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Sample records for protein hydrophobic dressing

  1. Development of nonstick and drug-loaded wound dressing based on the hydrolytic hydrophobic poly(carboxybetaine) ester analogue.

    PubMed

    Ji, Fangqin; Lin, Weifeng; Wang, Zhen; Wang, Longgang; Zhang, Juan; Ma, Guanglong; Chen, Shengfu

    2013-11-13

    A novel biocompatible polymer is developed for antimicrobial and nonstick coatings of wound dressing. The polymer is formed by copolymerization of carboxybetaine ester analogue methacrylate (CB-ester) and small partial poly(ethylene glycol) methacrylate (PEGMA) for cross-linking by hexamethylene diisocyanate (HDI), which is highly resistant to nonspecific protein adsorption and mammalian cell attachment after a quick hydrolysis. A small hydrophobic drug, aspirin, can be incorporated into the new polymer and slowly released to inhibit microorganism growth while the new polymer shows very low cytotoxicity. Moreover, the wound dressing, the new polymer coated medical gauze, shows good mechanic properties, such as flexibility and strength, for medical application. After all, this new nonfouling polymer offers great potential for an antimicrobial wound dressing and other applications.

  2. Stability of proteins inside a hydrophobic cavity

    NASA Astrophysics Data System (ADS)

    Radhakrishna, Mithun; Sharma, Sumit; Kumar, Sanat K.

    2011-03-01

    Previous studies have shown that enclosing a protein in an athermal cavity stabilizes the protein against reversible unfolding by virtue of eliminating many open chain conformations. Examples of such confined spaces include pores in chromatographic columns, Anfinsen's cage in Chaperonins, interiors of Ribosomes or regions of steric occlusion inside cells. However, the situation is more complex inside a hydrophobic cavity. The protein has a tendency to adsorb on the surface of the hydrophobic cavity, but at the same time it loses conformational entropy because of confinement. We study this system using a simple Hydrophobic Polar (HP) lattice protein model. Canonical Monte Carlo (MC) simulations at different temperatures and surface hydrophobicity show that proteins are stabilized at low and moderate hydrophobicity upon adsorption. The range of surface hydrophobicity over which a protein is stable increases with a decrease in radius of the cavity.

  3. Contribution of Hydrophobic Interactions to Protein Stability

    PubMed Central

    Pace, C. Nick; Fu, Hailong; Fryar, Katrina Lee; Landua, John; Trevino, Saul R.; Shirley, Bret A.; Hendricks, Marsha McNutt; Iimura, Satoshi; Gajiwala, Ketan; Scholtz, J. Martin; Grimsley, Gerald R.

    2011-01-01

    Our goal was to gain a better understanding of the contribution of hydrophobic interactions to protein stability. We measured the change in conformational stability, Δ(ΔG), for hydrophobic mutants of four proteins: villin head piece subdomain (VHP) with 36 residues, a surface protein from Borrelia burgdorferi (VlsE) with 341 residues, and two proteins previously studied in our laboratory, ribonucleases Sa and T1. We compare our results with previous studies and reach the following conclusions. 1. Hydrophobic interactions contribute less to the stability of a small protein, VHP (0.6 ± 0.3 kcal/mole per –CH2– group), than to the stability of a large protein, VlsE (1.6 ± 0.3 kcal/mol per –CH2– group). 2. Hydrophobic interactions make the major contribution to the stability of VHP (40 kcal/mol) and the major contributors are (in kcal/mol): Phe 18 (3.9), Met 13 (3.1), Phe 7 (2.9), Phe 11 (2.7), and Leu 21 (2.7). 3. Based on Δ(ΔG) values for 148 hydrophobic mutants in 13 proteins, burying a –CH2– group on folding contributes, on average, 1.1 ± 0.5 kcal/mol to protein stability. 4. The experimental Δ(ΔG) values for aliphatic side chains (Ala, Val, Ile, and Leu) are in good agreement with their ΔGtr values from water to cyclohexane. 5. For 22 proteins with 36 to 534 residues, hydrophobic interactions contribute 60 ± 4% and hydrogen bonds 40 ± 4% to protein stability. 6. Conformational entropy contributes about 2.4 kcal/mol per residue to protein instability. The globular conformation of proteins is stabilized predominately by hydrophobic interactions. PMID:21377472

  4. Chronic Wound Dressings Based on Collagen-Mimetic Proteins

    PubMed Central

    Cereceres, Stacy; Touchet, Tyler; Browning, Mary Beth; Smith, Clayton; Rivera, Jose; Höök, Magnus; Whitfield-Cargile, Canaan; Russell, Brooke; Cosgriff-Hernandez, Elizabeth

    2015-01-01

    Objective: Chronic wounds are projected to reach epidemic proportions due to the aging population and the increasing incidence of diabetes. There is a strong clinical need for an improved wound dressing that can balance wound moisture, promote cell migration and proliferation, and degrade at an appropriate rate to minimize the need for dressing changes. Approach: To this end, we have developed a bioactive, hydrogel microsphere wound dressing that incorporates a collagen-mimetic protein, Scl2GFPGER, to promote active wound healing. A redesigned Scl2GFPGER, engineered collagen (eColGFPGER), was created to reduce steric hindrance of integrin-binding motifs and increase overall stability of the triple helical backbone, thereby resulting in increased cell adhesion to substrates. Results: This study demonstrates the successful modification of the Scl2GFPGER protein to eColGFPGER, which displayed enhanced stability and integrin interactions. Fabrication of hydrogel microspheres provided a matrix with adaptive moisture technology, and degradation rates have potential for use in human wounds. Innovation: This collagen-mimetic wound dressing was designed to permit controlled modulation of cellular interactions and degradation rate without impact on other physical properties. Its fabrication into uniform hydrogel microspheres provides a bioactive dressing that can readily conform to irregular wounds. Conclusion: Overall, this new eColGFPGER shows strong promise in the generation of bioactive hydrogels for wound healing as well as a variety of tissue scaffolds. PMID:26244101

  5. How the hydrophobic factor drives protein folding.

    PubMed

    Baldwin, Robert L; Rose, George D

    2016-11-01

    How hydrophobicity (HY) drives protein folding is studied. The 1971 Nozaki-Tanford method of measuring HY is modified to use gases as solutes, not crystals, and this makes the method easy to use. Alkanes are found to be much more hydrophobic than rare gases, and the two different kinds of HY are termed intrinsic (rare gases) and extrinsic (alkanes). The HY values of rare gases are proportional to solvent-accessible surface area (ASA), whereas the HY values of alkanes depend on special hydration shells. Earlier work showed that hydration shells produce the hydration energetics of alkanes. Evidence is given here that the transfer energetics of alkanes to cyclohexane [Wolfenden R, Lewis CA, Jr, Yuan Y, Carter CW, Jr (2015) Proc Natl Acad Sci USA 112(24):7484-7488] measure the release of these shells. Alkane shells are stabilized importantly by van der Waals interactions between alkane carbon and water oxygen atoms. Thus, rare gases cannot form this type of shell. The very short (approximately picoseconds) lifetime of the van der Waals interaction probably explains why NMR efforts to detect alkane hydration shells have failed. The close similarity between the sizes of the opposing energetics for forming or releasing alkane shells confirms the presence of these shells on alkanes and supports Kauzmann's 1959 mechanism of protein folding. A space-filling model is given for the hydration shells on linear alkanes. The model reproduces the n values of Jorgensen et al. [Jorgensen WL, Gao J, Ravimohan C (1985) J Phys Chem 89:3470-3473] for the number of waters in alkane hydration shells.

  6. How the hydrophobic factor drives protein folding

    PubMed Central

    Baldwin, Robert L.; Rose, George D.

    2016-01-01

    How hydrophobicity (HY) drives protein folding is studied. The 1971 Nozaki–Tanford method of measuring HY is modified to use gases as solutes, not crystals, and this makes the method easy to use. Alkanes are found to be much more hydrophobic than rare gases, and the two different kinds of HY are termed intrinsic (rare gases) and extrinsic (alkanes). The HY values of rare gases are proportional to solvent-accessible surface area (ASA), whereas the HY values of alkanes depend on special hydration shells. Earlier work showed that hydration shells produce the hydration energetics of alkanes. Evidence is given here that the transfer energetics of alkanes to cyclohexane [Wolfenden R, Lewis CA, Jr, Yuan Y, Carter CW, Jr (2015) Proc Natl Acad Sci USA 112(24):7484–7488] measure the release of these shells. Alkane shells are stabilized importantly by van der Waals interactions between alkane carbon and water oxygen atoms. Thus, rare gases cannot form this type of shell. The very short (approximately picoseconds) lifetime of the van der Waals interaction probably explains why NMR efforts to detect alkane hydration shells have failed. The close similarity between the sizes of the opposing energetics for forming or releasing alkane shells confirms the presence of these shells on alkanes and supports Kauzmann's 1959 mechanism of protein folding. A space-filling model is given for the hydration shells on linear alkanes. The model reproduces the n values of Jorgensen et al. [Jorgensen WL, Gao J, Ravimohan C (1985) J Phys Chem 89:3470–3473] for the number of waters in alkane hydration shells. PMID:27791131

  7. 21 CFR 520.2380a - Thiabendazole top dressing and mineral protein block.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... protein block feeding for 3 days. Milk taken from animals during treatment and within 96 hours (8 milkings... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Thiabendazole top dressing and mineral protein... § 520.2380a Thiabendazole top dressing and mineral protein block. (a) Chemical name....

  8. 21 CFR 520.2380a - Thiabendazole top dressing and mineral protein block.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... protein block feeding for 3 days. Milk taken from animals during treatment and within 96 hours (8 milkings... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Thiabendazole top dressing and mineral protein... § 520.2380a Thiabendazole top dressing and mineral protein block. (a) Chemical name....

  9. 21 CFR 520.2380a - Thiabendazole top dressing and mineral protein block.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... protein block feeding for 3 days. Milk taken from animals during treatment and within 96 hours (8 milkings... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Thiabendazole top dressing and mineral protein... § 520.2380a Thiabendazole top dressing and mineral protein block. (a) Chemical name....

  10. Distance-dependent hydrophobic-hydrophobic contacts in protein folding simulations.

    PubMed

    Onofrio, Angelo; Parisi, Giovanni; Punzi, Giuseppe; Todisco, Simona; Di Noia, Maria Antonietta; Bossis, Fabrizio; Turi, Antonio; De Grassi, Anna; Pierri, Ciro Leonardo

    2014-09-21

    Successful prediction of protein folding from an amino acid sequence is a challenge in computational biology. In order to reveal the geometric constraints that drive protein folding, highlight those constraints kept or missed by distinct lattices and for establishing which class of intra- and inter-secondary structure element interactions is the most relevant for the correct folding of proteins, we have calculated inter-alpha carbon distances in a set of 42 crystal structures consisting of mainly helix, sheet or mixed conformations. The inter-alpha carbon distances were also calculated in several lattice "hydrophobic-polar" models built from the same protein set. We found that helix structures are more prone to form "hydrophobic-hydrophobic" contacts than beta-sheet structures. At a distance lower than or equal to 3.8 Å (very short-range interactions), "hydrophobic-hydrophobic" contacts are almost absent in the native structures, while they are frequent in all the analyzed lattice models. At distances in-between 3.8 and 9.5 Å (short-/medium-range interactions), the best performing lattice for reproducing mainly helix structures is the body-centered-cubic lattice. If protein structures contain sheet portions, lattice performances get worse, with few exceptions observed for double-tetrahedral and body-centered-cubic lattices. Finally, we can observe that ab initio protein folding algorithms, i.e. those based on the employment of lattices and Monte Carlo simulated annealings, can be improved simply and effectively by preventing the generation of "hydrophobic-hydrophobic" contacts shorter than 3.8 Å, by monitoring the "hydrophobic-hydrophobic/polar-polar" contact ratio in short-/medium distance ranges and by using preferentially a body-centered-cubic lattice.

  11. 21 CFR 520.2380a - Thiabendazole top dressing and mineral protein block.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Thiabendazole top dressing and mineral protein... § 520.2380a Thiabendazole top dressing and mineral protein block. (a) Chemical name. 2-(4-Thiazolyl...) Conditions of use. It is used as follows: (1) Horses—(i) Route of administration. In feed, as a top...

  12. 21 CFR 520.2380a - Thiabendazole top dressing and mineral protein block.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Thiabendazole top dressing and mineral protein... § 520.2380a Thiabendazole top dressing and mineral protein block. (a) Chemical name. 2-(4-Thiazolyl...) Conditions of use. It is used as follows: (1) Horses—(i) Route of administration. In feed, as a top...

  13. Prediction of transmembrane helices from hydrophobic characteristics of proteins.

    PubMed

    Ponnuswamy, P K; Gromiha, M M

    1993-10-01

    Membrane proteins, requiring to be embedded into the lipid bilayers, have evolved to have amino acid sequences that will fold with a hydrophobic surface in contact with the alkane chains of the lipids and polar surface in contact with the aqueous phases on both sides of the membrane and the polar head groups of the lipids. It is generally assumed that the characteristics of the aqueous parts of the membrane proteins are similar to those of normal globular proteins, and the embedded parts are highly hydrophobic. In our earlier works, we introduced the concept of 'surrounding hydrophobicity' and developed a hydrophobicity scale for the 20 amino acid residues, and applied it successfully to the study of the family of globular proteins. In this work we use the concept of surrounding hydrophobicity to indicate quantitatively how the aqueous parts of membrane proteins compare with the normal globular proteins, and how rich the embedded parts are in their hydrophobic activity. We then develop a surrounding hydrophobicity scale applicable to membrane proteins, by mixing judicially the surrounding hydrophobicities observed in the crystals of the membrane protein, photosynthetic reaction center from the bacterium Rhodopseudomonas viridis, porin from Rhodobacter capsulatus and a set of 64 globular proteins. A predictive scheme based on this scale predicts from amino acid sequence, transmembrane segments in PRC and randomly selected 26 membrane proteins to 80% level of accuracy. This is a much higher predictive power when compared to the existing popular methods. A new procedure to measure the amphipathicity of sequence segments is proposed, and it is used to characterize the transmembrane parts of the sample membrane proteins.

  14. Biochemical characterization of the small hydrophobic protein of avian metapneumovirus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Avian metapneumovirus (aMPV) is a paramyxovirus that has three membrane-associate proteins: glycoprotein (G), fusion (F), and small hydrophobic (SH) proteins. Among them, the SH protein is a small type II integral membrane protein that is incorporated into virions and is only present in certain para...

  15. Hydrophobicity – Shake Flasks, Protein Folding and Drug Discovery

    PubMed Central

    Sarkar, Aurijit; Kellogg, Glen E.

    2009-01-01

    Hydrophobic interactions are some of the most important interactions in nature. They are the primary driving force in a number of phenomena. This is mostly an entropic effect and can account for a number of biophysical events such as protein-protein or protein-ligand binding that are of immense importance in drug design. The earliest studies on this phenomenon can be dated back to the end of the 19th century when Meyer and Overton independently correlated the hydrophobic nature of gases to their anesthetic potency. Since then, significant progress has been made in this realm of science. This review briefly traces the history of hydrophobicity research along with the theoretical estimation of partition coefficients. Finally, the application of hydrophobicity estimation methods in the field of drug design and protein folding is discussed. PMID:19929828

  16. Fractionation and recovery of whey proteins by hydrophobic interaction chromatography.

    PubMed

    Santos, Maria João; Teixeira, José A; Rodrigues, Lígia R

    2011-03-01

    A method for the recovery and fractionation of whey proteins from a whey protein concentrate (80%, w/w) by hydrophobic interaction chromatography is proposed. Standard proteins and WPC 80 dissolved in phosphate buffer with ammonium sulfate 1 M were loaded in a HiPrep Octyl Sepharose FF column coupled to a fast protein liquid chromatography (FPLC) system and eluted by decreasing the ionic strength of the buffer using a salt gradient. The results showed that the most hydrophobic protein from whey is α-lactalbumin and the less hydrophobic is lactoferrin. It was possible to recover 45.2% of β-lactoglobulin using the HiPrep Octyl Sepharose FF column from the whey protein concentrate mixture with 99.6% purity on total protein basis.

  17. A script to highlight hydrophobicity and charge on protein surfaces

    PubMed Central

    Hagemans, Dominique; van Belzen, Ianthe A. E. M.; Morán Luengo, Tania; Rüdiger, Stefan G. D.

    2015-01-01

    The composition of protein surfaces determines both affinity and specificity of protein-protein interactions. Matching of hydrophobic contacts and charged groups on both sites of the interface are crucial to ensure specificity. Here, we propose a highlighting scheme, YRB, which highlights both hydrophobicity and charge in protein structures. YRB highlighting visualizes hydrophobicity by highlighting all carbon atoms that are not bound to nitrogen and oxygen atoms. The charged oxygens of glutamate and aspartate are highlighted red and the charged nitrogens of arginine and lysine are highlighted blue. For a set of representative examples, we demonstrate that YRB highlighting intuitively visualizes segments on protein surfaces that contribute to specificity in protein-protein interfaces, including Hsp90/co-chaperone complexes, the SNARE complex and a transmembrane domain. We provide YRB highlighting in form of a script that runs using the software PyMOL. PMID:26528483

  18. Transmembrane passage of hydrophobic compounds through a protein channel wall.

    PubMed

    Hearn, Elizabeth M; Patel, Dimki R; Lepore, Bryan W; Indic, Mridhu; van den Berg, Bert

    2009-03-19

    Membrane proteins that transport hydrophobic compounds have important roles in multi-drug resistance and can cause a number of diseases, underscoring the importance of protein-mediated transport of hydrophobic compounds. Hydrophobic compounds readily partition into regular membrane lipid bilayers, and their transport through an aqueous protein channel is energetically unfavourable. Alternative transport models involving acquisition from the lipid bilayer by lateral diffusion have been proposed for hydrophobic substrates. So far, all transport proteins for which a lateral diffusion mechanism has been proposed function as efflux pumps. Here we present the first example of a lateral diffusion mechanism for the uptake of hydrophobic substrates by the Escherichia coli outer membrane long-chain fatty acid transporter FadL. A FadL mutant in which a lateral opening in the barrel wall is constricted, but which is otherwise structurally identical to wild-type FadL, does not transport substrates. A crystal structure of FadL from Pseudomonas aeruginosa shows that the opening in the wall of the beta-barrel is conserved and delineates a long, hydrophobic tunnel that could mediate substrate passage from the extracellular environment, through the polar lipopolysaccharide layer and, by means of the lateral opening in the barrel wall, into the lipid bilayer from where the substrate can diffuse into the periplasm. Because FadL homologues are found in pathogenic and biodegrading bacteria, our results have implications for combating bacterial infections and bioremediating xenobiotics in the environment.

  19. Determining protein similarity by comparing hydrophobic core structure.

    PubMed

    Gadzała, M; Kalinowska, B; Banach, M; Konieczny, L; Roterman, I

    2017-02-01

    Formal assessment of structural similarity is - next to protein structure prediction - arguably the most important unsolved problem in proteomics. In this paper we propose a similarity criterion based on commonalities between the proteins' hydrophobic cores. The hydrophobic core emerges as a result of conformational changes through which each residue reaches its intended position in the protein body. A quantitative criterion based on this phenomenon has been proposed in the framework of the CASP challenge. The structure of the hydrophobic core - including the placement and scope of any deviations from the idealized model - may indirectly point to areas of importance from the point of view of the protein's biological function. Our analysis focuses on an arbitrarily selected target from the CASP11 challenge. The proposed measure, while compliant with CASP criteria (70-80% correlation), involves certain adjustments which acknowledge the presence of factors other than simple spatial arrangement of solids.

  20. Use and application of hydrophobic interaction chromatography for protein purification.

    PubMed

    McCue, Justin T

    2014-01-01

    The objective of this section is to provide the reader with guidelines and background on the use and experimental application of Hydrophobic Interaction chromatography (HIC) for the purification of proteins. The section will give step by step instructions on how to use HIC in the laboratory to purify proteins. General guidelines and relevant background information is also provided.

  1. Hydrophobicity of protein surfaces: Separating geometry from chemistry.

    PubMed

    Giovambattista, Nicolas; Lopez, Carlos F; Rossky, Peter J; Debenedetti, Pablo G

    2008-02-19

    To better understand the role of surface chemical heterogeneity in natural nanoscale hydration, we study via molecular dynamics simulation the structure and thermodynamics of water confined between two protein-like surfaces. Each surface is constructed to have interactions with water corresponding to those of the putative hydrophobic surface of a melittin dimer, but is flattened rather than having its native "cupped" configuration. Furthermore, peripheral charged groups are removed. Thus, the role of a rough surface topography is removed, and results can be productively compared with those previously observed for idealized, atomically smooth hydrophilic and hydrophobic flat surfaces. The results indicate that the protein surface is less hydrophobic than the idealized counterpart. The density and compressibility of water adjacent to a melittin dimer is intermediate between that observed adjacent to idealized hydrophobic or hydrophilic surfaces. We find that solvent evacuation of the hydrophobic gap (cavitation) between dimers is observed when the gap has closed to sterically permit a single water layer. This cavitation occurs at smaller pressures and separations than in the case of idealized hydrophobic flat surfaces. The vapor phase between the melittin dimers occupies a much smaller lateral region than in the case of the idealized surfaces; cavitation is localized in a narrow central region between the dimers, where an apolar amino acid is located. When that amino acid is replaced by a polar residue, cavitation is no longer observed.

  2. How protein chemists learned about the hydrophobic factor.

    PubMed Central

    Tanford, C.

    1997-01-01

    It is generally accepted today that the hydrophobic force is the dominant energetic factor that leads to the folding of polypeptide chains into compact globular entities. This principle was first explicitly introduced to protein chemists in 1938 by Irving Langmuir, past master in the application of hydrophobicity to other problems, and was enthusiastically endorsed by J.D. Bernal. But both proposal and endorsement came in the course of a debate about a quite different structural principle, the so-called "cyclol hypothesis" proposed by D. Wrinch, which soon proved to be theoretically and experimentally unsupportable. Being a more tangible idea, directly expressed in structural terms, the cyclol hypothesis received more attention than the hydrophobic principle and the latter never actually entered the mainstream of protein science until 1959, when it was thrust into the limelight in a lucid review by W. Kauzmann. A theoretical paper by H.S. Frank and M. Evans, not itself related to protein folding, probably played a major role in the acceptance of the hydrophobicity concept by protein chemists because it provided a crude but tangible picture of the origin of hydrophobicity per se in terms of water structure. PMID:9194199

  3. Protein folding, stability, and solvation structure in osmolyte solutions hydrophobicity

    NASA Astrophysics Data System (ADS)

    Montgomery Pettitt, B.

    2008-03-01

    The hydrophobic effect between solutes in aqueous solutions plays a central role in our understanding of recognition and folding of proteins and self assembly of lipids. Hydrophobicity induces nonideal solution behavior which plays a role in many aspects of biophysics. Work on the use of small biochemical compounds to crowd protein solutions indicates that a quantitative description of their non-ideal behavior is possible and straightforward. Here, we will show what the structural origin of this non-ideal solution behavior is from expression derived from a semi grand ensemble approach. We discuss the consequences of these findings regarding protein folding stability and solvation in crowded solutions through a structural analysis of the m-value or the change in free energy difference of a macromolecule in solution with respect to the concentration of a third component. This effect has recently been restudied and new mechanisms proposed for its origins in terms of transfer free energies and hydrophobicity.

  4. A computational solution to analyze hydrophobic characteristics in protein chains

    NASA Astrophysics Data System (ADS)

    Soares, Marilia Amável Gomes; Azevedo, Alexandre; Missailidis, Sotiris; Silva, Dilson

    2016-12-01

    This paper presents a program developed to facilitate calculations of the total or partial hidrophobicity value of polypeptides and proteins chains. It was built using the Fortran 77 language and performs additional functions, determining the total free energy and the electromotive force of an amino acid in a protein. These values were then used to estimate the average hydrophobicity of the protein or fragment sequence.

  5. Vector description of electric and hydrophobic interactions in protein homodimers.

    PubMed

    Mozo-Villarías, Angel; Cedano, Juan; Querol, Enrique

    2016-05-01

    This article describes the formation of homodimers from their constituting monomers, based on the rules set by a simple model of electric and hydrophobic interactions. These interactions are described in terms of the electric dipole moment (D) and hydrophobic moment vectors (H) of proteins. The distribution of angles formed by the two dipole moments of monomers constituting dimers were analysed, as well as the distribution of angles formed by the two hydrophobic moments. When these distributions were fitted to Gaussian curves, it was found that for biological dimers, the D vectors tend mostly to adopt a perpendicular arrangement with respect to each other, in which the constituting dipoles have the least interaction. A minor population tends towards an antiparallel arrangement implying maximum electric attraction. Also in biological dimers, the H vectors of most monomers tend to interact in such a way that the total hydrophobic moment of the dimer increases with respect to those of the monomers. This shows that hydrophobic moments have a tendency to align. In dimers originating in the crystallisation process, the distribution of angles formed by both hydrophobic and electric dipole moments appeared rather featureless, probably because of unspecific interactions in the crystallisation processes. The model does not describe direct interactions between H and D vectors although the distribution of angles formed by both vectors in dimers was analysed. It was found that in most cases these angles tended to be either small (both moments aligned parallel to each other) or large (antiparallel disposition).

  6. Structures of multidomain proteins adsorbed on hydrophobic interaction chromatography surfaces.

    PubMed

    Gospodarek, Adrian M; Sun, Weitong; O'Connell, John P; Fernandez, Erik J

    2014-12-05

    In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized.

  7. A comprehensive study to protein retention in hydrophobic interaction chromatography.

    PubMed

    Baca, Martyna; De Vos, Jelle; Bruylants, Gilles; Bartik, Kristin; Liu, Xiaodong; Cook, Ken; Eeltink, Sebastiaan

    2016-10-01

    The effect of different kosmotropic/chaotropic salt systems on retention characteristics of intact proteins has been examined in hydrophobic interaction chromatography (HIC). The performance was assessed using different column chemistries, i.e., polyalkylamide, alkylamine incorporating hydrophobic moieties, and a butyl chemistry. Selectivity in HIC is mainly governed by the salt concentration and by the molal surface tension increment of the salt. Typically, a linear relationship between the natural logarithm of the retention factor and the salt concentration is obtained. Using a 250mm long column packed with 5μm polyalkylamide functionalized silica particles and applying a 30min linear salt gradient, a peak capacity of 78 was achieved, allowing the baseline separation of seven intact proteins. The hydrophobicity index appeared to be a good indicator to predict the elution order of intact proteins in HIC mode. Furthermore, the effect of adding additives in the mobile phase, such as calcium chloride (stabilizing the 3D conformation of α-lactalbumin) and isopropanol, on retention properties has been assessed. Results indicate that HIC retention is also governed by conformational in the proteins which affect the number of accessible hydrophobic moieties.

  8. Marginally hydrophobic transmembrane α-helices shaping membrane protein folding

    PubMed Central

    De Marothy, Minttu T; Elofsson, Arne

    2015-01-01

    Cells have developed an incredible machinery to facilitate the insertion of membrane proteins into the membrane. While we have a fairly good understanding of the mechanism and determinants of membrane integration, more data is needed to understand the insertion of membrane proteins with more complex insertion and folding pathways. This review will focus on marginally hydrophobic transmembrane helices and their influence on membrane protein folding. These weakly hydrophobic transmembrane segments are by themselves not recognized by the translocon and therefore rely on local sequence context for membrane integration. How can such segments reside within the membrane? We will discuss this in the light of features found in the protein itself as well as the environment it resides in. Several characteristics in proteins have been described to influence the insertion of marginally hydrophobic helices. Additionally, the influence of biological membranes is significant. To begin with, the actual cost for having polar groups within the membrane may not be as high as expected; the presence of proteins in the membrane as well as characteristics of some amino acids may enable a transmembrane helix to harbor a charged residue. The lipid environment has also been shown to directly influence the topology as well as membrane boundaries of transmembrane helices—implying a dynamic relationship between membrane proteins and their environment. PMID:25970811

  9. Nanocarriers from GRAS Zein Proteins to Encapsulate Hydrophobic Actives.

    PubMed

    Weissmueller, Nikolas T; Lu, Hoang D; Hurley, Amanda; Prud'homme, Robert K

    2016-11-14

    One factor limiting the expansion of nanomedicines has been the high cost of the materials and processes required for their production. We present a continuous, scalable, low cost nanoencapsulation process, Flash Nanoprecipitation (FNP) that enables the production of nanocarriers (NCs) with a narrow size distribution using zein corn proteins. Zein is a low cost, GRAS protein (having the FDA status of "Generally Regarded as Safe") currently used in food applications, which acts as an effective encapsulant for hydrophobic compounds using FNP. The four-stream FNP configuration allows the encapsulation of very hydrophobic compounds in a way that is not possible with previous precipitation processes. We present the encapsulation of several model active compounds with as high as 45 wt % drug loading with respect to zein concentration into ∼100 nm nanocarriers. Three examples are presented: (1) the pro-drug antioxidant, vitamin E-acetate, (2) an anticholera quorum-sensing modulator CAI-1 ((S)-3-hydroxytridecan-4-one; CAI-1 that reduces Vibrio cholerae virulence by modulating cellular communication), and (3) hydrophobic fluorescent dyes with a range of hydrophobicities. The specific interaction between zein and the milk protein, sodium caseinate, provides stabilization of the NCs in PBS, LB medium, and in pH 2 solutions. The stability and size changes in the three media provide information on the mechanism of assembly of the zein/active/casein NC.

  10. Protein interactions in hydrophobic charge induction chromatography (HCIC).

    PubMed

    Ghose, Sanchayita; Hubbard, Brian; Cramer, Steven M

    2005-01-01

    A quantitative understanding of how proteins interact with hydrophobic charge induction chromatographic resins is provided. Selectivity on this mode of chromatography for monoclonal antibodies as compared to other model proteins is probed by means of a linear retention vs pH plot. The pH-dependent adsorption behavior on this mode of chromatography for a hydrophobic, charged solute is described by taking into account the equilibrium between a hydrophobic, charged solute and an ionizable, heterocyclic ligand. By analogy, an equation that is seen to adequately describe macromolecular retention under linear conditions over a range of pH is developed. A preparative, nonlinear isotherm that can capture both pH and salt concentration dependency for proteins is proposed by using an exponentially modified Langmuir isotherm model. This model is seen to successfully simulate adsorption isotherms for a variety of proteins over a range of pHs and mobile phase salt concentrations. Finally, the widely differing retention characteristics of two monoclonal antibodies are used to derive two different strategies for improving separations on this mode of chromatography. A better understanding of protein binding to this class of resins is seen as an important step to future exploitation of this mode of chromatography for industrial scale purification of proteins.

  11. Identification of hydrophobic proteins as biomarker candidates for colorectal cancer.

    PubMed

    Alvarez-Chaver, Paula; Rodríguez-Piñeiro, Ana M; Rodríguez-Berrocal, Francisco J; Martínez-Zorzano, Vicenta S; Páez de la Cadena, María

    2007-01-01

    Nowadays, colorectal cancer is one of the major causes of cancer death in Western countries. Due to the lack of biomarkers with clinical utility for this pathology, and considering that membrane and hydrophobic proteins have not been studied in depth, we performed a prefractionation of colorectal tissues prior to two-dimensional gel electrophoresis in order to identify hydrophobic proteins differentially expressed in colorectal cancer patients. Fractions enriched in hydrophobic proteins were obtained from healthy mucosa and tumor tissue by a specific extraction method based on temperature-dependent phase partitioning with Triton X-114. Proteins were separated by two-dimensional gel electrophoresis and gels were silver-stained, scanned and compared using the PDQuest software. Those spots presenting significantly different abundance were submitted to mass spectrometry for protein identification. Alterations in the expression of cytoskeletal proteins, including a decrease of vimentin and the absence of desmin, were found. We also detected alterations in antioxidant and transport proteins, chaperones, and in two isoforms of the calcium-binding protein S100A6. On the other hand, vimentin was chosen to corroborate the electrophoretic results by specific immunodetection. Most of the altered proteins have been related to cellular membranes, many of them to lipid rafts microdomains in the plasma membrane, and they have also been implicated in the control of cell proliferation, apoptosis, or metastasis. In conclusion, all the proteins found altered in colorectal tumor samples could be considered as candidates for future studies focused on their utility as markers for colorectal diagnosis and prognosis, or as targets for colorectal cancer therapy.

  12. Urea impedes the hydrophobic collapse of partially unfolded proteins.

    PubMed

    Stumpe, Martin C; Grubmüller, Helmut

    2009-05-06

    Proteins are denatured in aqueous urea solution. The nature of the molecular driving forces has received substantial attention in the past, whereas the question how urea acts at different phases of unfolding is not yet well understood at the atomic level. In particular, it is unclear whether urea actively attacks folded proteins or instead stabilizes unfolded conformations. Here we investigated the effect of urea at different phases of unfolding by molecular dynamics simulations, and the behavior of partially unfolded states in both aqueous urea solution and in pure water was compared. Whereas the partially unfolded protein in water exhibited hydrophobic collapses as primary refolding events, it remained stable or even underwent further unfolding steps in aqueous urea solution. Further, initial unfolding steps of the folded protein were found not to be triggered by urea, but instead, stabilized. The underlying mechanism of this stabilization is a favorable interaction of urea with transiently exposed, less-polar residues and the protein backbone, thereby impeding back-reactions. Taken together, these results suggest that, quite generally, urea-induced protein unfolding proceeds primarily not by active attack. Rather, thermal fluctuations toward the unfolded state are stabilized and the hydrophobic collapse of partially unfolded proteins toward the native state is impeded. As a result, the equilibrium is shifted toward the unfolded state.

  13. Iterative Assembly of Helical Proteins by Optimal Hydrophobic Packing

    PubMed Central

    Wu, G. Albert; Coutsias, Evangelos A.; Dill, Ken A.

    2008-01-01

    SUMMARY We present a method for the computer-based iterative assembly of native-like tertiary structures of helical proteins from alpha-helical fragments. For any pair of helices, our method, called MATCHSTIX, first generates an ensemble of possible relative orientations of the helices with various ways to form hydrophobic contacts between them. Those conformations having steric clashes, or a large radius of gyration of hydrophobic residues, or with helices too far separated to be connected by the intervening linking region, are discarded. Then, we attempt to connect the two helical fragments by using a robotics-based loop-closure algorithm. When loop closure is feasible, the algorithm generates an ensemble of viable interconnecting loops. After energy minimization and clustering, we use a representative set of conformations for further assembly with the remaining helices, adding one helix at a time. To efficiently sample the conformational space, the order of assembly generally proceeds from the pair of helices connected by the shortest loop, followed by joining one of its adjacent helices, always proceeding with the shorter connecting loop. We tested MATCHSTIX on 28 helical proteins each containing up to 5 helices and found it to heavily sample native-like conformations. The average RMSD of the best conformations for the 17 helix-bundle proteins that have 2 or 3 helices is less than 2 Å; errors increase somewhat for proteins containing more helices. Native-like states are even more densely sampled when disulfide bonds are known and imposed as restraints. We conclude that, at least for helical proteins, if the secondary structures are known, this rapid rigid-body maximization of hydrophobic interactions can lead to small ensembles of highly native-like structures. It may be useful for protein structure prediction. PMID:18682227

  14. Solvent and temperature effects on crambin, a hydrophobic protein

    SciTech Connect

    Llinas, M.; Lecomte, J.T.J.; De Marco, A.

    1980-10-01

    Crambin, a 5000-mol. wt. water-insoluble protein found in crambe abyssinica seeds is presently being studied by x-ray diffraction to 0.9 A resolution and /sup 1/H-nuclear magnetic resonance (NMR) spectroscopy. Preliminary /sup 1/H-NMR data at 250 and 600 MHz have suggested that this hydrophobic protein retains a similar globular conformation in both glacial acetic acid (AA), a Bronsted acid, and dimethylformamide (DMF), a Lewis base. These observations suggest that the globular conformation observed in these organic solvents is most likely the native structure present in the crystalline state. As suggested by the high intrinsic resolution of the crystallographic x-ray diffraction pattern, and demonstrated by the NMR data, crambin is a very rigid protein. Work is in progress to assign the /sup 1/H-resonances and to correlate H and /sup 13/C NMR dynamic data with the crystallographic model. It is hoped that unravelling conformational features of this hydrophobic protein will provide clues to help us understand other membrane-bound functional proteins.

  15. Protein-spanning water networks and implications for prediction of protein-protein interactions mediated through hydrophobic effects.

    PubMed

    Cui, Di; Ou, Shuching; Patel, Sandeep

    2014-12-01

    Hydrophobic effects, often conflated with hydrophobic forces, are implicated as major determinants in biological association and self-assembly processes. Protein-protein interactions involved in signaling pathways in living systems are a prime example where hydrophobic effects have profound implications. In the context of protein-protein interactions, a priori knowledge of relevant binding interfaces (i.e., clusters of residues involved directly with binding interactions) is difficult. In the case of hydrophobically mediated interactions, use of hydropathy-based methods relying on single residue hydrophobicity properties are routinely and widely used to predict propensities for such residues to be present in hydrophobic interfaces. However, recent studies suggest that consideration of hydrophobicity for single residues on a protein surface require accounting of the local environment dictated by neighboring residues and local water. In this study, we use a method derived from percolation theory to evaluate spanning water networks in the first hydration shells of a series of small proteins. We use residue-based water density and single-linkage clustering methods to predict hydrophobic regions of proteins; these regions are putatively involved in binding interactions. We find that this simple method is able to predict with sufficient accuracy and coverage the binding interface residues of a series of proteins. The approach is competitive with automated servers. The results of this study highlight the importance of accounting of local environment in determining the hydrophobic nature of individual residues on protein surfaces.

  16. Neutron structure of the hydrophobic plant protein crambin

    SciTech Connect

    Teeter, M.M.; Kossiakoff, A.A.

    1982-01-01

    Crystals of the small hydrophobic protein crambin have been shown to diffract to a resolution of at least 0.88 A. This means that crambin presents a rare opportunity to study a protein structure at virtually atomic resolution. The high resolution of the diffraction pattern coupled with the assets of neutron diffraction present the distinct possibility that crambin's analysis may surpass that of any other protein system in degree and accuracy of detail. The neutron crambin structure is currently being refined at 1.50 A (44.9% of the data to 1.2 A has also been included). It is expected that a nominal resolution of 1.0 A can be achieved. 15 references, 6 figures, 2 tables.

  17. What makes a protein a protein? Hydrophobic core designs that specify stability and structural properties.

    PubMed Central

    Munson, M.; Balasubramanian, S.; Fleming, K. G.; Nagi, A. D.; O'Brien, R.; Sturtevant, J. M.; Regan, L.

    1996-01-01

    Here we describe how the systematic redesign of a protein's hydrophobic core alters its structure and stability. We have repacked the hydrophobic core of the four-helix-bundle protein, Rop, with altered packing patterns and various side chain shapes and sizes. Several designs reproduce the structure and native-like properties of the wild-type, while increasing the thermal stability. Other designs, either with similar sizes but different shapes, or with decreased sizes of the packing residues, destabilize the protein. Finally, overpacking the core with the larger side chains causes a loss of native-like structure. These results allow us to further define the roles of tight residue packing and the burial of hydrophobic surface area in the construction of native-like proteins. PMID:8844848

  18. Protein patterning on silicon-based surface using background hydrophobic thin film.

    PubMed

    Lee, Chang-Soo; Lee, Sang-Ho; Park, Sung-Soo; Kim, Yong-Kweon; Kim, Byung-Gee

    2003-04-01

    A new and convenient protein patterning method on silicon-based surface was developed for protein array by spin coating of hydrophobic thin film (CYTOP). Photolithographic lift-off process was used to display two-dimensional patterns of spatially hydrophilic region. The background hydrophobic thin film was used to suppress nonspecific protein binding, and the hydrophilic target protein binding region was chemically modified to introduce aldehyde group after removal of the photoresist layer. The difference in surface energy between the hydrophilic pattern and background hydrophobic film would induce easier covalent binding of proteins onto defined hydrophilic areas having physical and chemical constraints. Below 1 microg/ml of total protein concentration, the CYTOP hydrophobic film effectively suppressed nonspecific binding of the protein. During the process of protein patterning, inherent property of the hydrophobic thin film was not changed judging from static and dynamic contact angle survey. Quantitative analysis of the protein binding was demonstrated by streptavidin-biotin system.

  19. A conserved patch of hydrophobic amino acids modulates Myb activity by mediating protein-protein interactions.

    PubMed

    Dukare, Sandeep; Klempnauer, Karl-Heinz

    2016-07-01

    The transcription factor c-Myb plays a key role in the control of proliferation and differentiation in hematopoietic progenitor cells and has been implicated in the development of leukemia and certain non-hematopoietic tumors. c-Myb activity is highly dependent on the interaction with the coactivator p300 which is mediated by the transactivation domain of c-Myb and the KIX domain of p300. We have previously observed that conservative valine-to-isoleucine amino acid substitutions in a conserved stretch of hydrophobic amino acids have a profound effect on Myb activity. Here, we have explored the function of the hydrophobic region as a mediator of protein-protein interactions. We show that the hydrophobic region facilitates Myb self-interaction and binding of the histone acetyl transferase Tip60, a previously identified Myb interacting protein. We show that these interactions are affected by the valine-to-isoleucine amino acid substitutions and suppress Myb activity by interfering with the interaction of Myb and the KIX domain of p300. Taken together, our work identifies the hydrophobic region in the Myb transactivation domain as a binding site for homo- and heteromeric protein interactions and leads to a picture of the c-Myb transactivation domain as a composite protein binding region that facilitates interdependent protein-protein interactions of Myb with regulatory proteins.

  20. Hydrophobic environment is a key factor for the stability of thermophilic proteins.

    PubMed

    Gromiha, M Michael; Pathak, Manish C; Saraboji, Kadhirvel; Ortlund, Eric A; Gaucher, Eric A

    2013-04-01

    The stability of thermophilic proteins has been viewed from different perspectives and there is yet no unified principle to understand this stability. It would be valuable to reveal the most important interactions for designing thermostable proteins for such applications as industrial protein engineering. In this work, we have systematically analyzed the importance of various interactions by computing different parameters such as surrounding hydrophobicity, inter-residue interactions, ion-pairs and hydrogen bonds. The importance of each interaction has been determined by its predicted relative contribution in thermophiles versus the same contribution in mesophilic homologues based on a dataset of 373 protein families. We predict that hydrophobic environment is the major factor for the stability of thermophilic proteins and found that 80% of thermophilic proteins analyzed showed higher hydrophobicity than their mesophilic counterparts. Ion pairs, hydrogen bonds, and interaction energy are also important and favored in 68%, 50%, and 62% of thermophilic proteins, respectively. Interestingly, thermophilic proteins with decreased hydrophobic environments display a greater number of hydrogen bonds and/or ion pairs. The systematic elimination of mesophilic proteins based on surrounding hydrophobicity, interaction energy, and ion pairs/hydrogen bonds, led to correctly identifying 95% of the thermophilic proteins in our analyses. Our analysis was also applied to another, more refined set of 102 thermophilic-mesophilic pairs, which again identified hydrophobicity as a dominant property in 71% of the thermophilic proteins. Further, the notion of surrounding hydrophobicity, which characterizes the hydrophobic behavior of residues in a protein environment, has been applied to the three-dimensional structures of elongation factor-Tu proteins and we found that the thermophilic proteins are enriched with a hydrophobic environment. The results obtained in this work highlight the

  1. Energetics of Intermolecular Hydrogen Bonds in a Hydrophobic Protein Cavity

    NASA Astrophysics Data System (ADS)

    Liu, Lan; Baergen, Alyson; Michelsen, Klaus; Kitova, Elena N.; Schnier, Paul D.; Klassen, John S.

    2014-05-01

    This work explores the energetics of intermolecular H-bonds inside a hydrophobic protein cavity. Kinetic measurements were performed on the gaseous deprotonated ions (at the -7 charge state) of complexes of bovine β-lactoglobulin (Lg) and three monohydroxylated analogs of palmitic acid (PA): 3-hydroxypalmitic acid (3-OHPA), 7-hydroxypalmitic acid (7-OHPA), and 16-hydroxypalmitic acid (16-OHPA). From the increase in the activation energy for the dissociation of the (Lg + X-OHPA)7- ions, compared with that of the (Lg + PA)7- ion, it is concluded that the -OH groups of the X-OHPA ligands participate in strong (5 - 11 kcal mol-1) intermolecular H-bonds in the hydrophobic cavity of Lg. The results of molecular dynamics (MD) simulations suggest that the -OH groups of 3-OHPA and 16-OHPA act as H-bond donors and interact with backbone carbonyl oxygens, whereas the -OH group of 7-OHPA acts as both H-bond donor and acceptor with nearby side chains. The capacity for intermolecular H-bonds within the Lg cavity, as suggested by the gas-phase measurements, does not necessarily lead to enhanced binding in aqueous solution. The association constant (Ka) measured for 7-OHPA [(2.3 ± 0.2) × 105 M-1] is similar to the value for the PA [(3.8 ± 0.1) × 105 M-1]; Ka for 3-OHPA [(1.1 ± 0.3) × 106 M-1] is approximately three-times larger, whereas Ka for 16-OHPA [(2.3 ± 0.2) × 104 M-1] is an order of magnitude smaller. Taken together, the results of this study suggest that the energetic penalty to desolvating the ligand -OH groups, which is necessary for complex formation, is similar in magnitude to the energetic contribution of the intermolecular H-bonds.

  2. Effects of the protein denaturant guanidinium chloride on aqueous hydrophobic contact-pair interactions.

    PubMed

    Macdonald, Ryan D; Khajehpour, Mazdak

    2015-01-01

    Guanidinium chloride (GdmCl) is one of the most common protein denaturants. Although GdmCl is well known in the field of protein folding, the mechanism by which it denatures proteins is not well understood. In fact, there are few studies looking at its effects on hydrophobic interactions. In this work the effect of GdmCl on hydrophobic interactions has been studied by observing how the denaturant influences model systems of phenyl and alkyl hydrophobic contact pairs. Contact pair formation is monitored through the use of fluorescence spectroscopy, i.e., measuring the intrinsic phenol fluorescence being quenched by carboxylate ions. Hydrophobic interactions are isolated from other interactions through a previously developed methodology. The results show that GdmCl does not significantly affect hydrophobic interactions between small moieties such as methyl groups and phenol; while on the other hand, the interaction of larger hydrophobes such as hexyl and heptyl groups with phenol is significantly destabilized.

  3. A simple atomic-level hydrophobicity scale reveals protein interfacial structure.

    PubMed

    Kapcha, Lauren H; Rossky, Peter J

    2014-01-23

    Many amino acid residue hydrophobicity scales have been created in an effort to better understand and rapidly characterize water-protein interactions based only on protein structure and sequence. There is surprisingly low consistency in the ranking of residue hydrophobicity between scales, and their ability to provide insightful characterization varies substantially across subject proteins. All current scales characterize hydrophobicity based on entire amino acid residue units. We introduce a simple binary but atomic-level hydrophobicity scale that allows for the classification of polar and non-polar moieties within single residues, including backbone atoms. This simple scale is first shown to capture the anticipated hydrophobic character for those whole residues that align in classification among most scales. Examination of a set of protein binding interfaces establishes good agreement between residue-based and atomic-level descriptions of hydrophobicity for five residues, while the remaining residues produce discrepancies. We then show that the atomistic scale properly classifies the hydrophobicity of functionally important regions where residue-based scales fail. To illustrate the utility of the new approach, we show that the atomic-level scale rationalizes the hydration of two hydrophobic pockets and the presence of a void in a third pocket within a single protein and that it appropriately classifies all of the functionally important hydrophilic sites within two otherwise hydrophobic pores. We suggest that an atomic level of detail is, in general, necessary for the reliable depiction of hydrophobicity for all protein surfaces. The present formulation can be implemented simply in a manner no more complex than current residue-based approaches.

  4. Production of hydrophobic amino acids from biobased resources: wheat gluten and rubber seed proteins.

    PubMed

    Widyarani; Sari, Yessie W; Ratnaningsih, Enny; Sanders, Johan P M; Bruins, Marieke E

    2016-09-01

    Protein hydrolysis enables production of peptides and free amino acids that are suitable for usage in food and feed or can be used as precursors for bulk chemicals. Several essential amino acids for food and feed have hydrophobic side chains; this property may also be exploited for subsequent separation. Here, we present methods for selective production of hydrophobic amino acids from proteins. Selectivity can be achieved by selection of starting material, selection of hydrolysis conditions, and separation of achieved hydrolysate. Several protease combinations were applied for hydrolysis of rubber seed protein concentrate, wheat gluten, and bovine serum albumin (BSA). High degree of hydrolysis (>50 %) could be achieved. Hydrophobic selectivity was influenced by the combination of proteases and by the extent of hydrolysis. Combination of Pronase and Peptidase R showed the highest selectivity towards hydrophobic amino acids, roughly doubling the content of hydrophobic amino acids in the products compared to the original substrates. Hydrophobic selectivity of 0.6 mol-hydrophobic/mol-total free amino acids was observed after 6 h hydrolysis of wheat gluten and 24 h hydrolysis of rubber seed proteins and BSA. The results of experiments with rubber seed proteins and wheat gluten suggest that this process can be applied to agro-industrial residues.

  5. Heating and reduction affect the reaction with tannins of wine protein fractions differing in hydrophobicity.

    PubMed

    Marangon, Matteo; Vincenzi, Simone; Lucchetta, Marco; Curioni, Andrea

    2010-02-15

    During the storage, bottled white wines can manifest haziness due to the insolubilisation of the grape proteins that may 'survive' in the fermentation process. Although the exact mechanism of this occurrence is not fully understood, proteins and tannins are considered two of the key factors involved in wine hazing, since their aggregation leads to the formation of insoluble particles. To better understand this complex interaction, proteins and tannins from the same unfined Pinot grigio wine were separated. Wine proteins were then fractionated by hydrophobic interaction chromatography (HIC). A significant correlation between hydrophobicity of the wine protein fractions and the haze formed after reacting with wine tannins was found, with the most reactive fractions revealing (by SDS-PAGE and RP-HPLC analyses) the predominant presence of thaumatin-like proteins. Moreover, the effects of both protein heating and disulfide bonds reduction (with dithiotreithol) on haze formation in the presence of tannins were assessed. These treatments generally resulted in an improved reactivity with tannins, and this phenomenon was related to both the surface hydrophobicity and composition of the protein fractions. Therefore, haze formation in wines seems to be related to hydrophobic interactions occurring among proteins and tannins. These interactions should occur on hydrophobic tannin-binding sites, whose exposition on the proteins can depend on both protein heating and reduction.

  6. Globular-disorder transition in proteins: a compromise between hydrophobic and electrostatic interactions?

    PubMed

    Baruah, Anupaul; Biswas, Parbati

    2016-08-17

    The charge-hydrophobicity correlation of globular and disordered proteins is explored using a generalized self-consistent field theoretical method combined with Monte Carlo simulations. Globular and disordered protein sequences with varied mean net charge and mean hydrophobicity are designed by theory, while Metropolis Monte Carlo generates a suitable ensemble of conformations. Results imply a transition of the dominant interactions between globular and disordered proteins across the charge-hydrophobicity boundary. It is observed that the charge-hydrophobicity boundary actually represents a trade-off between the repulsive and attractive interactions in a protein sequence. The attractive interactions predominate on the globular side of the boundary, while the repulsive interactions prevail on the disordered side. For globular proteins, core forming hydrophobic interactions are dominant leading to a minimally frustrated native conformation. For disordered proteins, the repulsive electrostatic interactions prevail yielding a minimally frustrated region comprising of an expanded, dynamic conformational ensemble. Thus, protein disorder, like protein folding, satisfies the principle of minimal frustration. All results are compared to real globular and disordered proteins. Thus this algorithm may be useful to probe the conformational characteristics of disordered proteins.

  7. Protein adsorption to hydrophobic Zeolite Y: salt effects and application to protein fractionation.

    PubMed

    Ghose, S; Mattiasson, B

    1993-12-01

    The binding equilibria of proteins with a hydrophobic variety of crystalline Zeolite Y is affected by salt and is a function of the type of salt and its concentration. The behaviour does not always follow the conventional pattern of increased binding at high salt concentrations and varies also for the different proteins involved. The overall process may be looked upon as a salting-in/salting-out mechanism. This material can be used as a surface for the selective adsorption of proteins and has been applied for the fractionation of ox heart homogenate in multi-stage operations. The presence of NaCl influences the protein binding, and this can be seen by monitoring the activity profile of lactate dehydrogenase. The bound protein can be reversed by treating the equilibrium mixture with low-molecular-mass poly(ethylene glycol)s.

  8. Protein adsorption onto polyelectrolyte layers: effects of protein hydrophobicity and charge anisotropy.

    PubMed

    Silva, Rubens A; Urzúa, Marcela D; Petri, Denise F S; Dubin, Paul L

    2010-09-07

    Ellipsometry was used to investigate the influence of ionic strength (I) and pH on the adsorption of bovine serum albumin (BSA) or beta-lactoglobulin (BLG) onto preabsorbed layers of two polycations: poly(diallyldimethylammonium chloride) (PDADMAC) or poly(4-vinylpyridine bromide) quaternized with linear aliphatic chains of two (QPVP-C2) or five (QPVP-C5) carbons. Comparisons among results for the three polycations reveal hydrophobic interactions, while comparisons between BSA and BLG-proteins of very similar isoelectric points (pI)-indicate the importance of protein charge anisotropy. At pH close to pI, the ionic strength dependence of the adsorbed amount of protein (Gamma) displayed maxima in the range 10 < I < 25 mM corresponding to Debye lengths close to the protein radii. Visualization of protein charge by Delphi suggested that these ionic strength conditions corresponded to suppression of long-range repulsion between polycations and protein positive domains, without diminution of short-range attraction between polycation segments and locally negative protein domains, in a manner similar to the behavior of PE-protein complexes in solution. (1-4) This description was consistent with the disappearance of the maxima at pH either above or below pI. In the former case, Gamma values decrease exponentially with I(1/2), due to screening of attractions, while in the latter case adsorption of both proteins decreased at low I due to strong repulsion. Close to or below pI both proteins adsorbed more strongly onto QPVP-C5 than onto QPVP-C2 or PDADMAC due to hydrophobic interactions with the longer alkyl group. Above pI, the adsorption was more pronounced with PDADMAC because these chains may assume more loosely bound layers due to lower linear charge density.

  9. Infrared spectral marker bands characterizing a transient water wire inside a hydrophobic membrane protein

    SciTech Connect

    Wolf, Steffen; Gerwert, Klaus; Freier, Erik; Cui, Qiang

    2014-12-14

    Proton conduction along protein-bound “water wires” is an essential feature in membrane proteins. Here, we analyze in detail a transient water wire, which conducts protons via a hydrophobic barrier within a membrane protein to create a proton gradient. It is formed only for a millisecond out of three water molecules distributed at inactive positions in a polar environment in the ground state. The movement into a hydrophobic environment causes characteristic shifts of the water bands reflecting their different chemical properties. These band shifts are identified by time-resolved Fourier Transform Infrared difference spectroscopy and analyzed by biomolecular Quantum Mechanical/Molecular Mechanical simulations. A non-hydrogen bonded (“dangling”) O–H stretching vibration band and a broad continuum absorbance caused by a combined vibration along the water wire are identified as characteristic marker bands of such water wires in a hydrophobic environment. The results provide a basic understanding of water wires in hydrophobic environments.

  10. The Hydrophobic Temperature Dependence of Amino Acids Directly Calculated from Protein Structures

    PubMed Central

    van Dijk, Erik; Hoogeveen, Arlo; Abeln, Sanne

    2015-01-01

    The hydrophobic effect is the main driving force in protein folding. One can estimate the relative strength of this hydrophobic effect for each amino acid by mining a large set of experimentally determined protein structures. However, the hydrophobic force is known to be strongly temperature dependent. This temperature dependence is thought to explain the denaturation of proteins at low temperatures. Here we investigate if it is possible to extract this temperature dependence directly from a large set of protein structures determined at different temperatures. Using NMR structures filtered for sequence identity, we were able to extract hydrophobicity propensities for all amino acids at five different temperature ranges (spanning 265-340 K). These propensities show that the hydrophobicity becomes weaker at lower temperatures, in line with current theory. Alternatively, one can conclude that the temperature dependence of the hydrophobic effect has a measurable influence on protein structures. Moreover, this work provides a method for probing the individual temperature dependence of the different amino acid types, which is difficult to obtain by direct experiment. PMID:26000449

  11. Topology and cellular localization of the small hydrophobic protein of avian metapneumovirus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The small hydrophobic protein (SH) is a type II integral membrane protein that is packaged into virions and is only present in certain paramyxoviruses including metapneumovirus. In addition to a highly divergent primary sequence, SH proteins vary significantly in size among the different viruses. Hu...

  12. Hydrophobic interaction chromatography of proteins. IV. Protein adsorption capacity and transport in preparative mode.

    PubMed

    To, Brian C S; Lenhoff, Abraham M

    2011-01-21

    The adsorption isotherms of four model proteins (lysozyme, α-lactalbumin, ovalbumin, and BSA) on eight commercial phenyl hydrophobic interaction chromatography media were measured. The isotherms were softer than those usually seen in ion-exchange chromatography of proteins, and the static capacities of the media were lower, ranging from 30 to 110 mg/mL, depending on the ammonium sulfate concentration and the protein and adsorbent types. The protein-accessible surface area appears to be the main factor determining the binding capacity, and little correlation was seen with the protein affinities of the adsorbents. Breakthrough experiments showed that the dynamic capacities of the adsorbents at 10% breakthrough were 20-80% of the static capacities, depending on adsorbent type. Protein diffusivities in the adsorbents were estimated from batch uptake experiments using the pore diffusion and homogeneous diffusion models. Protein transport was affected by the adsorbent pore structures. Apparent diffusivities were higher at lower salt concentrations and column loadings, suggesting that adsorbed proteins may retard intraparticle protein transport. The diffusivities estimated from the batch uptake experiments were used to predict column breakthrough behavior. Analytical solutions developed for ion-exchange systems were able to provide accurate predictions for lysozyme breakthrough but not for ovalbumin. Impurities in the ovalbumin solutions used for the breakthrough experiments may have affected the ovalbumin uptake and led to the discrepancies between the predictions and the experimental results.

