic acid) micelle enhances paclitaxel anti-glioblastoma effect.

    PubMed

    Zhan, Changyou; Gu, Bing; Xie, Cao; Li, Jin; Liu, Yu; Lu, Weiyue

    2010-04-02

    The use of glioblastoma-targeted drug delivery system facilitates efficient delivery of chemotherapeutic agents to malignant gliomas in the central nervous system while minimizing high systemic doses associated with debilitating toxicities. To employ the high binding affinity of a cyclic RGD peptide (c(RGDyK), cyclic Arginine-Glycine-Aspartic acid-D-Tyrosine-Lysine) with integrin alpha(v)beta(3) over-expressed on tumor neovasculature and U87MG glioblastoma cells, we prepared paclitaxel-loaded c(RGDyK)-Poly(ethylene glycol)-block-poly(lactic acid) micelle (c(RGDyK)-PEG-PLA-PTX). In vitro physicochemical characterization of these novel micelles showed satisfactory encapsulated efficiency, loading capacity and size distribution. In vitro cytotoxicity studies proved that the presence of c(RGDyK) enhanced the anti-glioblastoma cell cytotoxic efficacy by 2.5 folds. The binding affinity of c(RGDyK)-PEG-PLA micelle with U87MG cells was also investigated. The competitive binding IC(50) value of c(RGDyK)-PEG-PLA micelle was 26.30 nM, even lower than that of c(RGDyK) (56.23 nM). In U87MG glioblastoma-bearing nude mice model, biodistribution of (125)I-radiolabeled c(RGDyK)-PEG-PLA or DiR encapsulated micelles and anti-glioblastoma pharmacological effect was investigated after intravenous administration. c(RGDyK)-PEG-PLA micelle accumulated in the subcutaneous and intracranial tumor tissue, and when loaded with PTX (c(RGDyK)-PEG-PLA-PTX), exhibited the strongest tumor growth inhibition among the studied paclitaxel formulations. The anti-glioblastoma effect of c(RGDyK)-PEG-PLA-PTX micelle was also reflected in the median survival time of mice bearing intracranial U87MG tumor xenografts where the median survival time of c(RGDyK)-PEG-PLA-PTX micelle-treated mice (48 days) was significantly longer than that of mice treated with PEG-PLA-PTX micelle (41.5 days), Taxol (38.5 days) or saline (34 days). Therefore, our results suggested that c(RGDyK)-PEG-PLA micelle may be a potential

  2. Products and mechanism of acene dimerization. A computational study.

    PubMed

    Zade, Sanjio S; Zamoshchik, Natalia; Reddy, A Ravikumar; Fridman-Marueli, Galit; Sheberla, Dennis; Bendikov, Michael

    2011-07-20

    The high reactivity of acenes can reduce their potential applications in the field of molecular electronics. Although pentacene is an important material for use in organic field-effect transistors because of its high charge mobility, its reactivity is a major disadvantage hindering the development of pentacene applications. In this study, several reaction pathways for the thermal dimerization of acenes were considered computationally. The formation of acene dimers via a central benzene ring and the formation of acene-based polymers were found to be the preferred pathways, depending on the length of the monomer. Interestingly, starting from hexacene, acene dimers are thermodynamically disfavored products, and the reaction pathway is predicted to proceed instead via a double cycloaddition reaction (polymerization) to yield acene-based polymers. A concerted asynchronous reaction mechanism was found for benzene and naphthalene dimerization, while a stepwise biradical mechanism was predicted for the dimerization of anthracene, pentacene, and heptacene. The biradical mechanism for dimerization of anthracene and pentacene proceeds via syn or anti transition states and biradical minima through stepwise biradical pathways, while dimerization of heptacene proceeds via asynchronous ring closure of the complex formed by two heptacene molecules. The activation barriers for thermal dimerization decrease rapidly with increasing acene chain length and are calculated (at M06-2X/6-31G(d)+ZPVE) to be 77.9, 57.1, 33.3, -0.3, and -12.1 kcal/mol vs two isolated acene molecules for benzene, naphthalene, anthracene, pentacene, and heptacene, respectively. If activation energy is calculated vs the initially formed complex of two acene molecules, then the calculated barriers are 80.5, 63.2, 43.7, 16.7, and 12.3 kcal/mol. Dimerization is exothermic from anthracene onward, but it is endothermic at the terminal rings, even for heptacene. Phenyl substitution at the most reactive meso

  3. Physico-chemical properties of molten dimer ascorbate oxidase.

    PubMed

    Nicolai, Eleonora; Di Venere, Almerinda; Rosato, Nicola; Rossi, Antonello; Finazzi Agro', Alessandro; Mei, Giampiero

    2006-11-01

    The possible presence of dimeric unfolding intermediates might offer a clue to understanding the relationship between tertiary and quaternary structure formation in dimers. Ascorbate oxidase is a large dimeric enzyme that displays such an intermediate along its unfolding pathway. In this study the combined effect of high pressure and denaturing agents gave new insight on this intermediate and on the mechanism of its formation. The transition from native dimer to the dimeric intermediate is characterized by the release of copper ions forming the tri-nuclear copper center located at the interface between domain 2 and 3 of each subunit. This transition, which is pH-dependent, is accompanied by a decrease in volume, probably associated to electrostriction due to the loosening of intra-subunit electrostatic interactions. The dimeric species is present even at 3 x 10(8) Pa, providing evidence that mechanically or chemically induced unfolding lead to a similar intermediate state. Instead, dissociation occurs with an extremely large and negative volume change (DeltaV approximately -200 mL.mol(-1)) by pressurization in the presence of moderate amounts of denaturant. This volume change can be ascribed to the elimination of voids at the subunit interface. Furthermore, the combination of guanidine and high pressure uncovers the presence of a marginally stable (DeltaG approximately 2 kcal.mol(-1)) monomeric species (which was not observed in previous equilibrium unfolding measurements) that might be populated in the early folding steps of ascorbate oxidase. These findings provide new aspects of the protein folding pathway, further supporting the important role of quaternary interactions in the folding strategy of large dimeric enzymes.

  4. Theoretical studies on the dimerization of substituted paraphenylenediamine radical cations

    NASA Astrophysics Data System (ADS)

    Punyain, Kraiwan; Kelterer, Anne-Marie; Grampp, Günter

    2011-12-01

    Organic radical cations form dicationic dimers in solution, observed experimentally as diamagnetic species in temperature-dependent EPR and low temperature UV/Vis spectroscopy. Dimerization of paraphenylenediamine, N,N-dimethyl-paraphenylenediamine and 2,3,5,6-tetramethyl-paraphenylenediamine radical cation in ethanol/diethylether mixture was investigated theoretically according to geometry, energetics and UV/Vis spectroscopy. Density Functional Theory including dispersion correction describes stable dimers after geometry optimization with conductor-like screening model of solvation and inclusion of the counter-ion. Energy corrections were done on double-hybrid Density Functional Theory with perturbative second-order correlation (B2PLYP-D) including basis set superposition error (BSSE), and multireference Møller-Plesset second-order perturbation theory method (MRMP2) based on complete active space method (CASSCF(2,2)) single point calculation, respectively. All three dication π-dimers exhibit long multicenter π-bonds around 2.9 ± 0.1 Å with strongly interacting orbitals. Substitution with methyl groups does not influence the dimerization process substantially. Dispersion interaction and electrostatic attraction from counter-ion play an important role to stabilize the dication dimers in solution. Dispersion-corrected double hybrid functional B2PLYP-D and CASSCF(2,2) can describe the interaction energetics properly. Vertical excitations were computed with Tamm-Dancoff approximation for time-dependent Density Functional Theory (TDA-DFT) at the B3LYP level with the cc-pVTZ basis set including ethanol solvent molecules explicitly. A strong interaction of the counter-ion and the solvent ethanol with the monomeric species is observed, whereas in the dimers the strong interaction of both radical cation species is the dominating factor for the additional peak in UV/Vis spectra.

  5. Dimerization in Highly Concentrated Solutions of Phosphoimidazolide Activated Monomucleotides

    NASA Astrophysics Data System (ADS)

    Kanavarioti, Anastassia

    1997-08-01

    Phosphoimidazolide activated ribomononucleotides (*pN) are useful substrates for the non-enzymatic synthesis of polynucleotides. However, dilute neutral aqueous solutions of *pN typically yield small amounts of dimers and traces of polymers; most of *pN hydrolyzes to yield nucleoside 5'-monophosphate. Here we report the self-condensation of nucleoside 5'-phosphate 2-methylimidazolide (2-MeImpN with N = cytidine, uridine or guanosine) in the presence of Mg2+ in concentrated solutions, such as might have been found in an evaporating lagoon on prebiotic Earth. The product distribution indicates that oligomerization is favored at the expense of hydrolysis. At 1.0 M, 2-MeImpU and 2-MeImpC produce about 65% of oligomers including 4% of the 3',5'-linked dimer. Examination of the product distribution of the three isomeric dimers in a self-condensation allows identification of reaction pathways that lead to dimer formation. Condensations in a concentrated mixture of all three nucleotides (U,C,G mixtures) is made possible by the enhanced solubility of 2-MeImpG in such mixtures. Although percent yield of internucleotide linked dimers is enhanced as a function of initial monomer concentration, pyrophosphate dimer yields remain practically unchanged at about 20% for 2-MeImpU, 16% for 2-MeImpC and 25% of the total pyrophosphate in the U,C,G mixtures. The efficiency by which oligomers are produced in these concentrated solutions makes the evaporating lagoon scenario a potentially interesting medium for the prebiotic synthesis of dimers and short RNAs.

  6. Integrability and conformal data of the dimer model

    NASA Astrophysics Data System (ADS)

    Morin-Duchesne, Alexi; Rasmussen, Jørgen; Ruelle, Philippe

    2016-04-01

    The central charge of the dimer model on the square lattice is still being debated in the literature. In this paper, we provide evidence supporting the consistency of a c=-2 description. Using Lieb’s transfer matrix and its description in terms of the Temperley-Lieb algebra {{TL}}n at β =0, we provide a new solution of the dimer model in terms of the model of critical dense polymers on a tilted lattice and offer an understanding of the lattice integrability of the dimer model. The dimer transfer matrix is analyzed in the scaling limit, and the result for {L}0-\\frac{c}{24} is expressed in terms of fermions. Higher Virasoro modes are likewise constructed as limits of elements of {{TL}}n and are found to yield a c=-2 realization of the Virasoro algebra, familiar from fermionic bc ghost systems. In this realization, the dimer Fock spaces are shown to decompose, as Virasoro modules, into direct sums of Feigin-Fuchs modules, themselves exhibiting reducible yet indecomposable structures. In the scaling limit, the eigenvalues of the lattice integrals of motion are found to agree exactly with those of the c=-2 conformal integrals of motion. Consistent with the expression for {L}0-\\frac{c}{24} obtained from the transfer matrix, we also construct higher Virasoro modes with c = 1 and find that the dimer Fock space is completely reducible under their action. However, the transfer matrix is found not to be a generating function for the c = 1 integrals of motion. Although this indicates that Lieb’s transfer matrix description is incompatible with the c = 1 interpretation, it does not rule out the existence of an alternative, c = 1 compatible, transfer matrix description of the dimer model.

  7. Dimerization in Highly Concentrated Solutions of Phosphoimidazolide Activated Mononucleotides

    NASA Technical Reports Server (NTRS)

    Kanavarioti, Anastassia

    1997-01-01

    Phosphoimidazolide activated ribomononucleotides (*pN) are useful substrates for the non-enzymatic synthesis of polynucleotides. However, dilute neutral aqueous solutions of *pN typically yield small amounts of dimers and traces of polymers; most of *pN hydrolyzes to yield nucleoside 5'-monophosphate. Here we report the self-condensation of nucleoside 5'-phosphate 2- methylimidazolide (2-MeImpN with N = cytidine, uridine or guanosine) in the presence of Mg2(+) in concentrated solutions, such as might have been found in an evaporating lagoon on prebiotic Earth. The product distribution indicates that oligomerization is favored at the expense of hydrolysis. At 1.0 M, 2-MelmpU and 2-MelmpC produce about 65% of oligomers including 4% of the 3',5'-Iinked dimer. Examination of the product distribution of the three isomeric dimers in a self-condensation allows identification of reaction pathways that lead to dimer formation. Condensations in a concentrated mixture of all three nucleotides (U,C,G mixtures) is made possible by the enhanced solubility of 2-MeImpG in such mixtures. Although percent yield of intemucleotide linked dimers is enhanced as a function of initial monomer concentration, pyrophosphate dimer yields remain practically unchanged at about 20% for 2-MelmpU, 16% for 2-MeImpC and 25% of the total pyrophosphate in the U,C,G mixtures. The efficiency by which oligomers are produced in these concentrated solutions makes the evaporating lagoon scenario a potentially interesting medium for the prebiotic synthesis of dimers and short RNAs.

  8. Development of pre-implantation porcine embryos cultured within a three-dimensional alginate hydrogel system either conjugated with Arg-Gly-Asp (RGD) peptide or supplemented with secreted phosphoprotein 1 (SPP1)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many uterine specific factors have been shown to be increased within the uterine milieu as the porcine embryo initiates elongation. Secreted phosphoprotein 1 (SPP1) is increased during this time and contains an Arg-Gly-Asp (RGD) peptide sequence that has been shown to bind to cell surface integrins ...

  9. Integrin αvβ3 as a Promising Target to Image Neoangiogenesis Using In-House Generator-Produced Positron Emitter (68)Ga-Labeled DOTA-Arginine-Glycine-Aspartic Acid (RGD) Ligand.

    PubMed

    Vatsa, Rakhee; Bhusari, Priya; Kumar, Sunil; Chakraborty, Sudipta; Dash, Ashutosh; Singh, Gurpreet; Dhawan, Devinder Kumar; Shukla, Jaya; Mittal, Bhagwant Rai

    2015-06-01

    For the growth and spread of a tumor beyond 2 mm, angiogenesis plays a crucial role, and association of various integrins with angiogenesis is evidential. The aim of the study was radiolabeling of DOTA-chelated RGD (arginine-glycine-aspartic acid) peptide with (68)Ga for PET imaging in locally advanced breast carcinoma. DOTA-RGD was incubated with (68)GaCl3, eluted in 0.05 m HCl. Elution volume, peptide amount, and reaction pH were studied. Radio-ITLC, gas chromatography, endotoxin, and sterility testing were performed. Serial (n=3) and whole-body (n=2) PET/CT imaging was done on patients post i.v. injection of 111-185 MBq of (68)Ga-DOTA-RGD. Maximum radiolabeling yield was achieved with 3 mL elution volume of 15-20 μg peptide at pH 3.5-4.0 with 10 minutes of incubation at 95°C. Product samples were sterile having 99.5% radiochemical purity with residual ethanol content and endotoxins in injectable limits. Intense radiotracer uptake was noticed in the tumor with SUVmax 15.3 at 45 minutes in serial images. Physiological radiotracer uptake was seen in the liver, spleen, ventricles, and thyroid with excretion through the kidneys. The authors concluded that (68)Ga-DOTA-RGD has the potential for imaging α,vβ3 integrin-expressing tumors.