  13. Canine Distemper Virus Envelope Protein Interactions Modulated by Hydrophobic Residues in the Fusion Protein Globular Head

    PubMed Central

    Avila, Mislay; Khosravi, Mojtaba; Alves, Lisa; Ader-Ebert, Nadine; Bringolf, Fanny; Zurbriggen, Andreas; Plemper, Richard K.

    2014-01-01

    Membrane fusion for morbillivirus cell entry relies on critical interactions between the viral fusion (F) and attachment (H) envelope glycoproteins. Through extensive mutagenesis of an F cavity recently proposed to contribute to F's interaction with the H protein, we identified two neighboring hydrophobic residues responsible for severe F-to-H binding and fusion-triggering deficiencies when they were mutated in combination. Since both residues reside on one side of the F cavity, the data suggest that H binds the F globular head domain sideways. PMID:25355896

  14. Improvement of hydrophobic integral membrane protein identification by mild performic acid oxidation-assisted digestion.

    PubMed

    Cao, Rui; Liu, Yisong; Chen, Ping; Lv, Rong; Song, Qin; Sheng, Tingting; He, Quanyuan; Wang, Yin; Wang, Xianchun; Liang, Songping

    2010-12-15

    Integral membrane proteins (IMPs) are critical for the maintenance of biological systems and represent important targets for the treatment of disease. The hydrophobicity and low abundance of IMPs make them difficult to analyze. In proteomic analyses, hydrophobic peptides including transmembrane domains are often underrepresented, and this reduces the sequence coverage and reliability of the identified IMPs. Here we report a new strategy, mild performic acid oxidation treatment (mPAOT), for improvement of IMP identification. In the mPAOT strategy, the hydrophobicity of IMPs is significantly decreased by oxidizing their methionine and cysteine residues with performic acid, thereby improving the solubility and enzymolysis of these proteins. The application of the mPAOT strategy to the analysis of IMPs from human nasopharyngeal carcinoma CNE1 cell line demonstrated that many IMPs, including those with high hydrophobicity, could be reliably identified.

  15. Predicting the behaviour of proteins in hydrophobic interaction chromatography. 1: Using the hydrophobic imbalance (HI) to describe their surface amino acid distribution.

    PubMed

    Salgado, J Cristian; Rapaport, Ivan; Asenjo, Juan A

    2006-02-24

    This paper focuses on the prediction of the dimensionless retention time of proteins (DRT) in hydrophobic interaction chromatography (HIC) by means of mathematical models based on characteristics of the surface hydrophobicity distribution. We introduce a new parameter, called hydrophobic imbalance (HI), obtained from the three-dimensional structure of proteins. This parameter quantifies the displacement of the superficial geometric centre of the protein when the effect of the hydrophobicity of each amino acid is considered. This parameter is simpler and less expensive than those reported previously. We use HI as a way to incorporate information about the surface hydrophobicity distribution in order to improve the prediction of DRT. We tested the performance of our DRT predictive models in a set of 15 proteins. This set includes four proteins whose DRTs are known as very difficult to predict. By means of the variable HI, it was possible to improve the predictive characteristics obtained by models based on the average surface hydrophobicity (ASH) by 9.1%. Also, we studied linear multivariable models based on characteristics determined from the HI. By using this multivariable model, a correlation coefficient of 0.899 was obtained. With this model, we managed to improve the predictive characteristics shown by previous models based on ASH by 31.8%.

  16. Non-invasive high throughput approach for protein hydrophobicity determination based on surface tension.

    PubMed

    Amrhein, Sven; Bauer, Katharina Christin; Galm, Lara; Hubbuch, Jürgen

    2015-12-01

    The surface hydrophobicity of a protein is an important factor for its interactions in solution and thus the outcome of its production process. Yet most of the methods are not able to evaluate the influence of these hydrophobic interactions under natural conditions. In the present work we have established a high resolution stalagmometric method for surface tension determination on a liquid handling station, which can cope with accuracy as well as high throughput requirements. Surface tensions could be derived with a low sample consumption (800 μL) and a high reproducibility (<0.1‰ for water) within a reasonable time (3.5 min per sample). This method was used as a non-invasive HTP compatible approach to determine surface tensions of protein solutions dependent on protein content. The protein influence on the solutions' surface tension was correlated to the hydrophobicity of lysozyme, human lysozyme, BSA, and α-lactalbumin. Differences in proteins' hydrophobic character depending on pH and species could be resolved. Within this work we have developed a pH dependent hydrophobicity ranking, which was found to be in good agreement with literature. For the studied pH range of 3-9 lysozyme from chicken egg white was identified to be the most hydrophilic. α-lactalbumin at pH 3 exhibited the most pronounced hydrophobic character. The stalagmometric method occurred to outclass the widely used spectrophotometric method with bromophenol blue sodium salt as it gave reasonable results without restrictions on pH and protein species.

  17. Optimizing the selective recognition of protein isoforms through tuning of nanoparticle hydrophobicity

    NASA Astrophysics Data System (ADS)

    Chen, Kaimin; Rana, Subinoy; Moyano, Daniel F.; Xu, Yisheng; Guo, Xuhong; Rotello, Vincent M.

    2014-05-01

    We demonstrate that ligand hydrophobicity can be used to increase affinity and selectivity of binding between monolayer-protected cationic gold nanoparticles and β-lactoglobulin protein isoforms containing two amino acid mutations.We demonstrate that ligand hydrophobicity can be used to increase affinity and selectivity of binding between monolayer-protected cationic gold nanoparticles and β-lactoglobulin protein isoforms containing two amino acid mutations. Electronic supplementary information (ESI) available: Experimental details, ITC, and DLS analyses. See DOI: 10.1039/c4nr01085j

  18. Fluorescence based assessment of SDS induced hydrophobic collapse in globular proteins

    NASA Astrophysics Data System (ADS)

    Manjunath, S.; Makani, Venkata Krishna Kanth; Satyamoorthy, Kapaettu; Rao, Bola Sadashiva Satish; Bhat, Gopalkrishna; Kanth, Akriti Baby; Mahato, Krishna Kishore

    2016-03-01

    The molecular mechanism of interaction between SDS and proteins is not clearly understood so far. According to the current knowledge SDS is known to interact with the hydrophobic regions of the proteins. Tryptophan and tyrosine are hydrophobic and hydrophilic aromatic amino acids respectively, which are also known for their intrinsic fluorescence nature in proteins. By observing the autofluorescence of both these hydrophobic and hydrophilic amino acids upon SDS treatment, information about SDS-protein interactions could be obtained. In the present study we have recorded the autofluorescence spectra of five globular proteins [Bovine serum albumin (BSA), Human serum albumin (HSA), Ribonuclease A (RNase A), Lysozyme and Trypsin] by the sequential excitation from 260nm to 295nm at every 5nm intervals. The results obtained clearly indicated BSA and HSA undergone hydrophobic collapse around their tryptophan moieties due to the increased folding of their secondary and tertiary structures upon SDS treatment. Trypsin on the other hand showed complete unfolding upon treatment with SDS. Lysozyme and RNase A did not show any difference in their autofluorescence upon SDS treatment may be due to the stability and fluorophores composition in them. The above results obtained with specific UV excitations clearly shown the tertiary folding and ensembles of the secondary and tertiary structures upon SDS treatment is governed by their stability and bonds stabilizing the proteins.

  19. Effect of surface hydrophobicity on the function of the immobilized biomineralization protein Mms6

    SciTech Connect

    Liu, Xunpei; Zhang, Honghu; Nayak, Srikanth; Parada, German; Anderegg, James; Feng, Shuren; Nilsen-Hamilton, Marit; Akinc, Mufit; Mallapragada, Surya K.

    2015-08-13

    Magnetotactic bacteria produce magnetic nanocrystals with uniform shapes and sizes in nature, which has inspired in vitro synthesis of uniformly sized magnetite nanocrystals under mild conditions. Mms6, a biomineralization protein from magnetotactic bacteria with a hydrophobic N-terminal domain and a hydrophilic C-terminal domain, can promote formation of magnetite nanocrystals in vitro with well-defined shape and size in gels under mild conditions. Here we investigate the role of surface hydrophobicity on the ability of Mms6 to template magnetite nanoparticle formation on surfaces. Our results confirmed that Mms6 can form a protein network structure on a monolayer of hydrophobic octadecanethiol (ODT)-coated gold surfaces and facilitate magnetite nanocrystal formation with uniform sizes close to those seen in nature, in contrast to its behavior on more hydrophilic surfaces. We propose that this hydrophobicity effect might be due to the amphiphilic nature of the Mms6 protein and its tendency to incorporate the hydrophobic N-terminal domain into the hydrophobic lipid bilayer environment of the magnetosome membrane, exposing the hydrophilic C-terminal domain that promotes biomineralization. Supporting this hypothesis, the larger and well-formed magnetite nanoparticles were found to be preferentially located on ODT surfaces covered with Mms6 as compared to control samples, as characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy studies. A C-terminal domain mutant of this protein did not form the same network structure as wild-type Mms6, suggesting that the network structure is important for the magnetite nanocrystal formation. This article provides valuable insights into the role of surface hydrophilicity on the action of the biomineralization protein Mms6 to synthesize magnetic nanocrystals and provides a facile route to controlling bioinspired nanocrystal synthesis in vitro.

  20. Effect of surface hydrophobicity on the function of the immobilized biomineralization protein Mms6

    DOE PAGES

    Liu, Xunpei; Zhang, Honghu; Nayak, Srikanth; ...

    2015-08-13

    Magnetotactic bacteria produce magnetic nanocrystals with uniform shapes and sizes in nature, which has inspired in vitro synthesis of uniformly sized magnetite nanocrystals under mild conditions. Mms6, a biomineralization protein from magnetotactic bacteria with a hydrophobic N-terminal domain and a hydrophilic C-terminal domain, can promote formation of magnetite nanocrystals in vitro with well-defined shape and size in gels under mild conditions. Here we investigate the role of surface hydrophobicity on the ability of Mms6 to template magnetite nanoparticle formation on surfaces. Our results confirmed that Mms6 can form a protein network structure on a monolayer of hydrophobic octadecanethiol (ODT)-coated goldmore » surfaces and facilitate magnetite nanocrystal formation with uniform sizes close to those seen in nature, in contrast to its behavior on more hydrophilic surfaces. We propose that this hydrophobicity effect might be due to the amphiphilic nature of the Mms6 protein and its tendency to incorporate the hydrophobic N-terminal domain into the hydrophobic lipid bilayer environment of the magnetosome membrane, exposing the hydrophilic C-terminal domain that promotes biomineralization. Supporting this hypothesis, the larger and well-formed magnetite nanoparticles were found to be preferentially located on ODT surfaces covered with Mms6 as compared to control samples, as characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy studies. A C-terminal domain mutant of this protein did not form the same network structure as wild-type Mms6, suggesting that the network structure is important for the magnetite nanocrystal formation. This article provides valuable insights into the role of surface hydrophilicity on the action of the biomineralization protein Mms6 to synthesize magnetic nanocrystals and provides a facile route to controlling bioinspired nanocrystal synthesis in vitro.« less

  1. [Wound dressings].

    PubMed

    Breuninger, H

    1988-01-01

    The wide variety of dermatologic surgical procedures has resulted in a corresponding choice of wound dressings. Considering the chemical and physical properties as well as the function of the dressings, standardized dressing techniques can be performed with relatively few materials. This saves both time and money.

  2. Predicting the orientation of protein G B1 on hydrophobic surfaces using Monte Carlo simulations

    PubMed Central

    Harrison, Elisa T.; Weidner, Tobias; Castner, David G.; Interlandi, Gianluca

    2016-01-01

    A Monte Carlo algorithm was developed to predict the most likely orientations of protein G B1, an immunoglobulin G (IgG) antibody-binding domain of protein G, adsorbed onto a hydrophobic surface. At each Monte Carlo step, the protein was rotated and translated as a rigid body. The assumption about rigidity was supported by quartz crystal microbalance with dissipation monitoring experiments, which indicated that protein G B1 adsorbed on a polystyrene surface with its native structure conserved and showed that its IgG antibody-binding activity was retained. The Monte Carlo simulations predicted that protein G B1 is likely adsorbed onto a hydrophobic surface in two different orientations, characterized as two mutually exclusive sets of amino acids contacting the surface. This was consistent with sum frequency generation (SFG) vibrational spectroscopy results. In fact, theoretical SFG spectra calculated from an equal combination of the two predicted orientations exhibited reasonable agreement with measured spectra of protein G B1 on polystyrene surfaces. Also, in explicit solvent molecular dynamics simulations, protein G B1 maintained its predicted orientation in three out of four runs. This work shows that using a Monte Carlo approach can provide an accurate estimate of a protein orientation on a hydrophobic surface, which complements experimental surface analysis techniques and provides an initial system to study the interaction between a protein and a surface in molecular dynamics simulations. PMID:27923271

  3. Whey protein coating efficiency on surfactant-modified hydrophobic surfaces.

    PubMed

    Lin, Shih-Yu D; Krochta, John M

    2005-06-15

    Whey protein oxygen-barrier coatings on peanuts are not effective, due to incomplete peanut-surface coverage, as well as some cracking and flaking of the coating. Addition of sorbitan laurate (Span 20) in the whey protein coating solution up to the critical micelle concentration (cmc) of 0.05% (w/w) significantly improved coating coverage to 88% of the peanut surface. Increasing the Span 20 concentration in the coating solution to 3 times the cmc (0.15% w/w) produced a substantial increase in peanut surface energy (>70 dyn/cm), indicating adsorption of the surfactant to the peanut surface. With this level of Span 20, the whey protein coating coverage on peanuts increased to 95%. These results suggest that a concentration of surfactant above the cmc in the coating solution is required for formation of self-assembled structures of surfactant molecules on peanut surfaces, which significantly increases the hydrophilicity, and thus coatability, of peanut surfaces.

  4. Structural Reorganization Triggered by Charging of Lys Residues in the Hydrophobic Interior of a Protein

    SciTech Connect

    Chimenti M. S.; Heroux A.; Khangulov, V. S.; Robinson, A. C.; Majumdar, A.; Schlessman, J. L.; Garcia-Moreno, B.

    2012-06-06

    Structural consequences of ionization of residues buried in the hydrophobic interior of proteins were examined systematically in 25 proteins with internal Lys residues. Crystal structures showed that the ionizable groups are buried. NMR spectroscopy showed that in 2 of 25 cases studied, the ionization of an internal Lys unfolded the protein globally. In five cases, the internal charge triggered localized changes in structure and dynamics, and in three cases, it promoted partial or local unfolding. Remarkably, in 15 proteins, the ionization of the internal Lys had no detectable structural consequences. Highly stable proteins appear to be inherently capable of withstanding the presence of charge in their hydrophobic interior, without the need for specialized structural adaptations. The extent of structural reorganization paralleled loosely with global thermodynamic stability, suggesting that structure-based pK{sub a} calculations for buried residues could be improved by calculation of thermodynamic stability and by enhanced conformational sampling.

  5. Protein losses in ion-exchange and hydrophobic interaction high-performance liquid chromatography

    SciTech Connect

    Goheen, Steven C.; Gibbins, Betty M.

    2000-01-01

    Protein losses in ion-exchange and hydrophobic interaction HPLC were examined. The supports were allnon-porous, packed in columns of identical dimensions. Two ion-exchange chromatography (IEC), anion and cation, as well as a hydrophobic interaction chromatography (HIC) columns were tested. Proteins included cytochrome c, bovine serum albumin (BSA), immunoglobulin G and fibrinogen. Temperature effects on HIC supports were studied for cytochrome c and BSA. Both retention times and recoveries of the proteins were measured. The influence of column residence time on the recovery of proteins were also investigated. We found a linear relationship between the amount of protein recovered and the log of the molecular mass. Retention times also generally increased with temperature for both HIC and IEC. Other trends in retention behavior and recoveries are discussed.

  6. Hydrophobic-cluster analysis of plant protein sequences. A domain homology between storage and lipid-transfer proteins.

    PubMed Central

    Henrissat, B; Popineau, Y; Kader, J C

    1988-01-01

    Hydrophobic-cluster analysis was used to characterize a conserved domain located near the C-terminal amino acid sequence of wheat (Triticum aestivum) storage proteins. This domain was transformed into a linear template for a global search for similarities in over 5200 protein sequences. In addition to proteins that had already been found to exhibit homology to wheat storage proteins, a previously unreported homology was found with non-specific lipid-transfer proteins from castor bean (Ricinus communis) and from spinach (Spinacia oleracea) leaf. Hydrophobic-cluster analysis of various members of the present protein group clearly shows a typical domain structure where (i) variable and conserved domains are located along the sequence at precise positions, (ii) the conserved domains probably reflect a common ancestor, and (iii) the unique properties of a given protein (chain cut into subunits, repetitive domains, trypsin-inhibitor active site) are associated with the variable domains. PMID:3214430

  7. Lateral diffusion of membrane proteins: consequences of hydrophobic mismatch and lipid composition.

    PubMed

    Ramadurai, Sivaramakrishnan; Duurkens, Ria; Krasnikov, Victor V; Poolman, Bert

    2010-09-08

    Biological membranes are composed of a large number lipid species differing in hydrophobic length, degree of saturation, and charge and size of the headgroup. We now present data on the effect of hydrocarbon chain length of the lipids and headgroup composition on the lateral mobility of the proteins in model membranes. The trimeric glutamate transporter (GltT) and the monomeric lactose transporter (LacY) were reconstituted in giant unilamellar vesicles composed of unsaturated phosphocholine lipids of varying acyl chain length (14-22 carbon atoms) and various ratios of DOPE/DOPG/DOPC lipids. The lateral mobility of the proteins and of a fluorescent lipid analog was determined as a function of the hydrophobic thickness of the bilayer (h) and lipid composition, using fluorescence correlation spectroscopy. The diffusion coefficient of LacY decreased with increasing thickness of the bilayer, in accordance with the continuum hydrodynamic model of Saffman-Delbrück. For GltT, the mobility had its maximum at diC18:1 PC, which is close to the hydrophobic thickness of the bilayer in vivo. The lateral mobility decreased linearly with the concentration of DOPE but was not affected by the fraction of anionic lipids from DOPG. The addition of DOPG and DOPE did not affect the activity of GltT. We conclude that the hydrophobic thickness of the bilayer is a major determinant of molecule diffusion in membranes, but protein-specific properties may lead to deviations from the Saffman-Delbrück model.

  8. Algorithmic approach to quantifying the hydrophobic force contribution in protein folding.

    PubMed

    Backofen, R; Will, S; Clote, P

    2000-01-01

    Though the electrostatic, ionic, van der Waals, Lennard-Jones, hydrogen bonding, and other forces play an important role in the energy function minimized at a protein's native state, it is widely believed that the hydrophobic force is the dominant term in protein folding. Here we attempt to quantify the extent to which the hydrophobic force determines the positions of the backbone alpha-carbon atoms in PDB data, by applying Monte-Carlo and genetic algorithms to determine the predicted conformation with minimum energy, where only the hydrophobic force is considered (i.e. Dill's HP-model, and refinements using Woese's polar requirement). This is done by computing the root mean square deviation between the normalized distance matrix D = (di,j) (di,j is normalized Euclidean distance between residues ri and rj) for PDB data with that obtained from the output of our algorithms. Our program was run on the database of ancient conserved regions drawn from GenBank 101 generously supplied by W. Gilbert's lab, as well as medium-sized proteins (E. Coli RecA, 2reb, Erythrocruorin, 1eca, and Actinidin 2act). The root mean square deviation (RMSD) between distance matrices derived from the PDB data and from our program output is quite small, and by comparison with RMSD between PDB data and random coils, allows a quantification of the hydrophobic force contribution. A preliminary version of this paper appeared at GCB'99 (http:¿bibiserv.techfak.uni-bielefeld.de/gcb9 9/).

  9. Computer simulation of protein solvation, hydrophobic mapping, and the oxygen effect in radiation biology

    SciTech Connect

    Pratt, L.R.; Garcia, A.E.; Hummer, G.

    1997-08-01

    This is the final report of a three-year, Laboratory-Directed Research and Development project at the Los Alamos National Laboratory. Hydrophobic effects are central to the structural stability of biomolecules, particularly proteins, in solution but are not understood at a molecular level. This project developed a new theoretical approach to calculation of hydrophobic effects. This information theory approach can be implemented with experimental, including computer simulation-experimental, information. The new theory is consistent with, builds upon, and subsumes previous integral equation and scaled particle statistical thermodynamic modes of hydrophobic effects. the new theory is sufficiently simple to permit application directly to complex biomolecules in solution and to permit further expansion to incorporate more subtle effects.

  10. Frequencies of amino acid strings in globular protein sequences indicate suppression of blocks of consecutive hydrophobic residues

    PubMed Central

    Schwartz, Russell; Istrail, Sorin; King, Jonathan

    2001-01-01

    Patterns of hydrophobic and hydrophilic residues play a major role in protein folding and function. Long, predominantly hydrophobic strings of 20–22 amino acids each are associated with transmembrane helices and have been used to identify such sequences. Much less attention has been paid to hydrophobic sequences within globular proteins. In prior work on computer simulations of the competition between on-pathway folding and off-pathway aggregate formation, we found that long sequences of consecutive hydrophobic residues promoted aggregation within the model, even controlling for overall hydrophobic content. We report here on an analysis of the frequencies of different lengths of contiguous blocks of hydrophobic residues in a database of amino acid sequences of proteins of known structure. Sequences of three or more consecutive hydrophobic residues are found to be significantly less common in actual globular proteins than would be predicted if residues were selected independently. The result may reflect selection against long blocks of hydrophobic residues within globular proteins relative to what would be expected if residue hydrophobicities were independent of those of nearby residues in the sequence. PMID:11316883

  11. Protein dynamics and thermodynamics crossover at 10 °C: Different roles of hydration at hydrophilic and hydrophobic groups

    NASA Astrophysics Data System (ADS)

    Chong, Yuan; Kleinhammes, Alfred; Wu, Yue

    2016-11-01

    Water at hydrophilic and hydrophobic groups interact differently with proteins. Particularly, hydration properties at hydrophobic groups undergo qualitative changes as temperature decreases below 10 °C. The influence of such interfacial changes on protein dynamics and thermodynamics remains largely unexplored. Here, nanosecond to microsecond protein dynamics and the free energy, enthalpy, and entropy of protein hydration are investigated by in-situ NMR as a function of hydration level and temperature. A crossover at 10 °C in protein dynamics and thermodynamics is revealed. The influence of water at hydrophilic groups shows little temperature dependence, whereas water at hydrophobic groups has stronger effect above 10 °C.

  12. Novel hydrophobic surface binding protein, HsbA, produced by Aspergillus oryzae.

    PubMed

    Ohtaki, Shinsaku; Maeda, Hiroshi; Takahashi, Toru; Yamagata, Youhei; Hasegawa, Fumihiko; Gomi, Katsuya; Nakajima, Tasuku; Abe, Keietsu

    2006-04-01

    Hydrophobic surface binding protein A (HsbA) is a secreted protein (14.5 kDa) isolated from the culture broth of Aspergillus oryzae RIB40 grown in a medium containing polybutylene succinate-co-adipate (PBSA) as a sole carbon source. We purified HsbA from the culture broth and determined its N-terminal amino acid sequence. We found a DNA sequence encoding a protein whose N terminus matched that of purified HsbA in the A. ozyzae genomic sequence. We cloned the hsbA genomic DNA and cDNA from A. oryzae and constructed a recombinant A. oryzae strain highly expressing hsbA. Orthologues of HsbA were present in animal pathogenic and entomopathogenic fungi. Heterologously synthesized HsbA was purified and biochemically characterized. Although the HsbA amino acid sequence suggests that HsbA may be hydrophilic, HsbA adsorbed to hydrophobic PBSA surfaces in the presence of NaCl or CaCl(2). When HsbA was adsorbed on the hydrophobic PBSA surfaces, it promoted PBSA degradation via the CutL1 polyesterase. CutL1 interacts directly with HsbA attached to the hydrophobic QCM electrode surface. These results suggest that when HsbA is adsorbed onto the PBSA surface, it recruits CutL1, and that when CutL1 is accumulated on the PBSA surface, it stimulates PBSA degradation. We previously reported that when the A. oryzae hydrophobin RolA is bound to PBSA surfaces, it too specifically recruits CutL1. Since HsbA is not a hydrophobin, A. oryzae may use several types of proteins to recruit lytic enzymes to the surface of hydrophobic solid materials and promote their degradation.

  13. Local rules for protein folding on a triangular lattice and generalized hydrophobicity in the HP model

    SciTech Connect

    Agarwala, R.; Batzoglou, S.; Dancik, V.

    1997-06-01

    We consider the problem of determining the three-dimensional folding of a protein given its one-dimensional amino acid sequence. We use the HP model for protein folding proposed by Dill, which models protein as a chain of amino acid residues that are either hydrophobic or polar, and hydrophobic interactions are the dominant initial driving force for the protein folding. Hart and Istrail gave approximation algorithms for folding proteins on the cubic lattice under HP model. In this paper, we examine the choice of a lattice by considering its algorithmic and geometric implications and argue that triangular lattice is a more reasonable choice. We present a set of folding rules for a triangular lattice and analyze the approximation ratio which they achieve. In addition, we introduce a generalization of the HP model to account for residues having different levels of hydrophobicity. After describing the biological foundation for this generalization, we show that in the new model we are able to achieve similar constant factor approximation guarantees on the triangular lattice as were achieved in the standard HP model. While the structures derived from our folding rules are probably still far from biological reality, we hope that having a set of folding rules with different properties will yield more interesting folds when combined.

  14. Redesigning the hydrophobic core of a four-helix-bundle protein.

    PubMed Central

    Munson, M.; O'Brien, R.; Sturtevant, J. M.; Regan, L.

    1994-01-01

    Rationally redesigned variants of the 4-helix-bundle protein Rop are described. The novel proteins have simplified, repacked, hydrophobic cores and yet reproduce the structure and native-like physical properties of the wild-type protein. The repacked proteins have been characterized thermodynamically and their equilibrium and kinetic thermal and chemical unfolding properties are compared with those of wild-type Rop. The equilibrium stability of the repacked proteins to thermal denaturation is enhanced relative to that of the wild-type protein. The rate of chemically induced folding and unfolding of wild-type Rop is extremely slow when compared with other small proteins. Interestingly, although the repacked proteins are more thermally stable than the wild type, their rates of chemically induced folding and unfolding are greatly increased in comparison to wild type. Perhaps as a consequence of this, their equilibrium stabilities to chemical denaturants are slightly reduced in comparison to the wild type. PMID:7535612

  15. Automated hydrophobic interaction chromatography column selection for use in protein purification.

    PubMed

    Murphy, Patrick J M; Stone, Orrin J; Anderson, Michelle E

    2011-09-21

    In contrast to other chromatographic methods for purifying proteins (e.g. gel filtration, affinity, and ion exchange), hydrophobic interaction chromatography (HIC) commonly requires experimental determination (referred to as screening or "scouting") in order to select the most suitable chromatographic medium for purifying a given protein (1). The method presented here describes an automated approach to scouting for an optimal HIC media to be used in protein purification. HIC separates proteins and other biomolecules from a crude lysate based on differences in hydrophobicity. Similar to affinity chromatography (AC) and ion exchange chromatography (IEX), HIC is capable of concentrating the protein of interest as it progresses through the chromatographic process. Proteins best suited for purification by HIC include those with hydrophobic surface regions and able to withstand exposure to salt concentrations in excess of 2 M ammonium sulfate ((NH(4;))(2;)SO(4;)). HIC is often chosen as a purification method for proteins lacking an affinity tag, and thus unsuitable for AC, and when IEX fails to provide adequate purification. Hydrophobic moieties on the protein surface temporarily bind to a nonpolar ligand coupled to an inert, immobile matrix. The interaction between protein and ligand are highly dependent on the salt concentration of the buffer flowing through the chromatography column, with high ionic concentrations strengthening the protein-ligand interaction and making the protein immobile (i.e. bound inside the column) (2). As salt concentrations decrease, the protein-ligand interaction dissipates, the protein again becomes mobile and elutes from the column. Several HIC media are commercially available in pre-packed columns, each containing one of several hydrophobic ligands (e.g. S-butyl, butyl, octyl, and phenyl) cross-linked at varying densities to agarose beads of a specific diameter (3). Automated column scouting allows for an efficient approach for determining

  16. Hydrophobic enhancement of Dopa-mediated adhesion in a mussel foot protein

    PubMed Central

    Wei, Wei; Yu, Jing; Broomell, Christopher; Israelachvili, Jacob N.; Waite, J. Herbert

    2013-01-01

    Dopa (3,4-dihydroxyphenylalanine) is recognized as a key chemical signature of mussel adhesion and has been adopted into diverse synthetic polymer systems. Dopa’s notorious susceptibility to oxidation, however, poses significant challenges to the practical translation of mussel adhesion. Using a Surface Forces Apparatus to investigate the adhesion of Mfp3 (mussel foot protein 3) slow, a hydrophobic protein variant of the Mfp3 family in the plaque, we have discovered a subtle molecular strategy correlated with hydrophobicity that appears to compensate for Dopa instability. At pH 3, where Dopa is stable, Mfp3 slow like Mfp3 fast adhesion to mica is directly proportional to the mol% of Dopa present in the protein. At pH 5.5 and 7.5, however, loss of adhesion in Mfp3 slow was less than half that occurring in Mfp3 fast, purportedly because Dopa in Mfp3 slow is less prone to oxidation. Indeed, cyclic voltammetry showed that the oxidation potential of Dopa in Mfp3 slow is significantly higher than in Mfp3 fast at pH 7.5. A much greater difference between the two variants was revealed in the interaction energy of two symmetric Mfp3 slow films (Ead = −3 mJ/m2). This energy corresponds to the energy of protein cohesion which is notable for its reversibility and pH-independence. Exploitation of aromatic hydrophobic sequences to protect Dopa against oxidation as well as to mediate hydrophobic and H-bonding interactions between proteins provides new insights for developing effective artificial underwater adhesives. PMID:23214725

  17. Hydrophobic enhancement of Dopa-mediated adhesion in a mussel foot protein.

    PubMed

    Wei, Wei; Yu, Jing; Broomell, Christopher; Israelachvili, Jacob N; Waite, J Herbert

    2013-01-09

    Dopa (3,4-dihydroxyphenylalanine) is recognized as a key chemical signature of mussel adhesion and has been adopted into diverse synthetic polymer systems. Dopa's notorious susceptibility to oxidation, however, poses significant challenges to the practical translation of mussel adhesion. Using a surface forces apparatus to investigate the adhesion of mussel foot protein 3 (Mfp3) "slow", a hydrophobic protein variant of the Mfp3 family in the plaque, we have discovered a subtle molecular strategy correlated with hydrophobicity that appears to compensate for Dopa instability. At pH 3, where Dopa is stable, Mfp3 slow, like Mfp3 "fast" adhesion to mica, is directly proportional to the mol % of Dopa present in the protein. At pH of 5.5 and 7.5, however, loss of adhesion in Mfp3 slow was less than half that occurring in Mfp3 fast, purportedly because Dopa in Mfp3 slow is less prone to oxidation. Indeed, cyclic voltammetry showed that the oxidation potential of Dopa in Mfp3 slow is significantly higher than in Mfp3 fast at pH of 7.5. A much greater difference between the two variants was revealed in the interaction energy of two symmetric Mfp3 slow films (E(ad) = -3 mJ/m(2)). This energy corresponds to the energy of protein cohesion which is notable for its reversibility and pH independence. Exploitation of aromatic hydrophobic sequences to protect Dopa against oxidation as well as to mediate hydrophobic and H-bonding interactions between proteins provides new insights for developing effective artificial underwater adhesives.

  18. Fundamental processes of protein folding: measuring the energetic balance between helix formation and hydrophobic interactions.

    PubMed

    Xian, Wujing; Connolly, Peter J; Oslin, Marcela; Hausrath, Andrew C; Osterhout, John J

    2006-09-01

    Theories of protein folding often consider contributions from three fundamental elements: loops, hydrophobic interactions, and secondary structures. The pathway of protein folding, the rate of folding, and the final folded structure should be predictable if the energetic contributions to folding of these fundamental factors were properly understood. alphatalpha is a helix-turn-helix peptide that was developed by de novo design to provide a model system for the study of these important elements of protein folding. Hydrogen exchange experiments were performed on selectively 15N-labeled alphatalpha and used to calculate the stability of hydrogen bonds within the peptide. The resulting pattern of hydrogen bond stability was analyzed using a version of Lifson-Roig model that was extended to include a statistical parameter for tertiary interactions. This parameter, x, represents the additional statistical weight conferred upon a helical state by a tertiary contact. The hydrogen exchange data is most closely fit by the XHC model with an x parameter of 9.25. Thus the statistical weight of a hydrophobic tertiary contact is approximately 5.8x the statistical weight for helix formation by alanine. The value for the x parameter derived from this study should provide a basis for the understanding of the relationship between hydrophobic cluster formation and secondary structure formation during the early stages of protein folding.

  19. Dynamic hydration shell restores Kauzmann's 1959 explanation of how the hydrophobic factor drives protein folding.

    PubMed

    Baldwin, Robert L

    2014-09-09

    Kauzmann's explanation of how the hydrophobic factor drives protein folding is reexamined. His explanation said that hydrocarbon hydration shells are formed, possibly of clathrate water, and they explain why hydrocarbons have uniquely low solubilities in water. His explanation was not universally accepted because of skepticism about the clathrate hydration shell. A revised version is given here in which a dynamic hydration shell is formed by van der Waals (vdw) attraction, as proposed in 1985 by Jorgensen et al. [Jorgensen WL, Gao J, Ravimohan C (1985) J Phys Chem 89:3470-3473]. The vdw hydration shell is implicit in theories of hydrophobicity that contain the vdw interaction between hydrocarbon C and water O atoms. To test the vdw shell model against the known hydration energetics of alkanes, the energetics should be based on the Ben-Naim standard state (solute transfer between fixed positions in the gas and liquid phases). Then the energetics are proportional to n, the number of water molecules correlated with an alkane by vdw attraction, given by the simulations of Jorgensen et al. The energetics show that the decrease in entropy upon hydration is the root cause of hydrophobicity; it probably results from extensive ordering of water molecules in the vdw shell. The puzzle of how hydrophobic free energy can be proportional to nonpolar surface area when the free energy is unfavorable and the only known interaction (the vdw attraction) is favorable, is resolved by finding that the unfavorable free energy is produced by the vdw shell.

  20. The role of hydrophobic interactions in positioning of peripheral proteins in membranes

    PubMed Central

    Lomize, Andrei L; Pogozheva, Irina D; Lomize, Mikhail A; Mosberg, Henry I

    2007-01-01

    Background Three-dimensional (3D) structures of numerous peripheral membrane proteins have been determined. Biological activity, stability, and conformations of these proteins depend on their spatial positions with respect to the lipid bilayer. However, these positions are usually undetermined. Results We report the first large-scale computational study of monotopic/peripheral proteins with known 3D structures. The optimal translational and rotational positions of 476 proteins are determined by minimizing energy of protein transfer from water to the lipid bilayer, which is approximated by a hydrocarbon slab with a decadiene-like polarity and interfacial regions characterized by water-permeation profiles. Predicted membrane-binding sites, protein tilt angles and membrane penetration depths are consistent with spin-labeling, chemical modification, fluorescence, NMR, mutagenesis, and other experimental studies of 53 peripheral proteins and peptides. Experimental membrane binding affinities of peripheral proteins were reproduced in cases that did not involve a helix-coil transition, specific binding of lipids, or a predominantly electrostatic association. Coordinates of all examined peripheral proteins and peptides with the calculated hydrophobic membrane boundaries, subcellular localization, topology, structural classification, and experimental references are available through the Orientations of Proteins in Membranes (OPM) database. Conclusion Positions of diverse peripheral proteins and peptides in the lipid bilayer can be accurately predicted using their 3D structures that represent a proper membrane-bound conformation and oligomeric state, and have membrane binding elements present. The success of the implicit solvation model suggests that hydrophobic interactions are usually sufficient to determine the spatial position of a protein in the membrane, even when electrostatic interactions or specific binding of lipids are substantial. Our results demonstrate that

  1. Hsp90 protein interacts with phosphorothioate oligonucleotides containing hydrophobic 2'-modifications and enhances antisense activity.

    PubMed

    Liang, Xue-Hai; Shen, Wen; Sun, Hong; Kinberger, Garth A; Prakash, Thazha P; Nichols, Joshua G; Crooke, Stanley T

    2016-05-05

    RNase H1-dependent antisense oligonucleotides (ASOs) are chemically modified to enhance pharmacological properties. Major modifications include phosphorothioate (PS) backbone and different 2'-modifications in 2-5 nucleotides at each end (wing) of an ASO. Chemical modifications can affect protein binding and understanding ASO-protein interactions is important for better drug design. Recently we identified many intracellular ASO-binding proteins and found that protein binding could affect ASO potency. Here, we analyzed the structure-activity-relationships of ASO-protein interactions and found 2'-modifications significantly affected protein binding, including La, P54nrb and NPM. PS-ASOs containing more hydrophobic 2'-modifications exhibit higher affinity for proteins in general, although certain proteins, e.g. Ku70/Ku80 and TCP1, are less affected by 2'-modifications. We found that Hsp90 protein binds PS-ASOs containing locked-nucleic-acid (LNA) or constrained-ethyl-bicyclic-nucleic-acid ((S)-cEt) modifications much more avidly than 2'-O-methoxyethyl (MOE). ASOs bind the mid-domain of Hsp90 protein. Hsp90 interacts with more hydrophobic 2' modifications, e.g. (S)-cEt or LNA, in the 5'-wing of the ASO. Reduction of Hsp90 protein decreased activity of PS-ASOs with 5'-LNA or 5'-cEt wings, but not with 5'-MOE wing. Together, our results indicate Hsp90 protein enhances the activity of PS/LNA or PS/(S)-cEt ASOs, and imply that altering protein binding of ASOs using different chemical modifications can improve therapeutic performance of PS-ASOs.

  2. Favorable Influence of Hydrophobic Surfaces on Protein Structure in Porous Organically-modified Silica Glasses

    PubMed Central

    Menaa, Bouzid; Herrero, Mar; Rives, Vicente; Lavrenko, Mayya; Eggers, Daryl K.

    2008-01-01

    Organically-modified siloxanes were used as host materials to examine the influence of surface chemistry on protein conformation in a crowded environment. The sol-gel materials were prepared from tetramethoxysilane and a series of monosubstituted alkoxysilanes, RSi(OR′)3, featuring alkyl groups of increasing chain length in the R-position. Using circular dichroism spectroscopy in the far-UV region, apomyoglobin was found to transit from an unfolded state to a native-like helical state as the content of the hydrophobic precursor increased from 0–15%. At a fixed molar content of 5% RSi(OR’)3, the helical structure of apomyoglobin increased with the chain length of the R-group, i.e. methyl < ethyl < n-propyl < n-butyl < n-hexyl. This trend also was observed for the tertiary structure of ribonuclease A, suggesting that protein folding and biological activity are sensitive to the hydrophilic/hydrophobic balance of neighboring surfaces. The observed changes in protein structure did not correlate with total surface area or the average pore size of the modified glasses, but scanning electron microscopy images revealed an interesting relationship between surface morphology and alkyl chain length. The unexpected benefit of incorporating a low content of hydrophobic groups into a hydrophilic surface may lead to materials with improved biocompatibility for use in biosensors and implanted devices. PMID:18359512

  3. Interplay between hydrophobicity and the positive-inside rule in determining membrane-protein topology

    PubMed Central

    Elazar, Assaf; Weinstein, Jonathan Jacob; Prilusky, Jaime; Fleishman, Sarel Jacob

    2016-01-01

    The energetics of membrane-protein interactions determine protein topology and structure: hydrophobicity drives the insertion of helical segments into the membrane, and positive charges orient the protein with respect to the membrane plane according to the positive-inside rule. Until recently, however, quantifying these contributions met with difficulty, precluding systematic analysis of the energetic basis for membrane-protein topology. We recently developed the dsTβL method, which uses deep sequencing and in vitro selection of segments inserted into the bacterial plasma membrane to infer insertion-energy profiles for each amino acid residue across the membrane, and quantified the insertion contribution from hydrophobicity and the positive-inside rule. Here, we present a topology-prediction algorithm called TopGraph, which is based on a sequence search for minimum dsTβL insertion energy. Whereas the average insertion energy assigned by previous experimental scales was positive (unfavorable), the average assigned by TopGraph in a nonredundant set is −6.9 kcal/mol. By quantifying contributions from both hydrophobicity and the positive-inside rule we further find that in about half of large membrane proteins polar segments are inserted into the membrane to position more positive charges in the cytoplasm, suggesting an interplay between these two energy contributions. Because membrane-embedded polar residues are crucial for substrate binding and conformational change, the results implicate the positive-inside rule in determining the architectures of membrane-protein functional sites. This insight may aid structure prediction, engineering, and design of membrane proteins. TopGraph is available online (topgraph.weizmann.ac.il). PMID:27562165

  4. Interplay between hydrophobicity and the positive-inside rule in determining membrane-protein topology.

    PubMed

    Elazar, Assaf; Weinstein, Jonathan Jacob; Prilusky, Jaime; Fleishman, Sarel Jacob

    2016-09-13

    The energetics of membrane-protein interactions determine protein topology and structure: hydrophobicity drives the insertion of helical segments into the membrane, and positive charges orient the protein with respect to the membrane plane according to the positive-inside rule. Until recently, however, quantifying these contributions met with difficulty, precluding systematic analysis of the energetic basis for membrane-protein topology. We recently developed the dsTβL method, which uses deep sequencing and in vitro selection of segments inserted into the bacterial plasma membrane to infer insertion-energy profiles for each amino acid residue across the membrane, and quantified the insertion contribution from hydrophobicity and the positive-inside rule. Here, we present a topology-prediction algorithm called TopGraph, which is based on a sequence search for minimum dsTβL insertion energy. Whereas the average insertion energy assigned by previous experimental scales was positive (unfavorable), the average assigned by TopGraph in a nonredundant set is -6.9 kcal/mol. By quantifying contributions from both hydrophobicity and the positive-inside rule we further find that in about half of large membrane proteins polar segments are inserted into the membrane to position more positive charges in the cytoplasm, suggesting an interplay between these two energy contributions. Because membrane-embedded polar residues are crucial for substrate binding and conformational change, the results implicate the positive-inside rule in determining the architectures of membrane-protein functional sites. This insight may aid structure prediction, engineering, and design of membrane proteins. TopGraph is available online (topgraph.weizmann.ac.il).

  5. Effects of Polymer Hydrophobicity on Protein Structure and Aggregation Kinetics in Crowded Milieu.

    PubMed

    Breydo, Leonid; Sales, Amanda E; Frege, Telma; Howell, Mark C; Zaslavsky, Boris Y; Uversky, Vladimir N

    2015-05-19

    We examined the effects of water-soluble polymers of various degrees of hydrophobicity on the folding and aggregation of proteins. The polymers we chose were polyethylene glycol (PEG) and UCON (1:1 copolymer of ethylene glycol and propylene glycol). The presence of additional methyl groups in UCON makes it more hydrophobic than PEG. Our earlier analysis revealed that similarly sized PEG and UCON produced different changes in the solvent properties of water in their solutions and induced morphologically different α-synuclein aggregates [Ferreira, L. A., et al. (2015) Role of solvent properties of aqueous media in macromolecular crowding effects. J. Biomol. Struct. Dyn., in press]. To improve our understanding of molecular mechanisms defining behavior of proteins in a crowded environment, we tested the effects of these polymers on secondary and tertiary structure and aromatic residue solvent accessibility of 10 proteins [five folded proteins, two hybrid proteins; i.e., protein containing ordered and disordered domains, and three intrinsically disordered proteins (IDPs)] and on the aggregation kinetics of insulin and α-synuclein. We found that effects of both polymers on secondary and tertiary structures of folded and hybrid proteins were rather limited with slight unfolding observed in some cases. Solvent accessibility of aromatic residues was significantly increased for the majority of the studied proteins in the presence of UCON but not PEG. PEG also accelerated the aggregation of protein into amyloid fibrils, whereas UCON promoted aggregation to amyloid oligomers instead. These results indicate that even a relatively small change in polymer structure leads to a significant change in the effect of this polymer on protein folding and aggregation. This is an indication that protein folding and especially aggregation are highly sensitive to the presence of other macromolecules, and an excluded volume effect is insufficient to describe their effect.

  6. Acceleration through passive destabilization: protein folding in a weak hydrophobic environment

    NASA Astrophysics Data System (ADS)

    Jewett, Andrew; Baumketner, Andrij; Shea, Joan-Emma

    2004-03-01

    The GroEL chaperonin is a biomolecule which assists the folding of an extremely diverse range of proteins in Eubacteria. Some proteins undergo many rounds of ATP-regulated binding and dissociation from GroEL/ES before folding. It has been proposed that transient stress from ATP-regulated binding and release from GroEL/ES frees frustrated proteins from misfolded conformations. However recent evidence suggests that chaperonin-accelerated protein folding can take place entirely within a mutated GroEL+ES cavity that is unable to open and release the protein. Using molecular dynamics, we demonstrate that static confinement within a weakly hydrophobic (attractive) cavity (similar to the interior of the cavity formed by the GroEL+ES complex) is sufficient to significantly accelerate the folding of a highly frustrated protein-like heteropolymer. Our frustrated molecule benifits kinetically from a static hydrophobic environment that destabilizes misfolded conformations. This may shed light on the mechanisms used by other chaperones which do not depend on ATP.

  7. Hydrophobic Blocks Facilitate Lipid Compatibility and Translocon Recognition of Transmembrane Protein Sequences

    PubMed Central

    2016-01-01

    Biophysical hydrophobicity scales suggest that partitioning of a protein segment from an aqueous phase into a membrane is governed by its perceived segmental hydrophobicity but do not establish specifically (i) how the segment is identified in vivo for translocon-mediated insertion or (ii) whether the destination lipid bilayer is biochemically receptive to the inserted sequence. To examine the congruence between these dual requirements, we designed and synthesized a library of Lys-tagged peptides of a core length sufficient to span a bilayer but with varying patterns of sequence, each composed of nine Leu residues, nine Ser residues, and one (central) Trp residue. We found that peptides containing contiguous Leu residues (Leu-block peptides, e.g., LLLLLLLLLWSSSSSSSSS), in comparison to those containing discontinuous stretches of Leu residues (non-Leu-block peptides, e.g., SLSLLSLSSWSLLSLSLLS), displayed greater helicity (circular dichroism spectroscopy), traveled slower during sodium dodecyl sulfate–polyacrylamide gel electrophoresis, had longer reverse phase high-performance liquid chromatography retention times on a C-18 column, and were helical when reconstituted into 1-palmitoyl-2-oleoylglycero-3-phosphocholine liposomes, each observation indicating superior lipid compatibility when a Leu-block is present. These parameters were largely paralleled in a biological membrane insertion assay using microsomal membranes from dog pancreas endoplasmic reticulum, where we found only the Leu-block sequences successfully inserted; intriguingly, an amphipathic peptide (SLLSSLLSSWLLSSLLSSL; Leu face, Ser face) with biophysical properties similar to those of Leu-block peptides failed to insert. Our overall results identify local sequence lipid compatibility rather than average hydrophobicity as a principal determinant of transmembrane segment potential, while demonstrating that further subtleties of hydrophobic and helical patterning, such as circumferential hydrophobicity

  8. Hydrophobic blocks facilitate lipid compatibility and translocon recognition of transmembrane protein sequences.

    PubMed

    Stone, Tracy A; Schiller, Nina; von Heijne, Gunnar; Deber, Charles M

    2015-02-24

    Biophysical hydrophobicity scales suggest that partitioning of a protein segment from an aqueous phase into a membrane is governed by its perceived segmental hydrophobicity but do not establish specifically (i) how the segment is identified in vivo for translocon-mediated insertion or (ii) whether the destination lipid bilayer is biochemically receptive to the inserted sequence. To examine the congruence between these dual requirements, we designed and synthesized a library of Lys-tagged peptides of a core length sufficient to span a bilayer but with varying patterns of sequence, each composed of nine Leu residues, nine Ser residues, and one (central) Trp residue. We found that peptides containing contiguous Leu residues (Leu-block peptides, e.g., LLLLLLLLLWSSSSSSSSS), in comparison to those containing discontinuous stretches of Leu residues (non-Leu-block peptides, e.g., SLSLLSLSSWSLLSLSLLS), displayed greater helicity (circular dichroism spectroscopy), traveled slower during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, had longer reverse phase high-performance liquid chromatography retention times on a C-18 column, and were helical when reconstituted into 1-palmitoyl-2-oleoylglycero-3-phosphocholine liposomes, each observation indicating superior lipid compatibility when a Leu-block is present. These parameters were largely paralleled in a biological membrane insertion assay using microsomal membranes from dog pancreas endoplasmic reticulum, where we found only the Leu-block sequences successfully inserted; intriguingly, an amphipathic peptide (SLLSSLLSSWLLSSLLSSL; Leu face, Ser face) with biophysical properties similar to those of Leu-block peptides failed to insert. Our overall results identify local sequence lipid compatibility rather than average hydrophobicity as a principal determinant of transmembrane segment potential, while demonstrating that further subtleties of hydrophobic and helical patterning, such as circumferential hydrophobicity in

  9. Interaction between human BAP31 and respiratory syncytial virus small hydrophobic (SH) protein

    SciTech Connect

    Li, Yan; Jain, Neeraj; Limpanawat, Suweeraya; To, Janet; Quistgaard, Esben M.; Nordlund, Par; Thanabalu, Thirumaran; Torres, Jaume

    2015-08-15

    The small hydrophobic (SH) protein is a short channel-forming polypeptide encoded by the human respiratory syncytial virus (hRSV). Deletion of SH protein leads to the viral attenuation in mice and primates, and delayed apoptosis in infected cells. We have used a membrane-based yeast two-hybrid system (MbY2H) and a library from human lung cDNA to detect proteins that bind SH protein. This led to the identification of a membrane protein, B-cell associated protein 31 (BAP31). Transfected SH protein co-localizes with transfected BAP31 in cells, and pulls down endogenous BAP31. Titration of purified C-terminal endodomain of BAP31 against isotopically labeled SH protein in detergent micelles suggests direct interaction between the two proteins. Given the key role of BAP31 in protein trafficking and its critical involvement in pro- and anti-apoptotic pathways, this novel interaction may constitute a potential drug target. - Highlights: • A yeast two-hybrid system (MbY2H) detected BAP31 as a binder of RSV SH protein. • Transfected SH and BAP31 co-localize in lung epithelial cells. • Endogenous BAP31 is pulled down by RSV SH protein. • BAP31 endodomain interacts with the N-terminal α-helix of SH protein in micelles. • This interaction is proposed to be a potential drug target.

  10. Hydrophobic interaction adsorption of hen egg white proteins albumin, conalbumin, and lysozyme.

    PubMed

    Rojas, Edwin E Garcia; dos Reis Coimbra, Jane S; Minim, Luis A; Saraiva, Sérgio H; da Silva, César A Sodré

    2006-08-18

    Hydrophobic adsorption equilibrium data of the hen egg white proteins albumin, conalbumin, and lysozyme were obtained in batch systems, at 25 degrees C, using the Streamline Phenyl resin as adsorbent. The influence of three types of salt, NaCl, Na(2)SO(4), or (NH(4))(2)SO(4), and their concentration on the equilibrium data were evaluated. The salt Na(2)SO(4) showed the higher interaction with the studied proteins, thus favoring the adsorption of proteins by the adsorbent, even though each type of salt interacted in a distinct manner with each protein. The isotherm models of Langmuir, Langmuir exponential, and Chen and Sun were well fitted to the equilibrium data, with no significant difference being observed at the 5% level of significance. The mass transfer model applied simulated correctly adsorption kinetics of the proteins under the studied conditions.

  11. Local rules for protein folding on a triangular lattice and generalized hydrophobicity in the HP model

    SciTech Connect

    Agarwala, R.; Batzoglou, S.; Dancik, V.

    1997-12-01

    A long standing problem in molecular biology is to determine the three-dimensional structure of a protein, given its amino acid sequence. A variety of simplifying models have been proposed abstracting only the {open_quotes}essential physical properties{close_quotes} of real proteins. In these models, the three dimensional space is often represented by a lattice. Residues which are adjacent in the primary sequence (i.e. covalently linked) must be placed at adjacent points in the lattice. A conformation of a protein is simply a self-avoiding walk along the lattice. The protein folding problem STRING-FOLD is that of finding a conformation of the protein sequence on the lattice such that the overall energy is minimized, for some reasonable definition of energy. This formulation leaves open the choices of a lattice and an energy function. Once these choices are made, one may then address the algorithmic complexity of optimizing the energy function for the lattice. For a variety of such simple models, this minimization problem is in fact NP-hard. In this paper, we consider the Hydrophobic-Polar (HP) Model introduced by Dill. The HP model abstracts the problem by grouping the 20 amino acids into two classes: hydrophobic (or non-polar) residues and hydrophilic (or polar) residues. For concreteness, we will take our input to be a string from (H,P){sup +}, where P represents polar residues, and H represents hydrophobic residues. Dill et.al. survey the literature analyzing this model. 8 refs., 2 figs., 1 tab.

  12. Adaptive hydrophobic and hydrophilic interactions of mussel foot proteins with organic thin films.

    PubMed

    Yu, Jing; Kan, Yajing; Rapp, Michael; Danner, Eric; Wei, Wei; Das, Saurabh; Miller, Dusty R; Chen, Yunfei; Waite, J Herbert; Israelachvili, Jacob N

    2013-09-24

    The adhesion of mussel foot proteins (Mfps) to a variety of specially engineered mineral and metal oxide surfaces has previously been investigated extensively, but the relevance of these studies to adhesion in biological environments remains unknown. Most solid surfaces exposed to seawater or physiological fluids become fouled by organic conditioning films and biofilms within minutes. Understanding the binding mechanisms of Mfps to organic films with known chemical and physical properties therefore is of considerable theoretical and practical interest. Using self-assembled monolayers (SAMs) on atomically smooth gold substrates and the surface forces apparatus, we explored the force-distance profiles and adhesion energies of three different Mfps, Mfp-1, Mfp-3, and Mfp-5, on (i) hydrophobic methyl (CH3)- and (ii) hydrophilic alcohol (OH)-terminated SAM surfaces between pH 3 and pH 7.5. At acidic pH, all three Mfps adhered strongly to the CH3-terminated SAM surfaces via hydrophobic interactions (range of adhesive interaction energy = -4 to -9 mJ/m(2)) but only weakly to the OH-terminated SAM surfaces through H- bonding (adhesive interaction energy ≤ -0.5 mJ/m(2)). 3, 4-Dihydroxyphenylalanine (Dopa) residues in Mfps mediate binding to both SAM surface types but do so through different interactions: typical bidentate H-bonding by Dopa is frustrated by the longer spacing of OH-SAMs; in contrast, on CH3-SAMs, Dopa in synergy with other nonpolar residues partitions to the hydrophobic surface. Asymmetry in the distribution of hydrophobic residues in intrinsically unstructured proteins, the distortion of bond geometry between H-bonding surfaces, and the manipulation of physisorbed binding lifetimes represent important concepts for the design of adhesive and nonfouling surfaces.

  13. Adaptive hydrophobic and hydrophilic interactions of mussel foot proteins with organic thin films

    PubMed Central

    Yu, Jing; Kan, Yajing; Rapp, Michael; Danner, Eric; Wei, Wei; Das, Saurabh; Miller, Dusty R.; Chen, Yunfei; Waite, J. Herbert; Israelachvili, Jacob N.

    2013-01-01

    The adhesion of mussel foot proteins (Mfps) to a variety of specially engineered mineral and metal oxide surfaces has previously been investigated extensively, but the relevance of these studies to adhesion in biological environments remains unknown. Most solid surfaces exposed to seawater or physiological fluids become fouled by organic conditioning films and biofilms within minutes. Understanding the binding mechanisms of Mfps to organic films with known chemical and physical properties therefore is of considerable theoretical and practical interest. Using self-assembled monolayers (SAMs) on atomically smooth gold substrates and the surface forces apparatus, we explored the force–distance profiles and adhesion energies of three different Mfps, Mfp-1, Mfp-3, and Mfp-5, on (i) hydrophobic methyl (CH3)- and (ii) hydrophilic alcohol (OH)-terminated SAM surfaces between pH 3 and pH 7.5. At acidic pH, all three Mfps adhered strongly to the CH3-terminated SAM surfaces via hydrophobic interactions (range of adhesive interaction energy = −4 to −9 mJ/m2) but only weakly to the OH-terminated SAM surfaces through H- bonding (adhesive interaction energy ≤ −0.5 mJ/m2). 3, 4-Dihydroxyphenylalanine (Dopa) residues in Mfps mediate binding to both SAM surface types but do so through different interactions: typical bidentate H-bonding by Dopa is frustrated by the longer spacing of OH-SAMs; in contrast, on CH3-SAMs, Dopa in synergy with other nonpolar residues partitions to the hydrophobic surface. Asymmetry in the distribution of hydrophobic residues in intrinsically unstructured proteins, the distortion of bond geometry between H-bonding surfaces, and the manipulation of physisorbed binding lifetimes represent important concepts for the design of adhesive and nonfouling surfaces. PMID:24014592

  14. Importance of hydrophobic cluster formation through long-range contacts in the folding transition state of two-state proteins.

    PubMed

    Selvaraj, S; Gromiha, M Michael

    2004-06-01

    Understanding the folding pathways of proteins is a challenging task. The Phi value approach provides a detailed understanding of transition-state structures of folded proteins. In this work, we have computed the hydrophobicity associated with each residue in the folded state of 16 two-state proteins and compared the Phi values of each mutant residue. We found that most of the residues with high Phi value coincide with local maximum in surrounding hydrophobicity, or have nearby residues that show such maximum in hydrophobicity, indicating the importance of hydrophobic interactions in the transition state. We have tested our approach to different structural classes of proteins, such as alpha-helical, SH3 domains of all-beta proteins, beta-sandwich, and alpha/beta proteins, and we observed a good agreement with experimental results. Further, we have proposed a hydrophobic contact network pattern to relate the Phi values with long-range contacts, which will be helpful to understand the transition-state structures of folded proteins. The present approach could be used to identify potential hydrophobic clusters that may form through long-range contacts during the transition state.

  15. High-throughput protein precipitation and hydrophobic interaction chromatography: salt effects and thermodynamic interrelation.

    PubMed

    Nfor, Beckley K; Hylkema, Nienke N; Wiedhaup, Koenraad R; Verhaert, Peter D E M; van der Wielen, Luuk A M; Ottens, Marcel

    2011-12-09

    Salt-induced protein precipitation and hydrophobic interaction chromatography (HIC) are two widely used methods for protein purification. In this study, salt effects in protein precipitation and HIC were investigated for a broad combination of proteins, salts and HIC resins. Interrelation between the critical thermodynamic salting out parameters in both techniques was equally investigated. Protein precipitation data were obtained by a high-throughput technique employing 96-well microtitre plates and robotic liquid handling technology. For the same protein-salt combinations, isocratic HIC experiments were performed using two or three different commercially available stationary phases-Phenyl Sepharose low sub, Butyl Sepharose and Resource Phenyl. In general, similar salt effects and deviations from the lyotropic series were observed in both separation methods, for example, the reverse Hofmeister effect reported for lysozyme below its isoelectric point and at low salt concentrations. The salting out constant could be expressed in terms of the preferential interaction parameter in protein precipitation, showing that the former is, in effect, the net result of preferential interaction of a protein with water molecules and salt ions in its vicinity. However, no general quantitative interrelation was found between salting out parameters or the number of released water molecules in protein precipitation and HIC. In other words, protein solubility and HIC retention factor could not be quantitatively interrelated, although for some proteins, regular trends were observed across the different resins and salt types.

  16. Geometric Universality in Brain Allosteric Protein Dynamics: Complex Hydrophobic Transformation Predicts Mutual Recognition by Polypeptides and Proteins,

    DTIC Science & Technology

    1986-10-01

    example, hen egg white lysozyme (AG =- 350 kcal (AH) - 350 kcal (T’AS) - 0) exemplify the way protein dynamics mirror the hyperbolic stability of aqueous...8217 lie parallel to the given line A,A’, separated by their angle of parallel- ism 46 - f(r) lying between the limit lines of those contained in 0 that...optical rotatory dispersion as percent helix and related in part to the average amino acid hydrophobicity. For examples: lysozyme ,ith an average

  17. Topology and cellular localization of the small hydrophobic protein of avian metapneumovirus.

    PubMed

    Deng, Qiji; Weng, Yuejin; Lu, Wuxun; Demers, Andrew; Song, Minxun; Wang, Dan; Yu, Qingzhong; Li, Feng

    2011-09-01

    The small hydrophobic protein (SH) is a type II integral membrane protein that is packaged into virions and is only present in certain paramyxoviruses including metapneumovirus. In addition to a highly divergent primary sequence, SH proteins vary significantly in size amongst the different viruses. Human respiratory syncytial virus (HRSV) encodes the smallest SH protein consisting of only 64 amino acids, while metapneumoviruses have the longest SH protein ranging from 174 to 179 amino acids in length. Little is currently known about the cellular localization and topology of the metapneumovirus SH protein. Here we characterize for the first time metapneumovirus SH protein with respect to topology, subcellular localization, and transport using avian metapneumovirus subgroup C (AMPV-C) as a model system. We show that AMPV-C SH is an integral membrane protein with N(in)C(out) orientation located in both the plasma membrane as well as within intracellular compartments, which is similar to what has been described previously for SH proteins of other paramyxoviruses. Furthermore, we demonstrate that AMPV-C SH protein localizes in the endoplasmic reticulum (ER), Golgi, and cell surface, and is transported through ER-Golgi secretory pathway.

  18. Interaction between human BAP31 and respiratory syncytial virus small hydrophobic (SH) protein.

    PubMed

    Li, Yan; Jain, Neeraj; Limpanawat, Suweeraya; To, Janet; Quistgaard, Esben M; Nordlund, Par; Thanabalu, Thirumaran; Torres, Jaume

    2015-08-01

    The small hydrophobic (SH) protein is a short channel-forming polypeptide encoded by the human respiratory syncytial virus (hRSV). Deletion of SH protein leads to the viral attenuation in mice and primates, and delayed apoptosis in infected cells. We have used a membrane-based yeast two-hybrid system (MbY2H) and a library from human lung cDNA to detect proteins that bind SH protein. This led to the identification of a membrane protein, B-cell associated protein 31 (BAP31). Transfected SH protein co-localizes with transfected BAP31 in cells, and pulls down endogenous BAP31. Titration of purified C-terminal endodomain of BAP31 against isotopically labeled SH protein in detergent micelles suggests direct interaction between the two proteins. Given the key role of BAP31 in protein trafficking and its critical involvement in pro- and anti-apoptotic pathways, this novel interaction may constitute a potential drug target.

  19. Differential Effects of Hydrophobic Core Packing Residues for Thermodynamic and Mechanical Stability of a Hyperthermophilic Protein.

    PubMed

    Tych, Katarzyna M; Batchelor, Matthew; Hoffmann, Toni; Wilson, Michael C; Hughes, Megan L; Paci, Emanuele; Brockwell, David J; Dougan, Lorna

    2016-07-26

    Proteins from organisms that have adapted to environmental extremes provide attractive systems to explore and determine the origins of protein stability. Improved hydrophobic core packing and decreased loop-length flexibility can increase the thermodynamic stability of proteins from hyperthermophilic organisms. However, their impact on protein mechanical stability is not known. Here, we use protein engineering, biophysical characterization, single-molecule force spectroscopy (SMFS), and molecular dynamics (MD) simulations to measure the effect of altering hydrophobic core packing on the stability of the cold shock protein TmCSP from the hyperthermophilic bacterium Thermotoga maritima. We make two variants of TmCSP in which a mutation is made to reduce the size of aliphatic groups from buried hydrophobic side chains. In the first, a mutation is introduced in a long loop (TmCSP L40A); in the other, the mutation is introduced on the C-terminal β-strand (TmCSP V62A). We use MD simulations to confirm that the mutant TmCSP L40A shows the most significant increase in loop flexibility, and mutant TmCSP V62A shows greater disruption to the core packing. We measure the thermodynamic stability (ΔGD-N) of the mutated proteins and show that there is a more significant reduction for TmCSP L40A (ΔΔG = 63%) than TmCSP V62A (ΔΔG = 47%), as might be expected on the basis of the relative reduction in the size of the side chain. By contrast, SMFS measures the mechanical stability (ΔG*) and shows a greater reduction for TmCSP V62A (ΔΔG* = 8.4%) than TmCSP L40A (ΔΔG* = 2.5%). While the impact on the mechanical stability is subtle, the results demonstrate the power of tuning noncovalent interactions to modulate both the thermodynamic and mechanical stability of a protein. Such understanding and control provide the opportunity to design proteins with optimized thermodynamic and mechanical properties.

  20. Detergents as probes of hydrophobic binding cavities in serum albumin and other water-soluble proteins.

    PubMed Central

    Kragh-Hansen, U; Hellec, F; de Foresta, B; le Maire, M; Møller, J V

    2001-01-01

    As an extension of our studies on the interaction of detergents with membranes and membrane proteins, we have investigated their binding to water-soluble proteins. Anionic aliphatic compounds (dodecanoate and dodecylsulfate) were bound to serum albumin with high affinity at nine sites; related nonionic detergents (C12E8 and dodecylmaltoside) were bound at seven to eight sites, many in common with those of dodecanoate. The compounds were also bound in the hydrophobic cavity of beta-lactoglobulin, but not to ovalbumin. In addition to the generally recognized role of the Sudlow binding region II of serum albumin (localized at the IIIA subdomain) in fatty acid binding, quenching of the fluorescence intensity of tryptophan-214 by 7,8-dibromododecylmaltoside and 12-bromododecanoate also implicate the Sudlow binding region I (subdomain IIA) as a locus for binding of aliphatic compounds. Our data document the usefulness of dodecyl amphipathic compounds as probes of hydrophobic cavities in water-soluble proteins. In conjunction with recent x-ray diffraction analyses of fatty acid binding as the starting point we propose a new symmetrical binding model for the location of nine high-affinity sites on serum albumin for aliphatic compounds. PMID:11371462

  1. The sps Gene Products Affect the Germination, Hydrophobicity, and Protein Adsorption of Bacillus subtilis Spores

    PubMed Central

    Cangiano, Giuseppina; Sirec, Teja; Panarella, Cristina; Isticato, Rachele; Baccigalupi, Loredana; De Felice, Maurilio

    2014-01-01

    The multilayered surface of the Bacillus subtilis spore is composed of proteins and glycans. While over 70 different proteins have been identified as surface components, carbohydrates associated with the spore surface have not been characterized in detail yet. Bioinformatic data suggest that the 11 products of the sps operon are involved in the synthesis of polysaccharides present on the spore surface, but an experimental validation is available only for the four distal genes of the operon. Here, we report a transcriptional analysis of the sps operon and a functional study performed by constructing and analyzing two null mutants lacking either all or only the promoter-proximal gene of the operon. Our results show that both sps mutant spores apparently have normal coat and crust but have a small germination defect and are more hydrophobic than wild-type spores. We also show that spores lacking all Sps proteins are highly adhesive and form extensive clumps. In addition, sps mutant spores have an increased efficiency in adsorbing a heterologous enzyme, suggesting that hydrophobic force is a major determinant of spore adsorption and indicating that a deep understanding of the surface properties of the spore is essential for its full development as a surface display platform. PMID:25239894

  2. Soybean Hydrophobic Protein is Present in a Matrix Secreted by the Endocarp Epidermis during Seed Development

    PubMed Central

    Enstone, Daryl E.; Peterson, Carol A.; Gijzen, Mark

    2015-01-01

    Hydrophobic protein from soybean (HPS) is present in soybean dust and is an allergen (Gly m 1) that causes asthma in allergic individuals. Past studies have shown that HPS occurs on the seed surface. To determine the microscopic localization of HPS during seed development, monoclonal antibodies to HPS were used to visualize the protein by fluorescence and transmission electron microscopy. Seed coat and endocarp sections were also examined for pectin, cellulose, callose, starch, and protein by histochemical staining. HPS is present in the endocarp epidermal cells at 18 to 28 days post anthesis. At later stages of seed development, HPS occurs in extracellular secretions that accumulate unevenly on the endocarp epidermis and seed surface. HPS is synthesized by the endocarp epidermis and deposited on the seed surface as part of a heterogeneous matrix. PMID:26455712

  3. Preservation of protein in marine systems: Hydrophobic and other noncovalent associations as major stabilizing forces

    NASA Astrophysics Data System (ADS)

    Nguyen, Reno T.; Harvey, H. Rodger

    2001-05-01

    - The fate of proteins during early diagenesis was investigated in environments with low mineral content to assess preservation mechanisms other than mineral sorption. Preservation was examined in anoxic, organic-rich sediments of Mangrove Lake, a marine environment located in Bermuda, and for particulate material generated during oxic decay of diatoms. N-phenacylthiazolium bromide (PTB) treatment tested the hypothesis that proteins may undergo modification reactions with glucose to form advanced-glycation end products (AGEs). A small but significant release (additional 14%) of proteins was observed after PTB treatment in surficial sediments, indicating that some aggregations can proceed through an α-dicarbonyl intermediate of the AGE pathway. Size-exclusion high-pressure liquid chromatography with protein fluorescence, absorbance, and evaporative light-scattering detector measurements under native (phosphate or bicarbonate buffers) and denaturing (guanidine · HCl, urea, or acetonitrile) conditions point to the importance of hydrophobic and other noncovalent interactions in the stabilization of proteinaceous material in the environment. Soluble aggregates of substantial, relative molecular mass ( Mr ≳ 10 6) appear to be formed early in the diagenetic sequence. The preferential preservation of very high Mr, multisubunit phytoplankton proteins in sediments suggests that such aggregations confer resistance to degradation. Alternatively, some of the proteinaceous material may represent that fraction of organic matter that is highly prone to aggregations. Extended incubations (18 h; 37°C) with trypsin and proteinase-K showed that much of the aggregates that could be extracted are receptive to proteolytic cleavage. Buffer-, surfactant-, and NaOH-extractable aggregates comprised most of the acid-hydrolyzable proteinaceous material in detritus and surficial sediments but <35% in 9.7-m-deep sediments, suggesting additional mechanisms for preservation might be in

  4. Prediction of retention times of proteins in hydrophobic interaction chromatography using only their amino acid composition.

    PubMed

    Salgado, J Cristian; Rapaport, Ivan; Asenjo, Juan A

    2005-12-09

    This paper focuses on the prediction of the dimensionless retention time of proteins (DRT) in hydrophobic interaction chromatography (HIC) by means of mathematical models based, essentially, only on aminoacidic composition. The results show that such prediction is indeed possible. Our main contribution was the design of models that predict the DRT using the minimal information concerning a protein: its aminoacidic composition. The performance is similar to that observed in models that use much more sophisticated information such as the three-dimensional structure of proteins. Three models that, in addition to the amino acid composition, use different assumptions about the amino acids tendency to be exposed to the solvent, were evaluated in 12 proteins with known experimental DRT. In all the cases analyzed, the model that obtained the best results was the one based on a linear estimation of the aminoacidic surface composition. The models were adjusted using a collection of 74 vectors of aminoacidic properties plus a set of 6388 vectors derived from these using two mathematical tools: k-means and self-organizing maps (SOM) algorithms. The best vector was generated by the SOM algorithm and was interpreted as a hydrophobicity scale based partly on the tendency of the amino acids to be hidden in proteins. The prediction error (MSE(JK)) obtained by this model was almost 35% smaller than that obtained by the model that supposes that all the amino acids are completely exposed and 40% smaller than that obtained by the model that uses a simple correction factor considering the general tendency of each amino acid to be exposed to the solvent. In fact, the performance of the best model based on the aminoacidic composition was 5% better than that observed in the model based on the three-dimensional structure of proteins.

  5. Optimal Hydrophobicity in Ring-Opening Metathesis Polymerization-Based Protein Mimics Required for siRNA Internalization.

    PubMed

    deRonde, Brittany M; Posey, Nicholas D; Otter, Ronja; Caffrey, Leah M; Minter, Lisa M; Tew, Gregory N

    2016-06-13

    Exploring the role of polymer structure for the internalization of biologically relevant cargo, specifically siRNA, is of critical importance to the development of improved delivery reagents. Herein, we report guanidinium-rich protein transduction domain mimics (PTDMs) based on a ring-opening metathesis polymerization scaffold containing tunable hydrophobic moieties that promote siRNA internalization. Structure-activity relationships using Jurkat T cells and HeLa cells were explored to determine how the length of the hydrophobic block and the hydrophobic side chain compositions of these PTDMs impacted siRNA internalization. To explore the hydrophobic block length, two different series of diblock copolymers were synthesized: one series with symmetric block lengths and one with asymmetric block lengths. At similar cationic block lengths, asymmetric and symmetric PTDMs promoted siRNA internalization in the same percentages of the cell population regardless of the hydrophobic block length; however, with 20 repeat units of cationic charge, the asymmetric block length had greater siRNA internalization, highlighting the nontrivial relationships between hydrophobicity and overall cationic charge. To further probe how the hydrophobic side chains impacted siRNA internalization, an additional series of asymmetric PTDMs was synthesized that featured a fixed hydrophobic block length of five repeat units that contained either dimethyl (dMe), methyl phenyl (MePh), or diphenyl (dPh) side chains and varied cationic block lengths. This series was further expanded to incorporate hydrophobic blocks consisting of diethyl (dEt), diisobutyl (diBu), and dicyclohexyl (dCy) based repeat units to better define the hydrophobic window for which our PTDMs had optimal activity. High-performance liquid chromatography retention times quantified the relative hydrophobicities of the noncationic building blocks. PTDMs containing the MePh, diBu, and dPh hydrophobic blocks were shown to have superior

  6. Deconvoluting the Effect of the Hydrophobic and Hydrophilic Domains of an Amphiphilic Integral Membrane Protein in Lipid Bicontinuous Cubic Mesophases.

    PubMed

    van 't Hag, Leonie; Shen, Hsin-Hui; Lu, Jingxiong; Hawley, Adrian M; Gras, Sally L; Drummond, Calum J; Conn, Charlotte E

    2015-11-10

    Lipidic bicontinuous cubic mesophases with encapsulated amphiphilic proteins are widely used in a range of biological and biomedical applications, including in meso crystallization, as drug delivery vehicles for therapeutic proteins, and as biosensors and biofuel cells. However, the effect of amphiphilic protein encapsulation on the cubic phase nanostructure is not well-understood. In this study, we illustrate the effect of incorporating the bacterial amphiphilic membrane protein Ag43, and its individual hydrophobic β(43) and hydrophilic α(43) domains, in bicontinuous cubic mesophases. For the monoolein, monoalmitolein, and phytantriol cubic phases with and without 8% w/w cholesterol, the effect of the full length amphiphilic protein Ag43 on the cubic phase nanostructure was more significant than the sum of the individual hydrophobic β(43) and hydrophilic α(43) domains. Several factors were found to potentially influence the impact of the hydrophobic β(43) domain on the cubic phase internal nanostructure. These include the size of the hydrophobic β(43) domain relative to the thickness of the lipid bilayer, as well as its charge and diameter. The size of the hydrophilic α(43) domain relative to the water channel radius of the cubic mesophase was also found to be important. The secondary structure of the Ag43 proteins was affected by the hydrophobic thickness and physicochemical properties of the lipid bilayer and the water channel diameter of the cubic phase. Such structural changes may be small but could potentially affect membrane protein function.

  7. Effective protein separation by coupling hydrophobic interaction and reverse phase chromatography for top-down proteomics.

    PubMed

    Xiu, Lichen; Valeja, Santosh G; Alpert, Andrew J; Jin, Song; Ge, Ying

    2014-08-05

    One of the challenges in proteomics is the proteome's complexity, which necessitates the fractionation of proteins prior to the mass spectrometry (MS) analysis. Despite recent advances in top-down proteomics, separation of intact proteins remains challenging. Hydrophobic interaction chromatography (HIC) appears to be a promising method that provides high-resolution separation of intact proteins, but unfortunately the salts conventionally used for HIC are incompatible with MS. In this study, we have identified ammonium tartrate as a MS-compatible salt for HIC with comparable separation performance as the conventionally used ammonium sulfate. Furthermore, we found that the selectivity obtained with ammonium tartrate in the HIC mobile phases is orthogonal to that of reverse phase chromatography (RPC). By coupling HIC and RPC as a novel two-dimensional chromatographic method, we have achieved effective high-resolution intact protein separation as demonstrated with standard protein mixtures and a complex cell lysate. Subsequently, the separated intact proteins were identified by high-resolution top-down MS. For the first time, these results have shown the high potential of HIC as a high-resolution protein separation method for top-down proteomics.

  8. Molecular dynamics of the "hydrophobic patch" that immobilizes hydrophobin protein HFBII on silicon.

    PubMed

    Moldovan, Clara; Thompson, Damien

    2011-09-01

    The experimentally-observed stable, electrically-conducting interface formed between hydrophobin protein HFBII and silicon provides a model system for the Bio/ICT interfaces required for bionanoelectronics. The present work used molecular dynamics (MD) computer simulations to investigate the atom-scale details of the assembly and structure of the HFBII/silicon interface, using models on the order of 40,000 atoms to compute energy profiles for the full protein interacting with a bare Si(111) substrate in aqueous solution. Five nanoseconds of free, equilibrated dynamics were performed for six models with initial protein:silicon separations ranging from 1.2 to 0.2 nanometers in steps of 0.2 nm. Three of the models formed extensive protein:silicon van der Waals's interfacial contacts. The model with 0.2 nm starting separation serves as an illustrative example of the dynamic interface created, whereby hydrophobic patch residues cycle between flat and more protruding patch conformations that favor respectively close inter-patch and close patch-surface contacts, with protein:surface separations cycling between 0.2 and 0.4 nm over the 5 ns of dynamics. Analysis of residue-based binding energies at the interface reveal three leucines Leu19, Leu21 and Leu63, together with isoleucine Ile22 and alanine Ala61, as the primary drivers towards adhesion on bare silicon, providing the atom-scale details of HFBII’s hydrophobic patch which in turn provides leads for the engineering of more tightly-coupled interfaces.

  9. Generic folding and transition hierarchies for surface adsorption of hydrophobic-polar lattice model proteins.

    PubMed

    Li, Ying Wai; Wüst, Thomas; Landau, David P

    2013-01-01

    The thermodynamic behavior and structural properties of hydrophobic-polar (HP) lattice proteins interacting with attractive surfaces are studied by means of Wang-Landau sampling. Three benchmark HP sequences (48mer, 67mer, and 103mer) are considered with different types of surfaces, each of which attract either all monomers, only hydrophobic (H) monomers, or only polar (P) monomers, respectively. The diversity of folding behavior in dependence of surface strength is discussed. Analyzing the combined patterns of various structural observables, such as, e.g., the derivatives of the numbers of surface contacts, together with the specific heat, we are able to identify generic categories of folding and transition hierarchies. We also infer a connection between these transition categories and the relative surface strengths, i.e., the ratio of the surface attractive strength to the interchain attraction among H monomers. The validity of our proposed classification scheme is reinforced by the analysis of additional benchmark sequences. We thus believe that the folding hierarchies and identification scheme are generic for HP proteins interacting with attractive surfaces, regardless of chain length, sequence, or surface attraction.

  10. Generic folding and transition hierarchies for surface adsorption of hydrophobic-polar lattice model proteins

    NASA Astrophysics Data System (ADS)

    Li, Ying Wai; Wüst, Thomas; Landau, David P.

    2013-01-01

    The thermodynamic behavior and structural properties of hydrophobic-polar (HP) lattice proteins interacting with attractive surfaces are studied by means of Wang-Landau sampling. Three benchmark HP sequences (48mer, 67mer, and 103mer) are considered with different types of surfaces, each of which attract either all monomers, only hydrophobic (H) monomers, or only polar (P) monomers, respectively. The diversity of folding behavior in dependence of surface strength is discussed. Analyzing the combined patterns of various structural observables, such as, e.g., the derivatives of the numbers of surface contacts, together with the specific heat, we are able to identify generic categories of folding and transition hierarchies. We also infer a connection between these transition categories and the relative surface strengths, i.e., the ratio of the surface attractive strength to the interchain attraction among H monomers. The validity of our proposed classification scheme is reinforced by the analysis of additional benchmark sequences. We thus believe that the folding hierarchies and identification scheme are generic for HP proteins interacting with attractive surfaces, regardless of chain length, sequence, or surface attraction.

  11. PEGMA/MMA copolymer graftings: generation, protein resistance, and a hydrophobic domain.

    PubMed

    Stadler, Volker; Kirmse, Robert; Beyer, Mario; Breitling, Frank; Ludwig, Thomas; Bischoff, F Ralf

    2008-08-05

    We synthesized various graft copolymer films of poly(ethylene glycol) methacrylate (PEGMA) and methyl methacrylate (MMA) on silicon to examine the dependency of protein-surface interactions on grafting composition. We optimized atom transfer radical polymerizations to achieve film thicknesses from 25 to 100 nm depending on the monomer mole fractions, and analyzed the resulting surfaces by X-ray photoelectron spectroscopy (XPS), ellipsometry, contact angle measurements, and atomic force microscopy (AFM). As determined by XPS, the stoichiometric ratios of copolymer graftings correlated with the concentrations of provided monomer solutions. However, we found an unexpected and pronounced hydrophobic domain on copolymer films with a molar amount of 10-40% PEGMA, as indicated by advancing contact angles of up to 90 degrees . Nevertheless, a breakdown of the protein-repelling character was only observed for a fraction of 15% PEGMA and lower, far in the hydrophobic domain. Investigation of the structural basis of this exceptional wettability by high-resolution AFM demonstrated the independence of this property from morphological features.

  12. Disordered water within a hydrophobic protein cavity visualized by x-ray crystallography.

    PubMed

    Yu, B; Blaber, M; Gronenborn, A M; Clore, G M; Caspar, D L

    1999-01-05

    Water in the hydrophobic cavity of human interleukin 1beta, which was detected by NMR spectroscopy but was invisible by high resolution x-ray crystallography, has been mapped quantitatively by measurement and phasing of all of the low resolution x-ray diffraction data from a single crystal. Phases for the low resolution data were refined by iterative density modification of an initial flat solvent model outside the envelope of the atomic model. The refinement was restrained by the condition that the map of the difference between the electron density distribution in the full unit cell and that of the atomic model be flat within the envelope of the well ordered protein structure. Care was taken to avoid overfitting the diffraction data by maintaining phases for the high resolution data from the atomic model and by a resolution-dependent damping of the structure factor differences between data and model. The cavity region in the protein could accommodate up to four water molecules. The refined solvent difference map indicates that there are about two water molecules in the cavity region. This map is compatible with an atomic model of the water distribution refined by using XPLOR. About 70% of the time, there appears to be a water dimer in the central hydrophobic cavity, which is connected to the outside by two constricted channels occupied by single water molecules approximately 40% of the time on one side and approximately 10% on the other.

  13. A procedure for the automatic determination of hydrophobic cores in protein structures.

    PubMed Central

    Swindells, M. B.

    1995-01-01

    An algorithm is described for automatically detecting hydrophobic cores in proteins of known structure. Three pieces of information are considered in order to achieve this goal. These are: secondary structure, side-chain accessibility, and side-chain-side-chain contacts. Residues are considered to contribute to a core when they occur in regular secondary structure and have buried side chains that form predominantly nonpolar contacts with one another. This paper describes the algorithm's application to families of proteins with conserved topologies but low sequence similarities. The aim of this investigation is to determine the efficacy of the algorithm as well as to study the extent to which similar cores are identified within a common topology. PMID:7773181

  14. Effect of single-site mutations on hydrophobic-polar lattice proteins.

    PubMed

    Shi, Guangjie; Vogel, Thomas; Wüst, Thomas; Li, Ying Wai; Landau, David P

    2014-09-01

    We developed a heuristic method for determining the ground-state degeneracy of hydrophobic-polar (HP) lattice proteins, based on Wang-Landau and multicanonical sampling. It is applied during comprehensive studies of single-site mutations in specific HP proteins with different sequences. The effects in which we are interested include structural changes in ground states, changes of ground-state energy, degeneracy, and thermodynamic properties of the system. With respect to mutations, both extremely sensitive and insensitive positions in the HP sequence have been found. That is, ground-state energies and degeneracies, as well as other thermodynamic and structural quantities, may be either largely unaffected or may change significantly due to mutation.

  15. Effect of single-site mutations on hydrophobic-polar lattice proteins

    NASA Astrophysics Data System (ADS)

    Shi, Guangjie; Vogel, Thomas; Wüst, Thomas; Li, Ying Wai; Landau, David P.

    2014-09-01

    We developed a heuristic method for determining the ground-state degeneracy of hydrophobic-polar (HP) lattice proteins, based on Wang-Landau and multicanonical sampling. It is applied during comprehensive studies of single-site mutations in specific HP proteins with different sequences. The effects in which we are interested include structural changes in ground states, changes of ground-state energy, degeneracy, and thermodynamic properties of the system. With respect to mutations, both extremely sensitive and insensitive positions in the HP sequence have been found. That is, ground-state energies and degeneracies, as well as other thermodynamic and structural quantities, may be either largely unaffected or may change significantly due to mutation.

  16. Dynamics of Membrane Proteins within Synthetic Polymer Membranes with Large Hydrophobic Mismatch.

    PubMed

    Itel, Fabian; Najer, Adrian; Palivan, Cornelia G; Meier, Wolfgang

    2015-06-10

    The functioning of biological membrane proteins (MPs) within synthetic block copolymer membranes is an intriguing phenomenon that is believed to offer great potential for applications in life and medical sciences and engineering. The question why biological MPs are able to function in this completely artificial environment is still unresolved by any experimental data. Here, we have analyzed the lateral diffusion properties of different sized MPs within poly(dimethylsiloxane) (PDMS)-containing amphiphilic block copolymer membranes of membrane thicknesses between 9 and 13 nm, which results in a hydrophobic mismatch between the membrane thickness and the size of the proteins of 3.3-7.1 nm (3.5-5 times). We show that the high flexibility of PDMS, which provides membrane fluidities similar to phospholipid bilayers, is the key-factor for MP incorporation.

  17. Urea denatured state ensembles contain extensive secondary structure that is increased in hydrophobic proteins

    PubMed Central

    Nick Pace, C; Huyghues-Despointes, Beatrice M P; Fu, Hailong; Takano, Kazufumi; Scholtz, J Martin; Grimsley, Gerald R

    2010-01-01

    The goal of this article is to gain a better understanding of the denatured state ensemble (DSE) of proteins through an experimental and computational study of their denaturation by urea. Proteins unfold to different extents in urea and the most hydrophobic proteins have the most compact DSE and contain almost as much secondary structure as folded proteins. Proteins that unfold to the greatest extent near pH 7 still contain substantial amounts of secondary structure. At low pH, the DSE expands due to charge–charge interactions and when the net charge per residue is high, most of the secondary structure is disrupted. The proteins in the DSE appear to contain substantial amounts of polyproline II conformation at high urea concentrations. In all cases considered, including staph nuclease, the extent of unfolding by urea can be accounted for using the data and approach developed in the laboratory of Wayne Bolen (Auton et al., Proc Natl Acad Sci 2007; 104:15317–15323). PMID:20198681

  18. Are the interactions between recombinant prion proteins and polymeric surfaces related to the hydrophilic/hydrophobic balance?

    PubMed

    Vrlinic, Tjasa; Debarnot, Dominique; Legeay, Gilbert; Coudreuse, Arnaud; El Moualij, Benaissa; Zorzi, Willy; Perret-Liaudet, Armand; Quadrio, Isabelle; Mozetic, Miran; Poncin-Epaillard, Fabienne

    2012-06-01

    New non-fouling tubes are developed and their influence on the adhesion of neuroproteins is studied. Recombinant prion proteins are considered as a single component representative of hydrophobic proteins. Samples are stored for 24 h at 4 °C in tubes coated with two different coatings: poly(N-isopropylacrylamide) as a hydrophilic surface and a plasma-fluorinated coating as a hydrophobic one. The protein adhesion is monitored by ELISA tests, XPS and confocal microscopy. It appears that the highest recovery of recombinant prion protein in the liquid phase is obtained with the hydrophilic surface while the hydrophobic character of the storage tube induces an important amount of biological loss. However, the recovery is not complete even for tubes coated with poly(N-isopropylacrylamide).

  19. Magnitude and spatial orientation of the hydrophobic moments of multi-domain proteins.

    PubMed

    Zhou, Ruhong; Royyuru, Ajay; Athma, Prasanna; Suits, Frank

    2006-01-01

    The distributions of residue hydrophobicity for individual domains as well as for the aggregates of domains on a single chain have been found to exhibit well-defined second-order hydrophobic moment profiles. This indicates that most of the domains do fold into a stable entity with a core composed predominantly of hydrophobic residues as well as a prevalence of hydrophobic residues at the interface between domains. A simple scoring function based upon the relative hydrophobic moment dipole orientations shows that 80% of the dipoles of adjacent domains point to each other, highlighting hydrophobic residue prevalence at the domain interfaces.

  20. Thermal compaction of the intrinsically disordered protein tau: entropic, structural, and hydrophobic factors.

    PubMed

    Battisti, Anna; Ciasca, Gabriele; Grottesi, Alessandro; Tenenbaum, Alexander

    2017-03-28

    Globular denatured proteins have structural properties similar to those of random coils. Experiments on denatured proteins have shown that when the temperature is increased thermal compaction may take place, resulting in a reduction of their radius of gyration Rg to range between 5% and 35% of its initial value. This phenomenon has been attributed to various causes, namely entropic, hydrophobic, and structural factors. The intrinsically disordered protein tau, which helps in nucleating and stabilizing microtubules in the axons of the neurons, also undergoes a relevant compaction process: when its temperature is increased from 293 K to 333 K its gyration radius decreases by 18%. We have performed an atomistic simulation of this molecule, at the lowest and highest temperatures of the mentioned interval, using both standard molecular dynamics and metadynamics, in parallel with small-angle X-ray scattering experiments. Using the fit of the experimental data and a genetic algorithm to select the most probable configurations among those produced in both atomistic simulations (standard MD and metadynamics), we were able to compute relevant changes, related to the temperature increase, in the average angles between residues, in the transient secondary structures, in the solvent accessible surface area, and in the number of intramolecular H-bonds. The analysis of the data showed how to decompose the compaction phenomenon into three contributions. An estimate of the entropic contribution to the compaction was obtained using the changes in the mean values of the angles between contiguous residues. The computation of the solvent accessible surface at the two temperatures allowed an estimation of the second factor contributing to the compaction, namely the increase in the hydrophobic interaction. We also measured the change in the average number of residues temporarily being in α-helices, 3-helices, PP II helices, β-sheets and β-turns. Those changes in the secondary

  1. Effect of subdomain interactions on methyl group dynamics in the hydrophobic core of villin headpiece protein

    PubMed Central

    Vugmeyster, Liliya; Do, Tien; Ostrovsky, Dmitry; Fu, Riqianq

    2014-01-01

    Thermostable villin headpiece protein (HP67) consists of the N-terminal subdomain (residues 10–41) and the autonomously folding C-terminal subdomain (residues 42–76) which pack against each other to form a structure with a unified hydrophobic core. The X-ray structures of the isolated C-terminal subdomain (HP36) and its counterpart in HP67 are very similar for the hydrophobic core residues. However, fine rearrangements of the free energy landscape are expected to occur because of the interactions between the two subdomains. We detect and characterize these changes by comparing the µs-ms time scale dynamics of the methyl-bearing side chains in isolated HP36 and in HP67. Specifically, we probe three hydrophobic side chains at the interface of the two subdomains (L42, V50, and L75) as well as at two residues far from the interface (L61 and L69). Solid-state deuteron NMR techniques are combined with computational modeling for the detailed characterization of motional modes in terms of their kinetic and thermodynamic parameters. The effect of interdomain interactions on side chain dynamics is seen for all residues but L75. Thus, changes in dynamics because of subdomain interactions are not confined to the site of perturbation. One of the main results is a two-to threefold increase in the value of the activation energies for the rotameric mode of motions in HP67 compared with HP36. Detailed analysis of configurational entropies and heat capacities complement the kinetic view of the degree of the disorder in the folded state. PMID:24243806

  2. Appearance of a stress-response protein, phage-shock protein A, in Escherichia coli exposed to hydrophobic organic solvents.

    PubMed

    Kobayashi, H; Yamamoto, M; Aono, R

    1998-02-01

    A 28 kDa protein associated with the inner membrane was induced strongly in Escherichia coli K-12 cells grown in the presence of a hydrophobic organic solvent, n-hexane or cyclooctane. These organic solvents suppressed the growth (growth rate and yield) of E. coli. A partial amino acid sequence showed that this protein was the phage-shock protein PspA. PspA is known to be induced in E. coli cells under extreme stress conditions. The results suggest that E. coli cells are subject to strong stress in the presence of organic solvents. Introduction of a multi-copy plasmid vector carrying the psp operon into E. coli improved the survival frequency of cells exposed suddenly to n-hexane but not the growth rate of cells growing in the presence of n-hexane.

  3. Development of Cy5.5-Labeled Hydrophobically Modified Glycol Chitosan Nanoparticles for Protein Delivery

    NASA Astrophysics Data System (ADS)

    Chin, Amanda

    Therapeutic proteins are often highly susceptible to enzymatic degradation, thus restricting their in vivo stability. To overcome this limitation, delivery systems designed to promote uptake and reduce degradation kinetics have undergone a rapid shift from macro-scale systems to nanomaterial based carriers. Many of these nanomaterials, however, elicit immune responses and may have cytotoxic effects both in vitro and in vivo. The naturally derived polysaccharide chitosan has emerged as a promising biodegradable material and has been utilized for many biomedical applications; nevertheless, its function is often constrained by poor solubility. Glycol chitosan, a derivative of chitosan, can be hydrophobically modified to impart amphiphilic properties that enable the self-assembly into nanoparticles in aqueous media at neutral pH. This nanoparticle system has shown initial success as a therapeutic agent in several model cell culture systems, but little is known about its stability against enzymatic degradation. Therefore, the goal of this research was to investigate the resistance of hydrophobically modified glycol chitosan against enzyme-catalyzed degradation using an in vivo simulated system containing lysozyme. To synthesize the nanoparticles, hydrophobic cholanic acid was first covalently conjugated to glycol chitosan using of N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Conjugates were purified by dialysis, lyophilized, and ultra-sonicated to form nanoparticles. Fourier transform infrared (FT-IR) spectroscopy confirmed the binding of 5beta-cholanic acid to the glycol chitosan. Particle size and stability over time were determined with dynamic light scattering (DLS), and particle morphology was evaluated by transmission electron microscopy (TEM). The average diameter of the nanoparticles was approximately 200 nm, which remained stable at 4°C for up to 10 days. Additionally, a near infrared fluorescent (NIRF) dye

  4. Polymer monoliths with low hydrophobicity for strong cation-exchange capillary liquid chromatography of peptides and proteins.

    PubMed

    Gu, Binghe; Li, Yun; Lee, Milton L

    2007-08-01

    Two polymer monoliths were designed and synthesized from commercially available monomers with an attempt to decrease hydrophobicity for strong cation-exchange chromatography. One was prepared from the copolymerization of sulfoethyl methacrylate and poly(ethylene glycol) diacrylate, and the other was synthesized from vinylsulfonic acid and poly(ethylene glycol) diacrylate. Both of the monoliths were synthesized inside 75-microm i.d., UV-transparent fused-silica capillaries by photopolymerization. The hydrophobicities of the two monoliths were systematically evaluated using standard synthetic undecapeptides under ion-exchange conditions and propyl paraben under reversed-phase conditions. The poly(sulfoethyl methacrylate) monolith demonstrated similar hydrophobicity as a monolith prepared from copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid and poly(ethylene glycol) diacrylate, and 40% acetonitrile was required to suppress any hydrophobic interactions with peptides under ion-exchange conditions. However, with the use of vinylsulfonic acid as the functional monomer, a monolith with very low hydrophobicity was obtained, making it suitable for strong cation-exchange liquid chromatography of both peptides and proteins. It was found that monolith hydrophobicity could be adjusted by selection of monomers that differ in hydrocarbon content and type of vinyl group. Finally, excellent separations of model protein standards and high-density lipoproteins were achieved using the poly(vinylsulfonic acid) monolith. Five subclasses of high-density lipoproteins were resolved using a simple linear NaCl gradient.

  5. Unique motifs and hydrophobic interactions shape the binding of modified DNA ligands to protein targets

    PubMed Central

    Davies, Douglas R.; Gelinas, Amy D.; Zhang, Chi; Rohloff, John C.; Carter, Jeffrey D.; O’Connell, Daniel; Waugh, Sheela M.; Wolk, Steven K.; Mayfield, Wesley S.; Burgin, Alex B.; Edwards, Thomas E.; Stewart, Lance J.; Gold, Larry; Janjic, Nebojsa; Jarvis, Thale C.

    2012-01-01

    Selection of aptamers from nucleic acid libraries by in vitro evolution represents a powerful method of identifying high-affinity ligands for a broad range of molecular targets. Nevertheless, a sizeable fraction of proteins remain difficult targets due to inherently limited chemical diversity of nucleic acids. We have exploited synthetic nucleotide modifications that confer protein-like diversity on a nucleic acid scaffold, resulting in a new generation of binding reagents called SOMAmers (Slow Off-rate Modified Aptamers). Here we report a unique crystal structure of a SOMAmer bound to its target, platelet-derived growth factor B (PDGF-BB). The SOMAmer folds into a compact structure and exhibits a hydrophobic binding surface that mimics the interface between PDGF-BB and its receptor, contrasting sharply with mainly polar interactions seen in traditional protein-binding aptamers. The modified nucleotides circumvent the intrinsic diversity constraints of natural nucleic acids, thereby greatly expanding the structural vocabulary of nucleic acid ligands and considerably broadening the range of accessible protein targets. PMID:23139410

  6. Thermostability of salt bridges versus hydrophobic interactions in proteins probed by statistical potentials.

    PubMed

    Folch, Benjamin; Rooman, Marianne; Dehouck, Yves

    2008-01-01

    The temperature dependence of the interactions that stabilize protein structures is a long-standing issue, the elucidation of which would enable the prediction and the rational modification of the thermostability of a target protein. It is tackled here by deriving distance-dependent amino acid pair potentials from four datasets of proteins with increasing melting temperatures (Tm). The temperature dependence of the interactions is determined from the differences in the shape of the potentials derived from the four datasets. Note that, here, we use an unusual dataset definition, which is based on the Tm values, rather than on the living temperature of the host organisms. Our results show that the stabilizing weight of hydrophobic interactions (between Ile, Leu, and Val) remains constant as the temperature increases, compared to the other interactions. In contrast, the two minima of the Arg--Glu and Arg--Asp salt bridge potentials show a significant Tm dependence. These two minima correspond to two geometries: the fork--fork geometry, where the side chains point toward each other, and the fork--stick geometry, which involves the N(epsilon) side chain atom of Arg. These two types of salt bridges were determined to be significantly more stabilizing at high temperature. Moreover, a preference for more-compact salt bridges is noticeable in heat-resistant proteins, especially for the fork--fork geometry. The Tm-dependent potentials that have been defined here should be useful for predicting thermal stability changes upon mutation.

  7. Amphiphilic polybetaines: the effect of side-chain hydrophobicity on protein adsorption.

    PubMed

    Colak, Semra; Tew, Gregory N

    2012-05-14

    Novel amphiphilic polybetaines were synthesized and used as the base material for nonfouling coatings. The amphiphilicity of these polybetaines was systematically tuned by coupling chains of increasing hydrophobicity to the zwitterionic functionality side at the repeat unit level. An oligoethylene glycol (OEG) moiety was selected to yield the most hydrophilic coating, while octyl (C(8)) and fluorinated (F) groups were used to impart lipophilicity and lipophobicity to the coatings, respectively. This unique design allowed us to investigate the effect of the lipophilicity/lipophobicity of the side chain on the nonfouling properties of these zwitterionic systems. Adsorption studies, performed using six different proteins, showed that the fluorinated polybetaine, Poly[NFZI-co-NSi], resisted nonspecific adsorption as effectively as, and in some cases even better than, the most hydrophilic Poly[NOEGZI-co-NSi] coating. The comparison of Poly[NFZI-co-NSi] to its noncharged analog demonstrated the essential nature of the zwitterionic functionality in imparting nonfouling character to the coating.

  8. Functional Validation of Hydrophobic Adaptation to Physiological Temperature in the Small Heat Shock Protein αA-crystallin

    PubMed Central

    Posner, Mason; Kiss, Andor J.; Skiba, Jackie; Drossman, Amy; Dolinska, Monika B.; Hejtmancik, J. Fielding; Sergeev, Yuri V.

    2012-01-01

    Small heat shock proteins (sHsps) maintain cellular homeostasis by preventing stress and disease-induced protein aggregation. While it is known that hydrophobicity impacts the ability of sHsps to bind aggregation-prone denaturing proteins, the complex quaternary structure of globular sHsps has made understanding the significance of specific changes in hydrophobicity difficult. Here we used recombinant protein of the lenticular sHsp α A-crystallin from six teleost fishes environmentally adapted to temperatures ranging from -2°C to 40°C to identify correlations between physiological temperature, protein stability and chaperone-like activity. Using sequence and structural modeling analysis we identified specific amino acid differences between the warm adapted zebrafish and cold adapted Antarctic toothfish that could contribute to these correlations and validated the functional consequences of three specific hydrophobicity-altering amino acid substitutions in αA-crystallin. Site directed mutagenesis of three residues in the zebrafish (V62T, C143S, T147V) confirmed that each impacts either protein stability or chaperone-like activity or both, with the V62T substitution having the greatest impact. Our results indicate a role for changing hydrophobicity in the thermal adaptation of α A-crystallin and suggest ways to produce sHsp variants with altered chaperone-like activity. These data also demonstrate that a comparative approach can provide new information about sHsp function and evolution. PMID:22479631

  9. Increasing Sequence Diversity with Flexible Backbone Protein Design: The Complete Redesign of a Protein Hydrophobic Core

    SciTech Connect

    Murphy, Grant S.; Mills, Jeffrey L.; Miley, Michael J.; Machius, Mischa; Szyperski, Thomas; Kuhlman, Brian

    2015-10-15

    Protein design tests our understanding of protein stability and structure. Successful design methods should allow the exploration of sequence space not found in nature. However, when redesigning naturally occurring protein structures, most fixed backbone design algorithms return amino acid sequences that share strong sequence identity with wild-type sequences, especially in the protein core. This behavior places a restriction on functional space that can be explored and is not consistent with observations from nature, where sequences of low identity have similar structures. Here, we allow backbone flexibility during design to mutate every position in the core (38 residues) of a four-helix bundle protein. Only small perturbations to the backbone, 12 {angstrom}, were needed to entirely mutate the core. The redesigned protein, DRNN, is exceptionally stable (melting point >140C). An NMR and X-ray crystal structure show that the side chains and backbone were accurately modeled (all-atom RMSD = 1.3 {angstrom}).

  10. Aptamer binding to celiac disease-triggering hydrophobic proteins: a sensitive gluten detection approach.

    PubMed

    Amaya-González, Sonia; de-Los-Santos-Álvarez, Noemí; Miranda-Ordieres, Arturo J; Lobo-Castañón, M Jesús

    2014-03-04

    Celiac disease represents a significant public health problem in large parts of the world. A major hurdle in the effective management of the disease by celiac sufferers is the sensitivity of the current available methods for assessing gluten contents in food. In response, we report a highly sensitive approach for gluten analysis using aptamers as specific receptors. Gliadins, a fraction of gluten proteins, are the main constituent responsible for triggering the disease. However, they are highly hydrophobic and large molecules, regarded as difficult targets for in vitro evolution of aptamers without nucleobase modification. We describe the successful selection of aptamers for these water insoluble prolamins that was achieved choosing the immunodominant apolar peptide from α2-gliadin as a target for selection. All aptamers evolved are able to bind the target in its native environment within the natural protein. The best nonprotein receptor is the basis for an electrochemical competitive enzyme-linked assay on magnetic particles, which allows the measurement of as low as 0.5 ppb of gliadin standard (0.5 ppm of gluten). Reference immunoassay for detecting the same target has a limit of detection of 3 ppm, 6 times less sensitive than this method. Importantly, it also displays high specificity, detecting the other three prolamins toxic for celiac patients and not showing cross-reactivity to nontoxic proteins such as maize, soya, and rice. These features make the proposed method a valuable tool for gluten detection in foods.

  11. Wang-Landau sampling in face-centered-cubic hydrophobic-hydrophilic lattice model proteins.

    PubMed

    Liu, Jingfa; Song, Beibei; Yao, Yonglei; Xue, Yu; Liu, Wenjie; Liu, Zhaoxia

    2014-10-01

    Finding the global minimum-energy structure is one of the main problems of protein structure prediction. The face-centered-cubic (fcc) hydrophobic-hydrophilic (HP) lattice model can reach high approximation ratios of real protein structures, so the fcc lattice model is a good choice to predict the protein structures. The lacking of an effective global optimization method is the key obstacle in solving this problem. The Wang-Landau sampling method is especially useful for complex systems with a rough energy landscape and has been successfully applied to solving many optimization problems. We apply the improved Wang-Landau (IWL) sampling method, which incorporates the generation of an initial conformation based on the greedy strategy and the neighborhood strategy based on pull moves into the Wang-Landau sampling method to predict the protein structures on the fcc HP lattice model. Unlike conventional Monte Carlo simulations that generate a probability distribution at a given temperature, the Wang-Landau sampling method can estimate the density of states accurately via a random walk, which produces a flat histogram in energy space. We test 12 general benchmark instances on both two-dimensional and three-dimensional (3D) fcc HP lattice models. The lowest energies by the IWL sampling method are as good as or better than those of other methods in the literature for all instances. We then test five sets of larger-scale instances, denoted by the S, R, F90, F180, and CASP target instances on the 3D fcc HP lattice model. The numerical results show that our algorithm performs better than the other five methods in the literature on both the lowest energies and the average lowest energies in all runs. The IWL sampling method turns out to be a powerful tool to study the structure prediction of the fcc HP lattice model proteins.

  12. G protein antagonists. A novel hydrophobic peptide competes with receptor for G protein binding.

    PubMed

    Mukai, H; Munekata, E; Higashijima, T

    1992-08-15

    A substance P (SP) analog, [D-Pro4,D-Trp7,9,10] SP4-11, is known to inhibit the actions of various structurally unrelated messenger molecules as well as SP. Our studies on the effects of this peptide on the regulation of purified G proteins by receptor showed that at least some of the biological effects of the peptide can be explained by the ability of the peptide to block the activation of G proteins by receptors. Here we report that a novel truncated SP-related peptide, pGlu-Gln-D-Trp-Phe-D-Trp-D-Trp-Met-NH2, inhibited the activation of G(i) or G(o) by M2 muscarinic cholinergic receptor (M2 mAChR) or of Gs by beta-adrenergic receptor in the reconstituted phospholipid vesicles, assayed by receptor-promoted GTP hydrolysis. The inhibition by the peptide was apparently reversible and competitive with respect to receptor binding to G proteins; the inhibition could be overcome by increasing the concentration of receptor in the vesicles and was not altered by changes in the concentration of G protein. The competing effects of the peptide were used to analyze the effect of agonist on receptor-G protein interaction. The concentration change of muscarinic agonist did not alter the inhibitory effects of the peptide on M2 mAChR-promoted GTPase by G(o), which is consistent with the idea that agonist increases the regulatory efficiency of the receptor but does not alter its affinity for G proteins. This new group of compounds (G protein antagonists) is a promising tool to study receptor-G protein interaction quantitatively.

  13. Designability and cooperative folding in a four-letter hydrophobic-polar model of proteins

    NASA Astrophysics Data System (ADS)

    Liu, Hai-Guang; Tang, Lei-Han

    2006-11-01

    The two-letter hydrophobic-polar (HP) model of Lau and Dill [Macromolecules 22, 3986 (1989)] has been widely used in theoretical studies of protein folding due to its conceptual and computational simplicity. Despite its success in elucidating various aspects of the sequence-structure relationship, thermodynamic behavior of the model is not in agreement with a sharp two-state folding transition of many single-domain proteins. To gain a better understanding of this discrepancy, we consider an extension of the HP model by including an “antiferromagnetic” (AF) interaction in the contact potential that favors amino acid residues with complementary attributes. With an enlarged four-letter alphabet, the density of states on the low energy side can be significantly decreased. Computational studies of the four-letter HP model are performed on 36-mer sequences on a square lattice. It is found that the designability of folded structures in the extended model exhibits strong correlation with that of the two-letter HP model, while the AF interaction alone selects a very different class of structures that resembles the Greek key motif for beta sheets. A procedure is introduced to select sequences which have the largest energy gap to the native state. Based on density of states and specific heat calculations in the full configuration space, we show that the optimized sequence is able to fold nearly as cooperatively as a corresponding Gō model.

  14. Two homologous low-temperature-inducible genes from Arabidopsis encode highly hydrophobic proteins.

    PubMed Central

    Capel, J; Jarillo, J A; Salinas, J; Martínez-Zapater, J M

    1997-01-01

    We have characterized two related cDNAs (RCI2A and RCI2B) corresponding to genes from Arabidopsis thaliana, the expression of which is transiently induced by low, nonfreezing temperatures. RCI2A and RCI2B encode small (54 amino acids), highly hydrophobic proteins that bear two potential transmembrane domains. They show similarity to proteins encoded by genes from barley (Hordeum vulgare L.) and wheatgrass (Lophophyrum elongatum) that are regulated by different stress conditions. Their high level of sequence homology (78%) and their genomic location in a single restriction fragment suggest that both genes originated as a result of a tandem duplication. However, their regulatory sequences have diverged enough to confer on them different expression patterns. Like most of the cold-inducible plant genes characterized, the expression of RCI2A and RCI2B is also promoted by abscisic acid (ABA) and dehydration but is not a general response to stress conditions, since it is not induced by salt stress or by anaerobiosis. Furthermore, low temperatures are able to induce RCI2A and RCI2B expression in ABA-deficient and -insensitive genetic backgrounds, indicating that both ABA-dependent and -independent pathways regulate the low-temperature responsiveness of these two genes. PMID:9342870

  15. Predicting the behaviour of proteins in hydrophobic interaction chromatography. 2. Using a statistical description of their surface amino acid distribution.

    PubMed

    Salgado, J Cristian; Rapaport, Ivan; Asenjo, Juan A

    2006-02-24

    This paper focuses on the prediction of the dimensionless retention time (DRT) of proteins in hydrophobic interaction chromatography (HIC) by means of mathematical models based on the statistical description of the amino acid surface distribution. Previous models characterises the protein surface as a whole. However, most of the time it is not the whole protein but some of its specific regions that interact with the environment. It seems much more natural to use local measurements of the characteristics of the surface. Therefore, the statistical characterisation of the distribution of an amino acid property on the protein surface was carried out from the systematic calculation of the local average of this property in a neighbourhood placed sequentially on each of the amino acids on the protein surface. This process allowed us to characterise the distribution of this property quantitatively using three main statistics: average, standard deviation and maximum. In particular, if the property considered is a hydrophobicity scale, these statistics allowed us to characterise the average hydrophobicity and the hydrophobic content of the most hydrophobic cluster or hotspot, as well as the heterogeneity of the hydrophobicity distribution on the protein surface. We tested the performance of the DRT predictive models based on these statistics on a set of 15 proteins. We obtained better predictive results with respect to the models previously reported. The best predictive model was a linear model based on the maximum. This statistic was calculated using an index of the mobilities of amino acids in chromatography. The predictive performance of this model (measured as the Jack Knife MSE) was 26.9% better than those obtained by the best model which does not consider the amino acid distribution and 19.5% better than the model based on the hydrophobic imbalance (HI). In addition, the best performance was obtained by a linear multivariable model based on the HI and the maximum. The

  16. The fungal cerato-platanin protein EPL1 forms highly ordered layers at hydrophobic/hydrophilic interfaces.

    PubMed

    Bonazza, K; Gaderer, R; Neudl, S; Przylucka, A; Allmaier, G; Druzhinina, I S; Grothe, H; Friedbacher, G; Seidl-Seiboth, V

    2015-03-07

    Cerato-platanin proteins (CPPs) and hydrophobins are two classes of small, secreted proteins that are exclusively found in fungi. CPPs are known as chitin-binding proteins, and were recently also shown to form protein layers at air/water interfaces, but the features of these layers were not investigated on the molecular level yet. In this study, by means of atomic force microscopy (AFM), EPL1, a member of the CPP family was shown to form highly ordered monolayers at a hydrophobic surface/liquid-interface. Furthermore, two new hydrophobins were analysed, and the influence of EPL1 on hydrophobin layers was studied in situ. Hydrophobins are amphiphilic proteins that are able to self-assemble at hydrophobic/hydrophilic interfaces, thereby inverting the polarity of the surface. This renders fungal growth structures such as spores water repellent. The combination of AFM data and wettability experiments led to the conclusion that in presence of both, hydrophobins and EPL1, a previously unknown hybrid layer is formed. This mixed protein layer is on one hand not inverting but enhancing the hydrophobicity of HOPG (highly oriented pyrolytic graphite), typical for EPL1, and on the other hand, it is stable and water insoluble, which is reminiscent of hydrophobin layers.

  17. Reversible Interactions of Proteins with Mixed Shell Polymeric Micelles: Tuning the Surface Hydrophobic/Hydrophilic Balance toward Efficient Artificial Chaperones.

    PubMed

    Wang, Jianzu; Song, Yiqing; Sun, Pingchuan; An, Yingli; Zhang, Zhenkun; Shi, Linqi

    2016-03-22

    Molecular chaperones can elegantly fine-tune its hydrophobic/hydrophilic balance to assist a broad spectrum of nascent polypeptide chains to fold properly. Such precious property is difficult to be achieved by chaperone mimicking materials due to limited control of their surface characteristics that dictate interactions with unfolded protein intermediates. Mixed shell polymeric micelles (MSPMs), which consist of two kinds of dissimilar polymeric chains in the micellar shell, offer a convenient way to fine-tune surface properties of polymeric nanoparticles. In the current work, we have fabricated ca. 30 kinds of MSPMs with finely tunable hydrophilic/hydrophobic surface properties. We investigated the respective roles of thermosensitive and hydrophilic polymeric chains in the thermodenaturation protection of proteins down to the molecular structure. Although the three kinds of thermosensitive polymers investigated herein can form collapsed hydrophobic domains on the micellar surface, we found distinct capability to capture and release unfolded protein intermediates, due to their respective affinity for proteins. Meanwhile, in terms of the hydrophilic polymeric chains in the micellar shell, poly(ethylene glycol) (PEG) excels in assisting unfolded protein intermediates to refold properly via interacting with the refolding intermediates, resulting in enhanced chaperone efficiency. However, another hydrophilic polymer-poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) severely deteriorates the chaperone efficiency of MSPMs, due to its protein-resistant properties. Judicious combination of thermosensitive and hydrophilic chains in the micellar shell lead to MSPM-based artificial chaperones with optimal efficacy.

  18. The N-terminal repeat and the ligand binding domain A of SdrI protein is involved in hydrophobicity of S. saprophyticus.

    PubMed

    Kleine, Britta; Ali, Liaqat; Wobser, Dominique; Sakιnç, Türkân

    2015-03-01

    Staphylococcus saprophyticus is an important cause of urinary tract infection, and its cell surface hydrophobicity may contribute to virulence by facilitating adherence of the organism to uroepithelia. S. saprophyticus expresses the surface protein SdrI, a member of the serine-aspartate repeat (SD) protein family, which has multifunctional properties. The SdrI knock out mutant has a reduced hydrophobicity index (HPI) of 25%, and expressed in the non-hydrophobic Staphylococcus carnosus strain TM300 causes hydrophobicity. Using hydrophobic interaction chromatography (HIC), we confined the hydrophobic site of SdrI to the N-terminal repeat region. S. saprophyticus strains carrying different plasmid constructs lacking either the N-terminal repeats, both B or SD-repeats were less hydrophobic than wild type and fully complemented SdrI mutant (HPI: 51%). The surface hydrophobicity and HPI of both wild type and the complemented strain were also influenced by calcium (Ca(2+)) and were reduced from 81.3% and 82.4% to 10.9% and 12.3%, respectively. This study confirms that the SdrI protein of S. saprophyticus is a crucial factor for surface hydrophobicity and also gives a first significant functional description of the N-terminal repeats, which in conjunction with the B-repeats form an optimal hydrophobic conformation.

  19. Rescuing Those Left Behind: Recovering and Characterizing Underdigested Membrane and Hydrophobic Proteins To Enhance Proteome Measurement Depth.