  10. Visualization of Myc/Max/Mad family dimers and the competition for dimerization in living cells.

    PubMed

    Grinberg, Asya V; Hu, Chang-Deng; Kerppola, Tom K

    2004-05-01

    Myc and Mad family proteins play opposing roles in the control of cell growth and proliferation. We have visualized the subcellular locations of complexes formed by Myc/Max/Mad family proteins using bimolecular fluorescence complementation (BiFC) analysis. Max was recruited to different subnuclear locations by interactions with Myc versus Mad family members. Complexes formed by Max with Mxi1, Mad3, or Mad4 were enriched in nuclear foci, whereas complexes formed with Myc were more uniformly distributed in the nucleoplasm. Mad4 was localized to the cytoplasm when it was expressed separately, and Mad4 was recruited to the nucleus through dimerization with Max. The cytoplasmic localization of Mad4 was determined by a CRM1-dependent nuclear export signal located near the amino terminus. We compared the relative efficiencies of complex formation among Myc, Max, and Mad family proteins in living cells using multicolor BiFC analysis. Max formed heterodimers with the basic helix-loop-helix leucine zipper (bHLHZIP) domain of Myc (bMyc) more efficiently than it formed homodimers. Replacement of two amino acid residues in the leucine zipper of Max reversed the relative efficiencies of homo- and heterodimerization in cells. Surprisingly, Mad3 formed complexes with Max less efficiently than bMyc, whereas Mad4 formed complexes with Max more efficiently than bMyc. The distinct subcellular locations and the differences between the efficiencies of dimerization with Max indicate that Mad3 and Mad4 are likely to modulate transcription activation by Myc at least in part through distinct mechanisms.

  11. Visualization of Myc/Max/Mad Family Dimers and the Competition for Dimerization in Living Cells†

    PubMed Central

    Grinberg, Asya V.; Hu, Chang-Deng; Kerppola, Tom K.

    2004-01-01

    Myc and Mad family proteins play opposing roles in the control of cell growth and proliferation. We have visualized the subcellular locations of complexes formed by Myc/Max/Mad family proteins using bimolecular fluorescence complementation (BiFC) analysis. Max was recruited to different subnuclear locations by interactions with Myc versus Mad family members. Complexes formed by Max with Mxi1, Mad3, or Mad4 were enriched in nuclear foci, whereas complexes formed with Myc were more uniformly distributed in the nucleoplasm. Mad4 was localized to the cytoplasm when it was expressed separately, and Mad4 was recruited to the nucleus through dimerization with Max. The cytoplasmic localization of Mad4 was determined by a CRM1-dependent nuclear export signal located near the amino terminus. We compared the relative efficiencies of complex formation among Myc, Max, and Mad family proteins in living cells using multicolor BiFC analysis. Max formed heterodimers with the basic helix-loop-helix leucine zipper (bHLHZIP) domain of Myc (bMyc) more efficiently than it formed homodimers. Replacement of two amino acid residues in the leucine zipper of Max reversed the relative efficiencies of homo- and heterodimerization in cells. Surprisingly, Mad3 formed complexes with Max less efficiently than bMyc, whereas Mad4 formed complexes with Max more efficiently than bMyc. The distinct subcellular locations and the differences between the efficiencies of dimerization with Max indicate that Mad3 and Mad4 are likely to modulate transcription activation by Myc at least in part through distinct mechanisms. PMID:15121849

  12. Synthesis and Applications of Non-spherical Dimer Colloids

    NASA Astrophysics Data System (ADS)

    Yoon, Kisun

    Colloids are promising building blocks in material synthesis because of their controllability of size and surface properties. The synthesis of chemically and/or geometrically anisotropic colloidal particles has received attentions with the expectation of building blocks for complex structures. However, the synthesis of anisotropic colloidal particles is by far more difficult than the synthesis of spherical colloidal particles. Lack of monodispersity and productivity of many anisotropic particles often limits their applications as a building block for complex structures. Thus, it is highly desirable to develop methods which can produce a large amount of monodisperse non-spherical particles with controllable asymmetric surface properties. This dissertation details the work for developing such a method. The major result of this dissertation is a synthetic method to produce monodisperse non-spherical colloids with anisotropic surface property in a large quantity. The anisotropic colloid, which we call it as Dimer particle, has two fused lobes like a dumbbell and each lobe's size can be independently controlled. We present a novel method to synthesize sub-micron size Dimer particles. This method can produce a large amount of submicron-sized Dimer particles with good monodispersity and well-controlled shape. Submicron-sized Dimer particles have been highly desired since they can be used as a building block for self assembly using Brownian motion, colloidal surfactant for Pickering emulsion, and photonic materials. To fully take advantage of the anisotropy of the particles, we develop a facile method to tailor the surface property of each lobe independently by asymmetrically coating the particles with gold nanoparticles. This method doesn't need the arrangement of particles onto any type of interfaces. Asymmetric coating of gold nanoparticles can be carried out simply by mixing Dimer particles with gold nanoparticles. The formation mechanism of the submicron-sized Dimer

  13. Hydrogenated fullerenes dimer, peanut and capsule: An atomic comparison

    NASA Astrophysics Data System (ADS)

    EL-Barbary, A. A.

    2016-04-01

    Hydrogenated fullerenes are detected in the Universe in space but their identification is still unsolved task. Therefore, this paper provides useful information about hydrogenated fullerenes (dimer, peanut and capsule) using DFT method at the B3LYP/6-31G(d) level of theory. The stability, geometric structures, hydrogen adsorption energies and NMR chemical shifts are calculated. The results show that the energy of most stable isomer of C118 dimer is lower than the energies sum of C60 and C58 cages by 1.77 eV and the energy per carbon atom of C144 capsule is more stable than C60 cage by 126.98 meV. Also, endohedral Ti-doped C118 dimer and C128 peanut are found to be most stable structures than exohedral Ti-doped C118 dimer and C128 peanut by 2.19 eV/Ti and 3.52 eV/Ti, respectively. The hydrogenation process is found to be enhanced (especially at the caps) for endohedral Ti-doped C118 dimer and C128 peanut through electronic surface modifications. The most active hydrogenation sites are selected and it is found that the most stable hydrogenation sites are Houts1 and Houts3 for fullerenes and endohedral Ti-doped fullerenes, respectively.

  14. Effects of Dimerization of Serratia marcescens Endonuclease on Water Dynamics.

    SciTech Connect

    Chen, Chuanying; Beck, Brian W.; Krause, Kurt; Weksberg, Tiffany E.; Pettitt, Bernard M.

    2007-02-15

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The dynamics and structure of Serratia marcescens endonuclease and its neighboring solvent are investigated by molecular dynamics (MD). Comparisons are made with structural and biochemical experiments. The dimer form is physiologic and functions more processively than the monomer. We previously found a channel formed by connected clusters of waters from the active site to the dimer interface. Here, we show that dimerization clearly changes correlations in the water structure and dynamics in the active site not seen in the monomer. Our results indicate that water at the active sites of the dimer is less affected compared with bulk solvent than in the monomer where it has much slower characteristic relaxation times. Given that water is a required participant in the reaction, this gives a clear advantage to dimerization in the absence of an apparent ability to use both active sites simultaneously.

  15. Highly stable tetrathiafulvalene radical dimers in [3]catenanes

    SciTech Connect

    Spruell, Jason M.; Coskun, Ali; Friedman, Douglas C.; Forgan, Ross S.; Sarjeant, Amy A.; Trabolsi, Ali; Fahrenbach, Albert C.; Barin, Gokhan; Paxton, Walter F.; Dey, Sanjeev K.; Olson, Mark A.; Benítez, Diego; Tkatchouk, Ekaterina; Colvin, Michael T.; Carmielli, Raanan; Caldwell, Stuart T.; Rosair, Georgina M.; Hewage, Shanika Gunatilaka; Duclairoir, Florence; Seymour, Jennifer L.; Slawin, Alexandra M.Z.; Goddard, III, William A.; Wasielewski, Michael R.; Cooke, Graeme; Stoddart, J. Fraser

    2010-12-03

    Two [3]catenane 'molecular flasks' have been designed to create stabilized, redox-controlled tetrathiafulvalene (TTF) dimers, enabling their spectrophotometric and structural properties to be probed in detail. The mechanically interlocked framework of the [3]catenanes creates the ideal arrangement and ultrahigh local concentration for the encircled TTF units to form stable dimers associated with their discrete oxidation states. These dimerization events represent an affinity umpolung, wherein the inversion in electronic affinity replaces the traditional TTF-bipyridinium interaction, which is over-ridden by stabilizing mixed-valence (TTF){sub 2}{sup {sm_bullet}+} and radical-cation (TTF{sup {sm_bullet}+}){sub 2} states inside the 'molecular flasks.' The experimental data, collected in the solid state as well as in solution under ambient conditions, together with supporting quantum mechanical calculations, are consistent with the formation of stabilized paramagnetic mixed-valence dimers, and then diamagnetic radical-cation dimers following subsequent one-electron oxidations of the [3]catenanes.

  16. Altered Dimer Interface Decreases Stability in an Amyloidogenic Protein

    SciTech Connect

    Baden, Elizabeth M.; Owen, Barbara A.L.; Peterson, Francis C.; Volkman, Brian F.; Ramirez-Alvarado, Marina; Thompson, James R.

    2008-07-21

    Amyloidoses are devastating and currently incurable diseases in which the process of amyloid formation causes fatal cellular and organ damage. The molecular mechanisms underlying amyloidoses are not well known. In this study, we address the structural basis of immunoglobulin light chain amyloidosis, which results from deposition of light chains produced by clonal plasma cells. We compare light chain amyloidosis protein AL-09 to its wild-type counterpart, the kl O18/O8 light chain germline. Crystallographic studies indicate that both proteins form dimers. However, AL-09 has an altered dimer interface that is rotated 90 degrees from the kl O18/O8 dimer interface. The three non-conservative mutations in AL-09 are located within the dimer interface, consistent with their role in the decreased stability of this amyloidogenic protein. Moreover, AL-09 forms amyloid fibrils more quickly than kl O18/O8 in vitro. These results support the notion that the increased stability of the monomer and delayed fibril formation, together with a properly formed dimer, may be protective against amyloidogenesis. This could open a new direction into rational drug design for amyloidogenic proteins.

  17. Structure determination and conformation analysis of symmetrical dimers.

    PubMed

    Buevich, Alexei V; Chan, Tze-Ming; Wang, C H; McPhail, Andrew T; Ganguly, A K

    2005-03-01

    Conformational and stereochemical analysis of six new symmetrical dimers was performed using proton-proton vicinal coupling measured from (1)H NMR and (13)C satellites of (1)H NMR signals, natural abundance (13)C-edited nuclear overhauser effect (NOE) experiments, comprehensive NOE analysis and molecular modeling. The (13)C satellite analysis and (13)C-edited NOE experiments were carried out to extract spectral information between equivalent protons. Molecular modeling was applied for estimations of three-dimensional parameters of the studied dimers, which were subsequently used to generate a set of theoretical NOE for each possible conformation. The J-coupling, (13)C-edited NOE and quantitative NOE analyses showed the predominance of gauche conformation for three dimers, whereas a mixture of gauche and anti conformations (45:55) for three other dimers was established by quantitative NOE analysis. X-ray crystallographic study confirmed the stereochemistry of one of the dimers and revealed a discrepancy in conformation stability between liquid and solid states.

  18. Secreted CXCL12 (SDF-1) Forms Dimers under Physiologic Conditions

    PubMed Central

    Ray, Paramita; Lewin, Sarah A.; Mihalko, Laura Anne; Lesher-Perez, Sasha Cai; Takayama, Shuichi; Luker, Kathryn E.; Luker, Gary D.

    2015-01-01

    Chemokine CXCL12 signaling through receptors CXCR4 and CXCR7 has essential functions in development and underlies diseases including cancer, atherosclerosis, and autoimmunity. Chemokines may form homodimers that regulate receptor binding and signaling, but previous studies with synthetic CXCL12 have produced conflicting evidence for homodimerization. We used bioluminescence imaging with Gaussia luciferase fusions to investigate dimerization of CXCL12 secreted from mammalian cells. By column chromatography and Gaussia luciferase complementation, we established that CXCL12 was secreted from mammalian cells as both monomers and dimers. Secreted CXCL12 also formed homodimers in the extracellular space. Monomeric CXCL12 preferentially activated CXCR4 signaling through Gαi and AKT, while dimeric CXCL12 more effectively promoted recruitment of β-arrestin 2 to CXCR4 and chemotaxis of CXCR4-expressing breast cancer cells. We also showed that CXCR7 preferentially sequestered monomeric CXCL12 from the extracellular space and had minimal effects on dimeric CXCL12 in cell-based assays and an orthotopic tumor xenograft model of human breast cancer. These studies establish that CXCL12 secreted from mammalian cells forms homodimers under physiologic conditions. Since monomeric and dimeric CXCL12 have distinct effects on cell signaling and function, our results have important implications for ongoing efforts to target CXCL12 pathways for therapy. PMID:22142194

  19. Palladium dimers adsorbed on graphene: A DFT study

    SciTech Connect

    Kaur, Gagandeep; Gupta, Shuchi; Dharamvir, Keya

    2015-05-15

    The 2D structure of graphene shows a great promise for enhanced catalytic activity when adsorbed with palladium. We performed a systematic density functional theory (DFT) study of the adsorption of palladium dimer (Pd{sub 2}) on graphene using SIESTA package, in the generalized gradient approximation (GGA). The adsorption energy, geometry, and charge transfer of Pd{sub 2}-graphene system are calculated. Both horizontal and vertical orientations of Pd{sub 2} on graphene are studied. Our calculations revealed that the minimum energy configuration for Pd dimer is parallel to the graphene sheet with its two atoms occupying centre of adjacent hexagonal rings of graphene sheet. Magnetic moment is induced for Pd dimer adsorbed on graphene in vertical orientation while horizontal orientation of Pd dimer on graphene do not exhibit magnetism. Insignificant energy differences among adsorption sites means that dimer mobility on the graphene sheet is high. There is imperceptible distortion of graphene sheet perpendicular to its plane. However, some lateral displacements are seen.

  20. Revisiting the putative TCR Cα dimerization model through structural analysis.

    PubMed

    Wang, Jia-Huai; Reinherz, Ellis L

    2013-01-01

    Despite major advances in T cell receptor (TCR) biology and structure, how peptide-MHC complex (pMHC) ligands trigger αβ TCR activation remains unresolved. Two views exist. One model postulates that monomeric TCR-pMHC ligation events are sufficient while a second proposes that TCR-TCR dimerization in cis via Cα domain interaction plus pMHC binding is critical. We scrutinized 22 known TCR/pMHC complex crystal structures, and did not find any predicted molecular Cα-Cα contacts in these crystals that would allow for physiological TCR dimerization. Moreover, the presence of conserved glycan adducts on the outer face of the Cα domain preclude the hypothesized TCR dimerization through the Cα domain. Observed functional consequences of Cα mutations are likely indirect, with TCR microclusters at the immunological synapse driven by TCR transmembrane/cytoplasmic interactions via signaling molecules, scaffold proteins, and/or cytoskeletal elements.

  1. Polarization to the field enhancement by a gold dimer

    NASA Astrophysics Data System (ADS)

    Hong, Xin; Jin, Zheng

    2016-11-01

    Due to the effect of plasmonic coupling, gold nanoparticle dimers have been paid more attentions in bio-imaging. The coupling effect existing at the gap between a closely linked particle pair can make the local field strongly enhanced and in which the angle between the excitation polarization and the dimer axis plays a dominant role. We calculated the amplitude distribution under a highly focused illumination objective. The simulation results show that for such a model, 45 degrees between the excitation polarization and the dimer axis can produce an optimum signal. The enhancement thus obtained is 10.78 fold while the variation between peak-peak can reach 6.59 fold compared to a single plasmoic particle during the rotation of the polarization.

  2. Optofluidic taming of a colloidal dimer with a silicon nanocavity

    SciTech Connect

    Pin, C.; Renaut, C.; Cluzel, B. Fornel, F. de; Peyrade, D.; Picard, E.; Hadji, E.