    PubMed

    Giannone, Richard J; Wurch, Louie L; Podar, Mircea; Hettich, Robert L

    2015-08-04

    The marine archaeon Nanoarchaeum equitans is dependent on direct physical contact with its host, the hyperthermophile Ignicoccus hospitalis. As this interaction is thought to be membrane-associated, involving a myriad of membrane-anchored proteins, proteomic efforts to better characterize this difficult to analyze interface are paramount to uncovering the mechanism of their association. By extending multienzyme digestion strategies that use sample filtration to recover underdigested proteins for reprocessing/consecutive proteolytic digestion, we applied chymotrypsin to redigest the proteinaceous material left over after initial proteolysis with trypsin of sodium dodecyl sulfate (SDS)-extracted I. hospitalis-N. equitans proteins. Using this method, we show that proteins with increased hydrophobic character, including membrane proteins with multiple transmembrane helices, are enriched and recovered in the underdigested fraction. Chymotryptic reprocessing provided significant sequence coverage gains in both soluble and hydrophobic proteins alike, with the latter benefiting more so in terms of membrane protein representation. These gains were despite a large proportion of high-quality peptide spectra remaining unassigned in the underdigested fraction suggesting high levels of protein modification on these often surface-exposed proteins. Importantly, these gains were achieved without applying extensive fractionation strategies usually required for thorough characterization of membrane-associated proteins and were facilitated by the generation of a distinct, complementary set of peptides that aid in both the identification and quantitation of this important, under-represented class of proteins.

  20. A study of the hydration of ribonuclease A using densitometry: Effect of the protein hydrophobicity and polarity

    NASA Astrophysics Data System (ADS)

    Sirotkin, Vladimir A.; Khadiullina, Aigul V.

    2014-05-01

    The excess volumes of the binary system of ribonuclease A (RNase A) with water were obtained as a function of composition at 25 °C. The excess quantities for RNase A were compared with the published data for several unrelated proteins (lysozyme, serum albumin, lactoglobulin, and chymotrypsinogen A). The hydrophobicity of these proteins is gradually changed over a wide range. It was found that the more hydrophilic a protein is, the more significant the hydrophilic hydration contribution is. RNase A is the most hydrophilic protein in the present study, and it has the most significant hydrophilic hydration contribution.

  1. Role of the hydrophobic and hydrophilic sites in the dynamic crossover of the protein-hydration water

    NASA Astrophysics Data System (ADS)

    Köhler, Mateus Henrique; Barbosa, Rafael C.; da Silva, Leandro B.; Barbosa, Marcia C.

    2017-02-01

    Molecular dynamics simulations were performed to study the water structure and dynamics in the hydration shell of the globular TS-Kappa protein. The results show that for a wide range of temperatures the diffusion coefficient of water near the protein surface is lower than in bulk. A crossover in the diffusion behavior of hydration water is observed at different temperatures for hydrophilic and hydrophobic vicinities. We have found a correlation between the crossover in the hydrophilic case and the protein dynamical transition. An explanation in terms of the competition between water-water water-protein H-bond formation is provided based on H-bond network analysis.

  2. Preparation of a novel dual-function strong cation exchange/hydrophobic interaction chromatography stationary phase for protein separation.

    PubMed

    Zhao, Kailou; Yang, Li; Wang, Xuejiao; Bai, Quan; Yang, Fan; Wang, Fei

    2012-08-30

    We have explored a novel dual-function stationary phase which combines both strong cation exchange (SCX) and hydrophobic interaction chromatography (HIC) characteristics. The novel dual-function stationary phase is based on porous and spherical silica gel functionalized with ligand containing sulfonic and benzyl groups capable of electrostatic and hydrophobic interaction functionalities, which displays HIC character in a high salt concentration, and IEC character in a low salt concentration in mobile phase employed. As a result, it can be employed to separate proteins with SCX and HIC modes, respectively. The resolution and selectivity of the dual-function stationary phase were evaluated under both HIC and SCX modes with standard proteins and can be comparable to that of conventional IEC and HIC columns. More than 96% of mass and bioactivity recoveries of proteins can be achieved in both HIC and SCX modes, respectively. The results indicated that the novel dual-function column could replace two individual SCX and HIC columns for protein separation. Mixed retention mechanism of proteins on this dual-function column based on stoichiometric displacement theory (SDT) in LC was investigated to find the optimal balance of the magnitude of electrostatic and hydrophobic interactions between protein and the ligand on the silica surface in order to obtain high resolution and selectivity for protein separation. In addition, the effects of the hydrophobicity of the ligand of the dual-function packings and pH of the mobile phase used on protein separation were also investigated in detail. The results show that the ligand with suitable hydrophobicity to match the electrostatic interaction is very important to prepare the dual-function stationary phase, and a better resolution and selectivity can be obtained at pH 6.5 in SCX mode. Therefore, the dual-function column can replace two individual SCX and HIC columns for protein separation and be used to set up two-dimensional liquid

  3. Influence of preadsorbed milk proteins on adhesion of Listeria monocytogenes to hydrophobic and hydrophilic silica surfaces.

    PubMed Central

    al-Makhlafi, H; McGuire, J; Daeschel, M

    1994-01-01

    The adsorption of beta-lactoglobulin, bovine serum albumin, alpha-lactalbumin, and beta-casein for 8 h and beta-lactoglobulin and bovine serum albumin for 1 h at silanized silica surfaces of low and high hydrophobicity, followed by incubation in buffer and contact with Listeria monocytogenes, resulted in different numbers of cells adhered per unit of surface area. Adhesion to both surfaces was greatest when beta-lactoglobulin was present and was lowest when bovine serum albumin was present. Preadsorption of alpha-lactalbumin and beta-casein showed an intermediate effect on cell adhesion. Adsorption of beta-lactoglobulin for 1 h resulted in a generally lower number of cells adhered compared with the 8-h adsorption time, while the opposite result was observed with respect to bovine serum albumin. The adhesion data were explainable in terms of the relative rates of arrival to the surface and postadsorptive conformational change among the proteins, in addition to the extent of surface coverage in each case. PMID:7986033

  4. Adsorption of a Protein Monolayer via Hydrophobic Interactions Prevents Nanoparticle Aggregation under Harsh Environmental Conditions

    PubMed Central

    Dominguez-Medina, Sergio; Blankenburg, Jan; Olson, Jana; Landes, Christy F.; Link, Stephan

    2013-01-01

    We find that citrate-stabilized gold nanoparticles aggregate and precipitate in saline solutions below the NaCl concentration of many bodily fluids and blood plasma. Our experiments indicate that this is due to complexation of the citrate anions with Na+ cations in solution. A dramatically enhanced colloidal stability is achieved when bovine serum albumin is adsorbed to the gold nanoparticle surface, completely preventing nanoparticle aggregation under harsh environmental conditions where the NaCl concentration is well beyond the isotonic point. Furthermore, we explore the mechanism of the formation of this albumin ‘corona’ and find that monolayer protein adsorption is most likely ruled by hydrophobic interactions. As for many nanotechnology-based biomedical and environmental applications, particle aggregation and sedimentation are undesirable and could substantially increase the risk of toxicological side-effects, the formation of the BSA corona presented here provides a low-cost bio-compatible strategy for nanoparticle stabilization and transport in highly ionic environments. PMID:23914342

  5. Hydrophobicity, thermal and micro-structural properties of whey protein concentrate-pullulan-beeswax films.

    PubMed

    Jafari, Seid Mahdi; Khanzadi, Mehrdad; Mirzaei, Habibollah; Dehnad, Danial; Chegini, Faramarz Khodaian; Maghsoudlou, Yayha

    2015-09-01

    In this research, effects of beeswax (BW) on functional properties of whey protein concentrates (WPC):pullulan (PUL) films were investigated. For this purpose, 0, 10, 20 and 30w/w(glycerol)% BW rates and 30:70, 50:50 and 70:30w/w% WPC:PUL ratios were applied. Films containing 70% WPC:30% PUL (WPC70) and 30% BW (BW30) justified the highest contact angle (92.4°) among all films; SEM micrographs indicated that BW could come toward the surface of films during drying stage and resulted in a higher hydrophobic behavior of bilayer films compared with blend films. WPC70 supplied the lowest T(g) values (36-48 °C) among different proportions of WPC-PUL; the highest melting points were just assured in the absence of BW regardless of combination ratio for WPI:PUL. BW30 films deserved lower roughness rates than BW20 (and even BW10) films, indicating more advantageous microstructure and higher hydrogen connections in BW30 films and justifying similar melting points attained for BW30 films to BW20 or 10 ones. Overall, application of WPC70 and BW30 was recommended to obtain optimum combination of final properties for WPC-PUL-BW bilayer films as SEM exhibited flexible and elastic structures of such films.

  6. cDNA cloning and sequence of MAL, a hydrophobic protein associated with human T-cell differentiation.

    PubMed Central

    Alonso, M A; Weissman, S M

    1987-01-01

    We have isolated a human cDNA that is expressed in the intermediate and late stages of T-cell differentiation. The cDNA encodes a highly hydrophobic protein, termed MAL, that lacks a hydrophobic leader peptide sequence and contains four potential transmembrane domains separated by short hydrophilic segments. The predicted configuration of the MAL protein resembles the structure of integral proteins that form pores or channels in the plasma membrane and that are believed to act as transporters of water-soluble molecules and ions across the lipid bilayer. The presence of MAL mRNA in a panel of T-cell lines that express both the T-cell receptor and the T11 antigen suggests that MAL may be involved in membrane signaling in T cells activated via either T11 or T-cell receptor pathways. Images PMID:3494249

  7. Rescuing Those Left Behind: Recovering and Characterizing Underdigested Membrane and Hydrophobic Proteins To Enhance Proteome Measurement Depth

    SciTech Connect

    Giannone, Richard J.; Wurch, Louie L.; Podar, Mircea; Hettich, Robert L.

    2015-06-25

    The marine archaeon Nanoarchaeum equitans is dependent on direct physical contact with its host, the hyperthermophile Ignicoccus hospitalis. It is thought that this interaction is membrane-associated, involving a myriad of membrane-anchored proteins; proteomic efforts to better characterize this difficult to analyze interface are paramount to uncovering the mechanism of their association. By extending multienzyme digestion strategies that use sample filtration to recover underdigested proteins for reprocessing/consecutive proteolytic digestion, we applied chymotrypsin to redigest the proteinaceous material left over after initial proteolysis with trypsin of sodium dodecyl sulfate (SDS)-extracted I. hospitalis-N. equitansproteins. We show that proteins with increased hydrophobic character, including membrane proteins with multiple transmembrane helices, are enriched and recovered in the underdigested fraction. Chymotryptic reprocessing provided significant sequence coverage gains in both soluble and hydrophobic proteins alike, with the latter benefiting more so in terms of membrane protein representation. Moreover, these gains were despite a large proportion of high-quality peptide spectra remaining unassigned in the underdigested fraction suggesting high levels of protein modification on these often surface-exposed proteins. Importantly, these gains were achieved without applying extensive fractionation strategies usually required for thorough characterization of membrane-associated proteins and were facilitated by the generation of a distinct, complementary set of peptides that aid in both the identification and quantitation of this important, under-represented class of proteins.

  8. Rescuing Those Left Behind: Recovering and Characterizing Underdigested Membrane and Hydrophobic Proteins To Enhance Proteome Measurement Depth

    DOE PAGES

    Giannone, Richard J.; Wurch, Louie L.; Podar, Mircea; ...

    2015-06-25

    The marine archaeon Nanoarchaeum equitans is dependent on direct physical contact with its host, the hyperthermophile Ignicoccus hospitalis. It is thought that this interaction is membrane-associated, involving a myriad of membrane-anchored proteins; proteomic efforts to better characterize this difficult to analyze interface are paramount to uncovering the mechanism of their association. By extending multienzyme digestion strategies that use sample filtration to recover underdigested proteins for reprocessing/consecutive proteolytic digestion, we applied chymotrypsin to redigest the proteinaceous material left over after initial proteolysis with trypsin of sodium dodecyl sulfate (SDS)-extracted I. hospitalis-N. equitansproteins. We show that proteins with increased hydrophobic character, includingmore » membrane proteins with multiple transmembrane helices, are enriched and recovered in the underdigested fraction. Chymotryptic reprocessing provided significant sequence coverage gains in both soluble and hydrophobic proteins alike, with the latter benefiting more so in terms of membrane protein representation. Moreover, these gains were despite a large proportion of high-quality peptide spectra remaining unassigned in the underdigested fraction suggesting high levels of protein modification on these often surface-exposed proteins. Importantly, these gains were achieved without applying extensive fractionation strategies usually required for thorough characterization of membrane-associated proteins and were facilitated by the generation of a distinct, complementary set of peptides that aid in both the identification and quantitation of this important, under-represented class of proteins.« less

  9. A Conserved Hydrophobic Core in Gαi1 Regulates G Protein Activation and Release from Activated Receptor.

    PubMed

    Kaya, Ali I; Lokits, Alyssa D; Gilbert, James A; Iverson, T M; Meiler, Jens; Hamm, Heidi E

    2016-09-09

    G protein-coupled receptor-mediated heterotrimeric G protein activation is a major mode of signal transduction in the cell. Previously, we and other groups reported that the α5 helix of Gαi1, especially the hydrophobic interactions in this region, plays a key role during nucleotide release and G protein activation. To further investigate the effect of this hydrophobic core, we disrupted it in Gαi1 by inserting 4 alanine amino acids into the α5 helix between residues Gln(333) and Phe(334) (Ins4A). This extends the length of the α5 helix without disturbing the β6-α5 loop interactions. This mutant has high basal nucleotide exchange activity yet no receptor-mediated activation of nucleotide exchange. By using structural approaches, we show that this mutant loses critical hydrophobic interactions, leading to significant rearrangements of side chain residues His(57), Phe(189), Phe(191), and Phe(336); it also disturbs the rotation of the α5 helix and the π-π interaction between His(57) and Phe(189) In addition, the insertion mutant abolishes G protein release from the activated receptor after nucleotide binding. Our biochemical and computational data indicate that the interactions between α5, α1, and β2-β3 are not only vital for GDP release during G protein activation, but they are also necessary for proper GTP binding (or GDP rebinding). Thus, our studies suggest that this hydrophobic interface is critical for accurate rearrangement of the α5 helix for G protein release from the receptor after GTP binding.

  10. Water in Oil Emulsions: A New System for Assembling Water-soluble Chlorophyll-binding Proteins with Hydrophobic Pigments.

    PubMed

    Bednarczyk, Dominika; Noy, Dror

    2016-03-21

    Chlorophylls (Chls) and bacteriochlorophylls (BChls) are the primary cofactors that carry out photosynthetic light harvesting and electron transport. Their functionality critically depends on their specific organization within large and elaborate multisubunit transmembrane protein complexes. In order to understand at the molecular level how these complexes facilitate solar energy conversion, it is essential to understand protein-pigment, and pigment-pigment interactions, and their effect on excited dynamics. One way of gaining such understanding is by constructing and studying complexes of Chls with simple water-soluble recombinant proteins. However, incorporating the lipophilic Chls and BChls into water-soluble proteins is difficult. Moreover, there is no general method, which could be used for assembly of water-soluble proteins with hydrophobic pigments. Here, we demonstrate a simple and high throughput system based on water-in-oil emulsions, which enables assembly of water-soluble proteins with hydrophobic Chls. The new method was validated by assembling recombinant versions of the water-soluble chlorophyll binding protein of Brassicaceae plants (WSCP) with Chl a. We demonstrate the successful assembly of Chl a using crude lysates of WSCP expressing E. coli cell, which may be used for developing a genetic screen system for novel water-soluble Chl-binding proteins, and for studies of Chl-protein interactions and assembly processes.

  11. Single molecule force spectroscopy reveals critical roles of hydrophobic core packing in determining the mechanical stability of protein GB1.

    PubMed

    Bu, Tianjia; Wang, Hui-Chuan Eileen; Li, Hongbin

    2012-08-21

    Understanding molecular determinants of protein mechanical stability is important not only for elucidating how elastomeric proteins are designed and functioning in biological systems but also for designing protein building blocks with defined nanomechanical properties for constructing novel biomaterials. GB1 is a small α/β protein and exhibits significant mechanical stability. It is thought that the shear topology of GB1 plays an important role in determining its mechanical stability. Here, we combine single molecule atomic force microscopy and protein engineering techniques to investigate the effect of side chain reduction and hydrophobic core packing on the mechanical stability of GB1. We engineered seven point mutants and carried out mechanical φ-value analysis of the mechanical unfolding of GB1. We found that three mutations, which are across the surfaces of two subdomains that are to be sheared by the applied stretching force, in the hydrophobic core (F30L, Y45L, and F52L) result in significant decrease in mechanical unfolding force of GB1. The mechanical unfolding force of these mutants drop by 50-90 pN compared with wild-type GB1, which unfolds at around 180 pN at a pulling speed of 400 nm/s. These results indicate that hydrophobic core packing plays an important role in determining the mechanical stability of GB1 and suggest that optimizing hydrophobic interactions across the surfaces that are to be sheared will likely be an efficient method to enhance the mechanical stability of GB1 and GB1 homologues.

  12. Using in situ X-ray reflectivity to study protein adsorption on hydrophilic and hydrophobic surfaces: benefits and limitations.

    PubMed

    Richter, Andrew G; Kuzmenko, Ivan

    2013-04-30

    We have employed in situ X-ray reflectivity (IXRR) to study the adsorption of a variety of proteins (lysozyme, cytochrome c, myoglobin, hemoglobin, serum albumin, and immunoglobulin G) on model hydrophilic (silicon oxide) and hydrophobic surfaces (octadecyltrichlorosilane self-assembled monolayers), evaluating this recently developed technique for its applicability in the area of biomolecular studies. We report herein the highest resolution depiction of adsorbed protein films, greatly improving on the precision of previous neutron reflectivity (NR) results and previous IXRR studies. We were able to perform complete scans in 5 min or less with the maximum momentum transfer of at least 0.52 Å(-1), allowing for some time-resolved information about the evolution of the protein film structure. The three smallest proteins (lysozyme, cytochrome c, and myoglobin) were seen to deposit as fully hydrated, nondenatured molecules onto hydrophilic surfaces, with indications of particular preferential orientations. Time evolution was observed for both lysozyme and myoglobin films. The larger proteins were not observed to deposit on the hydrophilic substrates, perhaps because of contrast limitations. On hydrophobic surfaces, all proteins were seen to denature extensively in a qualitatively similar way but with a rough trend that the larger proteins resulted in lower coverage. We have generated high-resolution electron density profiles of these denatured films, including capturing the growth of a lysozyme film. Because the solution interface of these denatured films is diffuse, IXRR cannot unambiguously determine the film extent and coverage, a drawback compared to NR. X-ray radiation damage was systematically evaluated, including the controlled exposure of protein films to high-intensity X-rays and exposure of the hydrophobic surface to X-rays before adsorption. Our analysis showed that standard measuring procedures used for XRR studies may lead to altered protein films

  13. Expression and purification of short hydrophobic elastin-like polypeptides with maltose-binding protein as a solubility tag.

    PubMed

    Bataille, Laure; Dieryck, Wilfrid; Hocquellet, Agnès; Cabanne, Charlotte; Bathany, Katell; Lecommandoux, Sébastien; Garbay, Bertrand; Garanger, Elisabeth

    2015-06-01

    Elastin-like polypeptides (ELPs) are biodegradable polymers with interesting physico-chemical properties for biomedical and biotechnological applications. The recombinant expression of hydrophobic elastin-like polypeptides is often difficult because they possess low transition temperatures, and therefore form aggregates at sub-ambient temperatures. To circumvent this difficulty, we expressed in Escherichia coli three hydrophobic ELPs (VPGIG)n with variable lengths (n=20, 40, and 60) in fusion with the maltose-binding protein (MBP). Fusion proteins were soluble and yields of purified MBP-ELP ranged between 66 and 127mg/L culture. After digestion of the fusion proteins by enterokinase, the ELP moiety was purified by using inverse transition cycling. The purified fraction containing ELP40 was slightly contaminated by traces of undigested fusion protein. Purification of ELP60 was impaired because of co-purification of the MBP tag during inverse transition cycling. ELP20 was successfully purified to homogeneity, as assessed by gel electrophoresis and mass spectrometry analyses. The transition temperature of ELP20 was measured at 15.4°C in low salt buffer. In conclusion, this method can be used to produce hydrophobic ELP of low molecular mass.

  14. Perplexing cooperative folding and stability of a low-sequence complexity, polyproline 2 protein lacking a hydrophobic core.

    PubMed

    Gates, Zachary P; Baxa, Michael C; Yu, Wookyung; Riback, Joshua A; Li, Hui; Roux, Benoît; Kent, Stephen B H; Sosnick, Tobin R

    2017-02-13

    The burial of hydrophobic side chains in a protein core generally is thought to be the major ingredient for stable, cooperative folding. Here, we show that, for the snow flea antifreeze protein (sfAFP), stability and cooperativity can occur without a hydrophobic core, and without α-helices or β-sheets. sfAFP has low sequence complexity with 46% glycine and an interior filled only with backbone H-bonds between six polyproline 2 (PP2) helices. However, the protein folds in a kinetically two-state manner and is moderately stable at room temperature. We believe that a major part of the stability arises from the unusual match between residue-level PP2 dihedral angle bias in the unfolded state and PP2 helical structure in the native state. Additional stabilizing factors that compensate for the dearth of hydrophobic burial include shorter and stronger H-bonds, and increased entropy in the folded state. These results extend our understanding of the origins of cooperativity and stability in protein folding, including the balance between solvent and polypeptide chain entropies.

  15. Thermodynamics of protein denaturation at temperatures over 100 °C: CutA1 mutant proteins substituted with hydrophobic and charged residues.

    PubMed

    Matsuura, Yoshinori; Takehira, Michiyo; Joti, Yasumasa; Ogasahara, Kyoko; Tanaka, Tomoyuki; Ono, Naoko; Kunishima, Naoki; Yutani, Katsuhide

    2015-10-26

    Although the thermodynamics of protein denaturation at temperatures over 100 °C is essential for the rational design of highly stable proteins, it is not understood well because of the associated technical difficulties. We designed certain hydrophobic mutant proteins of CutA1 from Escherichia coli, which have denaturation temperatures (Td) ranging from 101 to 113 °C and show a reversible heat denaturation. Using a hydrophobic mutant as a template, we successfully designed a hyperthermostable mutant protein (Td = 137 °C) by substituting six residues with charged ones. Thermodynamic analyses of these mutant proteins indicated that the hydrophobic mutants were stabilized by the accumulation of denaturation enthalpy (ΔH) with no entropic gain from hydrophobic solvation around 100 °C, and that the stabilization due to salt bridges resulted from both the increase in ΔH from ion-ion interactions and the entropic effect of the electrostatic solvation over 113 °C. This is the first experimental evidence that has successfully overcome the typical technical difficulties.

  16. Properties of a new protein film from bitter vetch (Vicia ervilia) and effect of CaCl₂ on its hydrophobicity.

    PubMed

    Arabestani, Akram; Kadivar, Mahdi; Shahedi, Mohmmad; Goli, Sayed Amir Hossein; Porta, Raffaele

    2013-06-01

    This work was aimed to investigate the potential preparation of an edible film from bitter vetch seed proteins. The film was cast from bitter vetch protein concentrate (BPC) and glycerol. CaCl₂ at the ratio of 0.1-1% (w/w) of the BPC was tested to improve film properties, specially its hydrophobicity. Some physicochemical properties of the films obtained in the absence and presence of CaCl₂ were evaluated. The results indicated that moisture content, total soluble matter, water vapour permeability and contact angle of the films prepared in the presence of CaCl₂ were significantly modified in comparison with the control values, while their mechanical properties did not significantly change. The surface morphology of the films was also considerably affected by the presence of CaCl₂. Therefore, CaCl₂ could improve BPC-films barrier properties especially their hydrophobicity, even though calcium concentration seems to be a crucial factor.

  17. The Outer Membrane Protein OmpW Forms an Eight-Stranded beta-Barrel with a Hydrophobic Channel

    SciTech Connect

    Hong,H.; Patel, D.; Tamm, L.; van den Berg, B.

    2006-01-01

    Escherichia coli OmpW belongs to a family of small outer membrane (OM) proteins that are widespread in Gram-negative bacteria. Their functions are unknown, but recent data suggest that they may be involved in the protection of bacteria against various forms of environmental stress. In order to gain insight into the function of these proteins we have determined the crystal structure of Escherichia coli OmpW to 2.7 Angstroms resolution. The structure shows that OmpW forms an eight-stranded beta-barrel with a long and narrow hydrophobic channel that contains a bound LDAO detergent molecule. Single channel conductance experiments show that OmpW functions as an ion channel in planar lipid bilayers. The channel activity can be blocked by the addition of LDAO. Taken together, the data suggest that members of the OmpW family could be involved in the transport of small hydrophobic molecules across the bacterial OM.

  18. Analysis of Amphiphilic Lipids and Hydrophobic Proteins Using Nonresonant Femtosecond Laser Vaporization with Electrospray Post-Ionization

    NASA Astrophysics Data System (ADS)

    Brady, John J.; Judge, Elizabeth J.; Levis, Robert J.

    2011-04-01

    Amphiphilic lipids and hydrophobic proteins are vaporized at atmospheric pressure using nonresonant 70 femtosecond (fs) laser pulses followed by electrospray post-ionization prior to being transferred into a time-of-flight mass spectrometer for mass analysis. Measurements of molecules on metal and transparent dielectric surfaces indicate that vaporization occurs through a nonthermal mechanism. The molecules analyzed include the lipids 1-monooleoyl-rac-glycerol, 1,2-dihexanoyl- sn-glycero-3-phosphocholine, 1,2-dimyristoyl- sn-glycero-3-phosphocholine, and the hydrophobic proteins gramicidin A, B, and C. Vaporization of lipids from blood and milk are also presented to demonstrate that lipids in complex systems can be transferred intact into the gas phase for mass analysis.

  19. Hydrophobic tendency of polar group hydration as a major force in type I antifreeze protein recognition.

    PubMed

    Yang, Cheng; Sharp, Kim A

    2005-05-01

    The random network model of water quantitatively describes the different hydration heat capacities of polar and apolar solutes in terms of distortions of the water-water hydrogen bonding angle in the first hydration shell (Gallagher and Sharp, JACS 2003;125:9853). The distribution of this angle in pure water is bimodal, with a low-angle population and high-angle population. Polar solutes increase the high-angle population while apolar solutes increase the low-angle population. The ratio of the two populations quantifies the hydrophobicity of the solute and provides a sensitive measure of water structural distortions. This method of analysis is applied to study hydration of type I thermal hysteresis protein (THP) from winter flounder and three quadruple mutants of four threonine residues at positions 2, 13, 24, and 35. Wild-type and two mutants (VVVV and AAAA) have antifreeze (thermal hysteresis) activity, while the other mutant (SSSS) has no activity. The analysis reveals significant differences in the hydration structure of the ice-binding site. For the SSSS mutant, polar groups have a typical polar-like hydration, that is, more high-angle H-bonds than bulk water. For the wild-type and active mutants, polar groups have unusual, very apolar-like hydration, that is, more low-angle H-bonds than bulk water. This pattern of hydration was seen previously in the structurally distinct type III THPs (Yang & Sharp Biophys Chem 2004;109:137), suggesting for the first time a general mechanism for different THP classes. The specific shape, residue size, and clustering of both polar and apoler groups are essential for an active ice binding surface.

  20. Structural and thermodynamic consequences of burial of an artificial ion pair in the hydrophobic interior of a protein.

    PubMed

    Robinson, Aaron C; Castañeda, Carlos A; Schlessman, Jamie L; García-Moreno, E Bertrand

    2014-08-12

    An artificial charge pair buried in the hydrophobic core of staphylococcal nuclease was engineered by making the V23E and L36K substitutions. Buried individually, Glu-23 and Lys-36 both titrate with pKa values near 7. When buried together their pKa values appear to be normal. The ionizable moieties of the buried Glu-Lys pair are 2.6 Å apart. The interaction between them at pH 7 is worth 5 kcal/mol. Despite this strong interaction, the buried Glu-Lys pair destabilizes the protein significantly because the apparent Coulomb interaction is sufficient to offset the dehydration of only one of the two buried charges. Save for minor reorganization of dipoles and water penetration consistent with the relatively high dielectric constant reported by the buried ion pair, there is no evidence that the presence of two charges in the hydrophobic interior of the protein induces any significant structural reorganization. The successful engineering of an artificial ion pair in a highly hydrophobic environment suggests that buried Glu-Lys pairs in dehydrated environments can be charged and that it is possible to engineer charge clusters that loosely resemble catalytic sites in a scaffold protein with high thermodynamic stability, without the need for specialized structural adaptations.

  1. ON-COLUMN ENRICHMENT OF HYDROPHOBIC CYP450 PROTEINS IN HPLC FRACTIONATION OF MOUSE MICROSOMES PRIOR TO PROTEIN DIGESTION AND NANOSPRAY-LC/MSMS ANALYSIS

    EPA Science Inventory

    Introduction

    Membrane proteins play crucial role in many cellular processes and are promising candidates for biomarker discovery but are under-represented in the field of proteomics due to their hydrophobic nature. Although standard reversed-phase LC methods often exhibit ...

  2. Preparation of a weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography stationary phase for protein separation using click chemistry.

    PubMed

    Zhao, Kailou; Yang, Fan; Xia, Hongjun; Wang, Fei; Song, Qingguo; Bai, Quan

    2015-03-01

    In this study, 3-diethylamino-1-propyne was covalently bonded to the azide-silica by a click reaction to obtain a novel dual-function mixed-mode chromatography stationary phase for protein separation with a ligand containing tertiary amine and two ethyl groups capable of electrostatic and hydrophobic interaction functionalities, which can display hydrophobic interaction chromatography character in a high-salt-concentration mobile phase and weak anion exchange character in a low-salt-concentration mobile phase employed for protein separation. As a result, it can be employed to separate proteins with weak anion exchange and hydrophobic interaction modes, respectively. The resolution and selectivity of the stationary phase were evaluated in both hydrophobic interaction and ion exchange modes with standard proteins, respectively, which can be comparable to that of conventional weak anion exchange and hydrophobic interaction chromatography columns. Therefore, the synthesized weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography column can be used to replace two corresponding conventional weak anion exchange and hydrophobic interaction chromatography columns to separate proteins. Based on this mixed-mode chromatography stationary phase, a new off-line two-dimensional liquid chromatography technology using only a single dual-function mixed-mode chromatography column was developed. Nine kinds of tested proteins can be separated completely using the developed method within 2.0 h.

  3. Entropy reduction effect imposed by hydrogen bond formation on protein folding cooperativity: Evidence from a hydrophobic minimalist model

    NASA Astrophysics Data System (ADS)

    Barbosa, Marco Aurélio A.; Garcia, Leandro G.; Pereira de Araújo, Antônio F.

    2005-11-01

    Conformational restrictions imposed by hydrogen bond formation during protein folding are investigated by Monte Carlo simulations of a non-native-centric, two-dimensional, hydrophobic model in which the formation of favorable contacts is coupled to an effective reduction in lattice coordination. This scheme is intended to mimic the requirement that polar backbone groups of real proteins must form hydrogen bonds concomitantly to their burial inside the apolar protein core. In addition to the square lattice, with z=3 conformations per monomer, we use extensions in which diagonal step vectors are allowed, resulting in z=5 and z=7 . Thermodynamics are governed by the hydrophobic energy function, according to which hydrophobic monomers tend to make contacts unspecifically while the reverse is true for hydrophilic monomers, with the additional restriction that only contacts between monomers adopting one of zhhydrophobic model of 40 monomers and a more pronounced increase in cooperativity for a native-centric Go-model with the same native conformation, suggesting that this purely entropic effect is not an artifact of dimensionality and is likely to be of fundamental importance in the theoretical understanding of folding cooperativity.

  4. A Hydrophobic Pocket in the Active Site of Glycolytic Aldolase Mediates Interactions with Wiskott-Aldrich Syndrome Protein

    SciTech Connect

    St-Jean,M.; Izard, T.; Sygusch, J.

    2007-01-01

    Aldolase plays essential catalytic roles in glycolysis and gluconeogenesis. However, aldolase is a highly abundant protein that is remarkably promiscuous in its interactions with other cellular proteins. In particular, aldolase binds to highly acidic amino acid sequences, including the C-terminus of the Wiskott-Aldrich syndrome protein, an actin nucleation promoting factor. Here we report the crystal structure of tetrameric rabbit muscle aldolase in complex with a C-terminal peptide of Wiskott-Aldrich syndrome protein. Aldolase recognizes a short, 4-residue DEWD motif (residues 498-501), which adopts a loose hairpin turn that folds about the central aromatic residue, enabling its tryptophan side chain to fit into a hydrophobic pocket in the active site of aldolase. The flanking acidic residues in this binding motif provide further interactions with conserved aldolase active site residues, Arg-42 and Arg-303, aligning their side chains and forming the sides of the hydrophobic pocket. The binding of Wiskott-Aldrich syndrome protein to aldolase precludes intramolecular interactions of its C-terminus with its active site, and is competitive with substrate as well as with binding by actin and cortactin. Finally, based on this structure a novel naphthol phosphate-based inhibitor of aldolase was identified and its structure in complex with aldolase demonstrated mimicry of the Wiskott-Aldrich syndrome protein-aldolase interaction. The data support a model whereby aldolase exists in distinct forms that regulate glycolysis or actin dynamics.

  5. Volumetric interpretation of protein adsorption: Partition coefficients, interphase volumes, and free energies of adsorption to hydrophobic surfaces.

    PubMed

    Noh, Hyeran; Vogler, Erwin A

    2006-12-01

    The solution-depletion method of measuring protein adsorption is implemented using SDS gel electrophoresis as a separation and quantification tool. Experimental method is demonstrated using lysozyme (15kDa), alpha-amylase (51kDa), human serum albumin (66kDa), prothrombin (72kDa), immunoglobulin G (160kDa), and fibrinogen (341kDa) adsorption from aqueous-buffer solution to hydrophobic octyl-sepharose and silanized-glass particles. Interpretive mass-balance equations are derived from a model premised on the idea that protein reversibly partitions from bulk solution into a three-dimensional (3D) interphase volume separating the physical-adsorbent surface from bulk solution. Theory both anticipated and accommodated adsorption of all proteins to the two test surfaces, suggesting that the underlying model is descriptive of the essential physical chemistry of protein adsorption. Application of mass balance equations to experimental data quantify partition coefficients P, interphase volumes V(I), and the number of hypothetical layers M occupied by protein adsorbed within V(I). Partition coefficients quantify protein-adsorption avidity through the equilibrium ratio of interphase and bulk-solution-phase w/v (mg/mL) concentrations W(I) and W(B), respectively, such that P identical withW(I)/W(B). Proteins are found to be weak biosurfactants with 45proteins by hydrophobic-interaction chromatography. Proteins with molecular weight MW<100kDa occupy a single layer at surface saturation whereas the larger proteins IgG and fibrinogen required two layers.

  6. Interfacial energetics of globular–blood protein adsorption to a hydrophobic interface from aqueous-buffer solution

    PubMed Central

    Krishnan, Anandi; Liu, Yi-Hsiu; Cha, Paul; Allara, David; Vogler, Erwin A

    2005-01-01

    Adsorption isotherms of nine globular proteins with molecular weight (MW) spanning 10–1000 kDa confirm that interfacial energetics of protein adsorption to a hydrophobic solid/aqueous-buffer (solid–liquid, SL) interface are not fundamentally different than adsorption to the water–air (liquid–vapour, LV) interface. Adsorption dynamics dampen to a steady-state (equilibrium) within a 1 h observation time and protein adsorption appears to be reversible, following expectations of Gibbs' adsorption isotherm. Adsorption isotherms constructed from concentration-dependent advancing contact angles θa of buffered-protein solutions on methyl-terminated, self-assembled monolayer surfaces show that maximum advancing spreading pressure, Πamax, falls within a relatively narrow 10<Πamax<20mNm−1 band characteristic of all proteins studied, mirroring results obtained at the LV surface. Furthermore, Πa isotherms exhibited a ‘Traube-rule-like’ progression in MW similar to the ordering observed at the LV surface wherein molar concentrations required to reach a specified spreading pressure Πa decreased with increasing MW. Finally, neither Gibbs' surface excess quantities [Γsl−Γsv] nor Γlv varied significantly with protein MW. The ratio {[Γsl−Γsv]/Γlv}∼1, implying both that Γsv∼0 and chemical activity of protein at SL and LV surfaces was identical. These results are collectively interpreted to mean that water controls protein adsorption to hydrophobic surfaces and that the mechanism of protein adsorption can be understood from this perspective for a diverse set of proteins with very different composition. PMID:16849238

  7. Immobilizing PEO-PPO-PEO triblock copolymers on hydrophobic surfaces and its effect on protein and platelet: a combined study using QCM-D and DPI.

    PubMed

    Jin, Jing; Huang, Fujian; Hu, Yu; Jiang, Wei; Ji, Xiangling; Liang, Haojun; Yin, Jinghua

    2014-11-01

    Dual polarization interferometry was used to monitor the immobilization dynamics of four Pluronics on hydrophobic surfaces and to elucidate the effect of Pluronic conformation on protein adsorption. The proportion of hydrophobic chain segments and not the length of the hydrophobic chain can influence the chain densities of the Pluronics. The immobilized densities of the Pluronics resulted from competition between the hydration of polyethylene oxide (PEO) in the aqueous solution and the hydrophobic interaction of polypropylene oxide on the substrate. P-123 obtained the largest graft mass (2.89±0.25 ng/mm2) because of the dominant effect of hydrophobic interactions. Hydrophobic segments of P-123 were anchored slowly and step-wise on the C18 substrate. P-123 exhibited the largest hydrophobic chain segment proportion (propylene oxide/ethylene oxide=3.63) and formed a brush chain conformation, indicating excellent protein and platelet resistance. The result of quartz crystal microbalance with dissipation further confirmed that the PEO conformation in P-123 on the substrate exhibited a relatively extended brush chain, and that L-35 showed relatively loose and pancake-like structures. The PEO in P-123 regulated the conformation to maintain the native conformation and resist the adsorption of bovine serum albumin (BSA). Thus, the hemocompatibilities of the immobilized Pluronics were influenced by the proportion of hydrophobic chain segments and their PEO conformations.

  8. Interactions between hydrophobic and ionic solutes in aqueous guanidinium chloride and urea solutions: lessons for protein denaturation mechanism.

    PubMed

    O'Brien, Edward P; Dima, Ruxandra I; Brooks, Bernard; Thirumalai, D

    2007-06-13

    In order to clarify the mechanism of denaturant-induced unfolding of proteins we have calculated the interactions between hydrophobic and ionic species in aqueous guanidinium chloride and urea solutions using molecular dynamics simulations. Hydrophobic association is not significantly changed in urea or guanidinium chloride solutions. The strength of interaction between ion pairs is greatly diminished by the guanidinium ion. Although the changes in electrostatic interactions in urea are small, examination of structures, using appropriate pair functions, of urea and water around the solutes show strong hydrogen bonding between urea's carbonyl oxygen and the positively charged solute. Our results strongly suggest protein denaturation occurs by the direct interaction model according to which the most commonly used denaturants unfold proteins by altering electrostatic interactions either by solvating the charged residues or by engaging in hydrogen bonds with the protein backbone. To further validate the direct interaction model we show that, in urea and guanidinium chloride solutions, unfolding of an unusually stable helix (H1) from mouse PrPC (residues 144-153) occurs by hydrogen bonding of denaturants to charged side chains and backbone carbonyl groups.

  9. Protein-based emulsion electrosprayed micro- and submicroparticles for the encapsulation and stabilization of thermosensitive hydrophobic bioactives.

    PubMed

    Gómez-Mascaraque, Laura G; López-Rubio, Amparo

    2016-03-01

    This work shows the potential of emulsion electrospraying of proteins using food-grade emulsions for the microencapsulation and enhanced protection of a model thermosensitive hydrophobic bioactive. Specifically, gelatin, a whey protein concentrate (WPC) and a soy protein isolate (SPI) were compared as emulsion stabilizers and wall matrices for encapsulation of α-linolenic acid. In a preliminary stage, soy bean oil was used as the hydrophobic component for the implementation of the emulsion electrospraying process, investigating the effect of protein type and emulsion protocol used (i.e. with or without ultrasound treatment) on colloidal stability. This oil was then substituted by the ω-3 fatty acid and the emulsions were processed by electrospraying and spray-drying, comparing both techniques. While the latter resulted in massive bioactive degradation, electrospraying proved to be a suitable alternative, achieving microencapsulation efficiencies (MEE) of up to ∼70%. Although gelatin yielded low MEEs due to the need of employing acetic acid for its processing by electrospraying, SPI and WPC achieved MEEs over 60% for the non-sonicated emulsions. Moreover, the degradation of α-linolenic acid at 80°C was significantly delayed when encapsulated within both matrices. Whilst less than an 8% of its alkene groups were detected after 27h of thermal treatment for free α-linolenic acid, up to 43% and 67% still remained intact within the electrosprayed SPI and WPC capsules, respectively.

  10. High-performance liquid chromatography as a technique to determine protein adsorption onto hydrophilic/hydrophobic surfaces.

    PubMed

    Huang, Tongtong; Anselme, Karine; Sarrailh, Segolene; Ponche, Arnaud

    2016-01-30

    The purpose of this study is to evaluate the potential of simple high performance liquid chromatography (HPLC) setup for quantification of adsorbed proteins on various type of plane substrates with limited area (<3 cm(2)). Protein quantification was investigated with a liquid chromatography chain equipped with a size exclusion column or a reversed-phase column. By evaluating the validation of the method according to guidelines of the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH), all the results obtained by HPLC were reliable. By simple adsorption test at the contact of hydrophilic (glass) and hydrophobic (polydimethylsiloxane: PDMS) surfaces, kinetics of adsorption were determined and amounts of adsorbed bovine serum albumin, myoglobin and lysozyme were obtained: as expected for each protein, the amount adsorbed at the plateau on glass (between 0.15 μg/cm(2) and 0.4 μg/cm(2)) is lower than for hydrophobic PDMS surfaces (between 0.45 μg/cm(2) and 0.8 μg/cm(2)). These results were consistent with bicinchoninic acid protein determination. According to ICH guidelines, both Reversed Phase and Size Exclusion HPLC can be validated for quantification of adsorbed protein. However, we consider the size exclusion approach more interesting in this field because additional informations can be obtained for aggregative proteins. Indeed, monomer, dimer and oligomer of bovine serum albumin (BSA) were observed in the chromatogram. On increasing the temperature, we found a decrease of peak intensity of bovine serum albumin as well as the fraction of dimer and oligomer after contact with PDMS and glass surface. As the surface can act as a denaturation parameter, these informations can have a huge impact on the elucidation of the interfacial behavior of protein and in particular for aggregation processes in pharmaceutical applications.

  11. Hydrophobic cluster analysis: procedures to derive structural and functional information from 2-D-representation of protein sequences.

    PubMed

    Lemesle-Varloot, L; Henrissat, B; Gaboriaud, C; Bissery, V; Morgat, A; Mornon, J P

    1990-08-01

    Hydrophobic cluster analysis (HCA) [15] is a very efficient method to analyse and compare protein sequences. Despite its effectiveness, this method is not widely used because it relies in part on the experience and training of the user. In this article, detailed guidelines as to the use of HCA are presented and include discussions on: the definition of the hydrophobic clusters and their relationships with secondary and tertiary structures; the length of the clusters; the amino acid classification used for HCA; the HCA plot programs; and the working strategies. Various procedures for the analysis of a single sequence are presented: structural segmentation, structural domains and secondary structure evaluation. Like most sequence analysis methods, HCA is more efficient when several homologous sequences are compared. Procedures for the detection and alignment of distantly related proteins by HCA are described through several published examples along with 2 previously unreported cases: the beta-glucosidase from Ruminococcus albus is clearly related to the beta-glucosidases from Clostridum thermocellum and Hansenula anomala although they display a reverse organization of their constitutive domains; the alignment of the sequence of human GTPase activating protein with that of the Crk oncogene is presented. Finally, the pertinence of HCA in the identification of important residues for structure/function as well as in the preparation of homology modelling is discussed.

  12. Dress Codes for Teachers?

    ERIC Educational Resources Information Center

    Million, June

    2004-01-01

    In this article, the author discusses an e-mail survey of principals from across the country regarding whether or not their school had a formal staff dress code. The results indicate that most did not have a formal dress code, but agreed that professional dress for teachers was not only necessary, but showed respect for the school and had a…

  13. Physical origin of hydrophobicity studied in terms of cold denaturation of proteins: comparison between water and simple fluids.

    PubMed

    Yoshidome, Takashi; Kinoshita, Masahiro

    2012-11-14

    A clue to the physical origin of the hydrophobicity is in the experimental observations, which show that it is weakened at low temperatures. By considering a solvophobic model protein immersed in water and three species of simple solvents, we analyze the temperature dependence of the changes in free energy, energy, and entropy of the solvent upon protein unfolding. The angle-dependent and radial-symmetric integral equation theories and the morphometric approach are employed in the analysis. Each of the changes is decomposed into two terms, which depend on the excluded volume and on the area and curvature of the solvent-accessible surface, respectively. The excluded-volume term of the entropy change is further decomposed into two components representing the protein-solvent pair correlation and the protein-solvent-solvent triplet and higher-order correlation, respectively. We show that water crowding in the system becomes more serious upon protein unfolding but this effect becomes weaker as the temperature is lowered. If the hydrophobicity originated from the water structuring near a nonpolar solute, it would be strengthened upon lowering of the temperature. Among the three species of simple solvents, considerable weakening of the solvophobicity at low temperatures is observed only for the solvent where the particles interact through a strong attractive potential and the particle size is as small as that of water. Even in the case of this solvent, however, cold denaturation of a protein cannot be reproduced. It would be reproducible if the attractive potential was substantially enhanced, but such enhancement causes the appearance of the metastability limit for a single liquid phase.

  14. Ca2+-dependent hydrophobic-interaction chromatography. Isolation of a novel Ca2+-binding protein and protein kinase C from bovine brain.

    PubMed

    Walsh, M P; Valentine, K A; Ngai, P K; Carruthers, C A; Hollenberg, M D

    1984-11-15

    Several bovine brain proteins have been found to interact with a hydrophobic chromatography resin (phenyl-Sepharose CL-4B) in a Ca2+-dependent manner. These include calmodulin, the Ca2+/phospholipid-dependent protein kinase (protein kinase C) and a novel Ca2+-binding protein that has now been purified to electrophoretic homogeneity. This latter protein is acidic (pI 5.1) and, like calmodulin and some other high-affinity Ca2+-binding proteins, exhibits a Ca2+-dependent mobility shift on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, with an apparent Mr of 22 000 in the absence of Ca2+ and Mr 21 000 in the presence of Ca2+. This novel calciprotein is distinct from known Ca2+-binding proteins on the basis of Mr under denaturing conditions, Cleveland peptide mapping and amino acid composition analysis. It may be a member of the calmodulin superfamily of Ca2+-binding proteins. This calciprotein does not activate two calmodulin-dependent enzymes, namely cyclic nucleotide phosphodiesterase and myosin light-chain kinase, nor does it have any effect on protein kinase C. It may be a Ca2+-dependent regulatory protein of an as-yet-undefined enzymic activity. The Ca2+/phospholipid-dependent protein kinase is also readily purified by Ca2+-dependent hydrophobic-interaction chromatography followed by ion-exchange chromatography, during which it is easily separated from calmodulin. A preparation of protein kinase C that lacks contaminating kinase or phosphatase activities is thereby obtained rapidly and simply. Such a preparation is ideal for the study of phosphorylation reactions catalysed in vitro by protein kinase C.

  15. Characterization of hydrophobic-ligand-binding proteins of Taenia solium that are expressed specifically in the adult stage.

    PubMed

    Rahman, M; Lee, E-G; Kim, S-H; Bae, Y-A; Wang, H; Yang, Y; Kong, Y

    2012-09-01

    Taenia solium, a causative agent of taeniasis and cysticercosis, has evolved a repertoire of lipid uptake mechanisms. Proteome analysis of T. solium excretory-secretory products (TsESP) identified 10 kDa proteins displaying significant sequence identity with cestode hydrophobic-ligand-binding-proteins (HLBPs). Two distinct 362- and 352-bp-long cDNAs encoding 264- and 258-bp-long open reading frames (87 and 85 amino acid polypeptides) were isolated by mining the T. solium expressed sequence tags and a cDNA library screening (TsHLBP1 and TsHLBP2; 94% sequence identity). They clustered into the same clade with those found in Moniezia expansa and Hymenolepis diminuta. Genomic structure analysis revealed that these genes might have originated from a common ancestor. Both the crude TsESP and bacterially expressed recombinant proteins exhibited binding activity toward 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS), which was competitively inhibited by oleic acid. The proteins also bound to cis-parinaric acid (cPnA) and 16-(9-anthroyloxy) palmitic acid (16-AP), but showed no binding activity against 11-[(5-dimethylaminonaphthalene-1-sulfonyl) amino] undecanoic acid (DAUDA) and dansyl-DL-α-aminocaprylic acid (DACA). Unsaturated fatty acids (FAs) showed greater affinity than saturated FAs. The proteins were specifically expressed in adult worms throughout the strobila. The TsHLBPs might be involved in uptake and/or sequestration of hydrophobic molecules provided by their hosts, thus contributing to host-parasite interface interrelationships.

  16. Chemical studies of viral entry mechanisms: I. Hydrophobic protein-lipid interactions during Sendai virus membrane fusion. II. Kinetics of bacteriophage. lambda. DNA injection

    SciTech Connect

    Novick, S.L.

    1990-01-01

    Sendai virus glycoprotein interactions with target membranes during the early stages of fusion were examined using time-resolved hydrophobic photoaffinity labeling with the lipid-soluble carbene generator 3-(trifluoromethyl)-3-(m({sup 125}I) iodophenyl)diazirine. During Sendai virus fusion with liposomes composed of cardiolipin or phosphatidylserine, the viral fusion (F) protein is preferentially labeled at early time points, supporting the hypothesis that hydrophobic interaction of the fusion peptide at the N-terminus of the F{sub 1} subunit with the target membrane is an initiating event in fusion. Correlation of hydrophobic interactions with independently monitored fusion kinetics further supports this conclusion. The F{sub 1} subunit, containing the putative hydrophobic fusion sequence, is exclusively labeled, and the F{sub 2} subunit does not participate in fusion. Labeling shows temperature and pH dependence consistent with a need for protein conformational mobility and fusion at neutral pH. Higher amounts of labeling during fusion with CL vesicles than during virus-PS vesicle fusion reflects membrane packing regulation of peptide insertion into target membranes. Labeling of the viral hemagglutinin/neuraminidase (HN) at low pH indicates that HN-mediated fusion is triggered by hydrophobic interactions. Controls for diffusional labeling exclude a major contribution from this source. Labeling during reconstituted Sendai virus envelope-liposome fusion shows that functional reconstitution involves protein retention of the ability to undergo hydrophobic interactions. Examination of Sendai virus fusion with erythrocyte membranes indicates that hydrophobic interactions also trigger fusion between biological membranes. The data show that hydrophobic fusion protein interaction with both artificial and biological membranes is a triggering event in fusion.

  17. Protein-surfactant interactions at hydrophobic interfaces studied with total internal reflection fluorescence correlation spectroscopy (TIR-FCS).

    PubMed

    Sonesson, Andreas W; Blom, Hans; Hassler, Kai; Elofsson, Ulla M; Callisen, Thomas H; Widengren, Jerker; Brismar, Hjalmar

    2008-01-15

    The aim of this work was to study the dynamics of proteins near solid surfaces in the presence or absence of competing surfactants by means of total internal reflection fluorescence correlation spectroscopy (TIR-FCS). Two different proteins were studied, bovine serum albumin (BSA) and Thermomyces lanuginosus lipase (TLL). A nonionic/anionic (C12E6/LAS) surfactant composition was used to mimic a detergent formulation and the surfaces used were C18 terminated glass. It was found that with increasing surfactant concentrations the term in the autocorrelation function (ACF) representing surface binding decreased. This suggested that the proteins were competed off the hydrophobic surface by the surfactant. When fitting the measured ACF to a model for surface kinetics, it was seen that with raised C12E6/LAS concentration, the surface interaction rate increased for both proteins. Under these experimental conditions this meant that the time the protein was bound to the surface decreased. At 10 microM C12E6/LAS the surface interaction was not visible for BSA, whereas it was still distinguishable in the ACF for TLL. This indicated that TLL had a higher affinity than BSA for the C18 surface. The study showed that TIR-FCS provides a useful tool to quantify the surfactant effect on proteins adsorption.

  18. A hydrophobic patch in a charged alpha-helix is sufficient to target proteins to dense core secretory granules.

    PubMed

    Dikeakos, Jimmy D; Lacombe, Marie-Josée; Mercure, Chantal; Mireuta, Matei; Reudelhuber, Timothy L

    2007-01-12

    Many endocrine and neuroendocrine cells contain specialized secretory organelles called dense core secretory granules. These organelles are the repository of proteins and peptides that are secreted in a regulated manner when the cell receives a physiological stimulus. The targeting of proteins to these secretory granules is crucial for the generation of certain peptide hormones, including insulin and ACTH. Although previous work has demonstrated that proteins destined to a variety of cellular locations, including secretory granules, contain targeting sequences, no single consensus sequence for secretory granule-sorting signals has emerged. We have shown previously that alpha-helical domains in the C-terminal tail of the prohormone convertase PC1/3 play an important role in the ability of this region of the protein to direct secretory granule targeting (Jutras, I. Seidah, N. G., and Reudelhuber, T. L. (2000) J. Biol. Chem. 275, 40337-40343). In this study, we show that a variety of alpha-helical domains are capable of directing a heterologous secretory protein to granules. By testing a series of synthetic alpha-helices, we also demonstrate that the presence of charged (either positive or negative) amino acids spatially segregated from a hydrophobic patch in the alpha-helices of secretory proteins likely plays a critical role in the ability of these structures to direct secretory granule sorting.

  19. Preferential melting of secondary structures during protein unfolding in different solvents: Competition between hydrophobic solvation and hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Bagchi, Biman; Roy, Susmita; Ghosh, Rikhia

    2014-03-01

    Aqueous binary mixtures such as water-DMSO, water-urea, and water-ethanol are known to serve as denaturants of a host of proteins, although the detailed mechanism is often not known. Here we combine studies on several proteins in multiple binary mixtures to obtain a unified understanding of the phenomenon. We compare with experiments to support the simulation findings. The proteins considered include (i) chicken villin head piece (HP-36), (ii) immunoglobulin binding protein G (GB1), (iii) myoglobin and (iv) lysozyme. We find that for amphiphilic solvents like DMSO, the hydrophobic groups and the strong hydrogen bonding ability of the >S =O oxygen atom act together to facilitate the unfolding. However, the hydrophilic solvents like urea, due to the presence of more hydrophilic ends (C =O and two NH2) has a high propensity of forming hydrogen bonds with the side-chain residues and backbone of beta-sheet than the same of alpha helix. Such diversity among the unfolding pathways of a given protein in different chemical environments is especially characterized by the preferential solvation of a particular secondary structure.

  20. Influence of binding pH and protein solubility on the dynamic binding capacity in hydrophobic interaction chromatography.

    PubMed

    Baumann, Pascal; Baumgartner, Kai; Hubbuch, Jürgen

    2015-05-29

    Hydrophobic interaction chromatography (HIC) is one of the most frequently used purification methods in biopharmaceutical industry. A major drawback of HIC, however, is the rather low dynamic binding capacity (DBC) obtained when compared to e.g. ion exchange chromatography (IEX). The typical purification procedure for HIC includes binding at neutral pH, independently of the proteins nature and isoelectric point. Most approaches to process intensification are based on resin and salt screenings. In this paper a combination of protein solubility data and varying binding pH leads to a clear enhancement of dynamic binding capacity. This is shown for three proteins of acidic, neutral, and alkaline isoelectric points. High-throughput solubility screenings as well as miniaturized and parallelized breakthrough curves on Media Scout RoboColumns (Atoll, Germany) were conducted at pH 3-10 on a fully automated robotic workstation. The screening results show a correlation between the DBC and the operational pH, the protein's isoelectric point and the overall solubility. Also, an inverse relationship of DBC in HIC and the binding kinetics was observed. By changing the operational pH, the DBC could be increased up to 30% compared to the standard purification procedure performed at neutral pH. As structural changes of the protein are reported during HIC processes, the applied samples and the elution fractions were proven not to be irreversibly unfolded.

  1. Sum Frequency Generation Vibrational Spectroscopy of Adsorbed Amino Acids, Peptides and Proteins of Hydrophilic and Hydrophobic Solid-Water Interfaces

    SciTech Connect

    Holinga IV, George Joseph

    2010-09-01

    Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the interfacial properties of several amino acids, peptides, and proteins adsorbed at the hydrophilic polystyrene solid-liquid and the hydrophobic silica solid-liquid interfaces. The influence of experimental geometry on the sensitivity and resolution of the SFG vibrational spectroscopy technique was investigated both theoretically and experimentally. SFG was implemented to investigate the adsorption and organization of eight individual amino acids at model hydrophilic and hydrophobic surfaces under physiological conditions. Biointerface studies were conducted using a combination of SFG and quartz crystal microbalance (QCM) comparing the interfacial structure and concentration of two amino acids and their corresponding homopeptides at two model liquid-solid interfaces as a function of their concentration in aqueous solutions. The influence of temperature, concentration, equilibration time, and electrical bias on the extent of adsorption and interfacial structure of biomolecules were explored at the liquid-solid interface via QCM and SFG. QCM was utilized to quantify the biological activity of heparin functionalized surfaces. A novel optical parametric amplifier was developed and utilized in SFG experiments to investigate the secondary structure of an adsorbed model peptide at the solid-liquid interface.