    2014-10-27

    We report here the optical trapping of a heterogeneous colloidal dimer above a photonic crystal nanocavity used as an on-chip optical tweezer. The trapped dimer consists of a cluster of two dielectric microbeads of different sizes linked by van der Waals forces. The smallest bead, 1 μm in diameter, is observed to be preferentially trapped by the nanotweezer, leaving the second bead untrapped. The rotational nature of the trapped dimer Brownian motion is first evidenced. Then, in the presence of a fluid flow, control of its orientation and rotation is achieved. The whole system is found to show high rotational degrees of freedom, thereby acting as an effective flow-sensitive microscopic optical ball joint.

  3. D-dimer is elevated in acute aortic dissection.

    PubMed

    Martin, Thomas; Shariq, Sohail

    2010-08-31

    This case illustrates that d-dimer is elevated in patients with acute aortic dissection. A 49-year-old woman presented with central, crushing chest pain exacerbated on inspiration. The chest pain was associated with right-leg numbness and pain, although peripheral pulses and blood pressures were normal. Routine bloods demonstrated an elevated d-dimer with a normal ECG and chest x-ray radiograph. A differential diagnosis of pulmonary embolism and acute aortic dissection was made. CT-angiogram showed type B aortic dissection. This case report highlights the mounting evidence that d-dimer is elevated in practically all incidents of aortic dissection and could be useful as a negative predictive marker.

  4. An exploration of the ozone dimer potential energy surface

    SciTech Connect

    Azofra, Luis Miguel; Alkorta, Ibon; Scheiner, Steve

    2014-06-28

    The (O{sub 3}){sub 2} dimer potential energy surface is thoroughly explored at the ab initio CCSD(T) computational level. Five minima are characterized with binding energies between 0.35 and 2.24 kcal/mol. The most stable may be characterized as slipped parallel, with the two O{sub 3} monomers situated in parallel planes. Partitioning of the interaction energy points to dispersion and exchange as the prime contributors to the stability, with varying contributions from electrostatic energy, which is repulsive in one case. Atoms in Molecules analysis of the wavefunction presents specific O⋯O bonding interactions, whose number is related to the overall stability of each dimer. All internal vibrational frequencies are shifted to the red by dimerization, particularly the antisymmetric stretching mode whose shift is as high as 111 cm{sup −1}. In addition to the five minima, 11 higher-order stationary points are identified.

  5. Epoxidation of propylene dimers and isomerization of mixtures obtained

    SciTech Connect

    Dobrev, D.M.; Kurtev, K.S.

    1988-05-10

    Mixtures of hexenes are obtained in the dimerization of propylene on a Ziegler catalyst. By the epoxidation of this mixture by organic peroxides, followed by isomerization of the oxides, C/sub 6/ ketones, which are used as solvents, can be obtained. The hexenes were obtained by dimerization of propylene in the presence of a Ni(C/sub 5/H/sub 7/O/sub 2/)/sub 2/-P(C/sub 6/H/sub 5/)/sub 3/-(C/sub 3/H/sub 5/)/sub 2/AlCl catalytic system. The epoxidation was carried with technical grade isopropylbenzyl hydroperoxide (IPBHP). MoO/sub 2/(C/sub 5/H/sub 7/O/sub 2/)/sub 2/ was used as the catalyst. The relative rates of epoxidation of different isomers contained in the dimeric fraction, with respect to 2-methyl-1-pentene, was determined by means of competing reactions.

  6. Microwave Spectrum of the Isopropanol-Water Dimer

    NASA Astrophysics Data System (ADS)

    Mead, Griffin; Finneran, Ian A.; Carroll, Brandon; Blake, Geoffrey

    2016-06-01

    Microwave spectroscopy provides a unique opportunity to study model non-covalent interactions. Of particular interest is the hydrogen bonding of water, whose various molecular properties are influenced by both strong and weak intermolecular forces. More specifically, measuring the hydrogen bonded structures of water-alcohol dimers investigates both strong (OH ··· OH) and weak (CH ··· OH) hydrogen bond interactions. Recently, we have measured the pure rotational spectrum of the isopropanol-water dimer using chirped-pulse Fourier transform microwave spectroscopy (CP-FTMW) between 8-18 GHz. Here, we present the spectrum of this dimer and elaborate on the structure's strong and weak hydrogen bonding.

  7. Micellisation and immunoreactivities of dimeric beta-caseins.

    PubMed

    Yousefi, Reza; Gaudin, Jean-Charles; Chobert, Jean-Marc; Pourpak, Zahra; Moin, Mostafa; Moosavi-Movahedi, Ali Akbar; Haertle, Thomas

    2009-12-01

    Bovine beta-casein (beta-CN) is a highly amphiphilic micellising phospho-protein showing chaperone-like activity in vitro. Recently, existence of multiple sequential epitopes on beta-CN polypeptide chain in both hydrophilic-polar (psi) and hydrophobic-apolar domains (phi) has been evidenced. In order to clarify specific contribution of polar and apolar domains in micellisation process and in shaping immunoreactivity of beta-CN, its dimeric/bi-amphiphilic "quasi palindromic" forms covalently connected by a disulfide bond linking either N-terminal (C4 beta-CND) or C-terminal domain (C208 beta-CND) were produced and studied. Depending on the C- or N-terminal position of inserted cysteine, each dimeric beta-CN contains one polar/apolar region at the centre and two external hydrophobic/hydrophilic ends. Consequently, such casein dimers have radically different polarities/hydrophobicities on their outside surfaces. Dynamic light scattering (DLS) measurements indicate that these dimeric casein molecules form micelles of different sizes depending on arrangement of polar fragments of the beta-CN mutants in their constrained dimers. Non-aggregated dimers have different hydrodynamic diameters that could be explained by their different geometries. Measurements of fluorescence showed more hydrophobic environment of Trp residues of C208 beta-CND, while in similar experimental conditions Trp residues of C4 beta-CND and native beta-CN were more exposed to the polar medium. Both fluorescence and DLS studies showed greater propensity for micellisation of the dimeric beta-CNs, suggesting that the factors inducing the formation of micelles are stronger in the bi-amphiphilic dimers. 1-anilino-naphthalene-8-sulfonate (ANS) binding studies showed different binding of ANS by these dimers as well as different exposition of ANS binding (hydrophobic) regions in the micellar states. The differences in fluorescence resonance energy transfer (FRET) profiles of C4 beta-CND and C208 beta-CND can

  8. Fluxional σ-Bonds of the 2,5,8-Trimethylphenalenyl Dimer: Direct Observation of the Sixfold σ-Bond Shift via a π-Dimer.

    PubMed

    Uchida, Kazuyuki; Mou, Zhongyu; Kertesz, Miklos; Kubo, Takashi

    2016-04-06

    Direct evidence for σ-bond fluxionality in a phenalenyl σ-dimer was successfully obtained by a detailed investigation of the solution-state dynamics of 2,5,8-trimethylphenalenyl (TMPLY) using both experimental and theoretical approaches. TMPLY formed three diamagnetic dimers, namely, the σ-dimer (RR/SS), σ-dimer (RS), and π-dimer, which were fully characterized by (1)H NMR spectroscopy and electronic absorption measurements. The experimental findings gave the first quantitative insights into the essential preference of these competitive and unusual dimerization modes. The spectroscopic analyses suggested that the σ-dimer (RR/SS) is the most stable in terms of energy, whereas the others are metastable; the energy differences between these three isomers are less than 1 kcal mol(-1). Furthermore, the intriguing dynamics of the TMPLY dimers in the solution state were fully revealed by means of (1)H-(1)H exchange spectroscopy (EXSY) measurements and variable-temperature (1)H NMR studies. Surprisingly, the σ-dimer (RR/SS) demonstrated a sixfold σ-bond shift between the six sets of α-carbon pairs. This unusual σ-bond fluxionality is ascribed to the presence of a direct interconversion pathway between the σ-dimer (RR/SS) and the π-dimer, which was unambiguously corroborated by the EXSY measurements. The proposed mechanism of the sixfold σ-bond shift based on the experimental findings was well-supported by theoretical calculations.

  9. Covalent intermolecular interaction of the nitric oxide dimer (NO)2

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Zheng, Gui-Li; Lv, Gang; Geng, Yi-Zhao; Ji, Qing

    2015-09-01

    Covalent bonds arise from the overlap of the electronic clouds in the internucleus region, which is a pure quantum effect and cannot be obtained in any classical way. If the intermolecular interaction is of covalent character, the result from direct applications of classical simulation methods to the molecular system would be questionable. Here, we analyze the special intermolecular interaction between two NO molecules based on quantum chemical calculation. This weak intermolecular interaction, which is of covalent character, is responsible for the formation of the NO dimer, (NO)2, in its most stable conformation, a cis conformation. The natural bond orbital (NBO) analysis gives an intuitive illustration of the formation of the dimer bonding and antibonding orbitals concomitant with the breaking of the π bonds with bond order 0.5 of the monomers. The dimer bonding is counteracted by partially filling the antibonding dimer orbital and the repulsion between those fully or nearly fully occupied nonbonding dimer orbitals that make the dimer binding rather weak. The direct molecular mechanics (MM) calculation with the UFF force fields predicts a trans conformation as the most stable state, which contradicts the result of quantum mechanics (QM). The lesson from the investigation of this special system is that for the case where intermolecular interaction is of covalent character, a specific modification of the force fields of the molecular simulation method is necessary. Project supported by the National Natural Science Foundation of China (Grant Nos. 90403007 and 10975044), the Key Subject Construction Project of Hebei Provincial Universities, China, the Research Project of Hebei Education Department, China (Grant Nos. Z2012067 and Z2011133), the National Natural Science Foundation of China (Grant No. 11147103), and the Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Grant No. Y5

  10. Dimeric α-Cobratoxin X-ray Structure

    PubMed Central

    Osipov, Alexey V.; Rucktooa, Prakash; Kasheverov, Igor E.; Filkin, Sergey Yu.; Starkov, Vladislav G.; Andreeva, Tatyana V.; Sixma, Titia K.; Bertrand, Daniel; Utkin, Yuri N.; Tsetlin, Victor I.

    2012-01-01

    In Naja kaouthia cobra venom, we have earlier discovered a covalent dimeric form of α-cobratoxin (αCT-αCT) with two intermolecular disulfides, but we could not determine their positions. Here, we report the αCT-αCT crystal structure at 1.94 Å where intermolecular disulfides are identified between Cys3 in one protomer and Cys20 of the second, and vice versa. All remaining intramolecular disulfides, including the additional bridge between Cys26 and Cys30 in the central loops II, have the same positions as in monomeric α-cobratoxin. The three-finger fold is essentially preserved in each protomer, but the arrangement of the αCT-αCT dimer differs from those of noncovalent crystallographic dimers of three-finger toxins (TFT) or from the κ-bungarotoxin solution structure. Selective reduction of Cys26-Cys30 in one protomer does not affect the activity against the α7 nicotinic acetylcholine receptor (nAChR), whereas its reduction in both protomers almost prevents α7 nAChR recognition. On the contrary, reduction of one or both Cys26-Cys30 disulfides in αCT-αCT considerably potentiates inhibition of the α3β2 nAChR by the toxin. The heteromeric dimer of α-cobratoxin and cytotoxin has an activity similar to that of αCT-αCT against the α7 nAChR and is more active against α3β2 nAChRs. Our results demonstrate that at least one Cys26-Cys30 disulfide in covalent TFT dimers, similar to the monomeric TFTs, is essential for their recognition by α7 nAChR, although it is less important for interaction of covalent TFT dimers with the α3β2 nAChR. PMID:22223648

  11. Dimeric RNA recognition regulates HIV-1 genome packaging.

    PubMed

    Nikolaitchik, Olga A; Dilley, Kari A; Fu, William; Gorelick, Robert J; Tai, S-H Sheldon; Soheilian, Ferri; Ptak, Roger G; Nagashima, Kunio; Pathak, Vinay K; Hu, Wei-Shau

    2013-03-01

    How retroviruses regulate the amount of RNA genome packaged into each virion has remained a long-standing question. Our previous study showed that most HIV-1 particles contain two copies of viral RNA, indicating that the number of genomes packaged is tightly regulated. In this report, we examine the mechanism that controls the number of RNA genomes encapsidated into HIV-1 particles. We hypothesize that HIV-1 regulates genome packaging by either the mass or copy number of the viral RNA. These two distinct mechanisms predict different outcomes when the genome size deviates significantly from that of wild type. Regulation by RNA mass would result in multiple copies of a small genome or one copy of a large genome being packaged, whereas regulation by copy number would result in two copies of a genome being packaged independent of size. To distinguish between these two hypotheses, we examined the packaging of viral RNA that was larger (≈17 kb) or smaller (≈3 kb) than that of wild-type HIV-1 (≈9 kb) and found that most particles packaged two copies of the viral genome regardless of whether they were 17 kb or 3 kb. Therefore, HIV-1 regulates RNA genome encapsidation not by the mass of RNA but by packaging two copies of RNA. To further explore the mechanism that governs this regulation, we examined the packaging of viral RNAs containing two packaging signals that can form intermolecular dimers or intramolecular dimers (self-dimers) and found that one self-dimer is packaged. Therefore, HIV-1 recognizes one dimeric RNA instead of two copies of RNA. Our findings reveal that dimeric RNA recognition is the key mechanism that regulates HIV-1 genome encapsidation and provide insights into a critical step in the generation of infectious viruses.

  12. Dimerization of argon and the properties of its small clusters

    NASA Astrophysics Data System (ADS)

    Titov, S. V.; Serov, S. A.; Ostrovskii, G. M.

    2016-12-01

    Statistical thermodynamic means are used to study the bound state of a small cluster AN (2 ≤ N ≤ 5) of Lennard-Jones particles in a spherical cavity. The statistical sum is calculated by the Monte Carlo method. For the dimer, integration is reduced to quadratures. The integration region contains only phase space points corresponding to the bound cluster state. Dimerization constant 2A = A2 is calculated via the probability of finding a molecule in the bound state using the example of argon.

  13. Antagonizing STAT5B dimerization with an osmium complex

    PubMed Central

    Liu, Li-Juan; Wang, Wanhe; Kang, Tian-Shu; Liang, Jia-Xin; Liu, Chenfu; Kwong, Daniel W. J.; Wong, Vincent Kam Wai; Ma, Dik-Lung; Leung, Chung-Hang

    2016-01-01

    Targeting STAT5 is an appealing therapeutic strategy for the treatment of hematologic malignancies and inflammation. Here, we present the novel osmium(II) complex 1 as the first metal-based inhibitor of STAT5B dimerization. Complex 1 exhibited superior inhibitory activity against STAT5B DNA binding compared to STAT5A DNA binding. Moreover, 1 repressed STAT5B transcription and blocked STAT5B dimerization via binding to the STAT5B protein, thereby inhibiting STAT5B translocation to the nucleus. Furthermore, 1 was able to selectively inhibit STAT5B phosphorylation without affecting the expression level of STAT5B. PMID:27853239

  14. Facile dimer synthesis for DNA-binding polyamide ligands.

    PubMed

    Wetzler, Modi; Wemmer, David E

    2010-08-06

    Pyrrole-imidazole polyamide ligands are highly sequence specific synthetic DNA-binding ligands that bind with high affinity. To counter the synthetic difficulties associated with coupling the electron-rich heterocyclic acids to the electron-deficient nucleophilic imidazole amine, a novel approach is described for synthesis of Fmoc-protected dimers for solid-phase peptide synthesis (SPPS). This method produces the dimers in high yields, is broadly applicable to other heterocyclic-containing polyamides, and results in improved ligand yields and synthesis times.