  2. Novel Asymmetric Wettable AgNPs/Chitosan Wound Dressing: In Vitro and In Vivo Evaluation.

    PubMed

    Liang, Donghui; Lu, Zhong; Yang, Hao; Gao, Jingting; Chen, Rong

    2016-02-17

    A novel silver nanoparticles (AgNPs)/chitosan composite dressing with asymmetric wettability surfaces was successfully prepared via a simple two-step method for biomedical applications as wound healing materials. First, AgNPs were assembled into the chitosan sponge which was prepared by lyophilization process. Then one side of the sponge was modified by a thin layer of stearic acid. The incorporation of AgNPs into chitosan dressing could enhance the antibacterial activity against drug-sensitive and drug-resistant pathogenic bacteria. The asymmetric surface modification endows the dressing with both highly hydrophobic property and inherent hydrophilic nature of chitosan. The hydrophobic surface of the dressing shows waterproof and antiadhesion for contaminant properties, whereas the hydrophilic surface preserves its water-absorbing capability and efficiently inhibits the growth of bacteria. Furthermore, the AgNPs/chitosan composite dressing displays improved moisture retention and blood clotting ability compared to the unmodified dressings. Cytocompatibility test evaluated in vitro and in a wound infection model illustrates the nontoxic nature of the composite dressing. More importantly, the in vivo wound healing model evaluation in mice reveals that the asymmetric AgNPs/chitosan dressing promotes the wound healing and accelerates the reepithelialization and collagen deposition. The silver accumulation in mice body treated by the composite dressing is far lower than that of the clinically used Acasin nanosilver dressing treated mice. This work indicates the huge potential of the novel AgNPs/chitosan wound dressing with asymmetrical wettability for clinical use.

  3. Semi-Automated Hydrophobic Interaction Chromatography Column Scouting Used in the Two-Step Purification of Recombinant Green Fluorescent Protein

    PubMed Central

    Murphy, Patrick J. M.

    2014-01-01

    Background Hydrophobic interaction chromatography (HIC) most commonly requires experimental determination (i.e., scouting) in order to select an optimal chromatographic medium for purifying a given target protein. Neither a two-step purification of untagged green fluorescent protein (GFP) from crude bacterial lysate using sequential HIC and size exclusion chromatography (SEC), nor HIC column scouting elution profiles of GFP, have been previously reported. Methods and Results Bacterial lysate expressing recombinant GFP was sequentially adsorbed to commercially available HIC columns containing butyl, octyl, and phenyl-based HIC ligands coupled to matrices of varying bead size. The lysate was fractionated using a linear ammonium phosphate salt gradient at constant pH. Collected HIC eluate fractions containing retained GFP were then pooled and further purified using high-resolution preparative SEC. Significant differences in presumptive GFP elution profiles were observed using in-line absorption spectrophotometry (A395) and post-run fluorimetry. SDS-PAGE and western blot demonstrated that fluorometric detection was the more accurate indicator of GFP elution in both HIC and SEC purification steps. Comparison of composite HIC column scouting data indicated that a phenyl ligand coupled to a 34 µm matrix produced the highest degree of target protein capture and separation. Conclusions Conducting two-step protein purification using the preferred HIC medium followed by SEC resulted in a final, concentrated product with >98% protein purity. In-line absorbance spectrophotometry was not as precise of an indicator of GFP elution as post-run fluorimetry. These findings demonstrate the importance of utilizing a combination of detection methods when evaluating purification strategies. GFP is a well-characterized model protein, used heavily in educational settings and by researchers with limited protein purification experience, and the data and strategies presented here may aid in

  4. [Improper use of dressings].

    PubMed

    Candas, Emmanuelle

    2016-01-01

    Neither nurses nor doctors receive initial training in wounds and the use of dressings. They are however required in their daily practice to provide this type of care. Advances in wound healing techniques and the appearance of "modern" dressings offer a wide range of solutions to caregivers. Professionals must acquire skills in this area and make the best possible use of the dressings at their disposal to optimise the controlled wound healing.

  5. Immunoassay of C-reactive protein by hot electron induced electrochemiluminescence using integrated electrodes with hydrophobic sample confinement.

    PubMed

    Ylinen-Hinkka, T; Niskanen, A J; Franssila, S; Kulmala, S

    2011-09-19

    C-reactive protein (CRP) was determined in the concentration range 0.01-10 mg L(-1) using hot electron induced electrochemiluminescence (HECL) with devices combining both working and counter electrodes and sample confinement on a single chip. The sample area on the electrodes was defined by a hydrophobic ring, which enabled dispensing the reagents and the analyte directly on the electrode. Immunoassay of CRP by HECL using integrated electrodes is a good candidate for a high-sensitivity point-of-care CRP-test, because the concentration range is suitable, miniaturisation of the measurement system has been demonstrated and the assay method with integrated electrodes is easy to use. High-sensitivity CRP tests can be used to monitor the current state of cardiovascular disease and also to predict future cardiovascular problems in apparently healthy people.

  6. QID74 Cell wall protein of Trichoderma harzianum is involved in cell protection and adherence to hydrophobic surfaces.

    PubMed

    Rosado, Iván V; Rey, Manuel; Codón, Antonio C; Govantes, Javier; Moreno-Mateos, Miguel A; Benítez, Tahía

    2007-10-01

    Trichoderma is widely used as biocontrol agent against phytopathogenic fungi, and as biofertilizer because of its ability to establish mycorriza-like association with plants. The key factor to the ecological success of this genus is the combination of very active mycoparasitic mechanisms plus effective defense strategies induced in plants. This work, different from most of the studies carried out that address the attacking mechanisms, focuses on elucidating how Trichoderma is able to tolerate hostile conditions. A gene from Trichoderma harzianum CECT 2413, qid74, was strongly expressed during starvation of carbon or nitrogen sources; it encoded a cell wall protein of 74kDa that plays a significant role in mycelium protection. qid74 was originally isolated and characterized, in a previous work, by a differential hybridization approach under simulated mycoparasitism conditions. Heterologous expression of Qid74 in Saccharomyces cerevisiae indicated that the protein, located in the cell wall, interfered with mating and sporulation but not with cell integrity. The qid74 gene was disrupted by homologous recombination and it was overexpressed by isolating transformants selected for the amdS gene that carried several copies of qid74 gene under the control of the pki promoter. Disruptants and transformants showed similar growth rate and viability when they were cultivated in different media, temperatures and osmolarities, or were subjected to different abiotic stress conditions. However, disruptants produced about 70% mass yield under any condition and were substantially more sensitive than the wild type to cell wall degradation by different lytic preparations. Transformants had similar mass yield and were more resistant to lytic enzymes but more sensitive to copper sulfate than the wild type. When experiments of adherence to hydrophobic surfaces were carried out, the disruptants had a reduced capacity to adhere, whereas that capacity in the overproducer transformants was

  7. Theoretical and computational studies of hydrophobic and hydrophilic hydration: Towards a molecular description of the hydration of proteins

    NASA Astrophysics Data System (ADS)

    Garde, Shekhar

    The unique balance of forces underlying biological processes-such as protein folding, aggregation, molecular recognition, and the formation of biological membranes-owes its origin in large part to the surrounding aqueous medium. A quantitative description of fundamental noncovalent interactions, in particular hydrophobic and electrostatic interactions at molecular- scale separations, requires an accurate description of water structure. Thus, the primary goals of our research are to understand the role of water in mediating interactions between molecules and to incorporate this understanding into molecular theories for calculating water-mediated interactions. We have developed a molecular model of hydrophobic interactions that uses methods of information theory to relate hydrophobic effects to the density fluctuations in liquid water. This model provides a quantitative description of small-molecule hydration thermodynamics, as well as insights into the entropies of unfolding globular proteins. For larger molecular solutes, we relate the inhomogeneous water structure in their vicinity to their hydration thermodynamics. We find that the water structure in the vicinity of nonpolar solutes is only locally sensitive to the molecular details of the solute. Water structures predicted using this observation are used to study the association of two neopentane molecules and the conformational equilibria of n-pentane molecule. We have also studied the hydration of a model molecular ionic solute, a tetramethylammonium ion, over a wide range of charge states of the solute. We find that, although the charge dependence of the ion hydration free energy is quadratic, negative ions are more favorably hydrated compared to positive ions. Moreover, this asymmetry of hydration can be reconciled by considering the differences in water organization surrounding positive and negative ions. We have also developed methods for predicting water structure surrounding molecular ions and relating

  8. Hydrophobic charge-induction resin with 5-aminobenzimidazol as the functional ligand: preparation, protein adsorption and immunoglobulin G purification.

    PubMed

    Yan, Jun; Zhang, Qi-Lei; Tong, Hong-Fei; Lin, Dong-Qiang; Yao, Shan-Jing

    2015-07-01

    A new hydrophobic charge-induction chromatography resin was prepared with 5-aminobenzimidazol as functional ligand and polyacrylic ester beads as matrix. Adsorption isotherms and adsorption in columns were investigated using human immunoglobulin G and bovine serum albumin as model proteins, and the influence of pH and NaCl concentration was discussed. Results showed that the ligand density was 195 μmol/mL gel, and protein selectivity can be improved by controlling pH and salt addition. An optimized purification process (sample loading at pH 8.0 with 0.2 M NaCl and elution at pH 5.0) was performed to purify human immunoglobulin G from bovine serum albumin containing feedstock, which resulted in human immunoglobulin G purity of 99.7% and recovery of 94.6%. A similar process was applied for the purification of monoclonal antibody from cell culture supernatant, which showed antibody purity of 94.9% and recovery of 92.5%. The results indicated that the new resin developed had comparable performance as Protein A chromatography and would be suitable for antibody purification from complex feedstock.

  9. 2D-IR spectroscopy of the sulfhydryl band of cysteines in the hydrophobic core of proteins.

    PubMed

    Koziński, M; Garrett-Roe, S; Hamm, P

    2008-06-26

    We investigate the sulfhydryl band of cysteines as a new chromophore for two-dimensional IR (2D-IR) studies of the structure and dynamics of proteins. Cysteines can be put at almost any position in a protein by standard methods of site-directed mutagenesis and, hence, have the potential to be an extremely versatile local probe. Although being a very weak absorber in aqueous environment, the sulfhydryl group gets strongly polarized when situated in an alpha-helix inside the hydrophobic core of a protein because of a strong hydrogen bond to the backbone carbonyl group. The extinction coefficient (epsilon=150 M(-1) cm(-1)) then is sufficiently high to perform detailed 2D-IR studies even at low millimolar concentrations. Using porcine (carbonmonoxy)hemoglobin as an example, which contains two such cysteines in its wild-type form, we demonstrate that spectral diffusion deduced from the 2D-IR line shapes reports on the overall-breathing of the corresponding alpha-helix. The vibrational lifetime of the sulfhydryl group (T1 approximately 6 ps) is considerably longer than that of the much more commonly used amide I mode (approximately 1.0 ps), thereby significantly extending the time window in which spectral diffusion processes can be observed. The experiments are accompanied by molecular dynamics simulations revealing a good overall agreement.

  10. Displacement chromatography of proteins using a retained pH front in a hydrophobic charge induction chromatography column.

    PubMed

    Pinto, N D S; Frey, Douglas D

    2015-03-27

    The chromatographic separation of two proteins into a displacement train of two adjoined rectangular bands was accomplished using a novel method for hydrophobic charge induction chromatography (HCIC) which employs a self-sharpening pH front as the displacer. This method exploits the fact that protein elution in HCIC is promoted by a pH change, but is relatively independent of salt effects, so that a retained pH front can be used in place of a traditional displacer in displacement chromatography. The retained pH front was produced using the two adsorbed buffering species tricine and acetic acid. The separation of lysozyme and α-chymotrypsinogen A into adjoined, rectangular bands was accomplished with overall recoveries based on the total mass injected greater than 90 and 70%, respectively. The addition of urea to the buffer system increased the sharpness of the pH front by 36% while the yields of lysozyme and α-chymotrypsinogen A based on the total mass eluted increased from 76% to 99% and from 37% to 85%, respectively, when the purities of both proteins in their product fractions were fixed at 85%. The results demonstrate that the method developed in this study is a useful variant of HCIC and is also a useful alternative to other displacement chromatography methods.

  11. Role of NH{sub 2}-terminal hydrophobic motif in the subcellular localization of ATP-binding cassette protein subfamily D: Common features in eukaryotic organisms

    SciTech Connect

    Lee, Asaka; Asahina, Kota; Okamoto, Takumi; Kawaguchi, Kosuke; Kostsin, Dzmitry G.; Kashiwayama, Yoshinori; Takanashi, Kojiro; Yazaki, Kazufumi; Imanaka, Tsuneo; Morita, Masashi

    2014-10-24

    Highlights: • ABCD proteins classifies based on with or without NH{sub 2}-terminal hydrophobic segment. • The ABCD proteins with the segment are targeted peroxisomes. • The ABCD proteins without the segment are targeted to the endoplasmic reticulum. • The role of the segment in organelle targeting is conserved in eukaryotic organisms. - Abstract: In mammals, four ATP-binding cassette (ABC) proteins belonging to subfamily D have been identified. ABCD1–3 possesses the NH{sub 2}-terminal hydrophobic region and are targeted to peroxisomes, while ABCD4 lacking the region is targeted to the endoplasmic reticulum (ER). Based on hydropathy plot analysis, we found that several eukaryotes have ABCD protein homologs lacking the NH{sub 2}-terminal hydrophobic segment (H0 motif). To investigate whether the role of the NH{sub 2}-terminal H0 motif in subcellular localization is conserved across species, we expressed ABCD proteins from several species (metazoan, plant and fungi) in fusion with GFP in CHO cells and examined their subcellular localization. ABCD proteins possessing the NH{sub 2}-terminal H0 motif were localized to peroxisomes, while ABCD proteins lacking this region lost this capacity. In addition, the deletion of the NH{sub 2}-terminal H0 motif of ABCD protein resulted in their localization to the ER. These results suggest that the role of the NH{sub 2}-terminal H0 motif in organelle targeting is widely conserved in living organisms.

  12. Adamantane-based amphiphiles (ADAs) for membrane protein study: importance of a detergent hydrophobic group in membrane protein solubilisation.

    PubMed

    Chae, Pil Seok; Bae, Hyoung Eun; Das, Manabendra

    2014-10-21

    We prepared adamantane-containing amphiphiles and evaluated them using a large membrane protein complex in terms of protein solubilisation and stabilization efficacy. These agents were superior to conventional detergents, especially in terms of the membrane protein solubilisation efficiency, implying a new detergent structure-property relationship.

  13. Characterizing hydrophobicity of amino acid side chains in a protein environment via measuring contact angle of a water nanodroplet on planar peptide network.

    PubMed

    Zhu, Chongqin; Gao, Yurui; Li, Hui; Meng, Sheng; Li, Lei; Francisco, Joseph S; Zeng, Xiao Cheng

    2016-11-15

    Hydrophobicity of macroscopic planar surface is conventionally characterized by the contact angle of water droplets. However, this engineering measurement cannot be directly extended to surfaces of proteins, due to the nanometer scale of amino acids and inherent nonplanar structures. To measure the hydrophobicity of side chains of proteins quantitatively, numerous parameters were developed to characterize behavior of hydrophobic solvation. However, consistency among these parameters is not always apparent. Herein, we demonstrate an alternative way of characterizing hydrophobicity of amino acid side chains in a protein environment by constructing a monolayer of amino acids (i.e., artificial planar peptide network) according to the primary and the β-sheet secondary structures of protein so that the conventional engineering measurement of the contact angle of a water droplet can be brought to bear. Using molecular dynamics simulations, contact angles θ of a water nanodroplet on the planar peptide network, together with excess chemical potentials of purely repulsive methane-sized Weeks-Chandler-Andersen solute, are computed. All of the 20 types of amino acids and the corresponding planar peptide networks are studied. Expectedly, all of the planar peptide networks with nonpolar amino acids are hydrophobic due to θ [Formula: see text] 90°, whereas all of the planar peptide networks of the polar and charged amino acids are hydrophilic due to θ [Formula: see text] 90°. Planar peptide networks of the charged amino acids exhibit complete-wetting behavior due to θ [Formula: see text] 0°. This computational approach for characterization of hydrophobicity can be extended to artificial planar networks of other soft matter.

  14. Dress Codes and Uniforms.

    ERIC Educational Resources Information Center

    Lumsden, Linda; Miller, Gabriel

    2002-01-01

    Students do not always make choices that adults agree with in their choice of school dress. Dress-code issues are explored in this Research Roundup, and guidance is offered to principals seeking to maintain a positive school climate. In "Do School Uniforms Fit?" Kerry White discusses arguments for and against school uniforms and summarizes the…

  15. An ant colony optimisation algorithm for the 2D and 3D hydrophobic polar protein folding problem

    PubMed Central

    Shmygelska, Alena; Hoos, Holger H

    2005-01-01

    Background The protein folding problem is a fundamental problems in computational molecular biology and biochemical physics. Various optimisation methods have been applied to formulations of the ab-initio folding problem that are based on reduced models of protein structure, including Monte Carlo methods, Evolutionary Algorithms, Tabu Search and hybrid approaches. In our work, we have introduced an ant colony optimisation (ACO) algorithm to address the non-deterministic polynomial-time hard (NP-hard) combinatorial problem of predicting a protein's conformation from its amino acid sequence under a widely studied, conceptually simple model – the 2-dimensional (2D) and 3-dimensional (3D) hydrophobic-polar (HP) model. Results We present an improvement of our previous ACO algorithm for the 2D HP model and its extension to the 3D HP model. We show that this new algorithm, dubbed ACO-HPPFP-3, performs better than previous state-of-the-art algorithms on sequences whose native conformations do not contain structural nuclei (parts of the native fold that predominantly consist of local interactions) at the ends, but rather in the middle of the sequence, and that it generally finds a more diverse set of native conformations. Conclusions The application of ACO to this bioinformatics problem compares favourably with specialised, state-of-the-art methods for the 2D and 3D HP protein folding problem; our empirical results indicate that our rather simple ACO algorithm scales worse with sequence length but usually finds a more diverse ensemble of native states. Therefore the development of ACO algorithms for more complex and realistic models of protein structure holds significant promise. PMID:15710037

  16. Protein Aggregation/Folding: The Role of Deterministic Singularities of Sequence Hydrophobicity as Determined by Nonlinear Signal Analysis of Acylphosphatase and Aβ(1–40)

    PubMed Central

    Zbilut, Joseph P.; Colosimo, Alfredo; Conti, Filippo; Colafranceschi, Mauro; Manetti, Cesare; Valerio, MariaCristina; Webber, Charles L.; Giuliani, Alessandro

    2003-01-01

    The problem of protein folding vs. aggregation was investigated in acylphosphatase and the amyloid protein Aβ(1–40) by means of nonlinear signal analysis of their chain hydrophobicity. Numerical descriptors of recurrence patterns provided the basis for statistical evaluation of folding/aggregation distinctive features. Static and dynamic approaches were used to elucidate conditions coincident with folding vs. aggregation using comparisons with known protein secondary structure classifications, site-directed mutagenesis studies of acylphosphatase, and molecular dynamics simulations of amyloid protein, Aβ(1–40). The results suggest that a feature derived from principal component space characterized by the smoothness of singular, deterministic hydrophobicity patches plays a significant role in the conditions governing protein aggregation. PMID:14645049

  17. Concentration-dependent displacement of cholesterol in micelles by hydrophobic rice bran protein hydrolysates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The recent production of rice bran oil in Asia and the U.S. has resulted in large quantities of defatted rice bran as a low-value byproduct. Peptides from soy, milk, and other foods have been shown to have the potential hypocholesterolemic property and rice bran protein (RBP) may also contain bioact...

  18. Protein Denaturants at Aqueous–Hydrophobic Interfaces: Self-Consistent Correlation between Induced Interfacial Fluctuations and Denaturant Stability at the Interface

    PubMed Central

    2015-01-01

    The notion of direct interaction between denaturing cosolvent and protein residues has been proposed in dialogue relevant to molecular mechanisms of protein denaturation. Here we consider the correlation between free energetic stability and induced fluctuations of an aqueous–hydrophobic interface between a model hydrophobically associating protein, HFBII, and two common protein denaturants, guanidinium cation (Gdm+) and urea. We compute potentials of mean force along an order parameter that brings the solute molecule close to the known hydrophobic region of the protein. We assess potentials of mean force for different relative orientations between the protein and denaturant molecule. We find that in both cases of guanidinium cation and urea relative orientations of the denaturant molecule that are parallel to the local protein–water interface exhibit greater stability compared to edge-on or perpendicular orientations. This behavior has been observed for guanidinium/methylguanidinium cations at the liquid–vapor interface of water, and thus the present results further corroborate earlier findings. Further analysis of the induced fluctuations of the aqueous–hydrophobic interface upon approach of the denaturant molecule indicates that the parallel orientation, displaying a greater stability at the interface, also induces larger fluctuations of the interface compared to the perpendicular orientations. The correlation of interfacial stability and induced interface fluctuation is a recurring theme for interface-stable solutes at hydrophobic interfaces. Moreover, observed correlations between interface stability and induced fluctuations recapitulate connections to local hydration structure and patterns around solutes as evidenced by experiment (Cooper et al., J. Phys. Chem. A2014, 118, 5657.) and high-level ab initio/DFT calculations (Baer et al., Faraday Discuss2013, 160, 89). PMID:25536388

  19. Comparative studies on the effect of growth conditions on adhesion, hydrophobicity, and extracellular protein profile of Streptococcus sanguis G9B.

    PubMed Central

    Knox, K W; Hardy, L N; Markevics, L J; Evans, J D; Wicken, A J

    1985-01-01

    Streptococcus sanguis G9B was grown in continuous culture at different generation times and pH values in media containing either glucose or fructose and differing in the concentrations of Na+ and K+. The growth pH, carbohydrate, and cation concentration each affected the yield of organisms, their ability to adhere to saliva-coated hydroxyapatite beads, and their hydrophobicity, as measured by adhesion to hexadecane. There was no correlation between adhesion to saliva-coated hydroxyapatite beads and hydrophobicity, the values for hydrophobicity varying between 44 and 83% for organisms that adhered poorly and between 24 and 75% for those that adhered effectively. For organisms grown in batch culture at pH 6.0 or 7.0 there was similarly no correlation between adhesion and hydrophobicity. The growth conditions also had a considerable influence on the production of extracellular protein. The total amount was greater at pH 7.5 than at other pH values, and there were also differences in the individual components in response to changes in generation time, pH, carbohydrate source, and cation concentration. Two protein bands were identified, namely, glucosyltransferase and protein P1 (also called antigen B or I/II). However, there was no correlation between a particular protein component and adhesion. Images PMID:4055033

  20. The chaplins: a family of hydrophobic cell-surface proteins involved in aerial mycelium formation in Streptomyces coelicolor

    PubMed Central

    Elliot, Marie A.; Karoonuthaisiri, Nitsara; Huang, Jianqiang; Bibb, Maureen J.; Cohen, Stanley N.; Kao, Camilla M.; Buttner, Mark J.

    2003-01-01

    The filamentous bacterium Streptomyces coelicolor differentiates by forming specialized, spore-bearing aerial hyphae that grow into the air. Using microarrays, we identified genes that are down-regulated in a mutant unable to erect aerial hyphae. Through this route, we identified a previously unknown layer of aerial mycelium surface proteins (the “chaplins”). The chaplins share a hydrophobic domain of ∼40 residues (the “chaplin domain”), and all have a secretion signal. The five short chaplins (ChpD,E,F,G,H) have one chaplin domain, whereas the three long chaplins (ChpA,B,C) have two chaplin domains and a C-terminal “sorting signal” that targets them for covalent attachment to the cell wall by sortase enzyme. Expression of the two chaplin genes examined (chpE, chpH) depended on aerial hyphae formation but not sporulation, and egfp fusions showed their expression localized to aerial structures. Mass spectrometry of cell wall extracts confirmed that the short chaplins localized to the cell surface. Deletion of chaplin genes caused severe delays in aerial hyphae formation, a phenotype rescued by exogenous application of chaplin proteins. These observations implicate the chaplins in aerial mycelium formation, and suggest that coating of the envelope by the chaplins is required for aerial hyphae to grow out of the aqueous environment of the substrate mycelium into the air. PMID:12832397

  1. A key hydrophobic patch identified in an AAA⁺ protein essential for its in trans inhibitory regulation.

    PubMed

    Zhang, Nan; Simpson, Timothy; Lawton, Edward; Uzdavinys, Povilas; Joly, Nicolas; Burrows, Patricia; Buck, Martin

    2013-08-09

    Bacterial enhancer binding proteins (bEBPs) are a subclass of the AAA(+) (ATPases Associated with various cellular Activities) protein family. They are responsible for σ(54)-dependent transcription activation during infection and function under many stressful growth conditions. The majority of bEBPs are regulated in their formation of ring-shaped hexameric self-assemblies via an amino-terminal domain through its phosphorylation or ligand binding. In contrast, the Escherichia coli phage shock protein F (PspF) is negatively regulated in trans by phage shock protein A (PspA). Up to six PspA subunits suppress PspF hexamer action. Here, we present biochemical evidence that PspA engages across the side of a PspF hexameric ring. We identify three key binding determinants located in a surface-exposed 'W56 loop' of PspF, which form a tightly packed hydrophobic cluster, the 'YLW' patch. We demonstrate the profound impact of the PspF W56 loop residues on ATP hydrolysis, the σ(54) binding loop 1, and the self-association interface. We infer from single-chain studies that for complete PspF inhibition to occur, more than three PspA subunits need to bind a PspF hexamer with at least two binding to adjacent PspF subunits. By structural modelling, we propose that PspA binds to PspF via its first two helical domains. After PspF binding-induced conformational changes, PspA may then share structural similarities with a bEBP regulatory domain.

  2. Salts employed in hydrophobic interaction chromatography can change protein structure - insights from protein-ligand interaction thermodynamics, circular dichroism spectroscopy and small angle X-ray scattering.

    PubMed

    Komaromy, Andras Z; Kulsing, Chadin; Boysen, Reinhard I; Hearn, Milton T W

    2015-03-01

    Key requirements of protein purification by hydrophobic interaction chromatography (HIC) are preservation of the tertiary/quaternary structure, maintenance of biological function, and separation of the correctly folded protein from its unfolded forms or aggregates. This study examines the relationship between the HIC retention behavior of hen egg white lysozyme (HEWL) in high concentrations of several kosmotropic salts and its conformation, assessed by circular dichroism (CD) spectroscopy. Further, the physicochemical properties of HEWL in the presence of high concentrations of ammonium sulfate, sodium chloride and magnesium chloride were investigated by small angle X-ray scattering (SAXS) at different temperatures. Radii of gyration were extrapolated from Guinier approximations and the indirect transform program GNOM with protein-protein interaction and contrast variation taken into account. A bead model simulation provided information on protein structural changes using ab initio reconstruction with GASBOR. These results correlated to the secondary structure content obtained from CD spectroscopy of HEWL. These changes in SAXS and CD data were consistent with heat capacity ΔCp -values obtained from van't Hoff plot analyses of the retention data. Collectively, these insights enable informed decisions to be made on the choice of chromatographic conditions, leading to improved separation selectivity and opportunities for innovative column-assisted protein refolding methods.

  3. A hydrophobic loop in acyl-CoA binding protein is functionally important for binding to palmitoyl-coenzyme A: a molecular dynamics study.

    PubMed

    Vallejo, Diego F G; Grigera, J Raúl; Costabel, Marcelo D

    2008-04-01

    Acyl-CoA binding protein (ACBP) plays a key role in lipid metabolism, interacting via a partly unknown mechanism with high affinity with long chain fatty acyl-CoAs (LCFA-CoAs). At present there is no study of the microscopic way ligand binding is accomplished. We analyzed this process by molecular dynamics (MDs) simulations. We proposed a computational model of ligand, able to reproduce some evidence from nuclear magnetic resonance (NMR) data, quantitative time resolved fluorometry and X-ray crystallography. We found that a hydrophobic loop, not in the active site, is important for function. Besides, multiple sequence alignment shows hydrophobicity (and not the residues itselves) conservation.

  4. Hydrophobic-domain-dependent protein-protein interactions mediate the localization of GPAT enzymes to ER subdomains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The endoplasmic reticulum (ER) is a dynamic network that consists of numerous regions or subdomains with discrete morphological features and functional properties, including those involved in protein and oil-body formation, anterograde transport of secretory proteins, the exchange of macromolecules ...

  5. Cerato-populin and cerato-platanin, two non-catalytic proteins from phytopathogenic fungi, interact with hydrophobic inanimate surfaces and leaves.

    PubMed

    Martellini, Federica; Faoro, Franco; Carresi, Lara; Pantera, Barbara; Baccelli, Ivan; Maffi, Dario; Tiribilli, Bruno; Sbrana, Francesca; Luti, Simone; Comparini, Cecilia; Bernardi, Rodolfo; Cappugi, Gianni; Scala, Aniello; Pazzagli, Luigia

    2013-09-01

    Based on sequence homology, several fungal Cys-rich secreted proteins have been grouped in the cerato-platanin (CP) family, which comprises at least 40 proteins involved mainly in eliciting defense-related responses. The core member of this family is cerato-platanin, a moderately hydrophobic protein with a double ψ-β barrel fold. CP and the recently identified orthologous cerato-populin (Pop1) are involved in host-fungus interaction, and can be considered non-catalytic fungal PAMPs. CP is more active in inducing defense when in an aggregated conformation than in its native form, but little is known about other CP-orthologous proteins. Here, we cloned, expressed, and purified recombinant Pop1, which was used to characterize the protein aggregates. Our results suggest that the unfolded, self-assembled Pop1 is more active in inducing defense, and that the unfolding process can be induced by interaction with hydrophobic inanimate surfaces such as Teflon, treated mica, and gold sheets. In vivo, we found that both CP and Pop1 interact with the hydrophobic cuticle of leaves. Therefore, we propose that the interaction of these proteins with host cuticle waxes could induce unfolding and consequently trigger their PAMP-like activity.

  6. Role of hydrophobic core on the thermal stability of proteins - molecular dynamics simulations on a single point mutant of Sso7d abstract.

    PubMed

    Priyakumar, U Deva

    2012-01-01

    The role of salt bridges in chromatin protein Sso7d, from S. solfataricus has previously been shown to be crucial for its unusual high thermal stability. Experimental studies have shown that single site mutation of Sso7d (F31A) leads to a substantial decrease in the thermal stability of this protein due to distortion of the hydrophobic core. In the present study, we have performed a total of 0.2 s long molecular dynamics (MD) simulations on F31A at room temperature, and at 360 K, close to the melting temperature of the wild type (WT) protein to investigate the role of hydrophobic core on protein stability. Sso7d-WT was shown to be stable at both 300 and 360 K; however, F31A undergoes denaturation at 360 K, consistent with experimental results. The structural and energetic properties obtained using the analysis of MD trajectories indicate that the single mutation results in high flexibility of the protein, and loosening of intramolecular interactions. Correlation between the dynamics of the salt bridges with the structural transitions and the unfolding pathway indicate the importance of both salt bridges and hydrophobic in effecting thermal stability of proteins in general.

  7. Relevance of structural segregation and chain compaction for the thermodynamics of folding of a hydrophobic protein model.

    PubMed

    Barbosa, Marco Aurélio A; de Araújo, Antônio F Pereira

    2003-05-01

    The relevance of inside-outside segregation and chain compaction for the thermodynamics of folding of a hydrophobic protein model is probed by complete enumeration of two-dimensional chains of up to 18 monomers in the square lattice. The exact computation of Z scores for uniquely designed sequences confirms that Z tends to decrease linearly with sigma square root of N, as previously suggested by theoretical analysis and Monte Carlo simulations, where sigma, the standard deviation of the number of contacts made by different monomers in the target structure, is a measure of structural segregation and N is the chain length. The probability that the target conformation is indeed the unique global energy minimum of the designed sequence is found to increase dramatically with sigma, approaching unity at maximal segregation. However, due to the huge number of conformations with sub-maximal values of sigma, which correspond to intermediate, only mildly discriminative, values of Z, in addition to significant oscillations of Z around its estimated value, the probability that a correctly designed sequence corresponds to a maximally segregated conformation is small. This behavior of Z also explains the observed relation between sigma and different measures of folding cooperativity of correctly designed sequences.

  8. Energy-landscape paving for prediction of face-centered-cubic hydrophobic-hydrophilic lattice model proteins

    NASA Astrophysics Data System (ADS)

    Liu, Jingfa; Song, Beibei; Liu, Zhaoxia; Huang, Weibo; Sun, Yuanyuan; Liu, Wenjie

    2013-11-01

    Protein structure prediction (PSP) is a classical NP-hard problem in computational biology. The energy-landscape paving (ELP) method is a class of heuristic global optimization algorithm, and has been successfully applied to solving many optimization problems with complex energy landscapes in the continuous space. By putting forward a new update mechanism of the histogram function in ELP and incorporating the generation of initial conformation based on the greedy strategy and the neighborhood search strategy based on pull moves into ELP, an improved energy-landscape paving (ELP+) method is put forward. Twelve general benchmark instances are first tested on both two-dimensional and three-dimensional (3D) face-centered-cubic (fcc) hydrophobic-hydrophilic (HP) lattice models. The lowest energies by ELP+ are as good as or better than those of other methods in the literature for all instances. Then, five sets of larger-scale instances, denoted by S, R, F90, F180, and CASP target instances on the 3D FCC HP lattice model are tested. The proposed algorithm finds lower energies than those by the five other methods in literature. Not unexpectedly, this is particularly pronounced for the longer sequences considered. Computational results show that ELP+ is an effective method for PSP on the fcc HP lattice model.

  9. NPPD: A Protein-Protein Docking Scoring Function Based on Dyadic Differences in Networks of Hydrophobic and Hydrophilic Amino Acid Residues

    PubMed Central

    Shih, Edward S. C.; Hwang, Ming-Jing

    2015-01-01

    Protein-protein docking (PPD) predictions usually rely on the use of a scoring function to rank docking models generated by exhaustive sampling. To rank good models higher than bad ones, a large number of scoring functions have been developed and evaluated, but the methods used for the computation of PPD predictions remain largely unsatisfactory. Here, we report a network-based PPD scoring function, the NPPD, in which the network consists of two types of network nodes, one for hydrophobic and the other for hydrophilic amino acid residues, and the nodes are connected when the residues they represent are within a certain contact distance. We showed that network parameters that compute dyadic interactions and those that compute heterophilic interactions of the amino acid networks thus constructed allowed NPPD to perform well in a benchmark evaluation of 115 PPD scoring functions, most of which, unlike NPPD, are based on some sort of protein-protein interaction energy. We also showed that NPPD was highly complementary to these energy-based scoring functions, suggesting that the combined use of conventional scoring functions and NPPD might significantly improve the accuracy of current PPD predictions. PMID:25811640

  10. Dress Codes for Teachers.

    ERIC Educational Resources Information Center

    Phay, Robert E.

    1979-01-01

    Reviews Second Circuit Court of Appeals decision upholding right of school boards to adopt "reasonable" regulations governing teacher dress or hairstyle. Case offers the most exhaustive judicial examination of the issue to date. (Author/PKP)

  11. Ion-specific induced fluctuations and free energetics of aqueous protein hydrophobic interfaces: toward connecting to specific-ion behaviors at aqueous liquid-vapor interfaces.

    PubMed

    Cui, Di; Ou, Shuching; Peters, Eric; Patel, Sandeep

    2014-05-01

    We explore anion-induced interface fluctuations near protein-water interfaces using coarse-grained representations of interfaces as proposed by Willard and Chandler ( J. Phys. Chem. B 2010 , 114 , 1954 - 1958 ). We use umbrella sampling molecular dynamics to compute potentials of mean force along a reaction coordinate bridging the state where the anion is fully solvated and one where it is biased via harmonic restraints to remain at the protein-water interface. Specifically, we focus on fluctuations of an interface between water and a hydrophobic region of hydrophobin-II (HFBII), a 71 amino acid residue protein expressed by filamentous fungi and known for its ability to form hydrophobically mediated self-assemblies at interfaces such as a water/air interface. We consider the anions chloride and iodide that have been shown previously by simulations as displaying specific-ion behaviors at aqueous liquid-vapor interfaces. We find that as in the case of a pure liquid-vapor interface, at the hydrophobic protein-water interface, the larger, less charge-dense iodide anion displays a marginal interfacial stability compared with that of the smaller, more charge-dense chloride anion. Furthermore, consistent with the results at aqueous liquid-vapor interfaces, we find that iodide induces larger fluctuations of the protein-water interface than chloride.

  12. The cost of living in the membrane: a case study of hydrophobic mismatch for the multi-segment protein LeuT.

    PubMed

    Mondal, Sayan; Khelashvili, George; Shi, Lei; Weinstein, Harel

    2013-04-01

    Many observations of the role of the membrane in the function and organization of transmembrane (TM) proteins have been explained in terms of hydrophobic mismatch between the membrane and the inserted protein. For a quantitative investigation of this mechanism in the lipid-protein interactions of functionally relevant conformations adopted by a multi-TM segment protein, the bacterial leucine transporter (LeuT), we employed a novel method, Continuum-Molecular Dynamics (CTMD), that quantifies the energetics of hydrophobic mismatch by combining the elastic continuum theory of membrane deformations with an atomistic level description of the radially asymmetric membrane-protein interface from MD simulations. LeuT has been serving as a model for structure-function studies of the mammalian neurotransmitter:sodium symporters (NSSs), such as the dopamine and serotonin transporters, which are the subject of intense research in the field of neurotransmission. The membrane models in which LeuT was embedded for these studies were composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid, or 3:1 mixture of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) lipids. The results show that deformation of the host membrane alone is not sufficient to alleviate the hydrophobic mismatch at specific residues of LeuT. The calculations reveal significant membrane thinning and water penetration due to the specific local polar environment produced by the charged K288 of TM7 in LeuT, that is membrane-facing deep inside the hydrophobic milieu of the membrane. This significant perturbation is shown to result in unfavorable polar-hydrophobic interactions at neighboring hydrophobic residues in TM1a and TM7. We show that all the effects attributed to the K288 residue (membrane thinning, water penetration, and the unfavorable polar-hydrophobic interactions at TM1a and TM7), are abolished in calculations with the

  13. Hydrophobic drug-triggered self-assembly of nanoparticles from silk-elastin-like protein polymers for drug delivery.

    PubMed

    Xia, Xiao-Xia; Wang, Ming; Lin, Yinan; Xu, Qiaobing; Kaplan, David L

    2014-03-10

    Silk-elastin-like protein polymers (SELPs) combine the mechanical and biological properties of silk and elastin. These properties have led to the development of various SELP-based materials for drug delivery. However, SELPs have rarely been developed into nanoparticles, partially due to the complicated fabrication procedures, nor assessed for potential as an anticancer drug delivery system. We have recently constructed a series of SELPs (SE8Y, S2E8Y, and S4E8Y) with various ratios of silk to elastin blocks and described their capacity to form micellar-like nanoparticles upon thermal triggering. In this study, we demonstrate that doxorubicin, a hydrophobic antitumor drug, can efficiently trigger the self-assembly of SE8Y (SELPs with silk to elastin ratio of 1:8) into uniform micellar-like nanoparticles. The drug can be loaded in the SE8Y nanoparticles with an efficiency around 6.5% (65 ng doxorubicin/μg SE8Y), S2E8Y with 6%, and S4E8Y with 4%, respectively. In vitro studies with HeLa cell lines demonstrate that the protein polymers are not cytotoxic (IC50 > 200 μg/mL), while the doxorubicin-loaded SE8Y nanoparticles showed a 1.8-fold higher cytotoxicity than the free drug. Confocal laser scanning microscopy (CLSM) and flow cytometry indicate significant uptake of the SE8Y nanoparticles by the cells and suggest internalization of the nanoparticles through endocytosis. This study provides an all-aqueous, facile method to prepare nanoscale, drug-loaded SELPs packages with potential for tumor cell treatments.

  14. Stabilization of secondary structure elements by specific combinations of hydrophilic and hydrophobic amino acid residues is more important for proteins encoded by GC-poor genes.

    PubMed

    Khrustalev, Vladislav Victorovich; Barkovsky, Eugene Victorovich

    2012-12-01

    Stabilization of secondary structure elements by specific combinations of hydrophobic and hydrophilic amino acids has been studied by the way of analysis of pentapeptide fragments from twelve partial bacterial proteomes. PDB files describing structures of proteins from species with extremely high and low genomic GC-content, as well as with average G + C were included in the study. Amino acid residues in 78,009 pentapeptides from alpha helices, beta strands and coil regions were classified into hydrophobic and hydrophilic ones. The common propensity scale for 32 possible combinations of hydrophobic and hydrophilic amino acid residues in pentapeptide has been created: specific pentapeptides for helix, sheet and coil were described. The usage of pentapeptides preferably forming alpha helices is decreasing in alpha helices of partial bacterial proteomes with the increase of the average genomic GC-content in first and second codon positions. The usage of pentapeptides preferably forming beta strands is increasing in coil regions and in helices of partial bacterial proteomes with the growth of the average genomic GC-content in first and second codon positions. Due to these circumstances the probability of coil-sheet and helix-sheet transitions should be increased in proteins encoded by GC-rich genes making them prone to form amyloid in certain conditions. Possible causes of the described fact that importance of alpha helix and coil stabilization by specific combinations of hydrophobic and hydrophilic amino acids is growing with the decrease of genomic GC-content have been discussed.

  15. The fuzzy oil drop model, based on hydrophobicity density distribution, generalizes the influence of water environment on protein structure and function.

    PubMed

    Banach, Mateusz; Konieczny, Leszek; Roterman, Irena

    2014-10-21

    In this paper we show that the fuzzy oil drop model represents a general framework for describing the generation of hydrophobic cores in proteins and thus provides insight into the influence of the water environment upon protein structure and stability. The model has been successfully applied in the study of a wide range of proteins, however this paper focuses specifically on domains representing immunoglobulin-like folds. Here we provide evidence that immunoglobulin-like domains, despite being structurally similar, differ with respect to their participation in the generation of hydrophobic core. It is shown that β-structural fragments in β-barrels participate in hydrophobic core formation in a highly differentiated manner. Quantitatively measured participation in core formation helps explain the variable stability of proteins and is shown to be related to their biological properties. This also includes the known tendency of immunoglobulin domains to form amyloids, as shown using transthyretin to reveal the clear relation between amyloidogenic properties and structural characteristics based on the fuzzy oil drop model.

  16. Wound dressings for a proteolytic-rich environment.

    PubMed

    Vasconcelos, Andreia; Cavaco-Paulo, Artur

    2011-04-01

    Wound dressings have experienced continuous and significant changes over the years based on the knowledge of the biochemical events associated with chronic wounds. The development goes from natural materials used to just cover and conceal the wound to interactive materials that can facilitate the healing process, addressing specific issues in non-healing wounds. These new types of dressings often relate with the proteolytic wound environment and the bacteria load to enhance the healing. Recently, the wound dressing research is focusing on the replacement of synthetic polymers by natural protein materials to delivery bioactive agents to the wounds. This article provides an overview on the novel protein-based wound dressings such as silk fibroin keratin and elastin. The improved properties of these dressings, like the release of antibiotics and growth factors, are discussed. The different types of wounds and the effective parameters of healing process will be reviewed.

  17. Hydrophobic clustering in nonnative states of a protein: Interpretation of chemical shifts in NMR spectra of denatured states of lysozyme

    SciTech Connect

    Evans, P.A.; Topping, K.D.; Woolfson, D.N.; Dobson, C.M. )

    1991-01-01

    Chemical shifts of resonances of specific protons in the 1H NMR spectrum of thermally denatured hen lysozyme have been determined by exchange correlation with assigned native state resonances in 2D NOESY spectra obtained under conditions where the two states are interconverting. There are subtle but widespread deviations of the measured shifts from the values which would be anticipated for a random coil; in the case of side chain protons these are virtually all net upfield shifts and it is shown that this may be the averaged effect of interactions with aromatic rings in a partially collapsed denatured state. In a very few cases, notably that of two sequential tryptophan residues, it is possible to interpret these effects in terms of specific, local interresidue interactions. Generally, however, there is no correlation with either native state shift perturbations or with sequence proximity to aromatic groups. Diminution of most of the residual shift perturbations on reduction of the disulfide cross-links confirms that they are not simply effects of residues adjacent in the sequence. Similar effects of chemical denaturants, with the disulfides intact, demonstrate that the shift perturbations reflect an enhanced tendency to side chain clustering in the thermally denatured state. The temperature dependences of the shift perturbations suggest that this clustering is noncooperative and is driven by small, favorable enthalpy changes. While the extent of conformational averaging is clearly much greater than that observed for a homologous protein, alpha-lactalbumin, in its partially folded molten globule state, the results clearly show that thermally denatured lysozyme differs substantially from a random coil, principally in that it is partially hydrophobically collapsed.

  18. Influence of hydrophobic and electrostatic residues on SARS-coronavirus S2 protein stability: insights into mechanisms of general viral fusion and inhibitor design.

    PubMed

    Aydin, Halil; Al-Khooly, Dina; Lee, Jeffrey E

    2014-05-01

    Severe acute respiratory syndrome (SARS) is an acute respiratory disease caused by the SARS-coronavirus (SARS-CoV). SARS-CoV entry is facilitated by the spike protein (S), which consists of an N-terminal domain (S1) responsible for cellular attachment and a C-terminal domain (S2) that mediates viral and host cell membrane fusion. The SARS-CoV S2 is a potential drug target, as peptidomimetics against S2 act as potent fusion inhibitors. In this study, site-directed mutagenesis and thermal stability experiments on electrostatic, hydrophobic, and polar residues to dissect their roles in stabilizing the S2 postfusion conformation was performed. It was shown that unlike the pH-independent retroviral fusion proteins, SARS-CoV S2 is stable over a wide pH range, supporting its ability to fuse at both the plasma membrane and endosome. A comprehensive SARS-CoV S2 analysis showed that specific hydrophobic positions at the C-terminal end of the HR2, rather than electrostatics are critical for fusion protein stabilization. Disruption of the conserved C-terminal hydrophobic residues destabilized the fusion core and reduced the melting temperature by 30°C. The importance of the C-terminal hydrophobic residues led us to identify a 42-residue substructure on the central core that is structurally conserved in all existing CoV S2 fusion proteins (root mean squared deviation=0.4 Å). This is the first study to identify such a conserved substructure and likely represents a common foundation to facilitate viral fusion. We have discussed the role of key residues in the design of fusion inhibitors and the potential of the substructure as a general target for the development of novel therapeutics against CoV infections.

  19. Impaired Secretion of a Hydrophobic Cutinase by Saccharomyces cerevisiae Correlates with an Increased Association with Immunoglobulin Heavy-Chain Binding Protein (BiP)

    PubMed Central

    Sagt, C. M. J.; Müller, W. H.; Boonstra, J.; Verkleij, A. J.; Verrips, C. T.

    1998-01-01

    This study focuses on the different efficiencies of secretion of two fungal cutinases by Saccharomyces cerevisiae, a wild-type cutinase (CY000) and a hydrophobic mutant cutinase (CY028). Both cutinases are placed under control of the GAL7 promoter, by which the expression levels can be regulated. Wild-type cutinase was secreted at up to 25 mg per g (dry weight), while CY028 was secreted at a level of 2 mg per g (dry weight); this difference is nearly independent of the expression level. Pulse-chase experiments revealed that whereas CY000 cutinase is secreted, CY028 is irreversibly retained in the cell. Immunogold labelling followed by electron microscopy revealed colocalization of CY028 with immunoglobulin heavy-chain binding protein (BiP) in the endoplasmic reticulum (ER). The increase of wild-type cutinase expression did not result in higher levels of the molecular chaperone BiP, but BiP levels are raised by increased induction of the hydrophobic mutant cutinase. Immunoprecipitation studies showed that in contrast to the wild-type cutinase, the hydrophobic mutant cutinase interacts with BiP. These results indicate that the introduction of two exposed hydrophobic patches in cutinase results in a higher affinity for BiP which might cause the retention of this mutant cutinase in the ER. PMID:9435084

  20. Mia40 is a trans-site receptor that drives protein import into the mitochondrial intermembrane space by hydrophobic substrate binding

    PubMed Central

    Peleh, Valentina; Cordat, Emmanuelle; Herrmann, Johannes M

    2016-01-01

    Many proteins of the mitochondrial IMS contain conserved cysteines that are oxidized to disulfide bonds during their import. The conserved IMS protein Mia40 is essential for the oxidation and import of these proteins. Mia40 consists of two functional elements: an N-terminal cysteine-proline-cysteine motif conferring substrate oxidation, and a C-terminal hydrophobic pocket for substrate binding. In this study, we generated yeast mutants to dissect both Mia40 activities genetically and biochemically. Thereby we show that the substrate-binding domain of Mia40 is both necessary and sufficient to promote protein import, indicating that trapping by Mia40 drives protein translocation. An oxidase-deficient Mia40 mutant is inviable, but can be partially rescued by the addition of the chemical oxidant diamide. Our results indicate that Mia40 predominantly serves as a trans-site receptor of mitochondria that binds incoming proteins via hydrophobic interactions thereby mediating protein translocation across the outer membrane by a ‘holding trap’ rather than a ‘folding trap’ mechanism. DOI: http://dx.doi.org/10.7554/eLife.16177.001 PMID:27343349

  1. Wet to dry dressing changes

    MedlinePlus

    ... warm water before and after each dressing change. Put on a pair of non-sterile gloves. Carefully ... pads or packing tape from inside your wound. Put the old dressing, packing material, and your gloves ...

  2. Restricting Student Dress in Public Schools.

    ERIC Educational Resources Information Center

    Grantham, Kimberly

    1994-01-01

    Addresses the authority of school officials to regulate student dress by examining school dress codes, first with respect to communicative dress--or dress that communicates speech--and then with respect to noncommunicative dress. Provides a summary of the law on dress codes and a basic set of rules to assist school officials in drafting…

  3. Influence of poly(ethylene oxide)-based copolymer on protein adsorption and bacterial adhesion on stainless steel: modulation by surface hydrophobicity.

    PubMed

    Yang, Yi; Rouxhet, Paul G; Chudziak, Dorota; Telegdi, Judit; Dupont-Gillain, Christine C

    2014-06-01

    The aim of the present work is to study the adhesion of Pseudomonas NCIMB 2021, a typical aerobic marine microorganism, on stainless steel (SS) substrate. More particularly, the potential effect on adhesion of adsorbed poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer is investigated. Bacterial attachment experiments were carried out using a modified parallel plate flow chamber, allowing different surface treatments to be compared in a single experiment. The amount of adhering bacteria was determined via DAPI staining and fluorescence microscopy. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface chemical composition of SS and hydrophobized SS before and after PEO-PPO-PEO adsorption. The adsorption of bovine serum albumin (BSA), a model protein, was investigated to test the resistance of PEO-PPO-PEO layers to protein adsorption. The results show that BSA adsorption and Pseudomonas 2021 adhesion are significantly reduced on hydrophobized SS conditioned with PEO-PPO-PEO. Although PEO-PPO-PEO is also found to adsorb on SS, it does not prevent BSA adsorption nor bacterial adhesion, which is attributed to different PEO-PPO-PEO adlayer structures on hydrophobic and hydrophilic surfaces. The obtained results open the way to a new strategy to reduce biofouling on metal oxide surfaces using PEO-PPO-PEO triblock copolymer.

  4. The role of plastic β-hairpin and weak hydrophobic core in the stability and unfolding of a full sequence design protein

    NASA Astrophysics Data System (ADS)

    Lei, Hongxing; Duan, Yong

    2004-12-01

    In this study, the thermal stability of a designed α/β protein FSD (full sequence design) was studied by explicit solvent simulations at three moderate temperatures, 273 K, 300 K, and 330 K. The average properties of the ten trajectories at each temperature were analyzed. The thermal unfolding, as judged by backbone root-mean-square deviation and percentage of native contacts, was displayed with increased sampling outside of the native basin as the temperature was raised. The positional fluctuation of the hairpin residues was significantly higher than that of the helix residues at all three temperatures. The hairpin segment displayed certain plasticity even at 273 K. Apart from the terminal residues, the highest fluctuation was shown in the turn residues 7-9. Secondary structure analysis manifested the structural heterogeneity of the hairpin segment. It was also revealed by the simulation that the hydrophobic core was vulnerable to thermal denaturation. Consistent with the experiment, the I7Y mutation in the double mutant FSD-EY (FSD with mutations Q1E and I7Y) dramatically increased the protein stability in the simulation, suggesting that the plasticity of the hairpin can be partially compensated by a stronger hydrophobic core. As for the unfolding pathway, the breathing of the hydrophobic core and the separation of the two secondary structure elements (α helix and β hairpin) was the initiation step of the unfolding. The loss of global contacts from the separation further destabilized the hairpin structure and also led to the unwinding of the helix.

  5. Dress Codes. Legal Brief.

    ERIC Educational Resources Information Center

    Zirkel, Perry A.

    2000-01-01

    As illustrated by two recent decisions, the courts in the past decade have demarcated wide boundaries for school officials considering dress codes, whether in the form of selective prohibitions or required uniforms. Administrators must warn the community, provide legitimate justification and reasonable clarity, and comply with state law. (MLH)

  6. Student Dress Codes.

    ERIC Educational Resources Information Center

    Uerling, Donald F.

    School officials see a need for regulations that prohibit disruptive and inappropriate forms of expression and attire; students see these regulations as unwanted restrictions on their freedom. This paper reviews court litigation involving constitutional limitations on school authority, dress and hair codes, state law constraints, and school…

  7. Dresses Make the Girl: Gender and Identity from "The Hundred Dresses" to "10,000 Dresses"

    ERIC Educational Resources Information Center

    Smulders, Sharon

    2015-01-01

    This paper offers a close reading of two works, Eleanor Estes' "The Hundred Dresses" (1944) and Marcus Ewert's "10,000 Dresses" (2008), that feature in current anti-bullying campaigns. Starting with "The Hundred Dresses," this essay examines how Estes' use of the school story not only exposes the social dynamics of…

  8. Effects of salt or cosolvent addition on solubility of a hydrophobic solute in water: Relevance to those on thermal stability of a protein

    NASA Astrophysics Data System (ADS)

    Murakami, Shota; Hayashi, Tomohiko; Kinoshita, Masahiro

    2017-02-01

    The solubility of a nonpolar solute in water is changed upon addition of a salt or cosolvent. Hereafter, "solvent" is formed by water molecules for pure water, by water molecules, cations, and anions for water-salt solution, and by water and cosolvent molecules for water-cosolvent solution. Decrease and increase in the solubility, respectively, are ascribed to enhancement and reduction of the hydrophobic effect. Plenty of experimental data are available for the change in solubility of argon or methane arising from the addition. We show that the integral equation theory combined with a rigid-body model, in which the solute and solvent particles are modeled as hard spheres with different diameters, can reproduce the data for the following items: salting out by an alkali halide and salting in by tetramethylammonium bromide, increase in solubility by a monohydric alcohol, and decrease in solubility by sucrose or urea. The orders of cation or anion species in terms of the power of decreasing the solubility can also be reproduced for alkali halides. With the rigid-body model, the analyses are focused on the roles of entropy originating from the translational displacement of solvent particles. It is argued by decomposing the solvation entropy of a nonpolar solute into physically insightful constituents that the solvent crowding in the bulk is a pivotal factor of the hydrophobic effect: When the solvent crowding in the bulk becomes more serious, the effect is strengthened, and when it becomes less serious, the effect is weakened. It is experimentally known that the thermal stability of a protein is also influenced by the salt or cosolvent addition. The additions which decrease and increase the solubility of a nonpolar solute, respectively, usually enhance and lower the thermal stability. This suggests that the enhanced or reduced hydrophobic effect is also a principal factor governing the stability change. However, urea decreases the solubility but lowers the stability

  9. Label-free proteomic analysis of the hydrophobic membrane protein complement in articular chondrocytes: a technique for identification of membrane biomarkers

    PubMed Central

    Matta, Csaba; Zhang, Xiaofei; Liddell, Susan; Smith, Julia R.; Mobasheri, Ali

    2015-01-01

    Abstract Context: There is insufficient knowledge about the chondrocyte membranome and its molecular composition. Objective: To develop a Triton X-114 based separation technique using nanoLC-MS/MS combined with shotgun proteomics to identify chondrocyte membrane proteins. Materials and methods: Articular chondrocytes from equine metacarpophalangeal joints were separated into hydrophobic and hydrophilic fractions; trypsin-digested proteins were analysed by nanoLC-MS/MS. Results: A total of 315 proteins were identified. The phase extraction method yielded a high proportion of membrane proteins (56%) including CD276, S100-A6 and three VDAC isoforms. Discussion: Defining the chondrocyte membranome is likely to reveal new biomarker targets for conventional and biological drug discovery. PMID:26864288

  10. Wound Healing and the Dressing*

    PubMed Central

    Scales, John T.

    1963-01-01

    The evolution of surgical dressings is traced from 1600 b.c. to a.d. 1944. The availability of an increasing variety of man-made fibres and films from 1944 onwards has stimulated work on wound dressings, and some of the more important contributions, both clinical and experimental, are discussed. The functions of a wound dressing and the properties which the ideal wound dressing should possess are given. The necessity for both histological and clinical evaluation of wound dressings in animals and in man is stressed. Wound dressings are the most commonly used therapeutic agents, but there is no means whereby their performance can be assessed. An attempt should be made either nationally or internationally to establish a standard method of assessing the performance of wound dressings. For this it is necessary to have an internationally agreed standard dressing which could be used as a reference or control dressing in all animal and human work. The only animal with skin morphologically similar to that of man is the domestic pig. Three types of wounds could be used: (1) partial-thickness wounds; (2) full-thickness excisions; and (3) third-degree burns. The development of standard techniques for the assessment of the efficiency of wound dressings would be of considerable benefit to the research worker, the medical profession, the patient, and the surgical dressings industry. PMID:13976490

  11. Periodontal Dressing: A Review Article

    PubMed Central

    Baghani, Zahra; Kadkhodazadeh, Mahdi

    2013-01-01

    The purpose of this paper was to review the commercially available periodontal dressings, their physical and chemical properties, biocompatibility and therapeutic effects. Electronic search of scientific papers from 1956 to 2012 was carried out using PubMed, Scopus and Wiley InterScience search engines using the searched terms periodontal dressing, periodontal pack. Numerous in vitro and in vivo studies have evaluated various properties of periodontal dressings. Physical and chemical properties of dressings are directly related to their dimensional changes and adhesion properties. Their biocompatibility and therapeutic effect are among the other factors evaluated in the literature. Chlorhexidine is the most commonly used antibacterial agent in studies. In general, when comparing the advantages with the disadvantages, application of periodontal dressing seems to be beneficial. Numerous factors are involved in selection of an optimal dressing such as surgeon’s intention, required time for the dressing to remain on the surgery site and its dimensional changes. PMID:24578815

  12. Molecular Orbital Study of the Formation of Intramolecular Hydrogen Bonding of a Ligand Molecule in a Protein Aromatic Hydrophobic Pocket.

    PubMed

    Koseki, Jun; Gouda, Hiroaki; Hirono, Shuichi

    2016-01-01

    The natural product argadin is a cyclopentapeptide chitinase inhibitor that binds to chitinase B (ChiB) from the pathogenic bacteria Serratia marcescens. N(ω)-Acetyl-L-arginine and L-aminoadipic acid of argadin form intramolecular ionic hydrogen bonds in the aromatic hydrophobic pocket of ChiB. We performed ab initio molecular orbital and density functional theory calculations to elucidate the role of this intramolecular hydrogen bonding on intermolecular interactions between argadin and ChiB. We found that argadin accrues large stabilization energies from the van der Waals dispersion interactions, such as CH-π, π-π, and π-lone pair interactions, in the aromatic hydrophobic pocket of ChiB, although intramolecular hydrogen bonding within argadin might result in loss of entropy. The intramolecular ionic hydrogen bonding formation canceled local molecular charges and provided good van der Waals interactions with surrounding aromatic residues.

  13. Spot morphology of non-contact printed protein molecules on non-porous substrates with a range of hydrophobicities.

    PubMed

    Mujawar, Liyakat Hamid; Norde, Willem; van Amerongen, Aart

    2013-01-21

    Non-contact inkjet printing technology is one of the most promising tools for producing microarrays. The quality of the microarray depends on the type of the substrate used for printing biomolecules. Various porous and non-porous substrates have been used in the past, but due to low production cost and easy availability, non-porous substrates like glass and plastic are preferred over porous substrates. On these non-porous substrates, obtaining spot uniformity and a high signal to noise ratio is a big challenge. In our research work, we have modified pristine glass slides using various silanes to produce a range of hydrophobic glass substrates. The hydrophobicities of the slides expressed in the contact angle (θ) of a sessile drop of water were 49°, 61°, 75°, 88° and 103°. Using a non-contact inkjet printer, microarrays of biotinylated biomolecules (BSA and IgG) were produced on these modified glass substrates, pristine (untreated) glass and also on HTA polystyrene slides. The uniformity of the spots, reflecting the distribution of the biomolecules in the spots, was analyzed and compared using confocal laser scanning microscopy (CLSM). The quality of the spots was superior on the glass slide with a contact angle of ∼75°. We also investigated the influence of the hydrophobicity of the substrate on a two-step, real diagnostic antibody assay. This nucleic acid microarray immunoassay (NAMIA) for the detection of Staphylococcus aureus showed that on highly hydrophilic (θ < 10°) and hydrophobic substrates (θ > 100°) the assay signal was low, whereas an excellent signal was obtained on the substrates with intermediate contact angles, θ ∼ 61° and θ ∼ 75°, respectively.

  14. Three dimensional liquid chromatography coupling ion exchange chromatography/hydrophobic interaction chromatography/reverse phase chromatography for effective protein separation in top-down proteomics.

    PubMed

    Valeja, Santosh G; Xiu, Lichen; Gregorich, Zachery R; Guner, Huseyin; Jin, Song; Ge, Ying

    2015-01-01

    To address the complexity of the proteome in mass spectrometry (MS)-based top-down proteomics, multidimensional liquid chromatography (MDLC) strategies that can effectively separate proteins with high resolution and automation are highly desirable. Although various MDLC methods that can effectively separate peptides from protein digests exist, very few MDLC strategies, primarily consisting of 2DLC, are available for intact protein separation, which is insufficient to address the complexity of the proteome. We recently demonstrated that hydrophobic interaction chromatography (HIC) utilizing a MS-compatible salt can provide high resolution separation of intact proteins for top-down proteomics. Herein, we have developed a novel 3DLC strategy by coupling HIC with ion exchange chromatography (IEC) and reverse phase chromatography (RPC) for intact protein separation. We demonstrated that a 3D (IEC-HIC-RPC) approach greatly outperformed the conventional 2D IEC-RPC approach. For the same IEC fraction (out of 35 fractions) from a crude HEK 293 cell lysate, a total of 640 proteins were identified in the 3D approach (corresponding to 201 nonredundant proteins) as compared to 47 in the 2D approach, whereas simply prolonging the gradients in RPC in the 2D approach only led to minimal improvement in protein separation and identifications. Therefore, this novel 3DLC method has great potential for effective separation of intact proteins to achieve deep proteome coverage in top-down proteomics.

  15. Cell wall protein and glycoprotein constituents of Aspergillus fumigatus that bind to polystyrene may be responsible for the cell surface hydrophobicity of the mycelium.

    PubMed

    Peñalver, M C; Casanova, M; Martínez, J P; Gil, M L

    1996-07-01

    Cell surface hydrophobicity (CSH) of Aspergillus fumigatus grown both in complex medium (yeast extract/peptone/dextrose; YPD) and minimal (Vogel's N) medium was monitored by assessing attachment of polystyrene microspheres to the cell surface. It was found that mature mycelium was hydrophobic. Treatment of intact mycelium with beta-mercaptoethanol (beta ME) abolished binding of the microspheres to hyphal elements, and coating of the microspheres with beta ME extracts from mycelium inhibited their attachment to intact mycelial cells. A. fumigatus mycelium was tagged in vivo with biotin and treated with beta ME. The beta ME extracts were analysed by SDS-PAGE and Western blotting with both peroxidase-conjugated-ExtrAvidin and concanavalin A (ConA). This procedure allowed identification of cell wall surface proteins and glycoproteins. Rabbit polyclonal antisera were raised against beta ME extracts obtained from cells grown in YPD and Vogel's N media. These antisera defined some major cell-wall-bound antigens. SDS-PAGE and Western blotting analysis of the cell wall material released by beta ME and adsorbed on polystyrene microspheres revealed about 19 protein species with apparent molecular masses ranging from 20 to 70 kDa, and two high-molecular-mass glycoproteins of 115 and 210 kDa. Treatment of cells grown in YPD, but not those grown in Vogel's N medium, with beta ME released a 55 kDa polypeptide able to adsorb to polystyrene microspheres that was detectable with the antisera. The ability to bind to polystyrene particles exhibited by several protein and glycoprotein species released by beta ME treatment suggested that these cell wall moieties possess exposed hydrophobic domains that could be responsible for the CSH of mycelium.

  16. DRESS and Ischemic Stroke.

    PubMed

    Cahyanur, Rahmat; Oktavia, Dina; Koesno, Sukamto

    2012-07-01

    DRESS (drug rash eosinophilia and systemic symptoms) is a life threatening condition characterized by skin rash, fever, leucocytosis with eosinophilia or atypical lymphocytosis, lymphadenopathy, and internal organ involvement. This case report would like to describe an interesting case of DRESS coincidence with ischemic stroke. A 38 year old woman had been admitted with skin rash and fever since four days before. Four weeks before admission she received antibiotic and multivitamin for one week. The patient looked ill, with body temperature 38.0°C. Marked physical findings were cervical lymphadenopathy and hepatomegaly. Dermatological examination finding was generalized exanthema. Laboratory evaluation showed leucocytosis, eosinophilia, and increased level of ALT and AST. During hospitalization the patient also suffered from ischemic stroke. Treatments administered in this patient were oxygen, adequate intravenous fluid, parenteral nutrition, methyl prednisolone, cethirizin bid, ranitidin bid, and antibiotic. The antibiotic treatment in this case was performed with graded challenge or test dosing.

  17. Prevalence of DRESS syndrome.

    PubMed

    López-Rocha, Eunice; Blancas, Lizbeth; Rodríguez-Mireles, Karen; Gaspar-López, Arturo; O'Farrill-Romanillos, Patricia; Amaya-Mejía, Adela; Galindo-Pacheco, Lucy; Campos-Romero, Freya; Aguilar-Hinojosa, Nadia; Suárez, Guadalupe

    2014-01-01

    DRESS syndrome (Drug rash with Eosinophilia and Systemic Symptoms) is an idiosyncratic reaction (type B), characterized by peripheral eosinophilia and systemic symptoms, such as fever, rash, lymphadenopathy, hepatitis, atypical lymphocytes and elevation of liver enzymes at least twice its normal level or increase of alanine amino transferase (ALT) >100 U/L. Its incidence is of 1/1,000 to 10,000 exposures and its mortality is of 10%-20%. Treatment is based on steroids and on the suspension of the suspect drug. This paper reports the cases of six patients with DRESS syndrome attended at Centro Medico Nacional Siglo XXI, Mexico City, from September 2012 to September 2013, which accounted for 12.5% of patients attended with adverse reactions to drugs.

  18. Physical and biological assessments of the innovative bilayered wound dressing made of silk and gelatin for clinical applications.

    PubMed

    Hasatsri, Sukhontha; Yamdech, Rungnapha; Chanvorachote, Pithi; Aramwit, Pornanong

    2015-04-01

    The physical and biological assessments of the innovative bilayered wound dressing made of silk and gelatin that we have developed previously were performed to evaluate its efficacy for clinical applications. The absorption ability and dehydration rate of the dressing were assessed using the split-thickness skin graft and leg ulcer wound bed models. The bioactivities of the bilayered wound dressing were evaluated. The bilayered dressing showed continuous absorption rate of wound exudate, providing the suitability for the wound with extended inflammation phase. The dehydration rate of the bilayered dressing was comparable to the commercially available dressing of which the moisture maintenance capability is claimed. The bilayered dressing showed good conformability, as can be seen by the homogeneous distribution pattern of bromophenol blue absorbed. In terms of biological activities, the bilayered dressing was less toxic to skin cells than the commercially available dressing. The bilayered dressing was also shown to promote cell migration and collagen production due to the bioactive protein components. We here concluded that the superior properties of the bilayered dressing over the commercially available dressing were the conformability and biological activities to accelerate the wound healing, while the other properties were comparable to those of commercially available dressing. The data obtained in this study would be very useful for the further evaluation of the bilayered dressing in clinical trial.

  19. Draconian dress act repealed.

    PubMed

    Mhone, C

    1994-01-01

    The Dress Act was put into place in Malawi by the government of President Kamuzu Banda after the long period of direct colonialism. The act made it illegal for women in Malawi to be seen publicly wearing dresses which did not completely cover their knees or wearing pants; men had to wear their hair short. Police officers even scrutinized women's attire at private house parties and in homes. The autocratic political structure established by Banda, however, was voted out in a referendum June 14, 1993. Pressure by opposition forces such as the United Democratic Front forced a repeal of the act on November 16 of the same year. The repeal was vigorously attacked by female Parliament members as a move which would result in moral degradation and an increase in the level of sexual harassment against women. Other citizens and tourists have generally detested the act. The act has most certainly kept many potential visitors from vacationing in Malawi. Some expert observers think that repeals of the Dress Act, the Forfeiture Act, and legislation which allowed the government to detain opposition figures without trial were done to garner support from the Paris Club for the resumption of balance of payments support suspended due to the country's poor human rights record.

  20. The Hydrophobic Effect.

    ERIC Educational Resources Information Center

    Huque, Entazul M.

    1989-01-01

    Discusses the physical basis and current understanding of hydrophobic effects. The thermodynamic background of the effects, hydrophobic hydration, and hydrophobic interactions are described. Four existing controversies are outlined. (YP)

  1. Preparative electrophoretic method for the purification of a hydrophobic membrane protein: subunit c of the mitochondrial ATP synthase from rat liver.

    PubMed

    Hagopian, K

    1999-09-10

    A method is described for the purification of subunit c of ATP synthase from rat liver mitochondria. After sample preparation and solvent extraction, the protein was purified to homogeneity by a single-step preparative electrophoretic procedure, using aqueous buffer and containing lithium dodecyl sulfate. The subunit is an extremely hydrophobic and insoluble protein and all solubilization attempts, using a variety of detergents, were unsuccessful except for lithium dodecyl sulfate. Buffer exchange and FPLC gel filtration removed the detergent from the purified sample, leaving the protein in a soluble form. The mammalian protein is composed of 75 amino acid residues, with a molecular mass of 7602 Da and is classified as a proteolipid. Subunit c accounts for 25 and 85% of the intralysosomal accumulation, within neurons, of storage material in juvenile and late-infantile forms of Batten's disease, respectively. This purification procedure allows access to a continuous supply of pure subunit c from a conventional source such as rat liver and preserves precious autopsy materials. The protein could be used as substrate in future proteolytic studies involving pepstatin-insensitive lysosomal proteases and for raising of more specific antibodies. The procedure could also be adapted/modified and used as a model for purifying other extremely insoluble proteins.

  2. In Vivo Identification of the Outer Membrane Protein OmcA-MtrC Interaction Network in Shewanella oneidensis MR-1 Cells Using Novel Hydrophobic Chemical Cross-Linkers

    SciTech Connect

    Zhang, Haizhen; Tang, Xiaoting; Munske, Gerhard R.; Zakharova, Natalia L.; Yang, Li; Zheng, Chunxiang; Wolff, Meagan A.; Tolic, Nikola; Anderson, Gordon A.; Shi, Liang; Marshall, Matthew J.; Fredrickson, Jim K.; Bruce, James E.

    2008-04-01

    Outer membrane (OM) cytochromes OmcA (SO1779) and MtrC (SO1778) are the integral components of electron transfer used by Shewanella oneidensis for anaerobic respiration of metal (hydr)oxides. Here the OmcA-MtrC interaction was identified in vivo using a novel hydrophobic chemical cross-linker (MRN) combined with immunoprecipitation techniques. In addition, identification of other OM proteins from the cross-linked complexes allows first visualization of the OmcA-MtrC interaction network. Further experiments on omcA and mtrC mutant cells showed OmcA plays a central role in the network interaction. For comparison, two commercial cross-linkers were also used in parallel and both resulted in fewer OM protein identifications, indicating the superior properties of MRN for identification of membrane protein interactions. Finally, comparison experiments of in vivo cross-linking and cell lysate cross-linking resulted in significantly different protein interaction data, demonstrating the importance of in vivo cross-linking for study of protein-protein interactions in cells.

  3. Two variables dominating the retention of intact proteins under gradient elution with simultaneous ultrafast high-resolution separation by hydrophobic interaction chromatography.

    PubMed

    Geng, Xindu; Jia, Xiaodan; Liu, Peng; Wang, Fei; Yang, Xiaoming

    2015-10-07

    The retention of intact proteins under gradient elution in hydrophobic interaction chromatography (HIC) was found to be governed by two variables, the steady region (SR) and the migration region (MR). In the SR, the proteins are immobilized by the strong interactions with the stationary phase such that the retention time is independent of the column length. In the MR, the proteins also interact with the stationary phase, but they move normally, thus the retention time depends on their partition coefficients and the column length. The SR can be used as an operation space (OP) for high-throughput protein analysis by 1D-LC using short columns at high flow rates to maintain a high resolution. The OP can also be employed for all assisted operations in online 2D-LC. Based on the steady region/migration region optimization strategy developed in this study, five successive complete separations of seven intact proteins were performed in a HIC cake in less than 5 min, and a crude extract of ribonuclease A from bovine pancreas was purified using online 2D-LC to 95.8% purity with 93.2% mass recovery in 45 min. This approach can be used to expedite the purification of drug-target proteins and should therefore be of interest to the pharmaceutical industry.

  4. Overexpression and refolding of the hydrophobic ribosomal P0 protein from Trypanosoma cruzi: a component of the P1/P2/P0 complex.

    PubMed

    Juri Ayub, M; Levin, M J; Aguilar, C F

    2001-07-01

    The P0 protein is part of the ribosomal eukaryotic stalk, which is an elongated lateral protuberance of the large ribosomal subunit involved in the translocation step of protein synthesis. P0 is the minimal portion of the stalk that is able to support accurate protein synthesis. The P0 C-terminal peptide is highly antigenic and a major target of the antibody response in patients with systemic lupus erythematosus and patients suffering chronic heart disease produced by the Trypanosoma cruzi parasite. The T. cruzi P0 (TcP0) protein was cloned into the pRSET A vector and expressed in Escherichia coli fused to a His-tag. The identity of the protein was confirmed by immunoblotting. Due to the formation of inclusion bodies the protein was purified using the following steps: (i) differential centrifugation to separate the inclusion bodies from soluble proteins and (ii) affinity chromatography under denaturing conditions. TcP0 showed high tendency to aggregation during refolding assays. However, TcP0 could be efficiently folded in the presence of a low concentration of SDS. The folding of the protein was confirmed using urea gradient electrophoresis, limited proteolysis, circular dichroism, and tryptophan fluorescence. Native electrophoresis showed that the folded TcP0 (and not a folding intermediate) was the cause of aggregation in the absence of SDS. The protocol described here permitted us to obtain large amounts (up to 30 mg per culture liter) of pure and folded TcP0, a very hydrophobic protein with a high tendency to aggregation.

  5. Purification of chimeric heavy chain monoclonal antibody EG2-hFc using hydrophobic interaction membrane chromatography: an alternative to protein-A affinity chromatography.

    PubMed

    Sadavarte, Rahul; Spearman, Maureen; Okun, Natalie; Butler, Michael; Ghosh, Raja

    2014-06-01

    Heavy chain monoclonal antibodies are being considered as alternative to whole-IgG monoclonal antibodies for certain niche applications. Protein-A chromatography which is widely used for purifying IgG monoclonal antibodies is also used for purifying heavy chain monoclonal antibodies as these molecules possess fully functional Fc regions. However, the acidic conditions used to elute bound antibody may sometimes also leach protein-A, which is immunotoxic. Low pH conditions also tend to make the mAb molecules unstable and prone to aggregation. Moreover, protein-A affinity chromatography does not remove aggregates already present in the feed. Hydrophobic interaction membrane chromatography (or HIMC) has already been studied as an alternative to protein-A chromatography for purifying whole-IgG monoclonal antibodies. This paper describes the use of HIMC for capturing a humanized chimeric heavy chain monoclonal antibody (EG2-hFC). Binding and eluting conditions were suitably optimized using pure EG2-hFC. Based on this, an HIMC method was developed for capture of EG2-hFC directly from cell culture supernatant. The EG2-hFc purity obtained in this single-step process was high. The glycan profiles of protein-A and HIMC purified monoclonal antibody samples were similar, clearly demonstrating that both techniques captured similarly glycosylated population of EG2-hFc. Moreover, this technique was able to resolve aggregates from monomeric form of the EG2-hFc.

  6. Preparation of a novel weak cation exchange/hydrophobic interaction chromatography dual-function polymer-based stationary phase for protein separation using "thiol-ene click chemistry".

    PubMed

    Yang, Fan; Bai, Quan; Zhao, Kailou; Gao, Dong; Tian, Lei

    2015-02-01

    A novel dual-function mixed-mode stationary phase based on poly(glycidyl methacrylate-co-ethylene dimethacrylate) microspheres was synthesized by thiol-ene click chemistry and characterized by infrared spectroscopy and elemental analysis. The new system displays both hydrophobic interaction chromatography (HIC) character in a high salt concentration mobile phase, and weak cation exchange (WCX) chromatography character in a low salt concentration mobile phase. It can be used to separate proteins in both ion-exchange chromatography (IEC) mode and HIC mode. The resolution and selectivity of the stationary phase were evaluated in both HIC mode and IEC mode using protein standards. In comparison with the conventional WCX and HIC columns, the results were satisfactory and acceptable. Protein mass and bioactivity recoveries of more than 96% can be achieved in both HIC mode and IEC mode using this column. The results indicate that the novel dual-function mixed-mode column in many cases can replace the use of two individual WCX and HIC columns. In addition, the effects on protein separation of different ligand structures in the dual-function stationary phase and the pH of the mobile phase used were also investigated in detail. The results show that electrostatic interaction of the ligand with proteins must match the hydrophobicity of the ligand, which is an important factor to prepare the dual-function stationary phase. On the basis of this dual-function mixed-mode chromatography column, a new two-dimensional liquid chromatography technology with a single column system was also developed in this study, and was used to renature and purify recombinant human interferon-γ from inclusion bodies. The mass recovery, purity, and specific bioactivity obtained for the purified recombinant human interferon-γ were 87.2%, 92.4%, and 2.8 × 10(7) IU/mg, respectively, in IEC mode, and 83.4%, 95.2%, and 4.3 × 10(7) IU/mg, respectively, in HIC mode. The results indicate that the

  7. A C-terminal Hydrophobic, Solvent-protected Core and a Flexible N-terminus are Potentially Required for Human Papillomavirus 18 E7 Protein Functionality

    SciTech Connect

    Liu, S.; Tian, Y; Greenaway, F; Sun, M

    2010-01-01

    The oncogenic potential of the high-risk human papillomavirus (HPV) relies on the expression of genes specifying the E7 and E6 proteins. To investigate further the variation in oligomeric structure that has been reported for different E7 proteins, an HPV-18 E7 cloned from a Hispanic woman with cervical intraepithelial neoplasia was purified to homogeneity most probably as a stable monomeric protein in aqueous solution. We determined that one zinc ion is present per HPV-18 E7 monomer by amino acid and inductively coupled plasma-atomic emission spectroscopy analysis. Intrinsic fluorescence and circular dichroism spectroscopic results indicate that the zinc ion is important for the correct folding and thermal stability of HPV-18 E7. Hydroxyl radical mediated protein footprinting coupled to mass spectrometry and other biochemical and biophysical data indicate that near the C-terminus, the four cysteines of the two Cys-X{sub 2}-Cys motifs that are coordinated to the zinc ion form a solvent inaccessible core. The N-terminal LXCXE pRb binding motif region is hydroxyl radical accessible and conformationally flexible. Both factors, the relative flexibility of the pRb binding motif at the N-terminus and the C-terminal metal-binding hydrophobic solvent-protected core, combine together and facilitate the biological functions of HPV-18 E7.

  8. The Overriding Roles of Concentration and Hydrophobic Effect on Structure and Stability of Heme Protein Induced by Imidazolium-Based Ionic Liquids.

    PubMed

    Jha, Indrani; Kumar, Awanish; Venkatesu, Pannuru

    2015-07-02

    Spectroscopic and molecular docking investigations were carried out to characterize the effect of imidazolium-based ionic liquids (ILs) with varying chain length of the cation on the thermal stability as well as spectroscopic behavior of heme protein hemoglobin (Hb). The goal of this work is to investigate the role of concentration of ILs, the effect of alkyl chain length of the cation, and the related Hofmeister series on the structure of Hb. To achieve this goal, a series of ILs possessing same Cl(-) anion and a set of cation [Cnmim](+) with increasing chain length such as 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-hexyl-3-methylimidazolium chloride ([Hmim][Cl]), and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]) were used in this study. It was observed that the stability of the protein was concentration dependent as well as the hydrophobic interactions between [Cnmim](+) of ILs, and the amino acid residues in the protein played a major role in protein unfolding. As a consequence, the destabilization tendency of the ILs toward the Hb increases with increasing chain length of the cation of ILs. Additionally, the cations of the ILs obeyed the Hofmeister series when arranged in the order of providing stability to Hb structure.

  9. Assembly of water-soluble chlorophyll-binding proteins with native hydrophobic chlorophylls in water-in-oil emulsions.

    PubMed

    Bednarczyk, Dominika; Takahashi, Shigekazu; Satoh, Hiroyuki; Noy, Dror

    2015-03-01

    The challenges involved in studying cofactor binding and assembly, as well as energy- and electron transfer mechanisms in the large and elaborate transmembrane protein complexes of photosynthesis and respiration have prompted considerable interest in constructing simplified model systems based on their water-soluble protein analogs. Such analogs are also promising templates and building blocks for artificial bioinspired energy conversion systems. Yet, development is limited by the challenge of introducing the essential cofactors of natural proteins that are highly water-insoluble into the water-soluble protein analogs. Here we introduce a new efficient method based on water-in-oil emulsions for overcoming this challenge. We demonstrate the effectiveness of the method in the assembly of native chlorophylls with four recombinant variants of the water-soluble chlorophyll-binding protein of Brassicaceae plants. We use the method to gain new insights into the protein-chlorophyll assembly process, and demonstrate its potential as a fast screening system for developing novel chlorophyll-protein complexes.

  10. 21 CFR 169.115 - French dressing.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false French dressing. 169.115 Section 169.115 Food and... § 169.115 French dressing. (a) Description. French dressing is the separable liquid food or the... fabricated shall be safe and suitable. French dressing contains not less than 35 percent by weight...

  11. Preliminary structural studies of the hydrophobic ribosomal P0 protein from Trypanosoma cruzi, a part of the P0/P1/P2 complex.

    PubMed

    Ayub, Maximiliano Juri; Barroso, Juan A; Levin, Mariano J; Aguilar, Carlos F

    2005-08-01

    The Trypanosoma cruzi ribosomal P0 protein (TcP0) is part of the ribosomal stalk, which is an elongated lateral protuberance of the large ribosomal subunit involved in the translocation step of protein synthesis. The TcP0 C-terminal peptide is highly antigenic and a major target of the antibody response in patients with systemic lupus erythematosus and patients suffering chronic heart disease produced by Trypanosoma cruzi infection. The structural properties of TcP0 have been explored by circular dichroism, tryptophan fluorescence and limited proteolysis experiments. These studies were complemented by secondary structure consensus prediction analysis. The results suggest that the tertiary structure of TcP0 could be described as a compact, stable, trypsin-resistant, 200 residues long N-terminal domain belonging to the alpha/beta class and a more flexible, degradable, helical, 123 residues long C-terminal domain which could be involved in the formation of an unusual hydrophobic zipper with the ribosomal P1/P2 proteins to form the P0/P1/P2 complex.

  12. The Bactofilin Cytoskeleton Protein BacM of Myxococcus xanthus Forms an Extended β-Sheet Structure Likely Mediated by Hydrophobic Interactions

    PubMed Central

    Xie, Kefang; Engelhardt, Harald; Bosch, Jürgen; Hoiczyk, Egbert

    2015-01-01

    Bactofilins are novel cytoskeleton proteins that are widespread in Gram-negative bacteria. Myxococcus xanthus, an important predatory soil bacterium, possesses four bactofilins of which one, BacM (Mxan_7475) plays an important role in cell shape maintenance. Electron and fluorescence light microscopy, as well as studies using over-expressed, purified BacM, indicate that this protein polymerizes in vivo and in vitro into ~3 nm wide filaments that further associate into higher ordered fibers of about 10 nm. Here we use a multipronged approach combining secondary structure determination, molecular modeling, biochemistry, and genetics to identify and characterize critical molecular elements that enable BacM to polymerize. Our results indicate that the bactofilin-determining domain DUF583 folds into an extended β-sheet structure, and we hypothesize a left-handed β-helix with polymerization into 3 nm filaments primarily via patches of hydrophobic amino acid residues. These patches form the interface allowing head-to-tail polymerization during filament formation. Biochemical analyses of these processes show that folding and polymerization occur across a wide variety of conditions and even in the presence of chaotropic agents such as one molar urea. Together, these data suggest that bactofilins are comprised of a structure unique to cytoskeleton proteins, which enables robust polymerization. PMID:25803609

  13. An introduction to absorbent dressings.

    PubMed

    Jones, Menna Lloyd

    2014-12-01

    Exudate bathes the wound bed with a serous fluid that contains essential components that promote wound healing. However, excess exudate is often seen as a challenge for clinicians. Absorbent dressings are often used to aid in the management of exudate, with the aim of providing a moist but unmacerated environment. With so many different types of absorbent dressings available today-alongside making a holistic assessment-it is essential that clinicians also have the knowledge and skill to select the most appropriate absorbent dressing for a given patient.

  14. Pathogenic Mutations within the Hydrophobic Domain of the Prion Protein Lead to the Formation of Protease-Sensitive Prion Species with Increased Lethality

    PubMed Central

    Coleman, Bradley M.; Harrison, Christopher F.; Guo, Belinda; Masters, Colin L.; Barnham, Kevin J.; Lawson, Victoria A.

    2014-01-01

    ABSTRACT Prion diseases are a group of fatal and incurable neurodegenerative diseases affecting both humans and animals. The principal mechanism of these diseases involves the misfolding the host-encoded cellular prion protein, PrPC, into the disease-associated isoform, PrPSc. Familial forms of human prion disease include those associated with the mutations G114V and A117V, which lie in the hydrophobic domain of PrP. Here we have studied the murine homologues (G113V and A116V) of these mutations using cell-based and animal models of prion infection. Under normal circumstances, the mutant forms of PrPC share similar processing, cellular localization, and physicochemical properties with wild-type mouse PrP (MoPrP). However, upon exposure of susceptible cell lines expressing these mutants to infectious prions, very low levels of protease-resistant aggregated PrPSc are formed. Subsequent mouse bioassay revealed high levels of infectivity present in these cells. Thus, these mutations appear to limit the formation of aggregated PrPSc, giving rise to the accumulation of a relatively soluble, protease sensitive, prion species that is highly neurotoxic. Given that these mutations lie next to the glycine-rich region of PrP that can abrogate prion infection, these findings provide further support for small, protease-sensitive prion species having a significant role in the progression of prion disease and that the hydrophobic domain is an important determinant of PrP conversion. IMPORTANCE Prion diseases are transmissible neurodegenerative diseases associated with an infectious agent called a prion. Prions are comprised of an abnormally folded form of the prion protein (PrP) that is normally resistant to enzymes called proteases. In humans, prion disease can occur in individuals who inherited mutations in the prion protein gene. Here we have studied the effects of two of these mutations and show that they influence the properties of the prions that can be formed. We show that

  15. Antigen Presentation by MHC-Dressed Cells

    PubMed Central

    Nakayama, Masafumi

    2015-01-01

    Professional antigen-presenting cells (APCs) such as conventional dendritic cells (DCs) process protein antigens to MHC-bound peptides and then present the peptide–MHC complexes to T cells. In addition to this canonical antigen presentation pathway, recent studies have revealed that DCs and non-APCs can acquire MHC class I (MHCI) and/or MHC class II (MHCII) from neighboring cells through a process of cell–cell contact-dependent membrane transfer called trogocytosis. These MHC-dressed cells subsequently activate or regulate T cells via the preformed antigen peptide–MHC complexes without requiring any further processing. In addition to trogocytosis, intercellular transfer of MHCI and MHCII can be mediated by secretion of membrane vesicles such as exosomes from APCs, generating MHC-dressed cells. This review focuses on the physiological role of antigen presentation by MHCI- or MHCII-dressed cells, and also discusses differences and similarities between trogocytosis and exosome-mediated transfer of MHC. PMID:25601867

  16. Ectopic Expression of an Atypical Hydrophobic Group 5 LEA Protein from Wild Peanut, Arachis diogoi Confers Abiotic Stress Tolerance in Tobacco

    PubMed Central

    Sharma, Akanksha; Kumar, Dilip; Kumar, Sumit; Rampuria, Sakshi; Reddy, Attipalli R.; Kirti, Pulugurtha Bharadwaja

    2016-01-01

    Late embryogenesis abundant (LEA) proteins are a group of hydrophilic proteins, which accumulate in plants under varied stress conditions like drought, salinity, extreme temperatures and oxidative stress suggesting their role in the protection of plants against these stresses. A transcript derived fragment (TDF) corresponding to LEA gene, which got differentially expressed in wild peanut, Arachis diogoi against the late leaf spot pathogen, Phaeoisariopsis personata was used in this study. We have cloned its full length cDNA by RACE-PCR, which was designated as AdLEA. AdLEA belongs to the atypical Group 5C of LEA protein family as confirmed by sequence analysis. Group 5C LEA protein subfamily contains Pfam LEA_2 domain and is highly hydrophobic. In native conditions, expression of AdLEA was upregulated considerably upon hormonal and abiotic stress treatments emphasizing its role in abiotic stress tolerance. Subcellular localization studies showed that AdLEA protein is distributed in both nucleus and cytosol. Ectopic expression of AdLEA in tobacco resulted in enhanced tolerance of plants to dehydration, salinity and oxidative stress with the transgenic plants showing higher chlorophyll content and reduced lipid peroxidation as compared to wild type plants. Overexpressed AdLEA tobacco plants maintained better photosynthetic efficiency under drought conditions as demonstrated by chlorophyll fluorescence measurements. These plants showed enhanced transcript accumulation of some stress-responsive genes. Our study also elucidates that ROS levels were significantly reduced in leaves and stomatal guard cells of transgenic plants upon stress treatments. These results suggest that AdLEA confers multiple stress tolerance to plants, which make it a potential gene for genetic modification in plants. PMID:26938884

  17. Ectopic Expression of an Atypical Hydrophobic Group 5 LEA Protein from Wild Peanut, Arachis diogoi Confers Abiotic Stress Tolerance in Tobacco.

    PubMed

    Sharma, Akanksha; Kumar, Dilip; Kumar, Sumit; Rampuria, Sakshi; Reddy, Attipalli R; Kirti, Pulugurtha Bharadwaja

    2016-01-01

    Late embryogenesis abundant (LEA) proteins are a group of hydrophilic proteins, which accumulate in plants under varied stress conditions like drought, salinity, extreme temperatures and oxidative stress suggesting their role in the protection of plants against these stresses. A transcript derived fragment (TDF) corresponding to LEA gene, which got differentially expressed in wild peanut, Arachis diogoi against the late leaf spot pathogen, Phaeoisariopsis personata was used in this study. We have cloned its full length cDNA by RACE-PCR, which was designated as AdLEA. AdLEA belongs to the atypical Group 5C of LEA protein family as confirmed by sequence analysis. Group 5C LEA protein subfamily contains Pfam LEA_2 domain and is highly hydrophobic. In native conditions, expression of AdLEA was upregulated considerably upon hormonal and abiotic stress treatments emphasizing its role in abiotic stress tolerance. Subcellular localization studies showed that AdLEA protein is distributed in both nucleus and cytosol. Ectopic expression of AdLEA in tobacco resulted in enhanced tolerance of plants to dehydration, salinity and oxidative stress with the transgenic plants showing higher chlorophyll content and reduced lipid peroxidation as compared to wild type plants. Overexpressed AdLEA tobacco plants maintained better photosynthetic efficiency under drought conditions as demonstrated by chlorophyll fluorescence measurements. These plants showed enhanced transcript accumulation of some stress-responsive genes. Our study also elucidates that ROS levels were significantly reduced in leaves and stomatal guard cells of transgenic plants upon stress treatments. These results suggest that AdLEA confers multiple stress tolerance to plants, which make it a potential gene for genetic modification in plants.

  18. Localization of proteins to the 1,2-propanediol utilization microcompartment by non-native signal sequences is mediated by a common hydrophobic motif.

    PubMed

    Jakobson, Christopher M; Kim, Edward Y; Slininger, Marilyn F; Chien, Alex; Tullman-Ercek, Danielle

    2015-10-02

    Various bacteria localize metabolic pathways to proteinaceous organelles known as bacterial microcompartments (MCPs), enabling the metabolism of carbon sources to enhance survival and pathogenicity in the gut. There is considerable interest in exploiting bacterial MCPs for metabolic engineering applications, but little is known about the interactions between MCP signal sequences and the protein shells of different MCP systems. We found that the N-terminal sequences from the ethanolamine utilization (Eut) and glycyl radical-generating protein MCPs are able to target reporter proteins to the 1,2-propanediol utilization (Pdu) MCP, and that this localization is mediated by a conserved hydrophobic residue motif. Recapitulation of this motif by the addition of a single amino acid conferred targeting function on an N-terminal sequence from the ethanol utilization MCP system that previously did not act as a Pdu signal sequence. Moreover, the Pdu-localized signal sequences competed with native Pdu targeting sequences for encapsulation in the Pdu MCP. Salmonella enterica natively possesses both the Pdu and Eut operons, and our results suggest that Eut proteins might be localized to the Pdu MCP in vivo. We further demonstrate that S. enterica LT2 retained the ability to grow on 1,2-propanediol as the sole carbon source when a Pdu enzyme was replaced with its Eut homolog. Although the relevance of this finding to the native system remains to be explored, we show that the Pdu-localized signal sequences described herein allow control over the ratio of heterologous proteins encapsulated within Pdu MCPs.

  19. Teacher Dress Codes in Employee Handbooks: An Analysis

    ERIC Educational Resources Information Center

    Workman, Jane E.; Freeburg, Beth Winfrey

    2010-01-01

    This study used role theory to analyze dress codes for teachers to discern what dress items expressed role embracement and role distance. Inductive content analysis of teacher dress codes in 103 U.S. K-12 school handbooks revealed three categories of dress: (a) conventional dress (mentioned in 97.1% of the dress codes); (b) casual dress (mentioned…

  20. Paralogous proteins comprising the 150 kDa hydrophobic-ligand-binding-protein complex of the Taenia solium metacestode have evolved non-overlapped binding affinities toward fatty acid analogs.

    PubMed

    Kim, Seon-Hee; Bae, Young-An; Yang, Yichao; Hong, Sung-Tae; Kong, Yoon

    2011-09-01

    We previously identified a hydrophobic-ligand-binding protein (HLBP) of the Taenia solium metacestode (TsM), which might be involved in the uptake of fatty acids (FAs) from host environments. The TsM 150kDa HLBP was a hetero-oligomeric complex composed of multiple 7kDa (RS1) and 10kDa (CyDA, b1 and m13h) subunits, and displayed a wide spectrum of binding affinities toward various FA analogs. In this study, we analysed biochemical properties and phylogenetic relationships of the individual subunits. Despite the low sequence identity (average 26.5%), these subunit proteins conserved an α-helix-rich structural domain and the first introns inserted in each of the respective chromosomal genes were found to be orthologous to one another, suggesting their common evolutionary origin. The recombinant RS1 protein bound strongly to all of the FA analogs examined including 11-[(5-dimethylaminonaphthalene-1-sulfonyl)amino]undecanoic acid (DAUDA), but not to 16-(9-anthroyloxy)palmitic acid (16-AP). The interactive binding between RS1 and FA analogs was specifically interfered with by the addition of non-fluorescent FA molecules or antibodies specific to the 150kDa protein. Conversely, the 10kDa members reacted only with the palmitic acid-derived 16-AP, whose interactive force was strengthened by the presence of other FA molecules. The use of mutagenic RS1 proteins demonstrated that a structural/electrostatic integrity around the second α-helix, rather than the conventional Trp residue, was the major factor governing the hydrophobic interaction. The 7 and 10kDa proteins exhibited distinctive immunoreactive patterns against sera from neurocysticercosis patients. These collective data suggest that the paralogous protein family have gained diverse functions during their evolution, to ensure the maintenance of metabolic homeostasis and survival of TsMs in hostile host environments.

  1. An Information Theory of Hydrophobic Effects

    NASA Astrophysics Data System (ADS)

    Pratt, Lawrence R.

    1998-03-01

    The hydrophobic effect is a central concept in rationalizing the structure and stability of proteins in solution. However, a consensus has not been achieved on a molecular scale physical theory explaining the broad array of hydrophobic effects. Here we present an information theory designed to achieve consensus by identifying and limiting the physical information and assumptions sufficient to predict hydrophobic effects. The information theory is based upon the study of the probabilities of occupancy by water molecule centers of molecular scale volumes observed in neat liquid water. Predictions for hydrophobic effects can be extracted from this probability distribution. Simulation results show that this probability distribution is accurately predicted by a maximum entropy model using the two moments that are obtained from the experimental liquid density and the experimental radial distribution of oxygen atoms. We show the role of solvent molecule correlation functions of higher order than pairs. We show that this two moment model predicts known atomic scale hydrophobic effects: hydrophobic solubilities, potentials of mean force, and hydrophobic effects on conformational equilibria. We comment on the kinship between the two moment maximum entropy model and the earlier Pratt-Chandler theory of hydrophobic effects. We show that the model predicts the entropy convergence emphasized by high sensitivity calorimetry on the thermal denaturation of globular proteins and explains why this entropy convergence is insensitive to solute molecular details within the broad category of hydrophobic solutes. Finally, we consider the pressure denaturation of globular proteins and discuss the perspective that emerges from the information theory treatment: increasing pressure squeezes water molecules into the protein globule eventually separating hydrophobic components analogously to the separation of hydrophobic solutes in formation of clathrate hydrates.

  2. The respective roles of polar/nonpolar binary patterns and amino acid composition in protein regular secondary structures explored exhaustively using hydrophobic cluster analysis.

    PubMed

    Rebehmed, Joseph; Quintus, Flavien; Mornon, Jean-Paul; Callebaut, Isabelle

    2016-05-01

    Several studies have highlighted the leading role of the sequence periodicity of polar and nonpolar amino acids (binary patterns) in the formation of regular secondary structures (RSS). However, these were based on the analysis of only a few simple cases, with no direct mean to correlate binary patterns with the limits of RSS. Here, HCA-derived hydrophobic clusters (HC) which are conditioned binary patterns whose positions fit well those of RSS, were considered. All the HC types, defined by unique binary patterns, which were commonly observed in three-dimensional (3D) structures of globular domains, were analyzed. The 180 HC types with preferences for either α-helices or β-strands distinctly contain basic binary units typical of these RSS. Therefore a general trend supporting the "binary pattern preference" assumption was observed. HC for which observed RSS are in disagreement with their expected behavior (discordant HC) were also examined. They were separated in HC types with moderate preferences for RSS, having "weak" binary patterns and versatile RSS and HC types with high preferences for RSS, having "strong" binary patterns and then displaying nonpolar amino acids at the protein surface. It was shown that in both cases, discordant HC could be distinguished from concordant ones by well-differentiated amino acid compositions. The obtained results could, thus, help to complement the currently available methods for the accurate prediction of secondary structures in proteins from the only information of a single amino acid sequence. This can be especially useful for characterizing orphan sequences and for assisting protein engineering and design.

  3. Protection and mechanism of action of a novel human respiratory syncytial virus vaccine candidate based on the extracellular domain of small hydrophobic protein

    PubMed Central

    Schepens, Bert; Sedeyn, Koen; Vande Ginste, Liesbeth; De Baets, Sarah; Schotsaert, Michael; Roose, Kenny; Houspie, Lieselot; Van Ranst, Marc; Gilbert, Brian; van Rooijen, Nico; Fiers, Walter; Piedra, Pedro; Saelens, Xavier

    2014-01-01

    Infections with human respiratory syncytial virus (HRSV) occur globally in all age groups and can have devastating consequences in young infants. We demonstrate that a vaccine based on the extracellular domain (SHe) of the small hydrophobic (SH) protein of HRSV, reduced viral replication in challenged laboratory mice and in cotton rats. We show that this suppression of viral replication can be transferred by serum and depends on a functional IgG receptor compartment with a major contribution of FcγRI and FcγRIII. Using a conditional cell depletion method, we provide evidence that alveolar macrophages are involved in the protection by SHe-specific antibodies. HRSV-infected cells abundantly express SH on the cell surface and are likely the prime target of the humoral immune response elicited by SHe-based vaccination. Finally, natural infection of humans and experimental infection of mice or cotton rats does not induce a strong immune response against HRSV SHe. Using SHe as a vaccine antigen induces immune protection against HRSV by a mechanism that differs from the natural immune response and from other HRSV vaccination strategies explored to date. Hence, HRSV vaccine candidates that aim at inducing protective neutralizing antibodies or T-cell responses could be complemented with a SHe-based antigen to further improve immune protection. PMID:25298406

  4. Protection and mechanism of action of a novel human respiratory syncytial virus vaccine candidate based on the extracellular domain of small hydrophobic protein.

    PubMed

    Schepens, Bert; Sedeyn, Koen; Vande Ginste, Liesbeth; De Baets, Sarah; Schotsaert, Michael; Roose, Kenny; Houspie, Lieselot; Van Ranst, Marc; Gilbert, Brian; van Rooijen, Nico; Fiers, Walter; Piedra, Pedro; Saelens, Xavier

    2014-11-01

    Infections with human respiratory syncytial virus (HRSV) occur globally in all age groups and can have devastating consequences in young infants. We demonstrate that a vaccine based on the extracellular domain (SHe) of the small hydrophobic (SH) protein of HRSV, reduced viral replication in challenged laboratory mice and in cotton rats. We show that this suppression of viral replication can be transferred by serum and depends on a functional IgG receptor compartment with a major contribution of FcγRI and FcγRIII. Using a conditional cell depletion method, we provide evidence that alveolar macrophages are involved in the protection by SHe-specific antibodies. HRSV-infected cells abundantly express SH on the cell surface and are likely the prime target of the humoral immune response elicited by SHe-based vaccination. Finally, natural infection of humans and experimental infection of mice or cotton rats does not induce a strong immune response against HRSV SHe. Using SHe as a vaccine antigen induces immune protection against HRSV by a mechanism that differs from the natural immune response and from other HRSV vaccination strategies explored to date. Hence, HRSV vaccine candidates that aim at inducing protective neutralizing antibodies or T-cell responses could be complemented with a SHe-based antigen to further improve immune protection.

  5. Syntheses and self-assembly of novel asparagine-derived amphiphiles: Applications in the encapsulation of proteins, hydrophobic, and hydrophilic drug models

    NASA Astrophysics Data System (ADS)

    Mfuh, Adelphe Mbufung

    This thesis focuses mainly on the synthesis, characterization, and self-assembly of a novel series of asparagine-derived amphiphiles and their use in the preparation and stabilization of nano and microcapsules for the encapsulation of proteins, and hydrophilic and hydrophobic drug models. Chapter 1 gives a brief literature overview of lipid molecular assembly, which covers some aspects of morphological analyses, encapsulation of chemical entity and some reported characterization techniques of supramolecular assemblies. It introduces the scope of this dissertation and contains some information on stimulus responsive liposomal systems for controlled release of drug models. Chapter 2 introduces a novel asparagine-derived lipid bearing two fatty chains (C11 and C17) and a tetrahydropyrimidinone head group. It presents information on the synthesis and characterization of this lipid and describes the self-assembly and effects of this lipid in distearoyl phosphatidyl choline bilayer. Chapter 3 presents the synthesis and characterization of a series of ALAn,m (where n and m represent the length of the hydrocarbon chains on the asparagine-derived, heterocyclic head group). It contains data on the effect of chain length, solvent media and head group ionization on the conformational equilibrium about a tertiary amide bond in ALAn,m. The chapter also examines the influence of chain length on ALAn,m on the colloidal stability of DSPC liposomes. Chapter 4 presents the first example of an N,N-acetal linkage in a novel pH responsive nanocarrier system obtained from the cyclocondensation of dodecanal with sodium asparaginate. Data is presented on the spontaneous self-assembly, encapsulation studies and morphological characterization of the nano-systems with the inclusion of cholesterol as additive. Chapter 5 presents the development of a photoresponsive nanocarrier via the self- assembly of an asparagine-derived lipid containing a coumarin unit in the hydrophobic domain. The

  6. In vivo tests of a novel wound dressing based on biomaterials with tissue adhesion controlled through external stimuli.

    PubMed

    Ignacio, C; Barcellos, L; Ferreira, M D; Moura, S A L; Soares, I A; Oréfice, R L

    2011-05-01

    The high incidence of wounds by second intention and the high costs associated with their treatment give rise to the need for the development of wound dressings that protect not only the wounds themselves but that are also able to promote cell proliferation and skin regeneration. Moreover, it is also very important that no damage to the new regenerated tissue is generated while removing the dressing. In this work, a novel wound dressing, which would be able to favor tissue repair and be removed at an appropriate scheduled moment by means of an external stimulus without promoting extensive damage to the new tissue, was produced and tested. Polyurethane membranes were modified by grafting polymers based on poly(n-isopropylacrylamide) (P-N-IPAAm). P-N-IPAAm undergoes a phase transition at approximately 32°C, which changes its behavior from hydrophilic (below 32°C) to hydrophobic. It was hypothesized that, by reducing the temperature near the wound dressing to values lower than 32°C, the detachment of the dressing would become more effective. The wound dressings containing P-N-IPAAm grafts were tested in vivo by covering excisional wounds produced in mice. The produced dressings were placed in direct contact with the lesions for 3 days. Results showed that the hypothermia due to anesthesia required to remove the dressings from mice lowered the local temperature to 28°C and favored the detachment of the wound dressings containing P-N-IPAAm grafts. Histological analyses showed that lesions covered by dressings presented less intense inflammatory events and denser connective tissue than did the wounds without dressings. The wounds covered by polyurethane membranes with P-N-IPAAm grafts showed signs of more intense re-epithelization and angiogenesis than did the lesions covered by polyurethane without grafts.

  7. (15)N CSA tensors and (15)N-(1)H dipolar couplings of protein hydrophobic core residues investigated by static solid-state NMR.

    PubMed

    Vugmeyster, Liliya; Ostrovsky, Dmitry; Fu, Riqiang

    2015-10-01

    In this work, we assess the usefulness of static (15)N NMR techniques for the determination of the (15)N chemical shift anisotropy (CSA) tensor parameters and (15)N-(1)H dipolar splittings in powder protein samples. By using five single labeled samples of the villin headpiece subdomain protein in a hydrated lyophilized powder state, we determine the backbone (15)N CSA tensors at two temperatures, 22 and -35 °C, in order to get a snapshot of the variability across the residues and as a function of temperature. All sites probed belonged to the hydrophobic core and most of them were part of α-helical regions. The values of the anisotropy (which include the effect of the dynamics) varied between 130 and 156 ppm at 22 °C, while the values of the asymmetry were in the 0.32-0.082 range. The Leu-75 and Leu-61 backbone sites exhibited high mobility based on the values of their temperature-dependent anisotropy parameters. Under the assumption that most differences stem from dynamics, we obtained the values of the motional order parameters for the (15)N backbone sites. While a simple one-dimensional line shape experiment was used for the determination of the (15)N CSA parameters, a more advanced approach based on the "magic sandwich" SAMMY pulse sequence (Nevzorov and Opella, 2003) was employed for the determination of the (15)N-(1)H dipolar patterns, which yielded estimates of the dipolar couplings. Accordingly, the motional order parameters for the dipolar interaction were obtained. It was found that the order parameters from the CSA and dipolar measurements are highly correlated, validating that the variability between the residues is governed by the differences in dynamics. The values of the parameters obtained in this work can serve as reference values for developing more advanced magic-angle spinning recoupling techniques for multiple labeled samples.

  8. Wound dressings: selecting the most appropriate type.

    PubMed

    Broussard, Karen C; Powers, Jennifer Gloeckner

    2013-12-01

    Appropriate wound dressing selection is guided by an understanding of wound dressing properties and an ability to match the level of drainage and depth of a wound. Wounds should be assessed for necrosis and infection, which need to be addressed prior to selecting an ideal dressing. Moisture-retentive dressings include films, hydrogels, hydrocolloids, foams, alginates, and hydrofibers and are useful in a variety of clinical settings. Antimicrobial-impregnated dressings can be useful in wounds that are superficially infected or are at higher risk for infection. For refractory wounds that need more growth stimulation, tissue-engineered dressings have become a viable option in the past few decades, especially those that have been approved for burns, venous ulcers, and diabetic ulcers. As wounds heal, the ideal dressing type may change, depending on the amount of exudate and depth of the wound; thus success in wound dressing selection hinges on recognition of the changing healing environment.

  9. Enthalpic and Entropic Contributions to Hydrophobicity

    PubMed Central

    2016-01-01

    Hydrophobic hydration plays a key role in a vast variety of biological processes, ranging from the formation of cells to protein folding and ligand binding. Hydrophobicity scales simplify the complex process of hydration by assigning a value describing the averaged hydrophobic character to each amino acid. Previously published scales were not able to calculate the enthalpic and entropic contributions to the hydrophobicity directly. We present a new method, based on Molecular Dynamics simulations and Grid Inhomogeneous Solvation Theory, that calculates hydrophobicity from enthalpic and entropic contributions. Instead of deriving these quantities from the temperature dependence of the free energy of hydration or as residual of the free energy and the enthalpy, we directly obtain these values from the phase space occupied by water molecules. Additionally, our method is able to identify regions with specific enthalpic and entropic properties, allowing to identify so-called “unhappy water” molecules, which are characterized by weak enthalpic interactions and unfavorable entropic constraints. PMID:27442443

  10. Polymer-xerogel composites for controlled release wound dressings.

    PubMed

    Costache, Marius C; Qu, Haibo; Ducheyne, Paul; Devore, David I

    2010-08-01

    Many polymers and composites have been used to prepare active wound dressings. These materials have typically exhibited potentially toxic burst release of the drugs within the first few hours followed by a much slower, potentially ineffective drug release rate thereafter. Many of these materials also degraded to produce inflammatory and cytotoxic products. To overcome these limitations, composite active wound dressings were prepared here from two fully biodegradable and tissue compatible components, silicon oxide sol-gel (xerogel) microparticles that were embedded in tyrosine-poly(ethylene glycol)-derived poly(ether carbonate) copolymer matrices. Sustained, controlled release of drugs from these composites was demonstrated in vitro using bupivacaine and mepivacaine, two water-soluble local anesthetics commonly used in clinical applications. By systematically varying independent compositional parameters of the composites, including the hydrophilic:hydrophobic balance of the tyrosine-derived monomers and poly(ethylene glycol) in the copolymers and the porosity, weight ratio and drug content of the xerogels, drug release kinetics approaching zero-order were obtained. Composites with xerogel mass fractions up to 75% and drug payloads as high as 13% by weight in the final material were fabricated without compromising the physical integrity or the controlled release kinetics. The copolymer-xerogel composites thus provided a unique solution for the sustained delivery of therapeutic agents from tissue compatible wound dressings.

  11. Fournier's Gangrene: Conventional Dressings versus Dressings with Dakin's Solution

    PubMed Central

    Altunoluk, Bülent; Resim, Sefa; Efe, Erkan; Eren, Mustafa; Benlioglu, Can; Kankilic, Nazim; Baykan, Halit

    2012-01-01

    Purpose. Fournier's gangrene is a fulminant and destructive inflammation of the scrotum, penis, and perineum. The objective of this study was to compare 2 different approaches to wound management after aggressive surgical debridement. Methods. Data from 14 patients with Fournier's gangrene were retrospectively collected (2005–2011). Once the patients were stabilized following surgery, they were treated with either daily antiseptic (povidone iodine) dressings (group I, n = 6) or dressings with dakin's solution (sodium hypochloride) (group II, n = 8). Results. The mean age of the patients was 68.2 ± 7.8 (55–75) years in group I and 66.9 ± 10.2 (51–79) years in group II. Length of hospital stay was 13 ± 3.5 (7–16) days in group I and 8.9 ± 3.0 (4–12) days in group II (P < 0.05). The number and rate of mortality was 1/6 (16.7%) in group I, and 1/8 (12.5%) in group II. Conclusions. The hospitalization time can be reduced with the use of dakin's solution for the dressings in the treatment of FG. Also, dressings with dakin's solution seems to have favorable effects on morbidity and mortality. Consequently dakin's solution may alter the treatment of this disastrous disease by reducing cost, morbidity and mortality. PMID:22567424

  12. Preparation of hydrophobic coatings

    DOEpatents

    Branson, Eric D.; Shah, Pratik B.; Singh, Seema; Brinker, C. Jeffrey

    2009-02-03

    A method for preparing a hydrophobic coating by preparing a precursor sol comprising a metal alkoxide, a solvent, a basic catalyst, a fluoroalkyl compound and water, depositing the precursor sol as a film onto a surface, such as a substrate or a pipe, heating, the film and exposing the film to a hydrophobic silane compound to form a hydrophobic coating with a contact angle greater than approximately 150.degree.. The contact angle of the film can be controlled by exposure to ultraviolet radiation to reduce the contact angle and subsequent exposure to a hydrophobic silane compound to increase the contact angle.

  13. School Dress Codes and Uniform Policies.

    ERIC Educational Resources Information Center

    Anderson, Wendell

    2002-01-01

    Opinions abound on what students should wear to class. Some see student dress as a safety issue; others see it as a student-rights issue. The issue of dress codes and uniform policies has been tackled in the classroom, the boardroom, and the courtroom. This Policy Report examines the whole fabric of the debate on dress codes and uniform policies…

  14. Production of recombinant non-structural protein-3 hydrophobic domain deletion (NS3ΔHD) protein of bluetongue virus from prokaryotic expression system as an efficient diagnostic reagent.

    PubMed

    Mohanty, Nihar Nalini; Chacko, Nirmal; Biswas, Sanchay Kumar; Chand, Karam; Pandey, Awadh Bihari; Mondal, Bimalendu; Hemadri, Divakar; Shivachandra, Sathish Bhadravati

    2016-09-01

    Serological diagnostics for bluetongue (BT), which is an infectious, non-contagious and arthropod-borne virus disease of ruminants, are primarily dependent on availability of high quality native or recombinant antigen(s) based on either structural/non-structural proteins in sufficient quantity. Non-structural proteins (NS1-NS4) of BT virus are presumed candidate antigens in development of DIVA diagnostics. In the present study, NS3 fusion gene encoding for NS3 protein containing the N- and C-termini with a deletion of two hydrophobic domains (118A to S141 aa and 162S to A182 aa) and intervening variable central domain (142D to K161 aa) of bluetongue virus 23 was constructed, cloned and over-expressed using prokaryotic expression system. The recombinant NS3ΔHD fusion protein (∼38 kDa) including hexa-histidine tag on its both termini was found to be non-cytotoxic to recombinant Escherichia coli cells and purified by affinity chromatography. The purified rNS3ΔHD fusion protein was found to efficiently detect BTV-NS3 specific antibodies in indirect-ELISA format with diagnostic sensitivity (DSn = 94.4%) and specificity (DSp = 93.9%). The study indicated the potential utility of rNS3ΔHD fusion protein as candidate diagnostic reagent in developing an indirect-ELISA for sero-surveillance of animals for BTV antibodies under DIVA strategy, wherever monovalent/polyvalent killed BT vaccine formulations devoid of NS proteins are being practiced for immunization.

  15. Dress Codes and Gang Activity.

    ERIC Educational Resources Information Center

    Gluckman, Ivan B.

    1996-01-01

    Concern with school violence and efforts to reduce gang visibility at school have led to controversy about students' constitutional rights to freedom of expression. This document outlines legal precedents and offers guidelines for developing a sound school policy on dress codes. It answers the following questions: (1) Are gang clothing and symbols…

  16. Redressing Cross-Dressed Shakespeare

    ERIC Educational Resources Information Center

    Martin, Thomas L.; Pesta, Duke

    2003-01-01

    Gender critics obsess over the boy actors who played female roles on the Elizabethan stage. But, in their far-fetched interpretation of Shakespearean drama as a spectacle of cross dressing, these new historicists lose sight of a fundamental principle of theater. Thomas Martin and Duke Pesta argue that with their prurient chatter of "the…

  17. Methoxyflurane analgesia for burns dressings

    PubMed Central

    Packer, Kathleen J.