  15. A Pfaffian Formula for Monomer-Dimer Partition Functions

    NASA Astrophysics Data System (ADS)

    Giuliani, Alessandro; Jauslin, Ian; Lieb, Elliott H.

    2016-04-01

    We consider the monomer-dimer partition function on arbitrary finite planar graphs and arbitrary monomer and dimer weights, with the restriction that the only non-zero monomer weights are those on the boundary. We prove a Pfaffian formula for the corresponding partition function. As a consequence of this result, multipoint boundary monomer correlation functions at close packing are shown to satisfy fermionic statistics. Our proof is based on the celebrated Kasteleyn theorem, combined with a theorem on Pfaffians proved by one of the authors, and a careful labeling and directing procedure of the vertices and edges of the graph.

  16. Styrene dimers and trimers affect reproduction of daphnid (Ceriodaphnia dubia).

    PubMed

    Tatarazako, Norihisa; Takao, Yuji; Kishi, Katsuyuki; Onikura, Norio a; Arizono, Koji; Iguchi, Taisen

    2002-08-01

    The endocrine disruptor activity of styrene in humans and other vertebrates appears to be negligible. However, offspring numbers were reduced in Ceriodaphnia dubia bred in polystyrene cups. Styrene dimers and trimers were found to be eluted from the polystyrene cups by hexane and methanol with gas chromatography-mass spectrometry. Styrene dimers and trimers at concentrations of 0.04-1.7 microg/l affected C. dubia fertility (25% reduction after seven days), suggesting that styrenes have the potential to impair crustacean populations in the aquatic environment.

  17. Dimerization of polycyclic aromatic hydrocarbons in soot nucleation.

    PubMed

    Zhang, Hong-Bo; You, Xiaoqing; Wang, Hongmiao; Law, Chung K

    2014-02-27

    A possible pathway of soot nucleation, in which localized π electrons play an important role in binding the polycyclic aromatic hydrocarbon (PAH) molecules having multiradical characteristics to form stable polymer molecules through covalent bonds, is studied using density functional and semiempirical methods. Results show that the number of covalent bonds formed in the dimerization of two identical PAHs is determined by the radical character, and the sites to form bonds are related to the aromaticity of individual six-membered ring structure. It is further shown that the binding energy of dimerization increases linearly with the diradical character in the range relevant to soot nucleation.

  18. Dimeric acylphloroglucinols from Hypericum austrobrasiliense exhibiting antinociceptive activity in mice.

    PubMed

    Bridi, Henrique; Ccana-Ccapatinta, Gari V; Stolz, Eveline D; Meirelles, Gabriela C; Bordignon, Sérgio A L; Rates, Stela M K; von Poser, Gilsane L

    2016-02-01

    Three dimeric acylphloroglucinols, austrobrasilol A, austrobrasilol B and isoaustrobrasilol B were isolated from the flowers of Hypericum austrobrasiliense (Hypericaceae, section Trigynobrathys). Their structures were elucidated using mass spectrometry and NMR experiments (1D and 2D), and by comparison with previously reported data for other dimeric acylphloroglucinols isolated from Hypericum and Elaphoglossum genera. The three compounds were orally administered in mice at equimolar doses to uliginosin B (15mg/kg, p.o.) displaying antinociceptive activity in the hot-plate test. The compounds did not induce motor impairment in the rotarod apparatus.

  19. Self-assembled Biodegradable Nanoparticles and Polysaccharides as Biomimetic ECM Nanostructures for the Synergistic effect of RGD and BMP-2 on Bone Formation.

    PubMed

    Wang, Zhenming; Dong, Li; Han, Lu; Wang, Kefeng; Lu, Xiong; Fang, Liming; Qu, Shuxin; Chan, Chun Wai

    2016-04-28

    Producing biomimetic extracellular matrix (ECM) is an effective approach to improve biocompatibility of medical devices. In this study, biomimetic ECM nanostructures are constructed through layer-by-layer self-assembling positively charged chitosan (Chi), negatively charged oxidized sodium alginate (OAlg), and positively charged bovine serum albumin (BSA)-based nanoparticles. The BSA-based nanoparticles in the self-assembled films not only result in porous nanostructures similar to natural ECM, but also preserve the activity and realize the sustained release of Bone morphogenetic protein-2 (BMP-2). The results of bone marrow stem cells (BMSCs) culture demonstrate that the penta-peptide glycine-arginine-glycine-aspartate-serine (GRGDS) grafted Chi/OAlg films favor cell adhesion and proliferation. GRGDS and BMP-2 in biomimetic ECM nanostructures synergistically promote BMSC functions and new bone formation. The RGD and BMP incorporated biomimetic ECM coatings could be applied on a variety of biomedical devices to improve the bioactivity and biocompatibility.

  20. Angiopoietin-related growth factor (AGF) supports adhesion, spreading, and migration of keratinocytes, fibroblasts, and endothelial cells through interaction with RGD-binding integrins

    SciTech Connect

    Zhang Yueqing; Hu Xiaobo; Tian Ruiyang; Wei Wangui; Hu Wei; Chen Xia; Han Wei; Chen Huayou; Gong Yi . E-mail: ygong@sibs.ac.cn

    2006-08-18

    Angiopoietin-related growth factor (AGF) is a newly identified member of angiopoietin-related proteins (ARPs)/angiopoietin-like proteins (Angptls). AGF has been considered as a novel growth factor in accelerating cutaneous wound healing, as it is capable of stimulating keratinocytes proliferation as well as angiogenesis. But in our paper, we demonstrate that AGF stimulates keratinocytes proliferation only at high protein concentration, however, it can potently promote adhesion, spreading, and migration of keratinocytes, fibroblasts, and endothelial cells. Furthermore, we confirm that the adhesion and migration cellular events are mediated by RGD-binding integrins, most possibly the {alpha}{sub v}-containing integrins, by in vitro inhibition assays using synthetic competitive peptides. Our results strongly suggest that AGF is an integrin ligand as well as a mitogenic growth factor and theoretically participates in cutaneous wound healing in a more complex mechanism.

  1. Self-assembled Biodegradable Nanoparticles and Polysaccharides as Biomimetic ECM Nanostructures for the Synergistic effect of RGD and BMP-2 on Bone Formation

    PubMed Central

    Wang, Zhenming; Dong, Li; Han, Lu; Wang, Kefeng; Lu, Xiong; Fang, Liming; Qu, Shuxin; Chan, Chun Wai

    2016-01-01

    Producing biomimetic extracellular matrix (ECM) is an effective approach to improve biocompatibility of medical devices. In this study, biomimetic ECM nanostructures are constructed through layer-by-layer self-assembling positively charged chitosan (Chi), negatively charged oxidized sodium alginate (OAlg), and positively charged bovine serum albumin (BSA)-based nanoparticles. The BSA-based nanoparticles in the self-assembled films not only result in porous nanostructures similar to natural ECM, but also preserve the activity and realize the sustained release of Bone morphogenetic protein-2 (BMP-2). The results of bone marrow stem cells (BMSCs) culture demonstrate that the penta-peptide glycine-arginine-glycine-aspartate-serine (GRGDS) grafted Chi/OAlg films favor cell adhesion and proliferation. GRGDS and BMP-2 in biomimetic ECM nanostructures synergistically promote BMSC functions and new bone formation. The RGD and BMP incorporated biomimetic ECM coatings could be applied on a variety of biomedical devices to improve the bioactivity and biocompatibility. PMID:27121121

  2. Gingival Mesenchymal Stem Cell (GMSC) Delivery System Based on RGD-Coupled Alginate Hydrogel with Antimicrobial Properties: A Novel Treatment Modality for Peri-Implantitis

    PubMed Central

    Diniz, Ivana M. A.; Chen, Chider; Ansari, Sahar; Zadeh, Homayoun H.; Moshaverinia, Maryam; Chee, Daniel; Marques, Márcia M.; Shi, Songtao; Moshaverinia, Alireza

    2015-01-01

    Purpose Peri-implantitis is one of the most common inflammatory complications in dental implantology. Similar to periodontitis, in peri-implantitis, destructive inflammatory changes take place in the tissues surrounding a dental implant. Bacterial flora at the failing implant sites resemble the pathogens in periodontal disease and consist of Gram-negative anaerobic bacteria including Aggregatibacter actinomycetemcomitans (Aa). Here we demonstrate the effectiveness of a silver lactate (SL)-containing RGD-coupled alginate hydrogel scaffold as a promising stem cell delivery vehicle with antimicrobial properties. Materials and Methods Gingival mesenchymal stem cells (GMSCs) or human bone marrow mesenchymal stem cells (hBMMSCs) were encapsulated in SL-loaded alginate hydrogel microspheres. Stem cell viability, proliferation, and osteo-differentiation capacity were analyzed. Results Our results showed that SL exhibited antimicrobial properties against Aa in a dose-dependent manner, with 0.50 mg/ml showing the greatest antimicrobial properties while still maintaining cell viability. At this concentration, SL-containing alginate hydrogel was able to inhibit Aa on the surface of Ti discs and significantly reduce the bacterial load in Aa suspensions. Silver ions were effectively released from the SL-loaded alginate microspheres for up to 2 weeks. Osteogenic differentiation of GMSCs and hBMMSCs encapsulated in the SL-loaded alginate microspheres were confirmed by the intense mineral matrix deposition and high expression of osteogenesis-related genes. Conclusion Taken together, our findings confirm that GMSCs encapsulated in RGD-modified alginate hydrogel containing SL show promise for bone tissue engineering with antimicrobial properties against Aa bacteria in vitro. PMID:26216081

  3. Sialylation transmogrifies human breast and pancreatic cancer cells into 3D multicellular tumor spheroids using cyclic RGD-peptide induced self-assembly.

    PubMed

    Akasov, Roman; Haq, Sabah; Haxho, Fiona; Samuel, Vanessa; Burov, Sergey V; Markvicheva, Elena; Neufeld, Ronald J; Szewczuk, Myron R

    2016-10-04

    Multicellular tumor spheroids (MTS) have been at the forefront of cancer research, designed to mimic tumor-like developmental patterns in vitro. Tumor growth in vivo is highly influenced by aberrant cell surface-specific sialoglycan structures on glycoproteins. Aberrant sialoglycan patterns that facilitate MTS formation are not well defined. Matrix-free spheroids from breast MCF-7 and pancreatic PANC1 cancer cell lines and their respective tamoxifen (TMX) and gemcitabine (Gem) resistant variants were generated using the RGD platform of cyclic Arg-Gly-Asp-D-Phe-Lys peptide modified with 4-carboxybutyl-triphenylphosphonium bromide (cyclo-RGDfK (TPP)). MCF-7 and MCF-7 TMX cells formed tight spheroids both in the classical agarose-and RGD-based platforms while all PANC1 cells formed loose aggregates. Using lectin histochemistry staining, sialidase assay, neuraminidase (Vibrio cholerae) and oseltamivir phosphate (OP) neuraminidase inhibitor treatments, MCF-7 and PANC1 cells and their drug-resistant variants expressed different sialic acid (SA) content on their cell surfaces. α-2,3- and α-2,6-sialic acid surface residues facilitated spheroid formation under cyclo-RGDfK(TPP)-induced self-assembly. Pretreatment with α-2,3- SA specific Maackia amurensis (MAL-II) lectin, α-2,6-SA specific Sambucus nigra (SNA) lectin, and exogenous α-2,6-SA specific neuraminidase (Vibrio cholerae) dose-dependently reduced spheroid volume. OP enhanced cell aggregation and compaction forming spheroids. PANC1 and MDA-MB231 xenograft tumors from untreated and OP-treated RAGxCγ double mutant mice expressed significantly higher levels of α-2,3- SA over α-2,6-SA. MCF-7 spheroids also expressed a high α-2,3-SA to α-2,6-SA ratio. These results suggest that the relative levels of specific sialoglycan structures on the cell surface correlate with the ability of cancer cells to form avascular multicellular tumor spheroids and in vivo xenograft tumors.

  4. Structure and Mechanism of the Influenza A M218-60 Dimer of Dimers.

    PubMed

    Andreas, Loren B; Reese, Marcel; Eddy, Matthew T; Gelev, Vladimir; Ni, Qing Zhe; Miller, Eric A; Emsley, Lyndon; Pintacuda, Guido; Chou, James J; Griffin, Robert G

    2015-12-02

    We report a magic angle spinning (MAS) NMR structure of the drug-resistant S31N mutation of M218-60 from Influenza A. The protein was dispersed in diphytanoyl-sn-glycero-3-phosphocholine lipid bilayers, and the spectra and an extensive set of constraints indicate that M218-60 consists of a dimer of dimers. In particular, ∼280 structural constraints were obtained using dipole recoupling experiments that yielded well-resolved (13)C-(15)N, (13)C-(13)C, and (1)H-(15)N 2D, 3D, and 4D MAS spectra, all of which show cross-peak doubling. Interhelical distances were measured using mixed (15)N/(13)C labeling and with deuterated protein, MAS at ωr/2π = 60 kHz, ω0H/2π = 1000 MHz, and (1)H detection of methyl-methyl contacts. The experiments reveal a compact structure consisting of a tetramer composed of four transmembrane helices, in which two opposing helices are displaced and rotated in the direction of the membrane normal relative to a four-fold symmetric arrangement, yielding a two-fold symmetric structure. Side chain conformations of the important gating and pH-sensing residues W41 and H37 are found to differ markedly from four-fold symmetry. The rmsd of the structure is 0.7 Å for backbone heavy atoms and 1.1 Å for all heavy atoms. This two-fold symmetric structure is different from all of the previous structures of M2, many of which were determined in detergent and/or with shorter constructs that are not fully active. The structure has implications for the mechanism of H(+) transport since the distance between His and Trp residues on different helices is found to be short. The structure also exhibits two-fold symmetry in the vicinity of the binding site of adamantyl inhibitors, and steric constraints may explain the mechanism of the drug-resistant S31N mutation.

  5. Biophysical Characterization of the Dimer and Tetramer Interface Interactions of the Human Cytosolic Malic Enzyme

    PubMed Central

    Murugan, Sujithkumar; Hung, Hui-Chih

    2012-01-01

    The cytosolic NADP+-dependent malic enzyme (c-NADP-ME) has a dimer-dimer quaternary structure in which the dimer interface associates more tightly than the tetramer interface. In this study, the urea-induced unfolding process of the c-NADP-ME interface mutants was monitored using fluorescence and circular dichroism spectroscopy, analytical ultracentrifugation and enzyme activities. Here, we demonstrate the differential protein stability between dimer and tetramer interface interactions of human c-NADP-ME. Our data clearly demonstrate that the protein stability of c-NADP-ME is affected predominantly by disruptions at the dimer interface rather than at the tetramer interface. First, during thermal stability experiments, the melting temperatures of the wild-type and tetramer interface mutants are 8–10°C higher than those of the dimer interface mutants. Second, during urea denaturation experiments, the thermodynamic parameters of the wild-type and tetramer interface mutants are almost identical. However, for the dimer interface mutants, the first transition of the urea unfolding curves shift towards a lower urea concentration, and the unfolding intermediate exist at a lower urea concentration. Third, for tetrameric WT c-NADP-ME, the enzyme is first dissociated from a tetramer to dimers before the 2 M urea treatment, and the dimers then dissociated into monomers before the 2.5 M urea treatment. With a dimeric tetramer interface mutant (H142A/D568A), the dimer completely dissociated into monomers after a 2.5 M urea treatment, while for a dimeric dimer interface mutant (H51A/D90A), the dimer completely dissociated into monomers after a 1.5 M urea treatment, indicating that the interactions of c-NADP-ME at the dimer interface are truly stronger than at the tetramer interface. Thus, this study provides a reasonable explanation for why malic enzymes need to assemble as a dimer of dimers. PMID:23284632

  6. G domain dimerization controls dynamin's assembly-stimulated GTPase activity

    SciTech Connect

    Chappie, Joshua S.; Acharya, Sharmistha; Leonard, Marilyn; Schmid, Sandra L.; Dyda, Fred

    2010-06-14

    Dynamin is an atypical GTPase that catalyses membrane fission during clathrin-mediated endocytosis. The mechanisms of dynamin's basal and assembly-stimulated GTP hydrolysis are unknown, though both are indirectly influenced by the GTPase effector domain (GED). Here we present the 2.0 {angstrom} resolution crystal structure of a human dynamin 1-derived minimal GTPase-GED fusion protein, which was dimeric in the presence of the transition state mimic GDP.AlF{sub 4}{sup -}. The structure reveals dynamin's catalytic machinery and explains how assembly-stimulated GTP hydrolysis is achieved through G domain dimerization. A sodium ion present in the active site suggests that dynamin uses a cation to compensate for the developing negative charge in the transition state in the absence of an arginine finger. Structural comparison to the rat dynamin G domain reveals key conformational changes that promote G domain dimerization and stimulated hydrolysis. The structure of the GTPase-GED fusion protein dimer provides insight into the mechanisms underlying dynamin-catalysed membrane fission.