    1972-01-01

    The requirements for analgesia for burns dressings are discussed. Methoxyflurane has proved satisfactory in a clinical trial, and can be administered by one of two types of vaporizer. The possibility of nephrotoxicity due to methoxyflurane has not been eliminated. PMID:5024149

  18. Hydrophobic hydrophilic phenomena in biochemical processes.

    PubMed

    Ben-Naim, Arieh

    2003-09-01

    The evolution of concepts developed in the study of the hydrophobic affect is surveyed, within the more general context of solvent-induced effects. A systematic analysis of the solvent-induced contribution to the driving force for the process of protein folding has led to two important modifications in our understanding of these effects. First, the conventional concepts of hydrophobic solvation and hydrophobic interactions had to be replaced by their respective conditional effects. Second, each of the hydrophobic effects has also a corresponding hydrophilic counterpart. Some of the latter effects could contribute significantly to the total driving force for the process of protein folding, and perhaps even dominate the driving force for biochemical processes.

  19. Novel silk fibroin/elastin wound dressings.

    PubMed

    Vasconcelos, Andreia; Gomes, Andreia C; Cavaco-Paulo, Artur

    2012-08-01

    Silk fibroin (SF) and elastin (EL) scaffolds were successfully produced for the first time for the treatment of burn wounds. The self-assembly properties of SF, together with the excellent chemical and mechanical stability and biocompatibility, were combined with elastin protein to produce scaffolds with the ability to mimic the extracellular matrix (ECM). Porous scaffolds were obtained by lyophilization and were further crosslinked with genipin (GE). Genipin crosslinking induces the conformational transition from random coil to β-sheet of SF chains, yielding scaffolds with smaller pore size and reduced swelling ratios, degradation and release rates. All results indicated that the composition of the scaffolds had a significant effect on their physical properties, and that can easily be tuned to obtain scaffolds suitable for biological applications. Wound healing was assessed through the use of human full-thickness skin equivalents (EpidermFT). Standardized burn wounds were induced by a cautery and the best re-epithelialization and the fastest wound closure was obtained in wounds treated with 50SF scaffolds; these contain the highest amount of elastin after 6 days of healing in comparison with other dressings and controls. The cytocompatibility demonstrated with human skin fibroblasts together with the healing improvement make these SF/EL scaffolds suitable for wound dressing applications.

  20. Molecular recognition at the dimer interface of a class mu glutathione transferase: role of a hydrophobic interaction motif in dimer stability and protein function.

    PubMed

    Hornby, Judith A T; Codreanu, Simona G; Armstrong, Richard N; Dirr, Heini W

    2002-12-03

    Cytosolic glutathione (GSH) transferases (GSTs) exist as stable homo- and heterodimers. Interactions at the subunit interface serve an important role in stabilizing the subunit tertiary structures of all GSH transferases. In addition, the dimer is required to maintain functional conformations at the active site on each subunit and the nonsubstrate ligand binding site at the dimer interface [Dirr, H. W. (2001) Chem.-Biol. Interact. 133, 19-23]. In this study, we report on the contribution of a specific intersubunit hydrophobic motif in rGSTM1-1 to dimer stability and protein function. The motif consists of the side chain of F56 from one subunit intercalated between helices 4 and 5 of the second subunit. Replacement of F56 with the hydrophilic side chains of serine, arginine, and glutamate results in a change in the structure of the active site, a marked diminution in catalytic efficiency, and alterations in the ability to bind nonsubstrate ligands. The mutations also affect the ability of the enzyme to bind GSH and the substrate analogue glutathione sulfonate. The functionality of rGSTM1-1 was disrupted to the greatest extent for the F56E mutant. Though mutations at this position do not alter the three-state equilibrium folding process for rGSTM1-1 (i.e., N(2) <--> 2I <--> 2U), destabilizing mutations at position 56 shift the equilibrium between the folded dimer (N(2)) and the monomeric intermediate (I) toward the latter conformational state. The transition to the unfolded state (U) is not significantly affected. The folded monomeric intermediate is also observed by electrospray ionization mass spectrometry. The amount of the intermediate is dependent on protein concentration and the residue at position 56. Mutations at position 56 have little impact on the secondary structure and stability of the monomeric folding intermediate. The dimerization process is proposed to induce a conformational change in the loop containing F56, resulting in improved stability and

  1. Comparative spectroscopic studies on drug binding characteristics and protein surface hydrophobicity of native and modified forms of bovine serum albumin: Possible relevance to change in protein structure/function upon non-enzymatic glycation

    NASA Astrophysics Data System (ADS)

    Khodarahmi, Reza; Karimi, Seyyed Arash; Ashrafi Kooshk, Mohammad Reza; Ghadami, Seyyed Abolghasem; Ghobadi, Sirous; Amani, Mojtaba

    2012-04-01

    The interaction between serum albumin (SA) and drugs has provided an interesting ground for understanding of drug effects, especially in drug distribution and drug-drug interaction on SA, in the case of multi-drug therapy. Determination of the impact of various factors on drug-protein interaction is especially important upon significant binding of drug to albumin. In the present study, the interaction of two drugs (furosemide and indomethacin) with native and modified albumins were investigated by using various spectroscopic methods. Fluorescence data indicated that 1:1 binding of drugs to bovine serum albumin (BSA) is associated with quenching of albumin intrinsic fluorescence. The Job's plot also confirmed that drug binds to BSA via mentioned stoichiometry. Analysis of the quenching and thermodynamic parameters indicated that intermolecular interactions between drug and albumin may change upon protein modification. The theoretical analyses also suggested some conformational changes of interacting side chains in subdomain IIA binding site (at the vicinity of W237), which were in good agreement with experimental data. Decrease of protein surface hydrophobicity (PSH) was also observed upon both albumin modification and drug binding.

  2. Comparative spectroscopic studies on drug binding characteristics and protein surface hydrophobicity of native and modified forms of bovine serum albumin: possible relevance to change in protein structure/function upon non-enzymatic glycation.

    PubMed

    Khodarahmi, Reza; Karimi, Seyyed Arash; Ashrafi Kooshk, Mohammad Reza; Ghadami, Seyyed Abolghasem; Ghobadi, Sirous; Amani, Mojtaba

    2012-04-01

    The interaction between serum albumin (SA) and drugs has provided an interesting ground for understanding of drug effects, especially in drug distribution and drug-drug interaction on SA, in the case of multi-drug therapy. Determination of the impact of various factors on drug-protein interaction is especially important upon significant binding of drug to albumin. In the present study, the interaction of two drugs (furosemide and indomethacin) with native and modified albumins were investigated by using various spectroscopic methods. Fluorescence data indicated that 1:1 binding of drugs to bovine serum albumin (BSA) is associated with quenching of albumin intrinsic fluorescence. The Job's plot also confirmed that drug binds to BSA via mentioned stoichiometry. Analysis of the quenching and thermodynamic parameters indicated that intermolecular interactions between drug and albumin may change upon protein modification. The theoretical analyses also suggested some conformational changes of interacting side chains in subdomain IIA binding site (at the vicinity of W237), which were in good agreement with experimental data. Decrease of protein surface hydrophobicity (PSH) was also observed upon both albumin modification and drug binding.

  3. Designing a hydrophobic barrier within biomimetic nanopores.

    PubMed

    Trick, Jemma L; Wallace, E Jayne; Bayley, Hagan; Sansom, Mark S P

    2014-11-25

    Nanopores in membranes have a range of potential applications. Biomimetic design of nanopores aims to mimic key functions of biological pores within a stable template structure. Molecular dynamics simulations have been used to test whether a simple β-barrel protein nanopore can be modified to incorporate a hydrophobic barrier to permeation. Simulations have been used to evaluate functional properties of such nanopores, using water flux as a proxy for ionic conductance. The behavior of these model pores has been characterized as a function of pore size and of the hydrophobicity of the amino acid side chains lining the narrow central constriction of the pore. Potential of mean force calculations have been used to calculate free energy landscapes for water and for ion permeation in selected models. These studies demonstrate that a hydrophobic barrier can indeed be designed into a β-barrel protein nanopore, and that the height of the barrier can be adjusted by modifying the number of consecutive rings of hydrophobic side chains. A hydrophobic barrier prevents both water and ion permeation even though the pore is sterically unoccluded. These results both provide insights into the nature of hydrophobic gating in biological pores and channels, and furthermore demonstrate that simple design features may be computationally transplanted into β-barrel membrane proteins to generate functionally complex nanopores.

  4. Dress Nicer = Know More? Young Children's Knowledge Attribution and Selective Learning Based on How Others Dress.

    PubMed

    McDonald, Kyla P; Ma, Lili

    2015-01-01

    This research explored whether children judge the knowledge state of others and selectively learn novel information from them based on how they dress. The results indicated that 4- and 6-year-olds identified a formally dressed individual as more knowledgeable about new things in general than a casually dressed one (Study 1). Moreover, children displayed an overall preference to seek help from a formally dressed individual rather than a casually dressed one when learning about novel objects and animals (Study 2). These findings are discussed in relation to the halo effect, and may have important implications for child educators regarding how instructor dress might influence young students' knowledge attribution and learning preferences.

  5. Boron cluster-based development of potent nonsecosteroidal vitamin D receptor ligands: direct observation of hydrophobic interaction between protein surface and carborane.

    PubMed

    Fujii, Shinya; Masuno, Hiroyuki; Taoda, Yoshiyuki; Kano, Atsushi; Wongmayura, Angsuma; Nakabayashi, Makoto; Ito, Nobutoshi; Shimizu, Masato; Kawachi, Emiko; Hirano, Tomoya; Endo, Yasuyuki; Tanatani, Aya; Kagechika, Hiroyuki

    2011-12-28

    We report here the design and synthesis of a novel vitamin D receptor (VDR) agonist whose hydrophobic core structure is p-carborane (1,12-dicarba-closo-dodecaborane, an icosahedral carbon-containing boron cluster having remarkable thermal and chemical stability and a characteristically hydrophobic B-H surface). This carborane-based VDR ligand exhibited moderate vitamin D activity, comparable to that of the natural hormone, despite its simple and flexible structure. X-ray structure analysis provided direct evidence that the carborane cage binds to the hydrophobic surface of the ligand-binding pocket of the receptor, promoting transition to the active conformation. These results indicate that the spherical B-H surface of carborane can function efficiently as a hydrophobic anchor in binding to the receptor surface, thereby allowing induced fitting of the three essential hydroxyl groups on the alkyl chains to the appropriate positions for interaction with the VDR binding site, despite the entropic disadvantage of the flexible structure. We suggest that carborane structure is a promising option in the design of novel drug candidates.

  6. Hydrophobic motif site-phosphorylated protein kinase CβII between mTORC2 and Akt regulates high glucose-induced mesangial cell hypertrophy.

    PubMed

    Das, Falguni; Ghosh-Choudhury, Nandini; Mariappan, Meenalakshmi M; Kasinath, Balakuntalam S; Choudhury, Goutam Ghosh

    2016-04-01

    PKCβII controls the pathologic features of diabetic nephropathy, including glomerular mesangial cell hypertrophy. PKCβII contains the COOH-terminal hydrophobic motif site Ser-660. Whether this hydrophobic motif phosphorylation contributes to high glucose-induced mesangial cell hypertrophy has not been determined. Here we show that, in mesangial cells, high glucose increased phosphorylation of PKCβII at Ser-660 in a phosphatidylinositol 3-kinase (PI3-kinase)-dependent manner. Using siRNAs to downregulate PKCβII, dominant negative PKCβII, and PKCβII hydrophobic motif phosphorylation-deficient mutant, we found that PKCβII regulates activation of mechanistic target of rapamycin complex 1 (mTORC1) and mesangial cell hypertrophy by high glucose. PKCβII via its phosphorylation at Ser-660 regulated phosphorylation of Akt at both catalytic loop and hydrophobic motif sites, resulting in phosphorylation and inactivation of its substrate PRAS40. Specific inhibition of mTORC2 increased mTORC1 activity and induced mesangial cell hypertrophy. In contrast, inhibition of mTORC2 decreased the phosphorylation of PKCβII and Akt, leading to inhibition of PRAS40 phosphorylation and mTORC1 activity and prevented mesangial cell hypertrophy in response to high glucose; expression of constitutively active Akt or mTORC1 restored mesangial cell hypertrophy. Moreover, constitutively active PKCβII reversed the inhibition of high glucose-stimulated Akt phosphorylation and mesangial cell hypertrophy induced by suppression of mTORC2. Finally, using renal cortexes from type 1 diabetic mice, we found that increased phosphorylation of PKCβII at Ser-660 was associated with enhanced Akt phosphorylation and mTORC1 activation. Collectively, our findings identify a signaling route connecting PI3-kinase to mTORC2 to phosphorylate PKCβII at the hydrophobic motif site necessary for Akt phosphorylation and mTORC1 activation, leading to mesangial cell hypertrophy.

  7. Superabsorbent dressings for copiously exuding wounds.

    PubMed

    Faucher, Nathalie; Safar, Helene; Baret, Mylène; Philippe, Anne; Farid, Rachida

    Exudate control is important in the management of both acute and chronic wounds. A new category of absorbent dressings that contain superabsorbent particles promises high absorbency. The aim of this multicentre, prospective, non-comparative observational study was to evaluate the clinical efficacy and absorbent capacity of a superabsorbent dressing. Fifteen inpatients and outpatients with highly exuding wounds were included. Most patients (n=8) (53%) had chronic wounds; 20% (n=3) had ulcerating tumours. The superabsorbent dressing was used as a primary or a secondary dressing. Assessment was on day 0 (start), day 3 and day 7 (end of study). The study looked at wound bed and periwound skin condition, exudate production, pain upon dressing removal, reason for dressing removal, and frequency of dressing changes. A clinical visual scoring tool was used, together with digital photographs, which were assessed by the same experienced clinician. All 15 patients completed the study, during which no adverse events were noted. At day 7, maceration had reduced from 46.7% (n=7) at day 0 to 6.7% (n=1). After only 3 days, dressing change frequency was reduced from once daily to twice weekly in 80% (n=12) of patients. The superabsorbent dressing seems to reduce complications associated with exudate production, stimulate wound healing and increase patient comfort; it may also save time and costs for caregivers.

  8. Dressed qubits in nuclear spin baths

    SciTech Connect

    Wu Lianao

    2010-04-15

    We present a method to encode a dressed qubit into the product state of an electron spin localized in a quantum dot and its surrounding nuclear spins via a dressing transformation. In this scheme, the hyperfine coupling and a portion of a nuclear dipole-dipole interaction become logic gates, while they are the sources of decoherence in electron-spin qubit proposals. We discuss errors and corrections for the dressed qubits. Interestingly, the effective Hamiltonian of nuclear spins is equivalent to a pairing Hamiltonian, which provides the microscopic mechanism to protect dressed qubits against decoherence.

  9. Origin of hydrophobicity and enhanced water hydrogen bond strength near purely hydrophobic solutes

    PubMed Central

    Grdadolnik, Joze; Merzel, Franci; Avbelj, Franc

    2017-01-01

    Hydrophobicity plays an important role in numerous physicochemical processes from the process of dissolution in water to protein folding, but its origin at the fundamental level is still unclear. The classical view of hydrophobic hydration is that, in the presence of a hydrophobic solute, water forms transient microscopic “icebergs” arising from strengthened water hydrogen bonding, but there is no experimental evidence for enhanced hydrogen bonding and/or icebergs in such solutions. Here, we have used the redshifts and line shapes of the isotopically decoupled IR oxygen–deuterium (O-D) stretching mode of HDO water near small purely hydrophobic solutes (methane, ethane, krypton, and xenon) to study hydrophobicity at the most fundamental level. We present unequivocal and model-free experimental proof for the presence of strengthened water hydrogen bonds near four hydrophobic solutes, matching those in ice and clathrates. The water molecules involved in the enhanced hydrogen bonds display extensive structural ordering resembling that in clathrates. The number of ice-like hydrogen bonds is 10–15 per methane molecule. Ab initio molecular dynamics simulations have confirmed that water molecules in the vicinity of methane form stronger, more numerous, and more tetrahedrally oriented hydrogen bonds than those in bulk water and that their mobility is restricted. We show the absence of intercalating water molecules that cause the electrostatic screening (shielding) of hydrogen bonds in bulk water as the critical element for the enhanced hydrogen bonding around a hydrophobic solute. Our results confirm the classical view of hydrophobic hydration. PMID:28028244

  10. Fluoroalkyl and alkyl chains have similar hydrophobicities in binding to the "hydrophobic wall" of carbonic anhydrase.

    PubMed

    Mecinović, Jasmin; Snyder, Phillip W; Mirica, Katherine A; Bai, Serena; Mack, Eric T; Kwant, Richard L; Moustakas, Demetri T; Héroux, Annie; Whitesides, George M

    2011-09-07

    The hydrophobic effect, the free-energetically favorable association of nonpolar solutes in water, makes a dominant contribution to binding of many systems of ligands and proteins. The objective of this study was to examine the hydrophobic effect in biomolecular recognition using two chemically different but structurally similar hydrophobic groups, aliphatic hydrocarbons and aliphatic fluorocarbons, and to determine whether the hydrophobicity of the two groups could be distinguished by thermodynamic and biostructural analysis. This paper uses isothermal titration calorimetry (ITC) to examine the thermodynamics of binding of benzenesulfonamides substituted in the para position with alkyl and fluoroalkyl chains (H(2)NSO(2)C(6)H(4)-CONHCH(2)(CX(2))(n)CX(3), n = 0-4, X = H, F) to human carbonic anhydrase II (HCA II). Both alkyl and fluoroalkyl substituents contribute favorably to the enthalpy and the entropy of binding; these contributions increase as the length of chain of the hydrophobic substituent increases. Crystallography of the protein-ligand complexes indicates that the benzenesulfonamide groups of all ligands examined bind with similar geometry, that the tail groups associate with the hydrophobic wall of HCA II (which is made up of the side chains of residues Phe131, Val135, Pro202, and Leu204), and that the structure of the protein is indistinguishable for all but one of the complexes (the longest member of the fluoroalkyl series). Analysis of the thermodynamics of binding as a function of structure is compatible with the hypothesis that hydrophobic binding of both alkyl and fluoroalkyl chains to hydrophobic surface of carbonic anhydrase is due primarily to the release of nonoptimally hydrogen-bonded water molecules that hydrate the binding cavity (including the hydrophobic wall) of HCA II and to the release of water molecules that surround the hydrophobic chain of the ligands. This study defines the balance of enthalpic and entropic contributions to the

  11. Hydrophobic Compounds Reshape Membrane Domains

    PubMed Central

    Barnoud, Jonathan; Rossi, Giulia; Marrink, Siewert J.; Monticelli, Luca

    2014-01-01

    Cell membranes have a complex lateral organization featuring domains with distinct composition, also known as rafts, which play an essential role in cellular processes such as signal transduction and protein trafficking. In vivo, perturbations of membrane domains (e.g., by drugs or lipophilic compounds) have major effects on the activity of raft-associated proteins and on signaling pathways, but they are difficult to characterize because of the small size of the domains, typically below optical resolution. Model membranes, instead, can show macroscopic phase separation between liquid-ordered and liquid-disordered domains, and they are often used to investigate the driving forces of membrane lateral organization. Studies in model membranes have shown that some lipophilic compounds perturb membrane domains, but it is not clear which chemical and physical properties determine domain perturbation. The mechanisms of domain stabilization and destabilization are also unknown. Here we describe the effect of six simple hydrophobic compounds on the lateral organization of phase-separated model membranes consisting of saturated and unsaturated phospholipids and cholesterol. Using molecular simulations, we identify two groups of molecules with distinct behavior: aliphatic compounds promote lipid mixing by distributing at the interface between liquid-ordered and liquid-disordered domains; aromatic compounds, instead, stabilize phase separation by partitioning into liquid-disordered domains and excluding cholesterol from the disordered domains. We predict that relatively small concentrations of hydrophobic species can have a broad impact on domain stability in model systems, which suggests possible mechanisms of action for hydrophobic compounds in vivo. PMID:25299598

  12. Terbinafine-loaded wound dressing for chronic superficial fungal infections.

    PubMed

    Paskiabi, Farnoush Asghari; Bonakdar, Shahin; Shokrgozar, Mohammad Ali; Imani, Mohammad; Jahanshiri, Zahra; Shams-Ghahfarokhi, Masoomeh; Razzaghi-Abyaneh, Mehdi

    2017-04-01

    In spite of developing new drugs and modern formulations, the treatments of chronic fungal infections are still challenging. Fibrous wound dressings are new suggestions for the treatment of chronic superficial infections. In the present study, we formulated an antifungal agent, terbinafine hydrochloride (TFH), which is a hydrophobic drug, in wound dressings prepared by electrospun polycaprolactone, polycaprolactone/gelatin (50:50 w/w) and gelatin. To obtain more water-stable meshes, the preparations were treated by glutaraldehyde and their properties were determined before and after treatment. The morphology of fibrous meshes was observed by scanning electron microscopy. Drug loading efficiency and release rate were measured by high performance liquid chromatography (HPLC) and the release rate was monitored for 144h. Antifungal tests were performed on Trichophyton mentagrophytes, Aspergillus fumigatus and Candida albicans cultured on Muller-Hinton agar. The toxicity of the meshes was measured after 24h and 14days by MTT assay. Terbinafine loading of polycaprolactone/gelatin (50:50) was 100% and it released the highest amount of TFH too. In antifungal tests, all samples were able to hinderT. mentagrophytes and A. fumigatus but not C. albicans growth among them, polycaprolactone fibers made the largest inhibition zone. In MTT assay, none of prepared samples showed toxicity against L929 cells. Teken together, the prepared TFH-loaded PCL/gelatin electrospun meshes were able to release TFH slowly and in a steady state in time. With respect to no obvious cytotoxicity in MTT assay and stong antifungal activity toward T. mentagrophytesin vitro, these TFH-based meshes could be considered as potential candidates in clinical application as wound dressing for treatment of chronic dermatophytosis.

  13. Student Dress Codes Using Zero Tolerance?

    ERIC Educational Resources Information Center

    Essex, Nathan L.

    2004-01-01

    In this article, the author focuses on the issue involving zero tolerance in the Texas district whether the dress code policy is reasonable. In a small Texas school district, over 700 students were suspended in a single month for violating a zero-tolerance dress code policy. This suspension, which attracted national attention and threats of…

  14. Dress Codes: We Forget Our Own Advice

    ERIC Educational Resources Information Center

    Weinberger, Morris J.

    1970-01-01

    Eccentric dress on the part of adolescents should not be treated as a moral issue. The conflict between youth and adults over school dress codes is but another variation of the conflict between the needs and rights of the individual as opposed to those of a larger society. (CK)

  15. Role Conflict and Conformity in Dress.

    ERIC Educational Resources Information Center

    Jasper, Cynthia R.; Roach-Higgins, Mary Ellen

    1988-01-01

    Examined conflict regarding what form of dress is appropriate for Roman Catholic priest. Data from 5,475 American Catholic priests revealed that priests who conformed to church regulations regarding dress differed from nonconformists in beliefs about their roles as priests and in their opinions of church reform, commitment to the priesthood,…

  16. Honey: A Biologic Wound Dressing.

    PubMed

    Molan, Peter; Rhodes, Tanya

    2015-06-01

    Honey has been used as a wound dressing for thousands of years, but only in more recent times has a scientific explanation become available for its effectiveness. It is now realized that honey is a biologic wound dressing with multiple bioactivities that work in concert to expedite the healing process. The physical properties of honey also expedite the healing process: its acidity increases the release of oxygen from hemoglobin thereby making the wound environment less favorable for the activity of destructive proteases, and the high osmolarity of honey draws fluid out of the wound bed to create an outflow of lymph as occurs with negative pressure wound therapy. Honey has a broad-spectrum antibacterial activity, but there is much variation in potency between different honeys. There are 2 types of antibacterial activity. In most honeys the activity is due to hydrogen peroxide, but much of this is inactivated by the enzyme catalase that is present in blood, serum, and wound tissues. In manuka honey, the activity is due to methylglyoxal which is not inactivated. The manuka honey used in wound-care products can withstand dilution with substantial amounts of wound exudate and still maintain enough activity to inhibit the growth of bacteria. There is good evidence for honey also having bioactivities that stimulate the immune response (thus promoting the growth of tissues for wound repair), suppress inflammation, and bring about rapid autolytic debridement. There is clinical evidence for these actions, and research is providing scientific explanations for them.

  17. Hydrophobic, Porous Battery Boxes

    NASA Technical Reports Server (NTRS)

    Bragg, Bobby J.; Casey, John E., Jr.

    1995-01-01

    Boxes made of porous, hydrophobic polymers developed to contain aqueous potassium hydroxide electrolyte solutions of zinc/air batteries while allowing air to diffuse in as needed for operation. Used on other types of batteries for in-cabin use in which electrolytes aqueous and from which gases generated during operation must be vented without allowing electrolytes to leak out.

  18. Comparative Dynamics of Leucine Methyl Groups in FMOC-Leucine and in a Protein Hydrophobic Core Probed by Solid-State Deuteron Nuclear Magnetic Resonance over 7-324 K Temperature Range

    SciTech Connect

    Vugmeyster, Liliya; Ostrovsky, Dmitry; Moses, Mark; Ford, Joseph J.; Lipton, Andrew S.; Hoatson, Gina; Vold, Robert L.

    2010-12-09

    Quantitative dynamics of methyl groups in 9-fluorenylmethyloxycarbonyl-leucine (FMOC-leu) have been analyzed and compared with earlier studies of methyl dynamics in chicken villin headpiece subdomain protein (HP36) labeled at L69, a key hydrophobic core position. A combination of deuteron solid-state nuclear magnetic resonance experiments over the temperature range of 7-324 K and computational modeling indicated that while the two compounds show the same modes of motions, there are marked differences in the best-fit parameters of these motions. One of the main results is that the crossover observed in the dynamics of the methyl groups in the HP36 sample at 170 K is absent in FMOC-leu. A second crossover at around 95-88 K is present in both samples. The differences in the behavior of the two compounds suggest that some of the features of methyl dynamics reflect the complexity of the protein hydrophobic core and are not determined solely by local interactions.

  19. Online Capillary IsoElectric Focusing-ElectroSpray Ionization Mass Spectrometry (CIEF-ESI MS) in Glycerol-Water Media for the Separation and Characterization of Hydrophilic and Hydrophobic Proteins.

    PubMed

    Mokaddem, Meriem; d'Orlyé, Fanny; Varenne, Anne

    2016-01-01

    Capillary isoelectric focusing (CIEF) is a high-resolution technique for the separation of ampholytes, such as proteins, according to their isoelectric point. CIEF coupled online with MS is regarded as a promising alternative to 2-D PAGE for fast proteome analysis with high-resolving capabilities and enhanced structural information without the drawbacks of conventional slab-gel electrophoresis. However, online coupling has been rarely described, as it presents some difficulties. A new methodology for the online coupling of CIEF with electrospray ionization mass spectrometry (ESI-MS) has been developed in glycerol-water media. This new integrated methodology provides a mean for the characterization of a large number of hydrophilic and hydrophobic proteins.

  20. Molecular characterization and functional analysis by heterologous expression in E. coli under diverse abiotic stresses for OsLEA5, the atypical hydrophobic LEA protein from Oryza sativa L.

    PubMed

    He, Shuai; Tan, Lili; Hu, Zongli; Chen, Guoping; Wang, Guixue; Hu, Tingzhang

    2012-01-01

    In this study, we report the molecular characterization and functional analysis of OsLEA5 gene, which belongs to the atypical late embryogenesis abundant (LEA) group 5C from Oryza sativa L. The cDNA of OsLEA5 contains a 456 bp ORF encoding a polypeptide of 151 amino acids with a calculated molecular mass of 16.5 kDa and a theoretical pI of 5.07. The OsLEA5 polypeptide is rich in Leu (10%), Ser (8.6%), and Asp (8.6%), while Cys, Trp, and Gln residue contents are very low, which are 2, 1.3, and 1.3%, respectively. Bioinformatic analysis revealed that group 5C LEA protein subfamily contains a Pfam:LEA_2 domain architecture and is highly hydrophobic, intrinsically ordered with largely β-sheet and specific amino acid composition and distribution. Real-time PCR analysis showed that OsLEA5 was expressed in different tissue organs during different development stages of rice. The expression levels of OsLEA5 in the roots and panicles of full ripe stage were dramatically increased. The results of stress tolerance and cell viability assay demonstrated that recombinant E. coli cells producing OsLEA5 fusion protein exhibited improved resistance against diverse abiotic stresses: high salinity, osmotic, freezing, heat, and UV radiation. The OsLEA5 protein confers stabilization of the LDH under different abiotic stresses, such as heating, freeze-thawing, and drying in vitro. The combined results indicated that OsLEA5 protein was a hydrophobic atypical LEA and closely associated with resistance to multiple abiotic stresses. This research offered the valuable information for the development of crops with enhanced resistance to diverse stresses.

  1. Mechanism of formation of the C-terminal beta-hairpin of the B3 domain of the immunoglobulin binding protein G from Streptococcus. I. Importance of hydrophobic interactions in stabilization of beta-hairpin structure.

    PubMed

    Skwierawska, Agnieszka; Makowska, Joanna; Ołdziej, Stanisław; Liwo, Adam; Scheraga, Harold A

    2009-06-01

    We previously studied a 16-amino acid-residue fragment of the C-terminal beta-hairpin of the B3 domain (residues 46-61), [IG(46-61)] of the immunoglobulin binding protein G from Streptoccocus, and found that hydrophobic interactions and the turn region play an important role in stabilizing the structure. Based on these results, we carried out systematic structural studies of peptides derived from the sequence of IG (46-61) by systematically shortening the peptide by one residue at a time from both the C- and the N-terminus. To determine the structure and stability of two resulting 12- and 14-amino acid-residue peptides, IG(48-59) and IG(47-60), respectively, we carried out circular dichroism, NMR, and calorimetric studies of these peptides in pure water. Our results show that IG(48-59) possesses organized three-dimensional structure stabilized by hydrophobic interactions (Tyr50-Phe57 and Trp48-Val59) at T = 283 and 305 K. At T = 313 K, the structure breaks down because of increased chain entropy, but the turn region is preserved in the same position observed for the structure of the whole protein. The breakdown of structure occurs near the melting temperature of this peptide (T(m) = 310 K) measured by differential scanning calorimetry (DSC). The melting temperature of IG(47-60) determined by DSC is T(m) = 330 K and its structure is similar to that of the native beta-hairpin at all (lower) temperatures examined (283-313 K). Both of these truncated sequences are conserved in all known amino acid sequences of the B domains of the immunoglobulin binding protein G from bacteria. Thus, this study contributes to an understanding of the mechanism of folding of this whole family of proteins, and provides information about the mechanism of formation and stabilization of a beta-hairpin structural element.

  2. Structure and functional dynamics characterization of the ion channel of the human respiratory syncytial virus (hRSV) small hydrophobic protein (SH) transmembrane domain by combining molecular dynamics with excited normal modes.

    PubMed

    Araujo, Gabriela C; Silva, Ricardo H T; Scott, Luis P B; Araujo, Alexandre S; Souza, Fatima P; de Oliveira, Ronaldo Junio

    2016-12-01

    The human respiratory syncytial virus (hRSV) is the major cause of lower respiratory tract infection in children and elderly people worldwide. Its genome encodes 11 proteins including SH protein, whose functions are not well known. Studies show that SH protein increases RSV virulence degree and permeability to small compounds, suggesting it is involved in the formation of ion channels. The knowledge of SH structure and function is fundamental for a better understanding of its infection mechanism. The aim of this study was to model, characterize, and analyze the structural behavior of SH protein in the phospholipids bilayer environment. Molecular modeling of SH pentameric structure was performed, followed by traditional molecular dynamics (MD) simulations of the protein immersed in the lipid bilayer. Molecular dynamics with excited normal modes (MDeNM) was applied in the resulting system in order to investigate long time scale pore dynamics. MD simulations support that SH protein is stable in its pentameric form. Simulations also showed the presence of water molecules within the bilayer by density distribution, thus confirming that SH protein is a viroporin. This water transport was also observed in MDeNM studies with histidine residues of five chains (His22 and His51), playing a key role in pore permeability. The combination of traditional MD and MDeNM was a very efficient protocol to investigate functional conformational changes of transmembrane proteins that act as molecular channels. This protocol can support future investigations of drug candidates by acting on SH protein to inhibit viral infection. Graphical Abstract The ion channel of the human respiratory syncytial virus (hRSV) small hydrophobic protein (SH) transmembrane domainᅟ.

  3. Recommendations for road surface dressing

    NASA Astrophysics Data System (ADS)

    Guidance is provided for the preparation of specifications needed to cater to the wide range of traffic conditions and types of surfaces likely to be encountered on country lanes as well as other motorways. Both chippings and binders are considered as well as their application. Topics covered include surface preparation; application of the binder; spraying time; joining strips of sprayed binder; applying chips; rolling; and traffic management during and after operations. Special areas discussed include heavily trafficked high speed roads; hard shoulders; open-textured and porous bituminous surfaces; unbound surfaces; sealing roadbases, subgrades, and subbases; bituminous mist sprays; high stressed sites (epoxy resin based systems); the treatment of fatted surface dressings; and the control of materials and workmanship. Procedures for measuring hardness, and the rate of spread of spray binders and of chippings are included.

  4. The role of allogenic keratin - derived dressing in wound healing in a mouse model.

    PubMed

    Konop, Marek; Sulejczak, Dorota; Czuwara, Joanna; Kosson, Piotr; Misicka, Aleksandra; Lipkowski, Aandrzej W; Rudnicka, Lidia

    2016-12-20

    Keratin is an interesting protein needed for wound healing and tissue recovery. We have recently proposed a new, simple and inexpensive method to obtain fur and hair keratin-derived biomaterials suitable for medical application. The aim of the study was to evaluate the role of the fur keratin derived protein (FKDP) dressing in the allogenic full-thickness surgical skin wound model.

  5. Dress Codes in the Public Schools: Principals, Policies, and Precepts.

    ERIC Educational Resources Information Center

    DeMitchell, Todd A.; Fossey, Richard; Cobb, Casey

    2000-01-01

    Responses from 157 principals (65 percent of a national sample) showed strong support for dress codes. Research focuses on the perception of school principals regarding dress codes, analyzes dress codes for common features, and proposes a constitutional standard of review for contested dress codes. (58 footnotes) (MLF)

  6. Dress and Appearance Codes in Public Secondary School Handbooks.

    ERIC Educational Resources Information Center

    Herbon, Beth; Workman, Jane E.

    2000-01-01

    Analyzed and compared dress and appearance codes from 154 secondary school handbooks. Unacceptable dress and appearance was listed more frequently that acceptable or required dress; concerns about health, safety, and modesty were reflected; and 80 percent included a statement that dress should not be disruptive to the educational process.…

  7. Hydrophobic sugar holograms

    NASA Astrophysics Data System (ADS)

    Mejias-Brizuela, N. Y.; Olivares-Pérez, A.; Páez-Trujillo, G.; Hernández-Garay, M. P.; Fontanilla-Urdaneta, R.; Fuentes-Tapia, I.

    2008-02-01

    The sugar matrix is used to record of phase holograms; it was modified with the purpose of obtaining a hydrophobic material to improve the stability of the registered image and to stimulate the photosensitivity of the sugar. The new material is formed by a sugar, pectin and vanillin dissolution. The diffraction efficiency parameter increases in comparison with only the sugar matrix, obtaining already of 10%.

  8. Chitosan-aluminum monostearate composite sponge dressing containing asiaticoside for wound healing and angiogenesis promotion in chronic wound.

    PubMed

    Phaechamud, Thawatchai; Yodkhum, Kotchamon; Charoenteeraboon, Juree; Tabata, Yasuhiko

    2015-05-01

    There are many factors that delay healing in chronic wounds including lowering level of growth factors and increasing exudate level comprising high amount of tissue destructive enzymes. Asiaticoside possesses interesting wound healing and angiogenic activities that are employed to stimulate tissue regeneration in wound healing application. This study attempted to develop chitosan-aluminum monostearate (Alst) composite sponge containing asiaticoside for use as an absorbent medical dressing in chronic wound. N-methyl-2-pyrrolidone (NMP) was used to enhance homogeneity of asiaticoside in the polymer composite matrix. The sponge dressings were prepared by lyophilization and dehydrothermal treatment (DHT). Functional group interaction, crystallinity, and morphology of the prepared sponges were investigated using FT-IR, PXRD, and SEM, respectively. Physicochemical properties, porosity, hydrophilic/hydrophobic properties and mechanical property, were evaluated. Wound dressing properties, water vapor transmission rate (WVTR), fluid absorbency, oxygen permeation (OP), and bio-adhesive property, were investigated. In vitro asiaticoside release study was conducted using immersion method. Cytotoxicity was studied in normal human dermal fibroblast (NHDF) and normal human epidermal keratinocyte (NHEK). Angiogenic activity of asiaticoside was evaluated using chick-chorioallantoic membrane (CAM) assay. FT-IR and PXRD results revealed the amidation after DHT to enhance the crystallinity of the prepared sponges. The prepared sponges had high porosity comprising high Alst-loaded amount that exhibited more compact structure. Alst enhanced hydrophobicity therefore it reduced the fluid absorption and WVTR together with bio-adhesion of the prepared sponge dressings. Porosity of all sponges was more than 85% therefore resulting in their high OP. Enhancing hydrophobicity of the material by Alst and more homogeneity caused by NMP eventually retarded the asiaticoside release for 7 days. The

  9. Evaporation rate of water in hydrophobic confinement.

    PubMed

    Sharma, Sumit; Debenedetti, Pablo G

    2012-03-20

    The drying of hydrophobic cavities is believed to play an important role in biophysical phenomena such as the folding of globular proteins, the opening and closing of ligand-gated ion channels, and ligand binding to hydrophobic pockets. We use forward flux sampling, a molecular simulation technique, to compute the rate of capillary evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of gap, surface size, and temperature. Over the range of conditions investigated (gaps between 9 and 14 Å and surface areas between 1 and 9 nm(2)), the free energy barrier to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes the predominant contribution to the free energy barrier. The exponential dependence of the evaporation rate on the gap between confining surfaces causes a 10 order-of-magnitude decrease in the rate when the gap increases from 9 to 14 Å. The computed free energy barriers are of the order of 50 kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9 nm(2)) than by the smaller (1 nm(2)) surfaces considered here, at otherwise identical conditions. We show that this rate enhancement is a consequence of the dependence of hydrophobic hydration on the size of solvated objects. For sufficiently large surfaces, the critical nucleus for the evaporation process is a gap-spanning vapor tube.

  10. The effect of lithium ions on the hydrophobic effect: does lithium affect hydrophobicity differently than other ions?

    PubMed

    Beauchamp, David L; Khajehpour, Mazdak

    2012-04-01

    Ionic species have been shown to significantly perturb the interactions between non-polar solutes in aqueous solution. These perturbations are often analyzed in terms of the interactions existing between hydrophobic surfaces and ions. It has been known for some time, that ions with a high charge density are repelled from hydrophobic surfaces while ions with a low charge density tend to stick to these surfaces. Therefore, from a continuum model standpoint, small monovalent ions promote hydrophobicity by minimizing the exposed hydrophobic surface area, while "sticky" large monovalent ions interact with the hydrophobic surfaces and discourage aggregation. However, the charge-dense lithium ion often exhibits anomalous behaviour different from these predicted trends: instead of enhancing, the addition of lithium ions often seems to weaken the hydrophobic effect and on the contrary help dissolve hydrophobic molecules. This weakening of apparent hydrophobicity is considered to be one of the reasons for the protein denaturing properties of lithium salts. Recent theoretical and experimental results however have shown that lithium cations can interact with a variety of molecular functional groups. This suggests that this apparent lithium-induced lowering of hydrophobicity, that is often reported in the literature may be a result of specific interactions between these molecular functional groups and lithium, rather than weakening the interaction between hydrophobic surfaces. This work examines these possibilities by studying the effect of various cations on the simple hydrophobic interaction existing between methyl and phenyl contact-pairs and demonstrates that the effect of lithium cations on the hydrophobic effect follows the trend predicted by continuum models. In other words, the influence of an ion on the hydrophobic interaction between two non-polar surfaces is a function of the interaction of that ion and each non-polar surface.

  11. Protein and lipid binding parameters in rainbow trout (Oncorhynchus mykiss) blood and liver fractions to extrapolate from an in vitro metabolic degradation assay to in vivo bioaccumulation potential of hydrophobic organic chemicals.

    PubMed

    Escher, Beate I; Cowan-Ellsberry, Christina E; Dyer, Scott; Embry, Michelle R; Erhardt, Susan; Halder, Marlies; Kwon, Jung-Hwan; Johanning, Karla; Oosterwijk, Mattheus T T; Rutishauser, Sibylle; Segner, Helmut; Nichols, John

    2011-07-18

    Binding of hydrophobic chemicals to colloids such as proteins or lipids is difficult to measure using classical microdialysis methods due to low aqueous concentrations, adsorption to dialysis membranes and test vessels, and slow kinetics of equilibration. Here, we employed a three-phase partitioning system where silicone (polydimethylsiloxane, PDMS) serves as a third phase to determine partitioning between water and colloids and acts at the same time as a dosing device for hydrophobic chemicals. The applicability of this method was demonstrated with bovine serum albumin (BSA). Measured binding constants (K(BSAw)) for chlorpyrifos, methoxychlor, nonylphenol, and pyrene were in good agreement with an established quantitative structure-activity relationship (QSAR). A fifth compound, fluoxypyr-methyl-heptyl ester, was excluded from the analysis because of apparent abiotic degradation. The PDMS depletion method was then used to determine partition coefficients for test chemicals in rainbow trout (Oncorhynchus mykiss) liver S9 fractions (K(S9w)) and blood plasma (K(bloodw)). Measured K(S9w) and K(bloodw) values were consistent with predictions obtained using a mass-balance model that employs the octanol-water partition coefficient (K(ow)) as a surrogate for lipid partitioning and K(BSAw) to represent protein binding. For each compound, K(bloodw) was substantially greater than K(S9w), primarily because blood contains more lipid than liver S9 fractions (1.84% of wet weight vs 0.051%). Measured liver S9 and blood plasma binding parameters were subsequently implemented in an in vitro to in vivo extrapolation model to link the in vitro liver S9 metabolic degradation assay to in vivo metabolism in fish. Apparent volumes of distribution (V(d)) calculated from the experimental data were similar to literature estimates. However, the calculated binding ratios (f(u)) used to relate in vitro metabolic clearance to clearance by the intact liver were 10 to 100 times lower than values

  12. Peripherally inserted central catheter - dressing change

    MedlinePlus

    PICC - dressing change ... You have a peripherally inserted central catheter (PICC). This is a tube that goes into a vein in your arm. It carries nutrients and medicines into your body. It may also ...

  13. A dressed spin qubit in silicon

    SciTech Connect

    Laucht, Arne; Kalra, Rachpon; Simmons, Stephanie; Dehollain, Juan P.; Muhonen, Juha T.; Mohiyaddin, Fahd A.; Freer, Solomon; Hudson, Fay E.; Itoh, Kohei M.; Jamieson, David N.; McCallum, Jeffrey C.; Dzurak, Andrew S.; Morello, A.

    2016-10-17

    Coherent dressing of a quantum two-level system provides access to a new quantum system with improved properties—a different and easily tunable level splitting, faster control and longer coherence times. In our work we investigate the properties of the dressed, donor-bound electron spin in silicon, and assess its potential as a quantum bit in scalable architectures. The two dressed spin-polariton levels constitute a quantum bit that can be coherently driven with an oscillating magnetic field, an oscillating electric field, frequency modulation of the driving field or a simple detuning pulse. We measure coherence times of T*2p = 2.4 ms and THahn2p = 9 ms, one order of magnitude longer than those of the undressed spin. Moreover, the use of the dressed states enables coherent coupling of the solid-state spins to electric fields and mechanical oscillations.

  14. A dressed spin qubit in silicon

    DOE PAGES

    Laucht, Arne; Kalra, Rachpon; Simmons, Stephanie; ...

    2016-10-17

    Coherent dressing of a quantum two-level system provides access to a new quantum system with improved properties—a different and easily tunable level splitting, faster control and longer coherence times. In our work we investigate the properties of the dressed, donor-bound electron spin in silicon, and assess its potential as a quantum bit in scalable architectures. The two dressed spin-polariton levels constitute a quantum bit that can be coherently driven with an oscillating magnetic field, an oscillating electric field, frequency modulation of the driving field or a simple detuning pulse. We measure coherence times of T*2p = 2.4 ms and THahn2pmore » = 9 ms, one order of magnitude longer than those of the undressed spin. Moreover, the use of the dressed states enables coherent coupling of the solid-state spins to electric fields and mechanical oscillations.« less

  15. A dressed spin qubit in silicon

    NASA Astrophysics Data System (ADS)

    Laucht, Arne; Kalra, Rachpon; Simmons, Stephanie; Dehollain, Juan P.; Muhonen, Juha T.; Mohiyaddin, Fahd A.; Freer, Solomon; Hudson, Fay E.; Itoh, Kohei M.; Jamieson, David N.; McCallum, Jeffrey C.; Dzurak, Andrew S.; Morello, A.

    2017-01-01

    Coherent dressing of a quantum two-level system provides access to a new quantum system with improved properties—a different and easily tunable level splitting, faster control and longer coherence times. In our work we investigate the properties of the dressed, donor-bound electron spin in silicon, and assess its potential as a quantum bit in scalable architectures. The two dressed spin-polariton levels constitute a quantum bit that can be coherently driven with an oscillating magnetic field, an oscillating electric field, frequency modulation of the driving field or a simple detuning pulse. We measure coherence times of and , one order of magnitude longer than those of the undressed spin. Furthermore, the use of the dressed states enables coherent coupling of the solid-state spins to electric fields and mechanical oscillations.

  16. Colour Vision: Understanding #TheDress.

    PubMed

    Brainard, David H; Hurlbert, Anya C

    2015-06-29

    A widely-viewed image of a dress elicits striking individual variation in colour perception. Experiments with multiple variants of the image suggest that the individual differences may arise through the action of visual mechanisms that normally stabilise object colour.

  17. Electrospun zwitterionic poly(sulfobetaine methacrylate) for nonadherent, superabsorbent, and antimicrobial wound dressing applications.

    PubMed

    Lalani, Reza; Liu, Lingyun

    2012-06-11

    Zwitterionic poly(sulfobetaine methacrylate) (PSBMA) has been well studied for its superhydrophilic and ultralow biofouling properties, making it a promising material for superabsorbent and nonadherent wound dressings. Electrospinning provides multiple desirable features for wound dressings, including high absorptivity due to high surface-area-to-volume ratio, high gas permeation, and conformability to contour of the wound bed. The goal of this work is to develop a fibrous membrane of PSBMA via electrospinning and evaluate its properties related to wound dressing applications. Being superhydrophilic, PSBMA fibers fabricated by a conventional electrospinning method would readily dissolve in water, whereas if cross-linker is added, the formation of hydrogel would prevent electrospinning. A three-step polymerization-electrospinning-photo-cross-linking process was developed in this work to fabricate the cross-linked electrospun PSBMA fibrous membrane. Such electrospun membrane was stable in water and exhibited high water absorption of 353% (w/w), whereas the PSBMA hydrogel only absorbed 81% water. The electrospun membrane showed strong resistance to protein adsorption and cell attachment. Bacterial adhesion studies using Gram negative P. aeruginosa and Gram positive S. epidermidis showed that the PSBMA electrospun membrane was also highly resistant to bacterial adhesion. The Ag(+)-impregnated electrospun PSBMA membrane was shown microbicidal, against both S. epidermidis and P. aeruginosa. Such electrospun PSBMA membrane is ideal for a novel type of nonadherent, superabsorbent, and antimicrobial wound dressing. The superior water absorption aids in fluid removal from highly exudating wounds while keeping the wound hydrated to support healing. Because of the resistance to protein, cell, and bacterial adhesion, the dressing removal will neither cause patients' pain nor disturb the newly formed tissues. The dressing also prevents the attachment of environmental bacteria

  18. Strategies to reduce wound dressing waste.

    PubMed

    Denhartog, Lauren; Hallman, Laura

    2015-01-01

    Inappropriate use of dressing supplies and the amount of unused, unopened dressings, often stockpiled in patient rooms and discarded upon patient discharge begs the question about the environmental impact of this common practice. Thousands of dollars could be saved each year if nurses placed more emphasis on prevention and education, and addressed wound care in a standardized way that blends cost-effectiveness with evidence-based practice.

  19. Choosing a Wound Dressing Based on Common Wound Characteristics.

    PubMed

    Dabiri, Ganary; Damstetter, Elizabeth; Phillips, Tania

    2016-01-01

    Significance: Chronic wounds are a major healthcare burden.The practitioner should have an appropriate understanding of both the etiology of the wound as well as the optimal type of dressings to use. Fundamental wound characteristics may be used to guide the practitioner's choice of dressings. The identification of optimal dressings to use for a particular wound type is an important element in facilitating wound healing. Recent Advances: Researchers have sought to design wound dressings that aim to optimize each stage in the healing process. In addition, dressings have been designed to target and kill infection-causing bacteria, with the incorporation of antimicrobial agents. Critical Issues: Chronic wounds are frequently dynamic in presentation, and the numerous wound dressings available make dressing selection challenging for the practitioner. Choosing the correct dressing decreases time to healing, provides cost-effective care, and improves patient quality of life. Future Directions: Research into the mechanisms of wound healing has enhanced our ability to heal chronic wounds at a faster rate through the use of moisture-retentive dressings. Newer dressings are incorporating the use of nanotechnology by incorporating miniature electrical sensors into the dressing. These dressings are engineered to detect changes in a wound environment and alert the patient or practitioner by altering the color of the dressing or sending a message to a smartphone. Additional investigations are underway that incorporate biologic material such as stem cells into dressings.

  20. Adolescent Dress, Part I: Dress and Body Markings of Psychiatric Outpatients and Inpatients.

    ERIC Educational Resources Information Center

    Michelman, John D.; And Others

    1991-01-01

    Investigated dress and body markings of 100 hospitalized and never-hospitalized adolescent psychiatric patients using in-depth interviews. Found that hospitalized patients had higher incidence of self-scarring, but other individual expressions of appearance did not differentiate two groups. Suggests that dress and appearance observations,…

  1. 21 CFR 878.4022 - Hydrogel wound dressing and burn dressing.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hydrogel wound dressing and burn dressing. 878.4022 Section 878.4022 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  2. 21 CFR 878.4022 - Hydrogel wound dressing and burn dressing.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Hydrogel wound dressing and burn dressing. 878.4022 Section 878.4022 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  3. 21 CFR 878.4022 - Hydrogel wound dressing and burn dressing.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Hydrogel wound dressing and burn dressing. 878.4022 Section 878.4022 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  4. 21 CFR 878.4022 - Hydrogel wound dressing and burn dressing.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Hydrogel wound dressing and burn dressing. 878.4022 Section 878.4022 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  5. 21 CFR 878.4022 - Hydrogel wound dressing and burn dressing.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Hydrogel wound dressing and burn dressing. 878.4022 Section 878.4022 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  6. Students' Understanding of External Representations of the Potassium Ion Channel Protein, Part I: Affordances and Limitations of Ribbon Diagrams, Vines, and Hydrophobic/Polar Representations

    ERIC Educational Resources Information Center

    Harle, Marissa; Towns, Marcy H.

    2012-01-01

    Research on external representations in biochemistry has uncovered student difficulties in comprehending and interpreting external representations. This project focuses on students' understanding of three external representations of the potassium ion channel protein. This is part I of a two-part study, which focuses on the affordances and…

  7. Hydrophobic interactions and ionic networks play an important role in thermal stability and denaturation mechanism of the porcine odorant-binding protein.

    PubMed

    Stepanenko, Olesya V; Marabotti, Anna; Kuznetsova, Irina M; Turoverov, Konstantin K; Fini, Carlo; Varriale, Antonio; Staiano, Maria; Rossi, Mose'; D'Auria, Sabato

    2008-04-01

    Despite the fact that the porcine odorant-binding protein (pOBP) possesses a single tryptophan residue (Trp 16) that is characterized by a high density microenvironment (80 atoms in a sphere with radius 7 A) with only one polar group (Lys 120) and three bound water molecules, pOBP displayed a red shifted fluorescence emission spectrum (lambda(max) = 340 nm). The protein unfolding in 5M GdnHCl was accompanied by the red shift of the fluorescence emission spectrum (lambda(max) = 353 nm), by the increase of fluorescence quantum yield, and by the decrease of lifetime of the excited state (from 4.25 ns in native state to 3.15 ns in the presence of 5M GdnHCl). Taken together these data indicate the existence of an exciplex complex (Trp 16 with Lys 120 and/or with bound molecules of water) in the protein native state. Heat-induced denaturation of pOBP resulted in significant red shifts of the fluorescence emission spectra: the value of the ratio (I(320)/I(365)) upon excitation at lambda(ex) = 297 nm (parameter A) decreases from 1.07 to 0.64 passing from 60 to 85 degrees C, and the calculated midpoint of transition was centered at 70 degrees C. Interestingly, even at higher temperature, the values of the parameter A both in the absence and in the presence of GdnHCl did not coincide. This suggests that a portion of the protein structure is still preserved upon the temperature-induced denaturation of the protein in the absence of GdnHCl. CD experiments performed on pOBP in the absence and in the presence of GdnHCl and at different temperatures were in agreement with the fluorescence results. In addition, the obtained experimental data were corroborated by the analysis of the 3D structure of pOBP which revealed the amino acid residues that contribute to the protein dynamics and stability. Finally, molecular dynamics simulation experiments pointed out the important role of ion pair interactions as well as the molecular motifs that are responsible for the high thermal stability

  8. Establishing guidelines for employee dress and hygiene.

    PubMed

    Hills, Laura Sachs

    2003-01-01

    Can you tell your medical practice staff how you want them to look? Where in your office they can eat? Can they chew gum at work? Can they wear red nail polish or a charm bracelet? In the pages that follow, the author suggests not only that you can establish rules for employee dress and hygiene, but why you should. This article suggests several good ways to structure staff rules for wearing uniforms and street clothing. It also covers possible rules for wearing practice nametags, cosmetics, jewelry, hair styles, neatness, stowing of personal possessions, personal hygiene, drinking, eating, smoking, and gum chewing. Finally, this article offers practical suggestions for establishing your practice's dress and hygiene "first aid" kit as well as guidance for making your practice's dress and hygiene codes non-discriminatory.

  9. Investigation on Curcumin nanocomposite for wound dressing.

    PubMed

    Venkatasubbu, G Devanand; Anusuya, T

    2017-02-03

    Curcuma longa (turmeric) has a long history of use in medicine as a treatment for inflammatory conditions. The primary active constituent of turmeric and the one responsible for its vibrant yellow color is curcumin. Curcumin is used for treatment of wound and inflammation. It had antimicrobial and antioxidant property. It has low intrinsic toxicity and magnificent properties like with comparatively lesser side-effects. Cotton cloth is one of the most successful wound dressings which utilize the intrinsic properties of cotton fibers. Modern wound dressings, however, require other properties such as antibacterial and moisture maintaining capabilities. In this study, conventional cotton cloth was coated with Curcumin composite for achieving modern wound dressing properties. Curcumin nanocomposite is characterized. The results show that coated cotton cloth with Curcumin nanocomposite has increased drying time (74%) and water absorbency (50%). Furthermore, they show antibacterial efficiency against bacterial species present in wounds.

  10. Mutation of the Highly Conserved Ser-40 of the HIV-1 p6 Gag Protein to Phe Causes the Formation of a Hydrophobic Patch, Enhances Membrane Association, and Polyubiquitination of Gag

    PubMed Central

    Hahn, Friedrich; Setz, Christian; Friedrich, Melanie; Rauch, Pia; Solbak, Sara Marie; Frøystein, Nils Åge; Henklein, Petra; Votteler, Jörg; Fossen, Torgils; Schubert, Ulrich

    2014-01-01

    The HIV-1 p6 Gag protein contains two late assembly (l-) domains that recruit proteins of the endosomal sorting complex required for transport (ESCRT) pathway to mediate membrane fission between the nascent virion and the cell membrane. It was recently demonstrated that mutation of the highly conserved Ser-40 to Phe (S40F) disturbs CA-SP1 processing, virus morphogenesis, and infectivity. It also causes the formation of filopodia-like structures, while virus release remains unaffected. Here, we show that the mutation S40F, but not the conservative mutation to Asp (S40D) or Asn (S40N), augments membrane association, K48-linked polyubiquitination, entry into the 26S proteasome, and, consequently, enhances MHC-I antigen presentation of Gag derived epitopes. Nuclear magnetic resonance (NMR) structure analyses revealed that the newly introduced Phe-40, together with Tyr-36, causes the formation of a hydrophobic patch at the C-terminal α-helix of p6, providing a molecular rationale for the enhanced membrane association of Gag observed in vitro and in HIV-1 expressing cells. The extended exposure of the S40F mutant to unidentified membrane-resident ubiquitin E3-ligases might trigger the polyubiquitination of Gag. The cumulative data support a previous model of a so far undefined property of p6, which, in addition to MA, acts as membrane targeting domain of Gag. PMID:25279819

  11. Mutation of the highly conserved Ser-40 of the HIV-1 p6 gag protein to Phe causes the formation of a hydrophobic patch, enhances membrane association, and polyubiquitination of Gag.

    PubMed

    Hahn, Friedrich; Setz, Christian; Friedrich, Melanie; Rauch, Pia; Solbak, Sara Marie; Frøystein, Nils Age; Henklein, Petra; Votteler, Jörg; Fossen, Torgils; Schubert, Ulrich

    2014-10-02

    The HIV-1 p6 Gag protein contains two late assembly (l-) domains that recruit proteins of the endosomal sorting complex required for transport (ESCRT) pathway to mediate membrane fission between the nascent virion and the cell membrane. It was recently demonstrated that mutation of the highly conserved Ser-40 to Phe (S40F) disturbs CA-SP1 processing, virus morphogenesis, and infectivity. It also causes the formation of filopodia-like structures, while virus release remains unaffected. Here, we show that the mutation S40F, but not the conservative mutation to Asp (S40D) or Asn (S40N), augments membrane association, K48-linked polyubiquitination, entry into the 26S proteasome, and, consequently, enhances MHC-I antigen presentation of Gag derived epitopes. Nuclear magnetic resonance (NMR) structure analyses revealed that the newly introduced Phe-40, together with Tyr-36, causes the formation of a hydrophobic patch at the C-terminal α-helix of p6, providing a molecular rationale for the enhanced membrane association of Gag observed in vitro and in HIV-1 expressing cells. The extended exposure of the S40F mutant to unidentified membrane-resident ubiquitin E3-ligases might trigger the polyubiquitination of Gag. The cumulative data support a previous model of a so far undefined property of p6, which, in addition to MA, acts as membrane targeting domain of Gag.