  7. Comparative assay of antioxidant packages for dimer of estolide esters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A series of 26 different antioxidants and commercial antioxidant packages, containing both natural and synthetic-based materials, were evaluated with dimeric coconut-oleic estolide 2-ethylhexyl ester. The different antioxidants were broken down into different classes of materials: phenolic, aminic, ...

  8. The Internal Structure of Nanoparticle Dimers Linked by DNA

    NASA Astrophysics Data System (ADS)

    Vargas Lara, Fernando; Cheng, Ching-Jung; Gang, Oleg; Starr, Francis W.

    2012-02-01

    The self-assembly of inorganic units controlled by the interactions of biological molecules, like DNA, has received attention for the possibility to specify higher-order structure, with potential biological, optical and electronic applications. In biology, self-assembly of complex materials (eg. bone, spider silk) frequently occurs in a stepwise, hierarchical fashion. Here, we consider a first step towards a hierarchical approach for synthetic nanostructures of nanoparticles (NPs) linked by DNA. The most basic unit in this multiscale approach is a dimer of NPs linked by DNA. We use a coarse-grained molecular model to explain experimental measurements of the separation of two DNA-coated NPs connected by linking single-stranded DNA (ssDNA). We show that the dimer separation is primarily controlled by the number of DNA links between NPs. If these links are not constrained to lie along the axis between NPs, the separation is limited by off-axis connections that force the NPs to be closer. We also determine how the number of connections alters the effective persistence length of the ssDNA that connects the dimer. We discuss how these dimers might be used for subsequent assembly at larger scales.

  9. Cantharimide dimers from the Chinese blister beetle, Mylabris phalerate PALLAS.

    PubMed

    Nakatani, Takafumi; Jinpo, Katsuaki; Noda, Naoki

    2007-01-01

    Five cantharidin-related compounds were isolated from the Chinese blister beetle, Mylabris phalerate PALLAS (Meloidae). Their structures were determined based on spectroscopic and chemical evidence. Three of them were identified as cantharimide dimers, which consist of two units of cantharimide combined with a tri-, tetra-, or penta-methylene group.

  10. Dimeric pyrrole-imidazole alkaloids: synthetic approaches and biosynthetic hypotheses.

    PubMed

    Wang, Xiao; Ma, Zhiqiang; Wang, Xiaolei; De, Saptarshi; Ma, Yuyong; Chen, Chuo

    2014-08-14

    The pyrrole-imidazole alkaloids are a group of structurally unique and biologically interesting marine sponge metabolites. Among them, the cyclic dimers have caught synthetic chemists' attention particularly. Numerous synthetic strategies have been developed and various biosynthetic hypotheses have been proposed for these fascinating natural products. We discuss herein the synthetic approaches and the biosynthetic insights obtained from these studies.

  11. DNAzyme-Controlled Cleavage of Dimer and Trimer Origami Tiles.

    PubMed

    Wu, Na; Willner, Itamar

    2016-04-13

    Dimers of origami tiles are bridged by the Pb(2+)-dependent DNAzyme sequence and its substrate or by the histidine-dependent DNAzyme sequence and its substrate to yield the dimers T1-T2 and T3-T4, respectively. The dimers are cleaved to monomer tiles in the presence of Pb(2+)-ions or histidine as triggers. Similarly, trimers of origami tiles are constructed by bridging the tiles with the Pb(2+)-ion-dependent DNAzyme sequence and the histidine-dependent DNAzyme sequence and their substrates yielding the trimer T1-T5-T4. In the presence of Pb(2+)-ions and/or histidine as triggers, the programmed cleavage of trimer proceeds. Using Pb(2+) or histidine as trigger cleaves the trimer to yield T5-T4 and T1 or the dimer T1-T5 and T4, respectively. In the presence of Pb(2+)-ions and histidine as triggers, the cleavage products are the monomer tiles T1, T5, and T4. The different cleavage products are identified by labeling the tiles with 0, 1, or 2 streptavidin labels and AFM imaging.

  12. Asymptotics of Height Change on Toroidal Temperleyan Dimer Models

    NASA Astrophysics Data System (ADS)

    Dubédat, Julien; Gheissari, Reza

    2015-04-01

    The dimer model is an exactly solvable model of planar statistical mechanics. In its critical phase, various aspects of its scaling limit are known to be described by the Gaussian free field. For periodic graphs, criticality is an algebraic condition on the spectral curve of the model, determined by the edge weights (Kenyon et al. in Ann Math (2) 163(3):1019-1056, 2006); isoradial graphs provide another class of critical dimer models, in which the edge weights are determined by the local geometry. In the present article, we consider another class of graphs: general Temperleyan graphs, i.e. graphs arising in the (generalized) Temperley bijection between spanning trees and dimer models. Building in particular on Forman's formula and representations of Laplacian determinants in terms of Poisson operators, and under a minimal assumption—viz. that the underlying random walk converges to Brownian motion—we show that the natural topological observable on macroscopic tori converges in law to its universal limit, i.e. the law of the periods of the dimer height function converges to that of the periods of a compactified free field.

  13. Potential Energy Surface Database of Group II Dimer

    National Institute of Standards and Technology Data Gateway

    SRD 143 NIST Potential Energy Surface Database of Group II Dimer (Web, free access)   This database provides critical atomic and molecular data needed in order to evaluate the feasibility of using laser cooled and trapped Group II atomic species (Mg, Ca, Sr, and Ba) for ultra-precise optical clocks or quantum information processing devices.

  14. Hydrazine-mediated strongly coupled Re(CO)3 dimers.

    PubMed

    Hasheminasab, A; Rhoda, H M; Crandall, L A; Ayers, J T; Nemykin, V N; Herrick, R S; Ziegler, C J

    2015-10-21

    Dimeric metal complexes can often exhibit coupling interactions via bridging ligands. In this report, we present two Re(CO)3 dimers, where the metals are linked via a bis(pyca) hydrazine (pyca = pyridine-2-carbaldehyde imine) Schiff base ligand. For the dimeric compounds 4 and 5, we observe strong coupling across the dimer as measured by cyclic voltammetry: ∼480 mV separations between the first and the second reduction waves that correspond to comproportionation constants close to 1.5 × 10(8). Evidence for a mixed valence state upon one electron reduction was also observed by spectroelectrochemistry in which a clear inter-valence charge-transfer (IVCT) band was observed in [4]- and [5]-complexes. The electronic structures of all target compounds were probed by DFT and TDDFT computational methods. DFT calculations indicate that reduction takes place at the diimine units, and that the observed coupling is a ligand-based phenomenon, rather than one that involves metal-based orbitals.

  15. Ising anyons in frustration-free Majorana-dimer models

    NASA Astrophysics Data System (ADS)

    Ware, Brayden; Son, Jun Ho; Cheng, Meng; Mishmash, Ryan V.; Alicea, Jason; Bauer, Bela

    2016-09-01

    Dimer models have long been a fruitful playground for understanding topological physics. Here, we introduce a class, termed Majorana-dimer models, wherein bosonic dimers are decorated with pairs of Majorana modes. We find that the simplest examples of such systems realize an intriguing, intrinsically fermionic phase of matter that can be viewed as the product of a chiral Ising theory, which hosts deconfined non-Abelian quasiparticles, and a topological px-i py superconductor. While the bulk anyons are described by a single copy of the Ising theory, the edge remains fully gapped. Consequently, this phase can arise in exactly solvable, frustration-free models. We describe two parent Hamiltonians: one generalizes the well-known dimer model on the triangular lattice, while the other is most naturally understood as a model of decorated fluctuating loops on a honeycomb lattice. Using modular transformations, we show that the ground-state manifold of the latter model unambiguously exhibits all properties of the Ising×(px-i py) theory. We also discuss generalizations with more than one Majorana mode per site, which realize phases related to Kitaev's 16-fold way in a similar fashion.

  16. Transporting testosterone and its dimers by serum proteins.

    PubMed

    Chanphai, P; Vesper, A R; Bekale, L; Bérubé, G; Tajmir-Riahi, H A

    2015-12-01

    A substantial part of steroids is bound to serum proteins in vivo. We report the association of testosterone and it aliphatic dimer (alip) and aromatic dimer (arom) with human serum albumin (HSA) and bovine serum albumin (BSA) in aqueous solution at physiological pH. Multiple spectroscopic methods, transmission electron microscopy (TEM) and molecular modeling were used to characterize steroid-protein binding and protein aggregation process. Spectroscopic analysis showed that steroids bind protein via hydrophobic, hydrophilic and H-bonding interactions. HSA forms more stable complexes than BSA. The binding affinity of steroid-protein adducts is testosterone>dimer-aromatic>dimer-aliphatic. Transmission electron microscopy showed major changes in protein morphology as steroid-protein complexation occurred with increase in the diameter of the protein aggregate indicating encapsulation of steroids by serum proteins. Modeling showed the presence of H-bonding stabilized testosterone-protein complexes with the free binding energy of -12.95 for HSA and -11.55 kcal/mol for BSA, indicating that the interaction process is spontaneous at room temperature. Steroid complexation induced more perturbations of BSA conformation than HSA.

  17. Percolation of heteronuclear dimers irreversibly deposited on square lattices

    NASA Astrophysics Data System (ADS)

    Gimenez, M. C.; Ramirez-Pastor, A. J.

    2016-09-01

    The percolation problem of irreversibly deposited heteronuclear dimers on square lattices is studied. A dimer is composed of two segments, and it occupies two adjacent adsorption sites. Each segment can be either a conductive segment (segment type A ) or a nonconductive segment (segment type B ). Three types of dimers are considered: A A , B B , and A B . The connectivity analysis is carried out by accounting only for the conductive segments (segments type A ). The model offers a simplified representation of the problem of percolation of defective (nonideal) particles, where the presence of defects in the system is simulated by introducing a mixture of conductive and nonconductive segments. Different cases were investigated, according to the sequence of deposition of the particles, the types of dimers involved in the process, and the degree of alignment of the deposited objects. By means of numerical simulations and finite-size scaling analysis, the complete phase diagram separating a percolating from a nonpercolating region was determined for each case. Finally, the consistency of our results was examined by comparing with previous data in the literature for linear k -mers (particles occupying k adjacent sites) with defects.

  18. Centrosymmetric dimer of quinuclidine betaine and squaric acid complex

    NASA Astrophysics Data System (ADS)

    Dega-Szafran, Z.; Katrusiak, A.; Szafran, M.

    2012-12-01

    The complex of squaric acid (3,4-dihydroxy-3-cyclobuten-1,2-dion, H2SQ) with quinuclidine betaine (1-carboxymethyl-1-azabicyclo[2.2.2]octane inner salt, QNB), 1, has been characterized by single-crystal X-ray analysis, FTIR and NMR spectroscopies and by DFT calculations. In the crystal of 1, monoclinic space group P21/n, one proton from H2SQ is transferred to QNB. QNBH+ and HSQ- are linked together by a Osbnd H⋯O hydrogen bond of 2.553(2) Å. Two such QNBH+·HSQ- complexes form a centrosymmetric dimer bridged by two Osbnd H⋯O bonds of 2.536(2) Å. The FTIR spectrum is consistent with the X-ray results. The structures of monomer QNBH+·HSQ- (1a) and dimer [QNB·H2SQ]2 (2) have been optimized at the B3LYP/6-311++G(d,p) level of theory. Isolated dimer 2 optimized back to a molecular aggregate of H2SQ and QNB. The calculated frequencies for the optimized structure of dimer 2 have been used to explain the frequencies of the experimental FTIR spectrum. The interpretation of 1H and 13C NMR spectra has been based on the calculated GIAO/B3LYP/6-311++G(d,p) magnetic isotropic shielding constants for monomer 1a.

  19. Percolation of heteronuclear dimers irreversibly deposited on square lattices.

    PubMed

    Gimenez, M C; Ramirez-Pastor, A J

    2016-09-01

    The percolation problem of irreversibly deposited heteronuclear dimers on square lattices is studied. A dimer is composed of two segments, and it occupies two adjacent adsorption sites. Each segment can be either a conductive segment (segment type A) or a nonconductive segment (segment type B). Three types of dimers are considered: AA, BB, and AB. The connectivity analysis is carried out by accounting only for the conductive segments (segments type A). The model offers a simplified representation of the problem of percolation of defective (nonideal) particles, where the presence of defects in the system is simulated by introducing a mixture of conductive and nonconductive segments. Different cases were investigated, according to the sequence of deposition of the particles, the types of dimers involved in the process, and the degree of alignment of the deposited objects. By means of numerical simulations and finite-size scaling analysis, the complete phase diagram separating a percolating from a nonpercolating region was determined for each case. Finally, the consistency of our results was examined by comparing with previous data in the literature for linear k-mers (particles occupying k adjacent sites) with defects.

  20. Synthesis, characterization, OFET and electrochemical properties of novel dimeric metallophthalocyanines.

    PubMed

    Ozer, Lale Meyancı; Ozer, Metin; Altındal, Ahmet; Ozkaya, Ali Rıza; Salih, Bekir; Bekaroğlu, Ozer

    2013-05-14

    The synthesis of 4,4'-[6,6'-methylenebis (2-(2-(3,4-dicyanophenoxy)-5-methylbenzyl)-4-methyl-6,1-phenylene)] bis (oxy) diphthalonitrile 1 was achieved starting from 4-nitrophthalonitrile and 6,6'-methylenebis(2-(2-hydroxy-5-methylbenzyl)-4-methylphenol in DMF at 50 °C by the catalysis of K2CO3 under argon. The corresponding dimeric metallophthalocyanines (Zn2Pc2 2 and Co2Pc2 3) were tetramerized in dimethylaminoethanol with the appropriate metal salt. Newly synthesized compounds were characterized by elemental analysis, UV-vis, FT-IR (ATR), MALDI-TOF mass and (1)H-NMR spectroscopy techniques. The electrochemical properties of the complexes were examined by cyclic voltammetry, differential pulse voltammetry, controlled potential coulometry and in situ spectroelectrochemistry in nonaqueous media. The results showed that while there is considerable weak interactions between the two metal phthalocyanine units in dimeric zinc phthalocyanine, these interactions in dimeric cobalt phthalocyanine is remarkable. The catalytic performances of dimeric cobalt phthalocyanine in the reduction of oxygen in a medium similar to the working conditions of the polymer electrolyte membrane fuel-cells were found to be much higher than that of dinuclear zinc phthalocyanine. Solution-processed films of the complexes were utilized as an active semiconducting layer in the fabrication of organic field-effect transistors (OFETs) in the bottom-gate configurations. The output characteristics of the resulting p-type OFET devices were investigated to evaluate the performances such as the field effect mobility (μF). A relatively high field effect mobility of 7.3 × 10(-3) cm(2) V(-1) s(-1) was observed for dimeric cobalt phthalocyanine.

  1. Radiation-enhanced optical antenna based on nonperiodic metallic nanoparticle dimer chain

    NASA Astrophysics Data System (ADS)

    Chen, Xiaolin; Yu, Wenhai; Yue, Wencheng; Yao, Peijun; Liu, Wen

    2015-07-01

    With the aid of multi-sphere dyadic Green's function, we present a design of optical nanoantenna which is composed of a nonperiodic nanoparticle dimer chain. By breaking the periodicity of the dimer chain, the radiative emission of the dimer chain is significantly enhanced because the strong coupling which limits radiation enhancement is inhibited when the separations between dimers are reduced. Our work clearly shows the crucial role of nonperiodicity in the design of the Yagi-Uda nanoantenna.

  2. Dimeric States of Neural- and Epithelial-Cadherins are Distinguished by the Rate of Disassembly†

    PubMed Central

    Vunnam, Nagamani; Flint, Jon; Balbo, Andrea; Schuck, Peter; Pedigo, Susan

    2011-01-01

    Epithelial- and Neural-cadherins are specifically localized at synapses in neurons which can change shape and contact surface on a time scale of seconds to months. We have focused our studies on the role of the extracellular domains of cadherins in the dynamics of synapses. The kinetics of dimer disassembly of the first two extracellular domains of E- and N-cadherin, ECAD12 and NCAD12, were studied with analytical size exclusion chromatography and sedimentation velocity. NCAD12 forms three different dimers that are distinguished by assembly conditions and kinetics of dissociation. ECAD12 dimer disassembles rapidly regardless of the calcium concentration, whereas the disassembly of NCAD12 dimers was strongly dependent on calcium concentration. In addition to the apo- and saturated-dimeric forms of NCAD12, there is a third dimeric form that is a slow exchange dimer. This third dimeric form for NCAD12, formed by decalcification of the calcium-saturated dimer, was kinetically-trapped in apo-conditions and did not disassemble over a period of months. Sedimentation velocity experiments showed that this dimer, upon addition of calcium, had similar weighted averages as calcium-saturated dimer. These studies provide evidence that the kinetics of dimer disassembly of the extracellular domains may be a major contributor to the morphological dynamics of synapses in vivo. PMID:21375242

  3. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  4. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  5. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  6. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  7. 40 CFR 721.9484 - Dimer acid/rosin amidoamine reaction product (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Dimer acid/rosin amidoamine reaction... Specific Chemical Substances § 721.9484 Dimer acid/rosin amidoamine reaction product (generic). (a... generically as Dimer acid/rosin amidoamine reaction product (PMN P-99-0143) is subject to reporting under...

  8. Evaluation of stability difference between asymmetric homochiral dimer in (S)-thalidomide crystal and symmetric heterochiral dimer in (RS)-thalidomide crystal

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshiya; Tanaka, Masahito; Shiro, Motoo; Shibata, Norio; Osaka, Tetsuya; Asahi, Toru

    2010-03-01

    This article discusses differences in physicochemical properties such as solubility and melting point between (S)-thalidomide and (RS)-thalidomide based on crystal structures determined by X-ray diffraction experiments. Investigation of such differences is of great importance because thalidomide has attracted considerable attention again due to its wide-range bioactivity for intractable diseases. In this article, structures of hydrogen-bonded rings were compared between asymmetric homochiral dimers in (S)-thalidomide crystal and symmetric heterochiral dimers in (RS)-thalidomide crystal. The heterochiral dimer was evaluated to be more stable than the homochiral dimer by the energy calculations for hydrogen-bonded rings in those dimers. These results indicate that differences in physicochemical properties between enantiomeric and racemic thalidomides originate from the difference of structural stability between homochiral and heterochiral dimers.

  9. Magnitude and orientation dependence of intermolecular interaction of perfluoropropane dimer studied by high-level ab initio calculations: Comparison with propane dimer

    NASA Astrophysics Data System (ADS)

    Tsuzuki, Seiji; Uchimaru, Tadafumi; Mikami, Masuhiro; Urata, Shingo

    2004-11-01

    Intermolecular interaction energies of 12 orientations of C3F8 dimers were calculated with electron correlation correction by the second-order Møller-Plesset perturbation method. The antiparallel C2h dimer has the largest interaction energy (-1.45 kcal/mol). Electron correlation correction increases the attraction considerably. Electrostatic energy is not large. Dispersion is mainly responsible for the attraction. Orientation dependence of the interaction energy of the C3F8 dimer is substantially smaller than that of the C3H8 dimer. The calculated interaction energy of the C3F8 dimer at the potential minimum is 78% of that of the C3H8 dimer (-1.85 kcal/mol), whereas the interaction energies of the CF4 and C2F6 dimers are larger than those of the CH4 and C2H6 dimers. The intermolecular separation in the C3F8 dimer at the potential minimum is substantially larger than that in the C3H8 dimer. The larger intermolecular separation due to the steric repulsion between fluorine atoms is the cause of the smaller interaction energy of the C3F8 dimer at the potential minimum. The calculated intermolecular interaction energy potentials of the C3F8 dimers using an all atom model OPLS-AA (OPLS all atom model) force field and a united atom model force field were compared with the ab initio calculations. Although the two force fields well reproduces the experimental vapor and liquid properties of perfluoroalkenes, the comparison shows that the united atom model underestimates the potential depth and orientation dependence of the interaction energy. The potentials obtained by the OPLS-AA force field are close to those obtained by the ab initio calculations.

  10. Water-solubilizing Hydrophobic ZnAgInSe/ZnS QDs with Tumor-targeted cRGD-Sulfobetaine-PIMA-Histamine Ligands via a Self-assembly Strategy for Bio-Imaging.

    PubMed

    Deng, Tao; Peng, Yanan; Zhang, Rong; Wang, Jie; Zhang, Jie; Gu, Yue-Qing; Huang, Dechun; Deng, Dawei

    2017-03-15

    Exploring the organic-to-aqueous phase transfer of quantum dots (QDs) is significant for achieving their versatile applications in biomedαical fields. In this thematic issue, surface modification, size control and biocompatibility of QDs and QDs-based nanocomposites are core problems. Herein, the new highly fluorescent tumor-targeted QDs-clusters consisting of ZnAgInSe/ZnS (ZAISe/ZnS) QDs and sulfobetaine-PIMA-histamine (SPH) polymer with the ανβ3 integrin receptor cyclic RGD (c-RGD) were developed via ligand exchange and an accompanying self-assemble process. It was found that the structure of RGD-SPH QDs-clusters was propitious to reduce the capture of reticulo-endothelial system (RES) in virtue of external stealth ligands, and benefit to selectively accumulate at the tumor site after intravenous injection via active tumor targeting cooperated with the enhanced permeability and retention (EPR) effect. In the meantime, those clusters also recognized and enriched to cell surface when co-cultured with the ανβ3 integrin receptor overexpressed malignant cells (U87MG tumors). Based on the results, fabricating mutil-functional nanocomposites integrated with the long-term circulation and dual-targeting effects should be an interesting strategy for imaging cancer in vitro and in vivo.

  11. An algebra of dimerization and its implications for G-protein coupled receptor signaling.

    PubMed

    Woolf, Peter J; Linderman, Jennifer J

    2004-07-21

    Many species of receptors form dimers, but how can we use this information to make predictions about signal transduction? This problem is particularly difficult when receptors dimerize with many different species, leading to a combinatoric increase in the possible number of dimer pairs. As an example system, we focus on receptors in the G-protein coupled receptor (GPCR) family. GPCRs have been shown to reversibly form dimers, but this dimerization does not directly affect signal transduction. Here we present a new theoretical framework called a dimerization algebra. This algebra provides a systematic and rational way to represent, manipulate, and in some cases simplify large and often complicated networks of dimerization interactions. To compliment this algebra, Monte Carlo simulations are used to predict dimerization's effect on receptor organization on the membrane, signal transduction, and internalization. These simulation results are directly comparable to various experimental measures such as fluorescence resonance energy transfer (FRET), and as such provide a link between the dimerization algebra and experimental data. As an example, we show how the algebra and computational results can be used to predict the effects of dimerization on the dopamine D2 and somatastatin SSTR1 receptors. When these predictions were compared to experimental findings from the literature, good agreement was found, demonstrating the utility of our approach. Applications of this work to the development of a novel class of dimerization-modulating drugs are also discussed.

  12. Mechanisms for kinase-mediated dimerization of the epidermal growth factor receptor.

    PubMed

    Lu, Chafen; Mi, Li-Zhi; Schürpf, Thomas; Walz, Thomas; Springer, Timothy A

    2012-11-02

    We study a mechanism by which dimerization of the EGF receptor (EGFR) cytoplasmic domain is transmitted to the ectodomain. Therapeutic and other small molecule antagonists to the kinase domain that stabilize its active conformation, but not those that stabilize an inactive conformation, stabilize ectodomain dimerization. Inhibitor-induced dimerization requires an asymmetric kinase domain interface associated with activation. EGF and kinase inhibitors stimulate formation of identical dimer interfaces in the EGFR transmembrane domain, as shown by disulfide cross-linking. Disulfide cross-linking at an interface in domain IV in the ectodomain was also stimulated similarly; however, EGF but not inhibitors stimulated cross-linking in domain II. Inhibitors similarly induced noncovalent dimerization in nearly full-length, detergent-solubilized EGFR as shown by gel filtration. EGFR ectodomain deletion resulted in spontaneous dimerization, whereas deletion of exons 2-7, in which extracellular domains III and IV are retained, did not. In EM, kinase inhibitor-induced dimers lacked any well defined orientation between the ectodomain monomers. Fab of the therapeutic antibody cetuximab to domain III confirmed a variable position and orientation of this domain in inhibitor-induced dimers but suggested that the C termini of domain IV of the two monomers were in close proximity, consistent with dimerization in the transmembrane domains. The results provide insights into the relative energetics of intracellular and extracellular dimerization in EGFR and have significance for physiologic dimerization through the asymmetric kinase interface, bidirectional signal transmission in EGFR, and mechanism of action of therapeutics.

  13. Intramolecular hydrophobic interactions are critical mediators of STAT5 dimerization.

    PubMed

    Fahrenkamp, Dirk; Li, Jinyu; Ernst, Sabrina; Schmitz-Van de Leur, Hildegard; Chatain, Nicolas; Küster, Andrea; Koschmieder, Steffen; Lüscher, Bernhard; Rossetti, Giulia; Müller-Newen, Gerhard

    2016-10-18

    STAT5 is an essential transcription factor in hematopoiesis, which is activated through tyrosine phosphorylation in response to cytokine stimulation. Constitutive activation of STAT5 is a hallmark of myeloid and lymphoblastic leukemia. Using homology modeling and molecular dynamics simulations, a model of the STAT5 phosphotyrosine-SH2 domain interface was generated providing first structural information on the activated STAT5 dimer including a sequence, for which no structural information is available for any of the STAT proteins. We identified a novel intramolecular interaction mediated through F706, adjacent to the phosphotyrosine motif, and a unique hydrophobic interface on the surface of the SH2 domain. Analysis of corresponding STAT5 mutants revealed that this interaction is dispensable for Epo receptor-mediated phosphorylation of STAT5 but essential for dimer formation and subsequent nuclear accumulation. Moreover, the herein presented model clarifies molecular mechanisms of recently discovered leukemic STAT5 mutants and will help to guide future drug development.

  14. Identities between dimer partition functions on different surfaces

    NASA Astrophysics Data System (ADS)

    Cimasoni, David; Pham, Anh Minh

    2016-10-01

    Given a weighted graph G embedded in a non-orientable surface Σ , one can consider the corresponding weighted graph \\widetilde{G} embedded in the so-called orientation cover \\widetildeΣ of Σ . We prove identities relating twisted partition functions of the dimer model on these two graphs. When Σ is the Möbius strip or the Klein bottle, then \\widetildeΣ is the cylinder or the torus, respectively, and under some natural assumptions, these identities imply relations between the genuine dimer partition functions Z(G) and Z(\\widetilde{G}) . For example, we show that if G is a locally but not globally bipartite graph embedded in the Möbius strip, then Z(\\widetilde{G}) is equal to the square of Z(G). This extends results for the square lattice previously obtained by various authors.

  15. Microwave Spectrum of the Ethanol-Methanol Dimer

    NASA Astrophysics Data System (ADS)

    Finneran, Ian A.; Carroll, Brandon; Mead, Griffin; Blake, Geoffrey

    2016-06-01

    The hydrogen bond donor/acceptor competition in mixed alcohol clusters remains a fundamental question in physical chemistry. Previous theoretical work on the prototype ethanol-methanol dimer has been inconclusive in predicting the energetically preferred structure. Here, we report the microwave spectrum of the ethanol-methanol dimer between 8-18 GHz, using a chirped pulse Fourier transform microwave spectrometer. With the aid of ab initio calculations, 36 transitions have been fit and assigned to a t-ethanol-acceptor, methanol-donor structure in an argon-backed expansion. In a helium-backed expansion, a second excited conformer has been observed, and tentatively assigned to a g-ethanol-acceptor, methanol-donor structure. No ethanol-donor, methanol-acceptor structures have been found, suggesting such structures are energetically disfavored.

  16. Single nucleotide polymorphism analysis using different colored dye dimer probes

    NASA Astrophysics Data System (ADS)

    Marmé, Nicole; Friedrich, Achim; Denapaite, Dalia; Hakenbeck, Regine; Knemeyer, Jens-Peter

    2006-09-01

    Fluorescence quenching by dye dimer formation has been utilized to develop hairpin-structured DNA probes for the detection of a single nucleotide polymorphism (SNP) in the penicillin target gene pbp2x, which is implicated in the penicillin resistance of Streptococcus pneumoniae. We designed two specific DNA probes for the identification of the pbp2x genes from a penicillin susceptible strain R6 and a resistant strain Streptococcus mitis 661 using green-fluorescent tetramethylrhodamine (TMR) and red-fluorescent DY-636, respectively. Hybridization of each of the probes to its respective target DNA sequence opened the DNA hairpin probes, consequently breaking the nonfluorescent dye dimers into fluorescent species. This hybridization of the target with the hairpin probe achieved single nucleotide specific detection at nanomolar concentrations via increased fluorescence.

  17. Hydrogen bonding in the benzene-ammonia dimer

    NASA Technical Reports Server (NTRS)

    Rodham, David A.; Suzuki, Sakae; Suenram, Richard D.; Lovas, Frank J.; Dasgupta, Siddharth; Goddard, William A., III; Blake, Geoffrey A.

    1993-01-01

    High-resolution optical and microwave spectra of the gas-phase benzene-ammonia dimer were obtained, showing that the ammonia molecule resides above the benzene plane and undergoes free, or nearly free, internal rotation. To estimate the binding energy (De) and other global properties of the intermolecular potential, theoretical calculations were performed for the benzene-ammonia dimer, using the Gaussian 92 (Fritsch, 1992) program at the MP2/6-31G** level. The predicted De was found to be at the lowest end of the range commonly accepted for hydrogen bonding and considerably below that of C6H6-H2O, consistent with the gas-phase acidities of ammonia and water. The observed geometry greatly resembles the amino-aromatic interaction found naturally in proteins.

  18. Monomeric and dimeric hydrolysable tannins of Tamarix nilotica.

    PubMed

    Orabi, Mohamed A A; Taniguchi, Shoko; Hatano, Tsutomu

    2009-07-01

    An ellagitannin monomer, nilotinin M1 (1), and three dimers, nilotinins D1 (2), D2 (3), and D3 (4), were isolated from leaves of Tamarix nilotica (Ehrenb.) Bunge. Structures were elucidated based on analysis of spectroscopic data and chemical correlations with known compounds. In addition, six known tannins, hirtellin A (5) (dimer), remurin A (6), remurin B (7), 1,3-di-O-galloyl-4,6-O-(S)-hexahydroxydiphenoyl-beta-D-glucose (8), gemin D (9), and hippomanin A (10) (monomers), were isolated for the first time from this plant species. The reported (13)C NMR assignments of the dehydrodigalloyl moiety and glucose cores of 5 are revised, and the (13)C NMR spectroscopic data for 6 and 7 are also reported for the first time.

  19. Intramolecular hydrophobic interactions are critical mediators of STAT5 dimerization

    NASA Astrophysics Data System (ADS)

    Fahrenkamp, Dirk; Li, Jinyu; Ernst, Sabrina; Schmitz-van de Leur, Hildegard; Chatain, Nicolas; Küster, Andrea; Koschmieder, Steffen; Lüscher, Bernhard; Rossetti, Giulia; Müller-Newen, Gerhard

    2016-10-01

    STAT5 is an essential transcription factor in hematopoiesis, which is activated through tyrosine phosphorylation in response to cytokine stimulation. Constitutive activation of STAT5 is a hallmark of myeloid and lymphoblastic leukemia. Using homology modeling and molecular dynamics simulations, a model of the STAT5 phosphotyrosine-SH2 domain interface was generated providing first structural information on the activated STAT5 dimer including a sequence, for which no structural information is available for any of the STAT proteins. We identified a novel intramolecular interaction mediated through F706, adjacent to the phosphotyrosine motif, and a unique hydrophobic interface on the surface of the SH2 domain. Analysis of corresponding STAT5 mutants revealed that this interaction is dispensable for Epo receptor-mediated phosphorylation of STAT5 but essential for dimer formation and subsequent nuclear accumulation. Moreover, the herein presented model clarifies molecular mechanisms of recently discovered leukemic STAT5 mutants and will help to guide future drug development.

  20. Fermion fractionalization to Majorana fermions in a dimerized Kitaev superconductor

    NASA Astrophysics Data System (ADS)

    Wakatsuki, Ryohei; Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

    2014-07-01

    We study theoretically a one-dimensional dimerized Kitaev superconductor model which belongs to BDI class with time-reversal, particle-hole, and chiral symmetries. There are two sources of the particle-hole symmetry, i.e., the sublattice symmetry and superconductivity. Accordingly, we define two types of topological numbers with respect to the chiral indices of normal and Majorana fermions, which offers an ideal laboratory to examine the interference between the two different physics within the same symmetry class. Phase diagram, zero-energy bound states, and conductance at normal metal/superconductor junction of this model are unveiled from this viewpoint. Especially, the electron fractionalization to the Majorana fermions showing the splitting of the local density of states is realized at the soliton of the dimerization in this model.

  1. Fermion Fractionalization to Majorana Fermions in Dimerized Kitaev Superconductor

    NASA Astrophysics Data System (ADS)

    Wakatsuki, Ryohei; Ezawa, Motohiko; Tanaka, Yukio; Nagaosa, Naoto

    2015-03-01

    We study theoretically a one-dimensional dimerized Kitaev superconductor model which belongs to BDI class with time-reversal, particle-hole, and chiral symmetries. There are two sources of the particle-hole symmetry, i.e., the sublattice symmetry and superconductivity. Accordingly, we define two types of topological numbers with respect to the chiral indices of normal and Majorana fermions, which offers an ideal laboratory to examine the interference between the two different physics within the same symmetry class. Phase diagram, zero-energy bound states, and conductance at normal metal/superconductor junction of this model are unveiled from this viewpoint. Especially, the electron fractionalization to the Majorana fermions showing the splitting of the local density of states is realized at the soliton of the dimerization in this model.

  2. Self-assembly of dimeric tetraurea calix[4]pyrrole capsules

    PubMed Central

    Ballester, Pablo; Gil-Ramírez, Guzmán

    2009-01-01

    Calix[4]pyrroles having extended aromatic cavities have been functionalized with 4 ureas in the para position of their meso phenyl substituents. This elaboration of the upper rim was completed in 2 synthetic steps starting from the α,α,α,α-tetranitro isomer of the calix[4]pyrrole obtained in the acid catalyzed condensation of p-nitrophenyl methyl ketone and pyrrole. In dichloromethane solution and in the presence of 4,4′-bipyridine N-N′-dioxide the tetraurea calix[4]pyrrole dimerizes reversibly forming a cyclic array of 16 hydrogen bonds and encapsulating 1 molecule of bis-N-oxide. The encapsulated guest is bound in the cavity by hydrogen bonding to the 2 endohedral calix[4]pyrrole centers. Further evidence for dimerization of the tetraurea calix[4]pyrroles is provided by 1H-NMR experiments and by the formation of mixed capsules. PMID:19261848

  3. Cytotoxic bibenzyl dimers from the stems of Dendrobium fimbriatum Hook.

    PubMed

    Xu, Feng-Qing; Xu, Fang-Cheng; Hou, Bo; Fan, Wei-Wei; Zi, Cheng-Ting; Li, Yan; Dong, Fa-Wu; Liu, Yu-Qing; Sheng, Jun; Zuo, Zhi-Li; Hu, Jiang-Miao

    2014-11-15

    The bioassay-guided chemical investigation of the stems of Dendrobium fimbriatum Hook led to the isolation of seven first reported bibenzyl dimers with a linkage of a methylene moiety, fimbriadimerbibenzyls A-G (1-7), together with a new dihydrophenanthrene derivative (S)-2,4,5,9-tetrahydroxy-9,10-dihydrophenanthrene (8) and thirteen known compounds (9-21). The structure of the new compound was established by spectroscopic analysis. Biological evaluation of bibenzyl derivatives against five human cell lines indicated that seven of those compounds exhibited broad-spectrum and cytotoxic activities with IC50 values ranging from 2.2 to 21.2 μM. Those rare bibenzyl dimers exhibited cytotoxic activities in vitro and the cytotoxicity decreased as the number of oxygen-containing groups in the structure decreases.

  4. UV resonance Raman analysis of trishomocubane and diamondoid dimers

    SciTech Connect

    Meinke, Reinhard Thomsen, Christian; Maultzsch, Janina; Richter, Robert; Merli, Andrea; Fokin, Andrey A.; Koso, Tetyana V.; Schreiner, Peter R.; Rodionov, Vladimir N.

    2014-01-21

    We present resonance Raman measurements of crystalline trishomocubane and diamantane dimers containing a C=C double bond. Raman spectra were recorded with excitation energies between 2.33 eV and 5.42 eV. The strongest enhancement is observed for the C=C stretch vibration and a bending mode involving the two carbon atoms of the C=C bond, corresponding to the B{sub 2g} wagging mode of ethylene. This is associated with the localization of the π-HOMO and LUMO and the elongation of the C=C bond length and a pyramidalization of the two sp{sup 2}-hybridized carbon atoms at the optical excitation. The observed Raman resonance energies of the trishomocubane and diamantane dimers are significantly lower than the HOMO-LUMO gaps of the corresponding unmodified diamondoids.

  5. Antioxidant Properties of Aminoethylcysteine Ketimine Decarboxylated Dimer: A Review

    PubMed Central

    Macone, Alberto; Fontana, Mario; Barba, Marco; Botta, Bruno; Nardini, Mirella; Ghirga, Francesca; Calcaterra, Andrea; Pecci, Laura; Matarese, Rosa Marina

    2011-01-01

    Aminoethylcysteine ketimine decarboxylated dimer is a natural sulfur-containing compound detected in human plasma and urine, in mammalian brain and in many common edible vegetables. Over the past decade many studies have been undertaken to identify its metabolic role. Attention has been focused on its antioxidant properties and on its reactivity against oxygen and nitrogen reactive species. These properties have been studied in different model systems starting from plasma lipoproteins to specific cellular lines. All these studies report that aminoethylcysteine ketimine decarboxylated dimer is able to interact both with reactive oxygen and nitrogen species (hydrogen peroxide, superoxide anion, hydroxyl radical, peroxynitrite and its derivatives). Its antioxidant activity is similar to that of Vitamin E while higher than other hydrophilic antioxidants, such as trolox and N-acetylcysteine. PMID:21686170

  6. Inhibition of HIV-1 Reverse Transcriptase Dimerization by Small Molecules.

    PubMed

    Tintori, Cristina; Corona, Angela; Esposito, Francesca; Brai, Annalaura; Grandi, Nicole; Ceresola, Elisa Rita; Clementi, Massimo; Canducci, Filippo; Tramontano, Enzo; Botta, Maurizio

    2016-04-15

    Because HIV-1 reverse transcriptase is an enzyme whose catalytic activity depends on its heterodimeric structure, this system could be a target for inhibitors that perturb the interactions between the protein subunits, p51 and p66. We previously demonstrated that the small molecule MAS0 reduced the association of the two RT subunits and simultaneously inhibited both the polymerase and ribonuclease H activities. In this study, some analogues of MAS0 were rationally selected by docking studies and evaluated in vitro for their ability to disrupt dimeric assembly. Two inhibitors were identified with improved activity compared to MAS0. This study lays the basis for the rational design of more potent inhibitors of RT dimerization.

  7. UV resonance Raman analysis of trishomocubane and diamondoid dimers.

    PubMed

    Meinke, Reinhard; Richter, Robert; Merli, Andrea; Fokin, Andrey A; Koso, Tetyana V; Rodionov, Vladimir N; Schreiner, Peter R; Thomsen, Christian; Maultzsch, Janina

    2014-01-21

    We present resonance Raman measurements of crystalline trishomocubane and diamantane dimers containing a C=C double bond. Raman spectra were recorded with excitation energies between 2.33 eV and 5.42 eV. The strongest enhancement is observed for the C=C stretch vibration and a bending mode involving the two carbon atoms of the C=C bond, corresponding to the B2g wagging mode of ethylene. This is associated with the localization of the π-HOMO and LUMO and the elongation of the C=C bond length and a pyramidalization of the two sp(2)-hybridized carbon atoms at the optical excitation. The observed Raman resonance energies of the trishomocubane and diamantane dimers are significantly lower than the HOMO-LUMO gaps of the corresponding unmodified diamondoids.

  8. Intramolecular hydrophobic interactions are critical mediators of STAT5 dimerization

    PubMed Central

    Fahrenkamp, Dirk; Li, Jinyu; Ernst, Sabrina; Schmitz-Van de Leur, Hildegard; Chatain, Nicolas; Küster, Andrea; Koschmieder, Steffen; Lüscher, Bernhard; Rossetti, Giulia; Müller-Newen, Gerhard

    2016-01-01

    STAT5 is an essential transcription factor in hematopoiesis, which is activated through tyrosine phosphorylation in response to cytokine stimulation. Constitutive activation of STAT5 is a hallmark of myeloid and lymphoblastic leukemia. Using homology modeling and molecular dynamics simulations, a model of the STAT5 phosphotyrosine-SH2 domain interface was generated providing first structural information on the activated STAT5 dimer including a sequence, for which no structural information is available for any of the STAT proteins. We identified a novel intramolecular interaction mediated through F706, adjacent to the phosphotyrosine motif, and a unique hydrophobic interface on the surface of the SH2 domain. Analysis of corresponding STAT5 mutants revealed that this interaction is dispensable for Epo receptor-mediated phosphorylation of STAT5 but essential for dimer formation and subsequent nuclear accumulation. Moreover, the herein presented model clarifies molecular mechanisms of recently discovered leukemic STAT5 mutants and will help to guide future drug development. PMID:27752093

  9. Association of atoms into universal dimers using an oscillating magnetic field.

    PubMed

    Langmack, Christian; Smith, D Hudson; Braaten, Eric

    2015-03-13

    In a system of ultracold atoms near a Feshbach resonance, pairs of atoms can be associated into universal dimers by an oscillating magnetic field with a frequency near that determined by the dimer binding energy. We present a simple expression for the transition rate that takes into account many-body effects through a transition matrix element of the contact. In a thermal gas, the width of the peak in the transition rate as a function of the frequency is determined by the temperature. In a dilute Bose-Einstein condensate of atoms, the width is determined by the inelastic scattering rates of a dimer with zero-energy atoms. Near an atom-dimer resonance, there is a dramatic increase in the width from inelastic atom-dimer scattering and from atom-atom-dimer recombination. The recombination contribution provides a signature for universal tetramers that are Efimov states consisting of two atoms and a dimer.

  10. D-dimer: An Overview of Hemostasis and Fibrinolysis, Assays, and Clinical Applications.

    PubMed

    Olson, John D

    2015-01-01

    D-dimer is the smallest fibrinolysis-specific degradation product found in the circulation. The origins, assays, and clinical use of D-dimer will be addressed. Hemostasis (platelet and vascular function, coagulation, fibrinolysis, hemostasis) is briefly reviewed. D-dimer assays are reviewed. The D-dimer is very sensitive to intravascular thrombus and may be markedly elevated in disseminated intravascular coagulation, acute aortic dissection, and pulmonary embolus. Because of its exquisite sensitivity, negative tests are useful in the exclusion venous thromboembolism. Elevations occur in normal pregnancy, rising two- to fourfold by delivery. D-dimer also rises with age, limiting its use in those >80 years old. There is a variable rise in D-dimer in active malignancy and indicates increased thrombosis risk in active disease. Elevated D-dimer following anticoagulation for a thrombotic event indicates increased risk of recurrent thrombosis. These and other issues are addressed.

  11. Conformational Heterogeneity of Bax Helix 9 Dimer for Apoptotic Pore Formation

    NASA Astrophysics Data System (ADS)

    Liao, Chenyi; Zhang, Zhi; Kale, Justin; Andrews, David W.; Lin, Jialing; Li, Jianing

    2016-07-01

    Helix α9 of Bax protein can dimerize in the mitochondrial outer membrane (MOM) and lead to apoptotic pores. However, it remains unclear how different conformations of the dimer contribute to the pore formation on the molecular level. Thus we have investigated various conformational states of the α9 dimer in a MOM model — using computer simulations supplemented with site-specific mutagenesis and crosslinking of the α9 helices. Our data not only confirmed the critical membrane environment for the α9 stability and dimerization, but also revealed the distinct lipid-binding preference of the dimer in different conformational states. In our proposed pathway, a crucial iso-parallel dimer that mediates the conformational transition was discovered computationally and validated experimentally. The corroborating evidence from simulations and experiments suggests that, helix α9 assists Bax activation via the dimer heterogeneity and interactions with specific MOM lipids, which eventually facilitate proteolipidic pore formation in apoptosis regulation.

  12. Multiple-charge transfer and trapping in DNA dimers

    NASA Astrophysics Data System (ADS)

    Tornow, Sabine; Bulla, Ralf; Anders, Frithjof B.; Zwicknagl, Gertrud

    2010-11-01

    We investigate the charge transfer characteristics of one and two excess charges in a DNA base-pair dimer using a model Hamiltonian approach. The electron part comprises diagonal and off-diagonal Coulomb matrix elements such a correlated hopping and the bond-bond interaction, which were recently calculated by Starikov [E. B. Starikov, Philos. Mag. Lett. 83, 699 (2003)10.1080/0950083031000151374] for different DNA dimers. The electronic degrees of freedom are coupled to an ohmic or a superohmic bath serving as dissipative environment. We employ the numerical renormalization group method in the nuclear tunneling regime and compare the results to Marcus theory for the thermal activation regime. For realistic parameters, the rate that at least one charge is transferred from the donor to the acceptor in the subspace of two excess electrons significantly exceeds the rate in the single charge sector. Moreover, the dynamics is strongly influenced by the Coulomb matrix elements. We find sequential and pair transfer as well as a regime where both charges remain self-trapped. The transfer rate reaches its maximum when the difference of the on-site and intersite Coulomb matrix element is equal to the reorganization energy which is the case in a guanine/cytosine (GC)-dimer. Charge transfer is completely suppressed for two excess electrons in adenine/thymine (AT)-dimer in an ohmic bath and replaced by damped coherent electron-pair oscillations in a superohmic bath. A finite bond-bond interaction W alters the transfer rate: it increases as function of W when the effective Coulomb repulsion exceeds the reorganization energy (inverted regime) and decreases for smaller Coulomb repulsion.

  13. A new hydroxychavicol dimer from the roots of Piper betle.

    PubMed

    Lin, Chwan-Fwu; Hwang, Tsong-Long; Chien, Chun-Chien; Tu, Huei-Yu; Lay, Horng-Liang

    2013-02-26

    A new hydroxychavicol dimer, 2-(g'-hydroxychavicol)-hydroxychavicol (1), was isolated from the roots of Piper betle Linn. along with five known compounds, hydroxychavicol (2), aristololactam A II (3), aristololactam B II (4), piperolactam A (5) and cepharadione A (6). The structures of these isolated compounds were elucidated by spectroscopic methods. Compounds 1 and 2 exhibited inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.

  14. Monitoring Retroviral RNA Dimerization In Vivo via Hammerhead Ribozyme Cleavage

    PubMed Central

    Pal, Bijay K.; Scherer, Lisa; Zelby, Laurie; Bertrand, Edouard; Rossi, John J.

    1998-01-01

    We have used a strategy for colocalization of Psi (Ψ)-tethered ribozymes and targets to demonstrate that Ψ sequences are capable of specific interaction in the cytoplasm of both packaging and nonpackaging cells. These results indicate that current in vitro dimerization models may have in vivo counterparts. The methodology used may be applied to further genetic analyses on Ψ domain interactions in vivo. PMID:9733882

  15. Unexpected methyl migrations of ethanol dimer under synchrotron VUV radiation.

    PubMed

    Xiao, Weizhan; Hu, Yongjun; Li, Weixing; Guan, Jiwen; Liu, Fuyi; Shan, Xiaobin; Sheng, Liusi

    2015-01-14

    While methyl transfer is well known to occur in the enzyme- and metal-catalyzed reactions, the methyl transfer in the metal-free organic molecules induced by the photon ionization has been less concerned. Herein, vacuum ultraviolet single photon ionization and dissociation of ethanol dimer are investigated with synchrotron radiation photoionization mass spectroscopy and theoretical methods. Besides the protonated clusters cation (C2H5OH)⋅H(+) (m/z = 47) and the β-carbon-carbon bond cleavage fragment CH2O⋅(C2H5OH)H(+) (m/z = 77), the measured mass spectra revealed that a new fragment (C2H5OH)⋅(CH3)(+) (m/z = 61) appeared at the photon energy of 12.1 and 15.0 eV, where the neutral dimer could be vertically ionized to higher ionic state. Thereafter, the generated carbonium ions are followed by a Wagner-Meerwein rearrangement and then dissociate to produce this new fragment, which is considered to generate after surmounting a few barriers including intra- and inter-molecular methyl migrations by the aid of theoretical calculations. The appearance energy of this new fragment is measured as 11.55 ± 0.05 eV by scanning photoionization efficiency curve. While the signal intensity of fragment m/z = 61 starts to increase, the fragments m/z = 47 and 77 tend to slowly incline around 11.55 eV photon energy. This suggests that the additional fragment channels other than (C2H5OH)⋅H(+) and CH2O⋅(C2H5OH)H(+) have also been opened, which consume some dimer cations. The present report provides a clear description of the photoionization and dissociation processes of the ethanol dimer in the range of the photon energy 12-15 eV.

  16. Iron-Catalyzed gem-Specific Dimerization of Terminal Alkynes.

    PubMed

    Liang, Qiuming; Osten, Kimberly M; Song, Datong

    2017-03-13

    We report a gem-specific homo- and cross-dimerization of terminal alkynes catalyzed by a well-defined iron(II) complex containing Cp* and picolyl N-heterocyclic carbene (NHC) ligands, and featuring a piano-stool structure. This catalytic system requires no additives and is compatible with a broad range of substrates, including those with polar functional groups such as NH and OH.

  17. Plasmon excitations in the dimers formed by atom chains

    NASA Astrophysics Data System (ADS)

    Xue, Hong-jie; Hao, Da-peng; Zhang, Ming; Wang, Xiao-mei

    2017-02-01

    Based on the linear response theory in the random-phase approximation and the free-electron gas model, we study the plasmon excitations in the dimers formed by atom chains. With the help of energy absorption spectrum and charge distribution, the evolutions of longitudinal and transverse plasmon, and the effect of the system parameters such as size, atomic separation and electron filling on plasmon are obtained. In addition, the dipole, quadrupole, end and central plasmon are observed.

  18. Nonlinear optical response of cofacial phthalocyanine dimers and trimers

    SciTech Connect

    Manas, E.S.; Spano, F.C.; Chen, L.X.

    1997-07-01

    The effects of intermacrocycle interactions on the second hyperpolarizabilities {l_angle}{gamma}({minus}{omega};{omega},{minus}{omega},{omega}){r_angle} of cofacial phthalocyanine dimers and trimers are studied. A theoretical analysis is presented based on the Frenkel exciton model for a chain of three level molecules. Using a simplified analysis in the static and near-resonant regimes we identify two mechanisms which lead to enhancements in the dimer or trimer value of {l_angle}{gamma}({minus}{omega};{omega},{minus}{omega},{omega}){r_angle} over that of the monomer. The first mechanism is a disruption of the balance between type I and type II terms in the sum over states expression for the second hyperpolarizability tensor {gamma}{sub kjih}({minus}{omega};{omega},{minus}{omega},{omega}), caused by weak intermacrocycle interactions. The second is a near-resonance enhancement of the type II terms due to an intermacrocycle interaction induced shift in the monomer derived two-photon allowed states towards twice the laser photon energy. This analysis is in good agreement with recent degenerate four wave mixing experiments [SPIE Proc. {bold 2527}, 61 (1995)] which showed a strong enhancement of {l_angle}{gamma}({minus}{omega};{omega},{minus}{omega},{omega}){r_angle} for SiPcO oligomers as a function of the number of macrocycles. Our calculations suggest that the first mechanism is responsible for the 25-fold monomer to dimer enhancement measured in this system, and that the additional 4-fold enhancement found in going from the dimer to the trimer is primarily the result of the second mechanism. {copyright} {ital 1997 American Institute of Physics.}

  19. Excited State Pathways Leading to Formation of Adenine Dimers.

    PubMed

    Banyasz, Akos; Martinez-Fernandez, Lara; Ketola, Tiia-Maaria; Muñoz-Losa, Aurora; Esposito, Luciana; Markovitsi, Dimitra; Improta, Roberto

    2016-06-02

    The reaction intermediate in the path leading to UV-induced formation of adenine dimers A═A and AA* is identified for the first time quantum mechanically, using PCM/TD-DFT calculations on (dA)2 (dA: 2'deoxyadenosine). In parallel, its fingerprint is detected in the absorption spectra recorded on the millisecond time-scale for the single strand (dA)20 (dA: 2'deoxyadenosine).

  20. A DFT study of substituent effects in corannulene dimers.

    PubMed

    Josa, Daniela; Rodríguez Otero, Jesús; Cabaleiro Lago, Enrique M

    2011-12-21

    Corannulene dimers made up of corannulene monomers with different curvature and substituents were studied using M06-2X, B97D and ωB97XD functionals and 6-31+G* basis set. Corannulene molecules were substituted with five alternating Br, Cl, CH(3), C(2)H or CN units. Geometric results showed that substituents gave rise to small changes in the curvature of corannulene bowls. So, there was not a clear relationship between the curvature of bowls and the changes on interaction energy generated by addition of substituents in the bowl. Electron withdrawing substituents gave rise to a more positive molecular electrostatic potential (MEP) of the bowl, which was able to get a strong interaction with the negative MEP at the surface of a fullerene. Substitution with CN caused the largest effect, giving rise to the most positive MEP and to a large interaction energy of -24.64 kcal mol(-1), at the ωB97XD/6-31+G* level. Dispersive effects must be taken into account to explain the catching ability of the different substituted corannulenes. For unsubstituted dimers, calculations with DFT-D methods employing ωB97XD and B97D functionals led to similar results to those previously reported at the SCS-MP2/cc-pVTZ level for corannulene dimers (A. Sygula and S. Saebø, Int. J. Quant. Chem., 2009, 109, 65). In particular, the ωB97XD functional led to a difference of only 0.35 kcal mol(-1), regarding MP2 interaction energy for corannulene dimers. On the other hand, the M06-2X functional showed a general considerable underestimation of interaction energies. This functional worked quite well to study trends, but not to obtain absolute interaction energies.

  1. Subunit interface mutants of rabbit muscle aldolase form active dimers.

    PubMed Central

    Beernink, P. T.; Tolan, D. R.

    1994-01-01

    We report the construction of subunit interface mutants of rabbit muscle aldolase A with altered quaternary structure. A mutation has been described that causes nonspherocytic hemolytic anemia and produces a thermolabile aldolase (Kishi H et al., 1987, Proc Natl Acad Sci USA 84:8623-8627). The disease arises from substitution of Gly for Asp-128, a residue at the subunit interface of human aldolase A. To elucidate the role of this residue in the highly homologous rabbit aldolase A, site-directed mutagenesis is used to replace Asp-128 with Gly, Ala, Asn, Gln, or Val. Rabbit aldolase D128G purified from Escherichia coli is found to be similar to human D128G by kinetic analysis, CD, and thermal inactivation assays. All of the mutant rabbit aldolases are similar to the wild-type rabbit enzyme in secondary structure and kinetic properties. In contrast, whereas the wild-type enzyme is a tetramer, chemical crosslinking and gel filtration indicate that a new dimeric species exists for the mutants. In sedimentation velocity experiments, the mutant enzymes as mixtures of dimer and tetramer at 4 degrees C. Sedimentation at 20 degrees C shows that the mutant enzymes are > 99.5% dimeric and, in the presence of substrate, that the dimeric species is active. Differential scanning calorimetry demonstrates that Tm values of the mutant enzymes are decreased by 12 degrees C compared to wild-type enzyme. The results indicate that Asp-128 is important for interface stability and suggest that 1 role of the quaternary structure of aldolase is to provide thermostability. PMID:7833800

  2. Sialylation transmogrifies human breast and pancreatic cancer cells into 3D multicellular tumor spheroids using cyclic RGD-peptide induced self-assembly

    PubMed Central

    Akasov, Roman; Haq, Sabah; Haxho, Fiona; Samuel, Vanessa; Burov, Sergey V.; Markvicheva, Elena; Neufeld, Ronald J.; Szewczuk, Myron R.

    2016-01-01

    Multicellular tumor spheroids (MTS) have been at the forefront of cancer research, designed to mimic tumor-like developmental patterns in vitro. Tumor growth in vivo is highly influenced by aberrant cell surface-specific sialoglycan structures on glycoproteins. Aberrant sialoglycan patterns that facilitate MTS formation are not well defined. Matrix-free spheroids from breast MCF-7 and pancreatic PANC1 cancer cell lines and their respective tamoxifen (TMX) and gemcitabine (Gem) resistant variants were generated using the RGD platform of cyclic Arg-Gly-Asp-D-Phe-Lys peptide modified with 4-carboxybutyl-triphenylphosphonium bromide (cyclo-RGDfK (TPP)). MCF-7 and MCF-7 TMX cells formed tight spheroids both in the classical agarose-and RGD-based platforms while all PANC1 cells formed loose aggregates. Using lectin histochemistry staining, sialidase assay, neuraminidase (Vibrio cholerae) and oseltamivir phosphate (OP) neuraminidase inhibitor treatments, MCF-7 and PANC1 cells and their drug-resistant variants expressed different sialic acid (SA) content on their cell surfaces. α-2,3- and α-2,6-sialic acid surface residues facilitated spheroid formation under cyclo-RGDfK(TPP)-induced self-assembly. Pretreatment with α-2,3- SA specific Maackia amurensis (MAL-II) lectin, α-2,6-SA specific Sambucus nigra (SNA) lectin, and exogenous α-2,6-SA specific neuraminidase (Vibrio cholerae) dose-dependently reduced spheroid volume. OP enhanced cell aggregation and compaction forming spheroids. PANC1 and MDA-MB231 xenograft tumors from untreated and OP-treated RAGxCγ double mutant mice expressed significantly higher levels of α-2,3- SA over α-2,6-SA. MCF-7 spheroids also expressed a high α-2,3-SA to α-2,6-SA ratio. These results suggest that the relative levels of specific sialoglycan structures on the cell surface correlate with the ability of cancer cells to form avascular multicellular tumor spheroids and in vivo xenograft tumors. PMID:27608845

  3. Purification and characterization of dimeric dihydrodiol dehydrogenase from dog liver.

    PubMed

    Sato, K; Nakanishi, M; Deyashiki, Y; Hara, A; Matsuura, K; Ohya, I

    1994-09-01

    High NADP(+)-linked dihydrodiol dehydrogenase activity was detected in dog liver cytosol, from which a dimeric enzyme composed of M(r) 39,000 subunits was purified to homogeneity. The enzyme oxidized trans-cyclohexanediol, and trans-dihydrodiols of benzene and naphthalene, the [1R,2R]-isomers of which were selectively oxidized. In the reverse reaction in the presence of NADPH as a coenzyme, the enzyme reduced alpha-dicarbonyl compounds, such as methylglyoxal, 3-deoxyglucosone, and diacetyl, and some compounds with a carbonyl group, such as glyceraldehyde, lactaldehyde, and acetoin. 4-Hydroxyphenylketones and ascorbates inhibited the enzyme. The results of steady-state kinetic analyses indicated that the reaction proceeds through an ordered bi bi mechanism with the coenzyme binding to the free enzyme, and suggested that the inhibitors bind to the enzyme-NADP+ binary complex. The dimeric enzyme was detected in liver and kidney of dog, and was immunochemically similar to the dimeric enzymes from monkey kidney, rabbit lens, and pig liver. The sequences (total 127 amino acid residues) of eight peptides derived on enzymatic digestion of the dog liver enzyme did not show significant similarity with the primary structures of members of the aldo-keto reductase and short chain dehydrogenase superfamilies, which include monomeric dihydrodiol dehydrogenases and carbonyl reductase, respectively.

  4. Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures

    NASA Astrophysics Data System (ADS)

    Tian, Xiaorui; Fang, Yurui; Sun, Mengtao

    2015-12-01

    Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule.

  5. Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures

    PubMed Central

    Tian, Xiaorui; Fang, Yurui; Sun, Mengtao

    2015-01-01

    Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linea