  12. Hydrophobic encapsulation of hydrocarbon gases.

    PubMed

    Leontiev, Alexander V; Saleh, Anas W; Rudkevich, Dmitry M

    2007-04-26

    [reaction: see text] Encapsulation data for hydrophobic hydrocarbon gases within a water-soluble hemicarcerand in aqueous solution are reported. It is concluded that hydrophobic interactions serve as the primary driving force for the encapsulation, which can be used for the design of gas-separating polymers with intrinsic inner cavities.

  13. Wound Dressings and Comparative Effectiveness Data

    PubMed Central

    Sood, Aditya; Granick, Mark S.; Tomaselli, Nancy L.

    2014-01-01

    Significance: Injury to the skin provides a unique challenge, as wound healing is a complex and intricate process. Acute wounds have the potential to move from the acute wound to chronic wounds, requiring the physician to have a thorough understanding of outside interventions to bring these wounds back into the healing cascade. Recent Advances: The development of new and effective interventions in wound care remains an area of intense research. Negative pressure wound therapy has undoubtedly changed wound care from this point forward and has proven beneficial for a variety of wounds. Hydroconductive dressings are another category that is emerging with studies underway. Other modalities such as hyperbaric oxygen, growth factors, biologic dressings, skin substitutes, and regenerative materials have also proven efficacious in advancing the wound-healing process through a variety of mechanisms. Critical Issues: There is an overwhelming amount of wound dressings available in the market. This implies the lack of full understanding of wound care and management. The point of using advanced dressings is to improve upon specific wound characteristics to bring it as close to “ideal” as possible. It is only after properly assessing the wound characteristics and obtaining knowledge about available products that the “ideal” dressing may be chosen. Future Directions: The future of wound healing at this point remains unknown. Few high-quality, randomized controlled trials evaluating wound dressings exist and do not clearly demonstrate superiority of many materials or categories. Comparative effectiveness research can be used as a tool to evaluate topical therapy for wound care moving into the future. Until further data emerge, education on the available products and logical clinical thought must prevail. PMID:25126472

  14. Exploring Hydrophobic Binding Surfaces Using Comfa and Flexible Hydrophobic Ligands

    NASA Astrophysics Data System (ADS)

    Thakkar, Shraddha; Sanchez, Rosa. I.; Bhuveneswaran, Chidambaram; Compadre, Cesar M.

    2011-06-01

    Cysteine proteinases are a very important group of enzymes involved in a variety of physiological and pathological processes including cancer metastasis and rheumatoid arthritis. In this investigation we used 3D-Quantitative Structure Activity Relationships (3D-QSAR) techniques to model the binding of a variety of substrates to two cysteine proteinases, papain, and cathepsin B. The analysis was performed using Comparative Molecular Field Analysis (CoMFA). The molecules were constructed using standard bond angles and lengths, minimized and aligned. Charges were calculated using the PM3 method in MOPAC. The CoMFA models derived for the binding of the studied substrates to the two proteinases were compared with the expected results from the experimental X-ray crystal structures of the same proteinases. The results showed the value of CoMFA modeling of flexible hydrophobic ligands to analyze ligand binding to protein receptors, and could also serve as the basis to design specific inhibitors of cysteine proteinases with potential therapeutic value.

  15. Voltage-Gated Hydrophobic Nanopores

    SciTech Connect

    Lavrik, Nickolay V

    2011-01-01

    Hydrophobicity is a fundamental property that is responsible for numerous physical and biophysical aspects of molecular interactions in water. Peculiar behavior is expected for water in the vicinity of hydrophobic structures, such as nanopores. Indeed, hydrophobic nanopores can be found in two distinct states, dry and wet, even though the latter is thermodynamically unstable. Transitions between these two states are kinetically hindered in long pores but can be much faster in shorter pores. As it is demonstrated for the first time in this paper, these transitions can be induced by applying a voltage across a membrane with a single hydrophobic nanopore. Such voltage-induced gating in single nanopores can be realized in a reversible manner through electrowetting of inner walls of the nanopores. The resulting I-V curves of such artificial hydrophobic nanopores mimic biological voltage-gated channels.

  16. Changing water affinity from hydrophobic to hydrophilic in hydrophobic channels.

    PubMed

    Ohba, Tomonori; Yamamoto, Shotaro; Kodaira, Tetsuya; Hata, Kenji

    2015-01-27

    The behavior of water at hydrophobic interfaces can play a significant role in determining chemical reaction outcomes and physical properties. Carbon nanotubes and aluminophosphate materials have one-dimensional hydrophobic channels, which are entirely surrounded by hydrophobic interfaces. Unique water behavior was observed in such hydrophobic channels. In this article, changes in the water affinity in one-dimensional hydrophobic channels were assessed using water vapor adsorption isotherms at 303 K and grand canonical Monte Carlo simulations. Hydrophobic behavior of water adsorbed in channels wider than 3 nm was observed for both adsorption and desorption processes, owing to the hydrophobic environment. However, water showed hydrophilic properties in both adsorption and desorption processes in channels narrower than 1 nm. In intermediate-sized channels, the hydrophobic properties of water during the adsorption process were seen to transition to hydrophilic behavior during the desorption process. Hydrophilic properties in the narrow channels for both adsorption and desorption processes are a result of the relatively strong water-channel interactions (10-15 kJ mol(-1)). In the 2-3 nm channels, the water-channel interaction energy of 4-5 kJ mol(-1) was comparable to the thermal translational energy. The cohesive water interaction was approximately 35 kJ mol(-1), which was larger than the others. Thus, the water affinity change in the 2-3 nm channels for the adsorption and desorption processes was attributed to weak water-channel interactions and strong cohesive interactions. These results are inherently important to control the properties of water in hydrophobic environments.

  17. A simple dressing for hypospadias surgery in children

    PubMed Central

    Méndez-Gallart, Roberto; García-Palacios, María; Rodríguez-Barca, Pablo; Estévez-Martínez, Elina; Carril, Ana Lema; Bautista-Casasnovas, Adolfo

    2017-01-01

    One of the most controversial aspects of hypospadias surgery is the election of an appropriate wound dressing. In fact, there may be as many different types of dressing as there are types of surgical repair. Here, we describe a new, simple method for hypospadias dressing in children that minimizes painful removal. PMID:28163817

  18. Rationale for Student Dress Codes: A Review of School Handbooks

    ERIC Educational Resources Information Center

    Freeburg, Elizabeth W.; Workman, Jane E.; Lentz-Hees, Elizabeth S.

    2004-01-01

    Through dress codes, schools establish rules governing student appearance. This study examined stated rationales for dress and appearance codes in secondary school handbooks; 182 handbooks were received. Of 150 handbooks containing a rationale, 117 related dress and appearance regulations to students' right to a non-disruptive educational…

  19. A fitted neoprene garment to cover dressings in swine models.

    PubMed

    Mino, Matthew J; Mauskar, Neil A; Matt, Sara E; Pavlovich, Anna R; Prindeze, Nicholas J; Moffatt, Lauren T; Shupp, Jeffrey W

    2012-12-17

    Domesticated porcine species are commonly used in studies of wound healing, owing to similarities between porcine skin and human skin. Such studies often involve wound dressings, and keeping these dressings intact on the animal can be a challenge. The authors describe a novel and simple technique for constructing a fitted neoprene garment for pigs that covers dressings and maintains their integrity during experiments.

  20. Effect of periodontal dressings on human gingiva fibroblasts in vitro

    SciTech Connect

    Eber, R.M.; Shuler, C.F.; Buchanan, W.; Beck, F.M.; Horton, J.E. )

    1989-08-01

    In vitro cytotoxicity studies of periodontal dressings have not generally produced a result consistent with in vivo observations. These prior in vitro studies have not used human intraoral cell lines. We tested the effects of two eugenol containing and two non-eugenol periodontal dressings on cultured human gingival fibroblasts (HGF) (ATCC No. 1292). Replicate HGF cultures grown in microtiter plates were exposed to stock, 1:4 and 1:16 dilutions of extracts made from each of the four periodontal dressings. The HGF cultures were pulse labelled with tritiated thymidine (3HTdR) after 24, 48, and 72 hours. Incorporations of the labelled thymidine were measured using liquid scintillation counting and expressed as counts per minute. The results showed that undiluted extracts from all four periodontal dressings totally inhibited 3HTdR uptake (P less than 0.05). The 1:4 dilution of eugenol dressings inhibited 3HTdR uptake significantly more than non-eugenol dressings (P less than 0.05). Interestingly, at 72 hours the 1:16 dilution of the non-eugenol dressings caused significantly increased 3HTdR uptake which was not observed with the eugenol dressings. The present results suggest that the use of a human fibroblastic cell line for testing the effects of periodontal dressings may provide information about the relative biological effects of these dressings. Using this cell line, we have found that eugenol dressings inhibit fibroblast proliferation to a greater extent than non-eugenol dressings.

  1. Dressing of Cognitively Impaired Nursing Home Residents: Description and Analysis

    ERIC Educational Resources Information Center

    Cohen-Mansfield, Jiska; Creedon, Michael A.; Malone, Thomas; Parpura-Gill, Aleksandra; Dakheel-Ali, Maha; Heasly, Christopher

    2006-01-01

    Purpose: Getting dressed is an activity that is of particular difficulty for many persons with dementia, given the need for hand-eye coordination, fine motor skills, and overall planning skills. Despite several studies concerning interventions to improve dressing behavior, very little is known about the dressing process as it is currently…

  2. Fluoroalkyl and Alkyl Chains Have Similar Hydrophobicities in Binding to the “Hydrophobic Wall” of Carbonic Anhydrase

    PubMed Central

    Mecinović, Jasmin; Snyder, Phillip W.; Mirica, Katherine A.; Bai, Serena; Mack, Eric T.; Kwant, Richard L.; Moustakas, Demetri T.; Heroux, Annie; Whitesides, George M.

    2011-01-01

    The hydrophobic effect—the free-energetically favorable association of non-polar solutes in water—makes a dominant contribution to binding of many systems of ligands and proteins. The objective of this study was to examine the hydrophobic effect in biomolecular recognition using two chemically different, but structurally similar hydrophobic groups—aliphatic hydrocarbons and aliphatic fluorocarbons—and to determine whether the hydrophobicity of the two groups could be distinguished by thermodynamic and biostructural analysis. This paper uses isothermal titration calorimetry (ITC) to examine the thermodynamics of binding of benzenesulfonamides substituted in the para position with alkyl and fluoroalkyl chains (H2NSO2C6H4-CONHCH2(CX2)nCX3, n = 0–4, X = H, F) to human carbonic anhydrase II (HCA II). Both alkyl and fluoroalkyl substituents contribute favorably to the enthalpy and the entropy of binding; these contributions increase as the length of chain of the hydrophobic substituent increases. Crystallography of the protein-ligand complexes indicates that the benzenesulfonamide groups of all ligands examined bind with similar geometry, that the tail groups associate with the hydrophobic wall of HCA II (which is made up of the side chains of residues Phe131, Val135, Pro202, and Leu204), and that the structure of the protein is indistinguishable for all but one of the complexes (the longest member of the fluoroalkyl series). Analysis of the thermodynamics of binding as a function of structure is compatible with the hypothesis that hydrophobic binding of both alkyl and fluoroalkyl chains to hydrophobic surface of carbonic anhydrase is due primarily to the release of non-optimally hydrogen-bonded water molecules that hydrate the binding cavity (including the hydrophobic wall) of HCA II and to the release of water molecules that surround the hydrophobic chain of the ligands. This study defines the balance of enthalpic and entropic contributions to the hydrophobic

  3. Fluoroalkyl and Alkyl Chains Have Similar Hydrophobicities in Binding to the “Hydrophobic Wall” of Carbonic Anhydrase

    SciTech Connect

    J Mecinovic; P Snyder; K Mirica; S Bai; E Mack; R Kwant; D Moustakas; A Heroux; G Whitesides

    2011-12-31

    The hydrophobic effect, the free-energetically favorable association of nonpolar solutes in water, makes a dominant contribution to binding of many systems of ligands and proteins. The objective of this study was to examine the hydrophobic effect in biomolecular recognition using two chemically different but structurally similar hydrophobic groups, aliphatic hydrocarbons and aliphatic fluorocarbons, and to determine whether the hydrophobicity of the two groups could be distinguished by thermodynamic and biostructural analysis. This paper uses isothermal titration calorimetry (ITC) to examine the thermodynamics of binding of benzenesulfonamides substituted in the para position with alkyl and fluoroalkyl chains (H{sub 2}NSO{sub 2}C{sub 6}H{sub 4}-CONHCH{sub 2}(CX{sub 2}){sub n}CX{sub 3}, n = 0-4, X = H, F) to human carbonic anhydrase II (HCA II). Both alkyl and fluoroalkyl substituents contribute favorably to the enthalpy and the entropy of binding; these contributions increase as the length of chain of the hydrophobic substituent increases. Crystallography of the protein-ligand complexes indicates that the benzenesulfonamide groups of all ligands examined bind with similar geometry, that the tail groups associate with the hydrophobic wall of HCA II (which is made up of the side chains of residues Phe131, Val135, Pro202, and Leu204), and that the structure of the protein is indistinguishable for all but one of the complexes (the longest member of the fluoroalkyl series). Analysis of the thermodynamics of binding as a function of structure is compatible with the hypothesis that hydrophobic binding of both alkyl and fluoroalkyl chains to hydrophobic surface of carbonic anhydrase is due primarily to the release of nonoptimally hydrogen-bonded water molecules that hydrate the binding cavity (including the hydrophobic wall) of HCA II and to the release of water molecules that surround the hydrophobic chain of the ligands. This study defines the balance of enthalpic and

  4. Physico-chemical properties and efficacy of silk fibroin fabric coated with different waxes as wound dressing.

    PubMed

    Kanokpanont, Sorada; Damrongsakkul, Siriporn; Ratanavaraporn, Juthamas; Aramwit, Pornanong

    2013-04-01

    Silk fibroin (SF) has been widely used as a wound dressing material due to its suitable physical and biological characteristics. In this study, a non-adhesive wound dressing which applies to cover the wound surface as an absorbent pad that would absorb wound fluid while accelerate wound healing was developed. The modification of SF fabrics by wax coating was purposed to prepare the non-adhesive wound dressing that is required in order to minimize pain and risk of repeated injury. SF woven fabrics were coated with different types of waxes including shellac wax, beeswax, or carnauba wax. Physical and mechanical properties of the wax-coated SF fabrics were characterized. It was clearly observed that all waxes could be successfully coated on the SF fabrics, possibly due to the hydrophobic interactions between hydrophobic domains of SF and waxes. The wax coating improved tensile modulus and percentage of elongation of the SF fabrics due to the denser structure and the thicker fibers coated. The in vitro degradation study demonstrated that all wax-coated SF fabrics remained up to 90% of their original weights after 7 weeks of incubation in lysozyme solution under physiological conditions. The wax coating did not affect the degradation behavior of the SF fabrics. A peel test of the wax-coated SF fabrics was carried out in the partial- and full-thickness wounds of porcine skin in comparison to that of the commercial wound dressing. Any wax-coated SF fabrics were less adhesive than the control, as confirmed by less number of cells attached and less adhesive force. This might be that the wax-coated SF fabrics showed the hydrophobic property, allowing the loosely adherence to the hydrophilic wound surface. In addition, the in vivo biocompatibility test of the wax-coated SF fabrics was performed in Sprague-Dawley rats with subcutaneous model. The irritation scores indicated that the carnauba wax-coated SF fabric was not irritant while the shellac wax or beeswax-coated SF

  5. "Posh Music Should Equal Posh Dress": An Investigation into the Concert Dress and Physical Appearance of Female Soloists

    ERIC Educational Resources Information Center

    Griffiths, Noola K.

    2010-01-01

    This study investigates the effects of concert dress and physical appearance on perceptions of female classical soloists' musical abilities over a range of genres. Four female violinists were recorded playing three pieces, in four styles of dress of varying formality. Each combination of performer, piece and dress was recorded twice, once as the…

  6. Student Dress Policies. ERIC Digest, Number 117.

    ERIC Educational Resources Information Center

    Isaacson, Lynne

    Educators and the public are divided over the value of implementing school-uniform policies in the public schools. This digest examines arguments for and against school-uniform policies, identifies legal considerations, and offers guidelines for implementing policies on student dress. Most parents have responded favorably to uniform policies,…

  7. Student Dress Codes and Uniforms. Research Brief

    ERIC Educational Resources Information Center

    Johnston, Howard

    2009-01-01

    According to an Education Commission of the States "Policy Report", research on the effects of dress code and school uniform policies is inconclusive and mixed. Some researchers find positive effects; others claim no effects or only perceived effects. While no state has legislatively mandated the wearing of school uniforms, 28 states and…

  8. The Effects of Dress on School Discipline.

    ERIC Educational Resources Information Center

    Sommers, Norman L.

    This report presents the results of a study to determine the effects of student dress on behavior while at school. The study took place at 5 high schools, 4 junior high schools, and 10 elementary schools during the 2000-01 school year. The total enrollment of the schools was 8,194. The study involved two or three sets consisting of three days…

  9. Dressed fluxon in a Josephson window junction

    NASA Astrophysics Data System (ADS)

    Caputo, Jean Guy; Flytzanis, Nikos; Devoret, Michel

    1994-09-01

    The static fluxon solutions of a Josephson window junction have been studied numerically. We show that the effect of the idle region surrounding the junction is to ``dress'' the fluxon causing its energy to increase. This effect can be predicted accurately by a simple model.

  10. Swellability of Silver (I) Antimicrobial Wound Dressings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An important characteristic of moist wound dressings is their ability to swell and absorb exudates from the wound, while maintaining a moist atmosphere at the wound site. At the Southern Regional Research Center, we have developed antimicrobial silver- CM-cotton print cloth from CM-Printcloth with l...

  11. 21 CFR 169.115 - French dressing.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... emulsified viscous fluid food prepared from vegetable oil(s) and one or both of the acidifying ingredients... this section may also be used. The vegetable oil(s) used may contain an optional crystallization... vegetable oil. French dressing may be mixed and packed in an atmosphere in which air is replaced in whole...

  12. 21 CFR 169.115 - French dressing.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... emulsified viscous fluid food prepared from vegetable oil(s) and one or both of the acidifying ingredients... this section may also be used. The vegetable oil(s) used may contain an optional crystallization... vegetable oil. French dressing may be mixed and packed in an atmosphere in which air is replaced in whole...

  13. 21 CFR 169.115 - French dressing.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... emulsified viscous fluid food prepared from vegetable oil(s) and one or both of the acidifying ingredients... this section may also be used. The vegetable oil(s) used may contain an optional crystallization... vegetable oil. French dressing may be mixed and packed in an atmosphere in which air is replaced in whole...

  14. 21 CFR 169.115 - French dressing.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... emulsified viscous fluid food prepared from vegetable oil(s) and one or both of the acidifying ingredients... this section may also be used. The vegetable oil(s) used may contain an optional crystallization... vegetable oil. French dressing may be mixed and packed in an atmosphere in which air is replaced in whole...

  15. Dressing plantar wounds with foam dressings, is it too much pressure?

    PubMed Central

    Scott Causby, Ryan; Pod, M; Jones, Sara

    2011-01-01

    Diabetes and its associated complications have become a major concern locally, nationally and internationally. One such complication is lower extremity amputation, commonly preceded by chronic ulceration. The cause of this tissue breakdown is multi-faceted, but includes an increase in pressure, particularly plantar pressure. As such, the choice of dressing to be applied to a plantar wound should ideally not increase this pressure further. A commonly used and possibly more bulky dressing is the foam dressing. This pilot study investigates the plantar pressures associated with three common foam dressings (Allevyn®, Lyofoam® and Mepilex®) compared with a control dressing (Melolin®). Twelve healthy males and 19 females [SD] age 36.6 [10.4] were measured using the F-scan plantar pressure measurement system. Substantial variations in individual pressure changes occurred across the foot. No significant differences were identified, once a Bonferroni correction was applied. In healthy adults, it could be concluded that foam dressings do not have any effect on the plantar pressures of the foot. However, the need remains for a robust trial on a pathological population. PMID:22396822

  16. Expression of the chaplin and rodlin hydrophobic sheath proteins in Streptomyces venezuelae is controlled by σ(BldN) and a cognate anti-sigma factor, RsbN.

    PubMed

    Bibb, Maureen J; Domonkos, Agota; Chandra, Govind; Buttner, Mark J

    2012-06-01

    The chaplin and rodlin proteins together constitute the major components of the hydrophobic sheath that coats the aerial hyphae and spores in Streptomyces, and mutants lacking the chaplins are unable to erect aerial hyphae and differentiate on minimal media. We have gained insight into the developmental regulation of the chaplin (chp) and rodlin (rdl) genes by exploiting a new model species, Streptomyces venezuelae, which sporulates in liquid culture. Using microarrays, the chaplin and rodlin genes were found to be highly induced during submerged sporulation in a bldN-dependent manner. Using σ(BldN) ChIP-chip, we show that this dependence arises because the chaplin and rodlin genes are direct biochemical targets of σ(BldN) . sven3186 (here named rsbN for regulator of sigma BldN), the gene lying immediately downstream of bldN, was also identified as a target of σ(BldN) . Disruption of rsbN causes precocious sporulation and biochemical experiments demonstrate that RsbN functions as a σ(BldN) -specific anti-sigma factor.

  17. Case study of hydrogen bonding in a hydrophobic cavity.

    PubMed

    Chen, Yi-Chen; Cheng, Chao-Sheng; Tjong, Siu-Cin; Yin, Hsien-Sheng; Sue, Shih-Che

    2014-12-18

    Protein internal hydrogen bonds and hydrophobicity determine protein folding and structure stabilization, and the introduction of a hydrogen bond has been believed to represent a better interaction for consolidating protein structure. We observed an alternative example for chicken IL-1β. The native IL-1β contains a hydrogen bond between the Y157 side-chain OηH and I133 backbone CO, whereby the substitution from Tyr to Phe abolishes the connection and the mutant without the hydrogen bond is more stable. An attempt to explain the energetic view of the presence of the hydrogen bond fails when only considering the nearly identical X-ray structures. Here, we resolve the mechanism by monitoring the protein backbone dynamics and interior hydrogen bond network. IL-1β contains a hydrophobic cavity in the protein interior, and Y157 is one of the surrounding residues. The Y157 OηH group introduces an unfavorable energy in the hydrophobic cavity, therefore sequestering itself by forming a hydrogen bond with the proximate residue I133. The hydrogen bonding confines Y157 orientation but exerts a force to disrupt the hydrogen bond network surrounding the cavity. The effect propagates over the entire protein and reduces the stability, as reflected in the protein backbone dynamics observed by an NMR hydrogen-deuterium (H/D) exchange experiment. We describe the particular case in which a hydrogen bond does not necessarily confer enhanced protein stability while the disruption of hydrophobicity must be integrally considered.

  18. Method for producing hydrophobic aerogels

    DOEpatents

    Hrubesh, Lawrence W.; Poco, John F.; Coronado, Paul R.

    1999-01-01

    A method for treating a dried monolithic aerogel containing non-dispersed particles, with an organometallic surface modifying agent to produce hydrophobic aerogels. The dried, porous hydrophobic aerogels contain a protective layer of alkyl groups, such as methyl groups, on the modified surfaces of the pores of the aerogel. The alkyl groups at the aerogel surface typically contain at least one carbon-metal bond per group.

  19. Functional analysis of FarA transcription factor in the regulation of the genes encoding lipolytic enzymes and hydrophobic surface binding protein for the degradation of biodegradable plastics in Aspergillus oryzae.

    PubMed

    Garrido, Sharon Marie; Kitamoto, Noriyuki; Watanabe, Akira; Shintani, Takahiro; Gomi, Katsuya

    2012-05-01

    FarA is a Zn(II)(2)Cys(6) transcription factor which upregulates genes required for growth on fatty acids in filamentous fungi like Aspergillus nidulans. FarA is also highly similar to the cutinase transcription factor CTF1α of Fusarium solani which binds to the cutinase gene promoter in this plant pathogen. This study determines whether FarA transcriptional factor also works in the regulation of genes responsible for the production of cutinase for the degradation of a biodegradable plastic, poly-(butylene succinate-co-adipate) (PBSA), in Aspergillus oryzae. The wild-type and the farA gene disruption strains were grown in minimal agar medium with emulsified PBSA, and the wild-type showed clear zone around the colonies while the disruptants did not. Western blot analysis revealed that the cutinase protein CutL1 and a hydrophobic surface binding protein such as HsbA were produced by the wild-type but not by the disruptants. In addition, the expressions of cutL1, triacylglycerol lipase (tglA), and mono- and di-acylglycerol lipase (mdlB) genes as well as the hsbA gene were significantly lower in the disruptants compared to the wild-type. These results indicated that the FarA transcriptional factor would be implicated in the expression of cutL1 and hsbA genes that are required for the degradation of PBSA as well as lipolytic genes such as mdlB and tglA for lipid hydrolysis.

  20. Spontaneous formation of hydrophobic domains in isolated peptides.

    PubMed

    Gloaguen, Eric; Loquais, Yohan; Thomas, Jessica A; Pratt, David W; Mons, Michel

    2013-05-02

    Aromatic amino acids are known for their hydrophobicity and the active role they play in protein folding. Here, we investigate the intrinsic propensity of small peptides to form hydrophobic domains in the absence of solvent water molecules. The structures of three aromatic-rich isolated peptides, Ac-Phe-Phe-NH2 (FF), Ac-Trp-Tyr-NH2 (WY), and Ac-Phe-Phe-Phe-NH2 (FFF), all in the gas phase, have been studied by infrared-ultraviolet (IR/UV) double resonance laser spectroscopy, aided by dispersion-corrected density functional theory (DFT-D) calculations. Spontaneous formation of hydrophobic domains is systematically observed, whatever the secondary structure adopted by the backbone. Various types of aromatic-aromatic arrangements have been identified and associated to specific secondary structures, illustrating the interplay between the hydrophobic clusters and the backbone. Backbone NH amide groups surrounded by aromatic rings have also been evidenced and are found to contribute significantly to the stabilization of aromatic pairs. These results suggest that the formation of aromatic clusters involving contiguous residues might be a very efficient process leading to the formation of hydrophobic domains in the early stages of protein folding, well before a hydrophobic collapse into the tertiary structure.

  1. Inverse colloidal crystal membranes for hydrophobic interaction membrane chromatography.

    PubMed

    Vu, Anh T; Wang, Xinying; Wickramasinghe, S Ranil; Yu, Bing; Yuan, Hua; Cong, Hailin; Luo, Yongli; Tang, Jianguo

    2015-08-01

    Hydrophobic interaction membrane chromatography has gained interest due to its excellent performance in the purification of humanized monoclonal antibodies. The membrane material used in hydrophobic interaction membrane chromatography has typically been commercially available polyvinylidene fluoride. In this contribution, newly developed inverse colloidal crystal membranes that have uniform pores, high porosity and, therefore, high surface area for protein binding are used as hydrophobic interaction membrane chromatography membranes for humanized monoclonal antibody immunoglobulin G purification. The capacity of the inverse colloidal crystal membranes developed here is up to ten times greater than commercially available polyvinylidene fluoride membranes with a similar pore size. This work highlights the importance of developing uniform pore size high porosity membranes in order to maximize the capacity of hydrophobic interaction membrane chromatography.

  2. Compositional fingerprint of soy sauces via hydrophobic surface interaction.

    PubMed

    Jakobi, Victoria; Salmen, Paul; Paulus, Michael; Tolan, Metin; Rosenhahn, Axel

    2017-03-01

    In this work, the interaction of soy sauces with hydrophobic surfaces has been analyzed. Hydrophobic self-assembled monolayers on gold or silicon dioxide were used to harvest conditioning layers from soy sauce products with varying amounts of additives. The data was compared to adsorption of soy protein and glutamic acid as common ingredients. Spectral ellipsometry revealed that all tested sauces led to the formation of thin overlayers on hydrophobic surfaces. Products with less additives yielded adlayers in the same thickness range as pure soy protein. In contrast, sauces with more ingredients create distinctly thicker films. Using water contact angle goniometry, it is shown that all adlayers render the substrate more hydrophilic. Infrared spectroscopy provided a deeper insight into the adlayer chemistry and revealed that the adlayer composition is dominated by protein rich components. X-ray reflectivity on selected films provided further insight into the density profiles within the adlayers on the molecular scale.

  3. LapF and Its Regulation by Fis Affect the Cell Surface Hydrophobicity of Pseudomonas putida

    PubMed Central

    Lahesaare, Andrio; Ainelo, Hanna; Teppo, Annika; Kivisaar, Maia; Heipieper, Hermann J.; Teras, Riho

    2016-01-01

    The ability of bacteria to regulate cell surface hydrophobicity is important for the adaptation to different environmental conditions. The hydrophobicity of cell surface can be determined by several factors, including outer membrane and surface proteins. In this study, we report that an adhesin LapF influences cell surface hydrophobicity of Pseudomonas putida. Cells lacking LapF are less hydrophobic than wild-type cells in stationary growth phase. Moreover, the overexpression of the global regulator Fis decreases surface hydrophobicity by repressing the expression of lapF. Flow cytometry analysis revealed that bacteria producing LapF are more viable when confronted with methanol (a hydrophilic compound) but are more susceptible to 1-octanol (a hydrophobic compound). Thus, these results revealed that LapF is the hydrophobicity factor for the cell surface of P. putida. PMID:27812186

  4. Dressings and Products in Pediatric Wound Care

    PubMed Central

    King, Alice; Stellar, Judith J.; Blevins, Anne; Shah, Kara Noelle

    2014-01-01

    Significance: The increasing complexity of medical and surgical care provided to pediatric patients has resulted in a population at significant risk for complications such as pressure ulcers, nonhealing surgical wounds, and moisture-associated skin damage. Wound care practices for neonatal and pediatric patients, including the choice of specific dressings or other wound care products, are currently based on a combination of provider experience and preference and a small number of published clinical guidelines based on expert opinion; rigorous evidence-based clinical guidelines for wound management in these populations is lacking. Recent Advances: Advances in the understanding of the pathophysiology of wound healing have contributed to an ever-increasing number of specialized wound care products, most of which are predominantly marketed to adult patients and that have not been evaluated for safety and efficacy in the neonatal and pediatric populations. This review aims to discuss the available data on the use of both more traditional wound care products and newer wound care technologies in these populations, including medical-grade honey, nanocrystalline silver, and soft silicone-based adhesive technology. Critical Issues: Evidence-based wound care practices and demonstration of the safety, efficacy, and appropriate utilization of available wound care dressings and products in the neonatal and pediatric populations should be established to address specific concerns regarding wound management in these populations. Future Directions: The creation and implementation of evidence-based guidelines for the treatment of common wounds in the neonatal and pediatric populations is essential. In addition to an evaluation of currently marketed wound care dressings and products used in the adult population, newer wound care technologies should also be evaluated for use in neonates and children. In addition, further investigation of the specific pathophysiology of wound healing in

  5. Quantum dress for a naked singularity

    NASA Astrophysics Data System (ADS)

    Casals, Marc; Fabbri, Alessandro; Martínez, Cristián; Zanelli, Jorge

    2016-09-01

    We investigate semiclassical backreaction on a conical naked singularity space-time with a negative cosmological constant in (2 + 1)-dimensions. In particular, we calculate the renormalized quantum stress-energy tensor for a conformally coupled scalar field on such naked singularity space-time. We then obtain the backreacted metric via the semiclassical Einstein equations. We show that, in the regime where the semiclassical approximation can be trusted, backreaction dresses the naked singularity with an event horizon, thus enforcing (weak) cosmic censorship.

  6. DRESS syndrome: à propos de trois observations

    PubMed Central

    Chebbi, Wafa; Souissi, Jihed; Chelli, Jihène; Larbi, Fatma; Zantour, Baha; Habib Sfar, Mohamed

    2014-01-01

    Le syndrome d'hypersensibilité médicamenteuse ou Drug Rash with Eosinophilia and Systemic Symptoms (DRESS) est une toxidermie rare mais sévère. Nous rapportons trois observations de DRESS syndromes secondaires à la prise de carbamazipine dans deux cas et de salazopyrine dans un cas. Le délai moyen entre la prise médicamenteuse et la survenue du DRESS syndrome était de six semaines. Le médicament incriminé était arrêté d'une façon définitive dans tous les cas. Une corticothérapie par voie générale était instaurée chez tous les patients devant l'atteinte hépatique sévère. L’évolution était favorable avec disparation des lésions cutanées et normalisation du bilan hépatique. Le diagnostic du syndrome DRESS doit être évoqué devant un tableau associant une éruption fébrile et des signes systémiques faisant suite à une prise médicamenteuse. La précocité du diagnostic est fondamentale pour l'arrêt définitif des médicaments suspects. Le traitement n'est pas bien codifié mais repose actuellement sur la corticothérapie générale. PMID:25810802

  7. Role of Surgical Dressings in Total Joint Arthroplasty: A Randomized Controlled Trial.

    PubMed

    Springer, Bryan D; Beaver, Walter B; Griffin, William L; Mason, J Bohannon; Odum, Susan M

    2015-09-01

    We conducted a randomized controlled trial to compare efficacy of an occlusive antimicrobial barrier dressing and a standard surgical dressing in patients who underwent primary total joint arthroplasty. Two hundred sixty-two patients were randomized to receive either an occlusive dressing or a standard dressing. Wounds were closed in identical fashion. Outcomes included wound complications, dressing changes, and patient satisfaction. With use of occlusive dressing (vs standard dressing), wound complications (including skin blistering) were significantly (P = 0.15) reduced; there were significantly (P < .0001) fewer dressing changes; and patient satisfaction was significantly (P < .0001) higher. Use of occlusive dressings can reduce wound complications and promote wound healing after total joint arthroplasty.

  8. Interaction of Hydrophobic Molecules with Heme Proteins

    DTIC Science & Technology

    1988-08-29

    tetracaine are capable of altering the spin state of the iron of myoglobin and cytochrome a3 of cytochrome oxidase. Tetracaine is a powerful...Cytochrome Oxidase Activity . H.J. Harmon and J. Swartz. American Society of Biological Chemists. June 9-12, 1986, Washington, D.C. 1987 Electron...May 2-6, 1988, Las Vegas. Published Articles 1. "Effect of Naphthalene on Cytochrome Oxidase Activity " H. James Harmon. Bull. Environ. Contam

  9. Interplay Between Hydrophobic Effect and Dipole Interactions in Peptide Aggregation

    NASA Astrophysics Data System (ADS)

    Ganesan, Sai; Matysiak, Silvina

    In the past decade, the development of various coarse-grained models for proteins have provided key insights into the driving forces in folding and aggregation.We recently developed a low resolution Water Explicit Polarizable PROtein coarse-grained Model by adding oppositely charged dummy particles inside protein backbone beads.With this model,we were able to achieve significant α/ β secondary structure content,without any added bias.We now extend the model to study peptide aggregation at hydrophobic-hydrophilic interface using elastin-like octapeptides (GV)4 as a model system.A condensation-ordering mechanism of aggregation is observed in water.Our results suggest that backbone interpeptide dipolar interactions,not hydrophobicity,plays a more significant role in fibril-like peptide aggregation.We observe a cooperative effect in hydrogen bonding or dipolar interactions, with increase in aggregate size in water and interface.Based on this cooperative effect, we provide a potential explanation for the observed nucleus size in peptide aggregation pathways.Without dipolar particles,peptide aggregation is not observed at the hydrophilic-hydrophobic interface.Thus,the presence of dipoles,not hydrophobicity plays a key role in aggregation observed at hydrophobic interfaces.

  10. Hydrophobic gating in ion channels.

    PubMed

    Aryal, Prafulla; Sansom, Mark S P; Tucker, Stephen J

    2015-01-16

    Biological ion channels are nanoscale transmembrane pores. When water and ions are enclosed within the narrow confines of a sub-nanometer hydrophobic pore, they exhibit behavior not evident from macroscopic descriptions. At this nanoscopic level, the unfavorable interaction between the lining of a hydrophobic pore and water may lead to stochastic liquid-vapor transitions. These transient vapor states are "dewetted", i.e. effectively devoid of water molecules within all or part of the pore, thus leading to an energetic barrier to ion conduction. This process, termed "hydrophobic gating", was first observed in molecular dynamics simulations of model nanopores, where the principles underlying hydrophobic gating (i.e., changes in diameter, polarity, or transmembrane voltage) have now been extensively validated. Computational, structural, and functional studies now indicate that biological ion channels may also exploit hydrophobic gating to regulate ion flow within their pores. Here we review the evidence for this process and propose that this unusual behavior of water represents an increasingly important element in understanding the relationship between ion channel structure and function.

  11. How does a hydrocarbon staple affect peptide hydrophobicity?

    PubMed

    Sim, Adelene Y L; Verma, Chandra

    2015-04-15

    Water is essential for the proper folding of proteins and the assembly of protein-protein/ligand complexes. How water regulates complex formation depends on the chemical and topological details of the interface. The dynamics of water in the interdomain region between an E3 ubiquitin ligase (MDM2) and three different peptides derived from the tumor suppressor protein p53 are studied using molecular dynamics. The peptides show bimodal distributions of interdomain water densities across a range of distances. The addition of a hydrocarbon chain to rigidify the peptides (in a process known as stapling) results in an increase in average hydrophobicity of the peptide-protein interface. Additionally, the hydrophobic staple shields a network of water molecules, kinetically stabilizing a water chain hydrogen-bonded between the peptide and MDM2. These properties could result in a decrease in the energy barrier associated with dehydrating the peptide-protein interface, thereby regulating the kinetics of peptide binding.

  12. Gentamicin-loaded wound dressing with polyvinyl alcohol/dextran hydrogel: gel characterization and in vivo healing evaluation.

    PubMed

    Hwang, Ma-Ro; Kim, Jong Oh; Lee, Jeong Hoon; Kim, Yong Il; Kim, Jeong Hoon; Chang, Sun Woo; Jin, Sung Gju; Kim, Jung Ae; Lyoo, Won Seok; Han, Sung Soo; Ku, Sae Kwang; Yong, Chul Soon; Choi, Han-Gon

    2010-09-01

    To develop a gentamicin-loaded wound dressing, cross-linked hydrogel films were prepared with polyvinyl alcohol (PVA) and dextran using the freezing-thawing method. Their gel properties such as gel fraction, swelling, water vapor transmission test, morphology, tensile strength, and thermal property were investigated. In vitro protein adsorption test, in vivo wound healing test, and histopathology were performed. Dextran decreased the gel fraction, maximum strength, and thermal stability of hydrogels. However, it increased the swelling ability, water vapor transmission rate, elasticity, porosity, and protein adsorption. The drug gave a little positive effect on the gel properties of hydrogels. The gentamicin-loaded wound dressing composed of 2.5% PVA, 1.13% dextran, and 0.1% drug was more swellable, flexible, and elastic than that with only PVA because of its cross-linking interaction with PVA. In particular, it could provide an adequate level of moisture and build up the exudates on the wound area. From the in vivo wound healing and histological results, this gentamicin-loaded wound dressing enhanced the healing effect more compared to conventional product because of the potential healing effect of gentamicin. Thus, this gentamicin-loaded wound dressing would be used as a potential wound dressing with excellent forming and improved healing effect in wound care.

  13. Managers, Teachers, Students, and Parents' Opinions Concerning Changes on Dress Code Practices as an Educational Policy

    ERIC Educational Resources Information Center

    Birel, Firat Kiyas

    2016-01-01

    Problem Statement: Dressing for school has been intensely disputed and has led to periodic changes in dress codes since the foundation of the Turkish republic. Practitioners have tried to put some new practices related to school dress codes into practice for redressing former dress code issues involving mandatory dress standards for both students…

  14. A vapour-permeable film dressing used on superficial wounds.

    PubMed

    Meuleneire, Frans

    2014-08-12

    Films are an extremely versatile dressing type that can be effectively used in the treatment of many superficial wounds, such as skin grafts, surgical wounds and superficial burns; they provide an optimal moist environment to promote healing, act as a barrier to bacteria, and afford protection from urine and faecal contamination. Unfortunately, many film dressings are difficult to handle and use traditional adhesives, which can cause trauma to the wound and surrounding skin, as well as increased wound pain at dressing removal. Mepitel® Film is a new, easy-to-use wound dressing designed with Safetac® technology that helps to minimise dressing-related trauma and pain and assist undisturbed wound healing. This article presents case studies that examine Mepitel Film's use on a variety of wounds, and reviews the findings of research that was undertaken to evaluate the benefits of using this recently developed dressing.

  15. Construction, application and biosafety of silver nanocrystalline chitosan wound dressing.

    PubMed

    Lu, Shuangyun; Gao, Wenjuan; Gu, Hai Ying

    2008-08-01

    A novel wound dressing composed of nano-silver and chitosan was fabricated using a nanometer and self-assembly technology. Sterility and pyrogen testing assessed biosafety, and efficacy was evaluated using Sprague-Dawley rats with deep partial-thickness wounds. Silver sulfadiazine and chitosan film dressings were used as controls. At intervals wound areas were measured, wound tissues biopsied and blood samples taken. Compared with the controls, the silver nanocrystalline chitosan dressing significantly (p<0.01) increased the rate of wound healing and was associated with silver levels in blood and tissues lower than levels associated with the silver sulfadiazine dressing (p<0.01). Sterility and pyrogen tests of the silver nanocrystalline chitosan dressing were negative. Thus this dressing should have wide application in clinical settings.

  16. Comparison of 10 Different Hemostatic Dressings in an Aortic Injury

    DTIC Science & Technology

    2003-02-01

    group (n 5) received suture repair (4-0 Prolene , Ethicon, Inc., Somerville, NJ). Two of the dressings were commercially available, Surgicel and Avitene...hole was closed using a continuous running suture with 4-0 cardiovascular Prolene suture with an atraumatic RB-1 half-circle needle. After the dressing...translucent polyglactin mesh /fibrin clot matrix (Fig. 2). No evidence of intralumi- nal clotting was observed in any animal for any of the dressings. Fig. 1

  17. Mafenide acetate solution dressings: an adjunct in burn wound care.

    PubMed

    Shuck, J M; Thorne, L W; Cooper, C G

    1975-07-01

    A continuation of the study of 5% aqueous Sulfamylon solution dressings in burned patients was analyzed in 150 consecutive cases. The rate of invasive infection and mortality was not excessive. Dressings were used as an adjunct to other topical chemotherapeutic agents as well as homo/heterograft skin in the overall burn care program. Sulfamylon soaks were shown to be effective for debridement, granulation tissue protection and preparation, and bacterial control. The dressings were comfortable when in place and the wounds appeared clean. Epithelialization was not hampered so that the dressings could be utilized in partial thickness wounds as well as for mesh autografts on extensive burn surfaces=

  18. Constructing medical social authority on dress in Victorian Canada.

    PubMed

    O'Connor, Eileen

    2008-01-01

    During the late-Victorian period, campaigns to "reform" middle-class women's dress were grounded in discourses on health, eugenics, declining birth rates, comfort, and aesthetics. In Britain, the United States and Germany, organized "dress reform" movements emerged in the latter half of the 19th century, while in Canada the campaign was led primarily by physicians through public health education. This article explores the discussion on women's dress in public health literature in Canadian circulation between 1860-1900 and interprets findings within a feminist poststructuralist framework that posits the understanding of women's bodies and gender regulation to be central to knowledge construction on women's dress.

  19. The role of dressings in the prevention of pressure ulcers.

    PubMed

    Brown, Julie

    2016-08-11

    Pressure ulceration is a significant global healthcare problem and represents a considerable burden on healthcare resources. Within the literature an increasing number of studies have examined the role prophylactic dressings play in redistributing pressure and helping to protect the skin from the effects of friction and shear. The use of dressings to prevent pressure ulcers may be considered a controversial issue, as previous opinion has been that dressings do not reduce the effects of pressure. This article will critically evaluate the literature to examine the role dressings play in the prevention of pressure ulceration.

  20. Dress Nicer = Know More? Young Children’s Knowledge Attribution and Selective Learning Based on How Others Dress

    PubMed Central

    McDonald, Kyla P.; Ma, Lili

    2015-01-01

    This research explored whether children judge the knowledge state of others and selectively learn novel information from them based on how they dress. The results indicated that 4- and 6-year-olds identified a formally dressed individual as more knowledgeable about new things in general than a casually dressed one (Study 1). Moreover, children displayed an overall preference to seek help from a formally dressed individual rather than a casually dressed one when learning about novel objects and animals (Study 2). These findings are discussed in relation to the halo effect, and may have important implications for child educators regarding how instructor dress might influence young students’ knowledge attribution and learning preferences. PMID:26636980

  1. Prototype Development of a Responsive Emotive Sensing System (DRESS) to aid older persons with dementia to dress independently

    PubMed Central

    Mahoney, Diane Feeney; Burleson, Winslow; Lozano, Cecil; Ravishankar, Vijay; Mahoney, Edward Leo

    2015-01-01

    Background Prior research has critiqued the lack of attention to the stressors associated with dementia related dressing issues, stigmatizing patient clothing, and wearable technology challenges. This paper describes the conceptual development and feasibility testing of an innovative ‘smart dresser’ context aware affective system (DRESS) to enable dressing by people with moderate memory loss through individualized audio and visual task prompting in real time. Methods Mixed method feasibility study involving qualitative focus groups with 25 Alzheimer’s family caregivers experiencing dressing difficulties to iteratively inform system design and a quantitative usability trial with 10 healthy subjects in a controlled laboratory setting to assess validity of technical operations. Results Caregivers voiced the need for tangible dressing assistance to reduce their frustration from time spent in repetitive cueing and power struggles over dressing. They contributed 6 changes that influenced the prototype development, most notably adding a dresser top iPad to mimic a familiar ‘TV screen’ for the audio and visual cueing. DRESS demonstrated promising overall functionality, however the validity of identification of dressing status ranged from 0% for the correct pants dressing to 100% for all shirts dressing scenarios. Adjustments were made to the detection components of the system raising the accuracy of detection of all acted dressing scenarios for pants from 50% to 82%. Conclusions Findings demonstrate family caregiver acceptability of the proposed system, the successful interoperability of the built system’s components, and the system’s ability to interpret correct and incorrect dressing actions in controlled laboratory simulations. Future research will advance the system to the alpha stage and subsequent testing with end users in real world settings. PMID:26321895

  2. Autoactivation of blood factor XII at hydrophilic and hydrophobic surfaces.

    PubMed

    Zhuo, Rui; Siedlecki, Christopher A; Vogler, Erwin A

    2006-08-01

    Contact activation of blood factor XII (FXII, Hageman factor) in neat-buffer solution is shown not to be specific for anionic hydrophilic procoagulants as proposed by the accepted biochemistry of surface activation. Rather, FXII activation in the presence of plasma proteins leads to an apparent specificity for hydrophilic surfaces that is actually due to a relative diminution of the FXII-->FXIIa reaction at hydrophobic surfaces. FXII activation in neat-buffer solution was effectively instantaneous upon contact with either hydrophilic (fully water-wettable clean glass) or hydrophobic (poorly water-wettable silanized glass) procoagulant particles, with greater FXIIa yield obtained by activation with hydrophobic procoagulants. In sharp contrast, both activation rate and yield was found to be significantly attenuated at hydrophobic surfaces in the presence of plasma proteins. Putative FXIIa produced by surface activation with both hydrophilic and hydrophobic procoagulants was shown to hydrolyze blood factor XI (FXI) to the activated form FXIa (FXIFXIIa-->FXIa) that causes FXI-deficient plasma to rapidly coagulate.

  3. Molecular origins of fluorocarbon hydrophobicity

    PubMed Central

    Dalvi, Vishwanath H.; Rossky, Peter J.

    2010-01-01

    We have undertaken atomistic molecular simulations to systematically determine the structural contributions to the hydrophobicity of fluorinated solutes and surfaces compared to the corresponding hydrocarbon, yielding a unified explanation for these phenomena. We have transformed a short chain alkane, n-octane, to n-perfluorooctane in stages. The free-energy changes and the entropic components calculated for each transformation stage yield considerable insight into the relevant physics. To evaluate the effect of a surface, we have also conducted contact-angle simulations of water on self-assembled monolayers of hydrocarbon and fluorocarbon thiols. Our results, which are consistent with experimental observations, indicate that the hydrophobicity of the fluorocarbon, whether the interaction with water is as solute or as surface, is due to its “fatness.” In solution, the extra work of cavity formation to accommodate a fluorocarbon, compared to a hydrocarbon, is not offset by enhanced energetic interactions with water. The enhanced hydrophobicity of fluorinated surfaces arises because fluorocarbons pack less densely on surfaces leading to poorer van der Waals interactions with water. We find that interaction of water with a hydrophobic solute/surface is primarily a function of van der Waals interactions and is substantially independent of electrostatic interactions. This independence is primarily due to the strong tendency of water at room temperature to maintain its hydrogen bonding network structure at an interface lacking hydrophilic sites. PMID:20643968

  4. Hydrophobic Solvation: Aqueous Methane Solutions

    ERIC Educational Resources Information Center

    Konrod, Oliver; Lankau, Timm

    2007-01-01

    A basic introduction to concept of a solvation shell around an apolar solute as well as its detection is presented. The hydrophobic solvation of toluene is found to be a good teaching example which connects macroscopic, phenomenological thermodynamic results with an atomistic point of view.

  5. [Wound healing and wound dressing].

    PubMed

    Eitel, F; Sklarek, J

    1988-01-01

    This review article intends to discuss the clinical management of wounds in respect to a pathophysiological background. Recent results of research in the field of wound healing are demonstrated. Wound healing can be seen as aseptic inflammatory response to a traumatic stimulus. The activation of the clotting cascade by the trauma induces a sequence of humoral and cellular reactions. Platelets, granulocytes and macrophages are activated stepwisely. In the first phase of wound healing the wounded tissue area will be prepared for phagocytosis by enzymatic degradation of ground substance and depolymerisation of protein macromolecules (wound edema). Following the phagocytic microdebridement mesenchymal cells proliferate and produce matrix substance. Microcirculation within the traumatized area will be restored by angiogenesis, macroscopically observed as new formed granulation tissue. This leads to the wound healing phase of scar tissue formation. In this complexity of reactions naturally many possibilities of impairment are given. The most common complication during wound healing is the infection. It can be seen as self reinforcing process. The therapy of the impairment of wound healing consists in the disruption of the specific vicious circle, in the case of an osseus infection that would be a macrodebridement (that is necrectomy) and biomechanical stabilization. The surgical management of wounds principally consists in ensuring an undisturbed sequence of the healing process. This can be done by the wound excision that supports the phagocytic microdebridement. A further possibility is to avoid overwhelming formation of edema by eliminating the traumatic stimulus, by immobilization of the injured region and by ensuring a physiological microenvironment with a primary suture if possible. There are up to the present no drugs available to enhance cell proliferation and to regulate wound healing but it seems that experimental research is successful in characterizing

  6. One Dress, Two Dress: Dialectal Influence on Spelling of English Words among Kindergarten Children in Singapore

    ERIC Educational Resources Information Center

    Dixon, L. Quentin; Zhao, Jing; Joshi, R. Malatesha

    2012-01-01

    The present study examined the influence of Singapore Colloquial English (SCE) on Standard English word spelling through a plural formation task of four words ("man", "tooth", "dress" and "child") among 168 Singaporean bilingual children with Chinese background. It was found that "dropping the…

  7. An Inexpensive Bismuth-Petrolatum Dressing for Treatment of Burns

    PubMed Central

    Chattopadhyay, Arhana; Chang, Kathleen; Nguyen, Khoa; Galvez, Michael G.; Legrand, Anais; Davis, Christopher; McGoldrick, Rory; Long, Chao; Pham, Hung

    2016-01-01

    Background: Xeroform remains the current standard for treating superficial partial-thickness burns but can be prohibitively expensive in developing countries with prevalent burn injuries. This study (1) describes the production of an alternative low-cost dressing and (2) compares the alternative dressing and Xeroform using the metrics of cost-effectiveness, antimicrobial activity, and biocompatibility in vitro, and wound healing in vivo. Methods: To produce the alternative dressing, 3% bismuth tribromophenate powder was combined with petroleum jelly by hand and applied to Kerlix gauze. To assess cost-effectiveness, the unit costs of Xeroform and components of the alternative dressing were compared. To assess antimicrobial properties, the dressings were placed on agar plated with Escherichia coli and the Kirby-Bauer assay performed. To assess biocompatibility, the dressings were incubated with human dermal fibroblasts and cells stained with methylene blue. To assess in vivo wound healing, dressings were applied to excisional wounds on rats and the rate of re-epithelialization calculated. Results: The alternative dressing costs 34% of the least expensive brand of Xeroform. Antimicrobial assays showed that both dressings had similar bacteriostatic effects. Biocompatibility assays showed that there was no statistical difference (P < 0.05) in the cytotoxicity of Xeroform, alternative dressing, and Kerlix gauze. Finally, the in vivo healing model showed no statistical difference (P < 0.05) in mean re-epithelialization time between Xeroform (13.0 ± 1.6 days) and alternative dressing (13.5 ± 1.0 days). Conclusions: Xeroform is biocompatible, reduces infection, and enhances healing of burn wounds by preventing desiccation and mechanical trauma. Handmade petrolatum gauze may be a low-cost replacement for Xeroform. Future studies will focus on clinical trials in burn units. PMID:27482485

  8. Effects of TLC-Ag dressings on skin inflammation.

    PubMed

    Bisson, Jean-François; Hidalgo-Lucas, Sophie; Bouschbacher, Marielle; Thomassin, Laetitia

    2013-06-01

    The TLC-Ag dressings, a combination of technology lipido-colloid and silver salts, are used to promote healing in wounds with risks or signs of local infection, thanks to the antimicrobial properties of the silver salts. Nanocrystalline silver dressings containing nanocrystalline silver, also used to improve wound healing, present both antimicrobial and anti-inflammatory effects. The aim of this study was to investigate the anti-inflammatory effects of TLC-Ag dressings in a model of chronic skin inflammation induced by repeated application of 12-O-tetradecanoylphorbol-13-acetate to the skin of hairless mice, in comparison with TLC dressing, Silcryst nanocrystalline dressing, desonide cream 0.05%, a corticoid cream used as positive control, and gauze. Daily treatments of the mice began 7 days after the start of induction of chronic skin inflammation and lasted for 7 days. A macroscopic score was performed daily during the treatment period until the mice killing on day 15 and skin samples were taken for histopathological analysis. TLC-Ag reduced significantly the macroscopic score of chronic skin inflammation from day 10 in comparison with gauze and TLC dressing, similarly to Silcryst nanocrystalline dressing and desonide cream, which presented the best anti-inflammatory effects. No significant differences were observed between TLC dressing and gauze. TLC-Ag reduced significantly the microscopic score of chronic skin inflammation in comparison with TLC dressing and gauze, similarly to Silcryst nanocrystalline dressing but significantly less than desonide cream. These results demonstrate that TLC-Ag dressings present significant anti-inflammatory effects on chronic skin inflammation. They can improve wound healing, due to both the antimicrobial and anti-inflammatory properties.

  9. [DRESS syndrome. A clinical case report].

    PubMed

    Muciño-Bermejo, Jimena; Díaz de León-Ponce, Manuel; Briones-Vega, Carlos Gabriel; Guerrero-Hernández, Antonio; Sandoval-Ayala, Oswaldo Israel; Sáenz-Coronado, Ana Gabriela; Briones-Garduño, Jesús Carlos

    2013-01-01

    Introducción: el síndrome de DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) o la reacción a fármacos con eosinofilia y síntomas sistémicos es una reacción medicamentosa grave, asociada al uso de anticonvulsivos aromáticos y alopurinol. Se han descrito por lo menos 44 fármacos asociados a DRESS. El propósito es presentar el caso clínico de una paciente con síndrome de DRESS asociado a fenitoína. Caso clínico: paciente femenina de 20 años, con antecedente de crisis convulsivas desde la infancia, durante tres meses previos presentó crisis convulsivas tónico-clónicas generalizadas, por lo que inició tratamiento con fenitoína: 100 mg vía oral cada 8 horas. Tres semanas después presentó fiebre de hasta 42 grados, pápulas en manos con extensión a tronco y extremidades, rubicundez generalizada, prurito, dolor al orinar, además de hiporexia, disfagia y tos seca, por lo que acudió al servicio de urgencias. Discusión: el diagnóstico es clínico y se establece según los criterios de la escala de RegiSCAR. Debido a que las manifestaciones iniciales son poco específicas, el diagnóstico y el tratamiento definitivo pueden retrasarse. La importancia del reconocimiento y tratamiento temprano de esta entidad radica en la incidencia de mortalidad de hasta 10 %.

  10. Large energy superpositions via Rydberg dressing

    NASA Astrophysics Data System (ADS)

    Khazali, Mohammadsadegh; Lau, Hon Wai; Humeniuk, Adam; Simon, Christoph

    2016-08-01

    We propose to create superposition states of over 100 strontium atoms in a ground state or metastable optical clock state using the Kerr-type interaction due to Rydberg state dressing in an optical lattice. The two components of the superposition can differ by an order of 300 eV in energy, allowing tests of energy decoherence models with greatly improved sensitivity. We take into account the effects of higher-order nonlinearities, spatial inhomogeneity of the interaction, decay from the Rydberg state, collective many-body decoherence, atomic motion, molecular formation, and diminishing Rydberg level separation for increasing principal number.

  11. 40 CFR 94.907 - Engine dressing exemption.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Engine dressing exemption. 94.907... (CONTINUED) CONTROL OF EMISSIONS FROM MARINE COMPRESSION-IGNITION ENGINES Exclusion and Exemption Provisions § 94.907 Engine dressing exemption. (a) General provisions. If you are an engine manufacturer,...

  12. 40 CFR 94.907 - Engine dressing exemption.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 20 2014-07-01 2013-07-01 true Engine dressing exemption. 94.907... (CONTINUED) CONTROL OF EMISSIONS FROM MARINE COMPRESSION-IGNITION ENGINES Exclusion and Exemption Provisions § 94.907 Engine dressing exemption. (a) General provisions. If you are an engine manufacturer,...

  13. 40 CFR 94.907 - Engine dressing exemption.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 21 2012-07-01 2012-07-01 false Engine dressing exemption. 94.907... (CONTINUED) CONTROL OF EMISSIONS FROM MARINE COMPRESSION-IGNITION ENGINES Exclusion and Exemption Provisions § 94.907 Engine dressing exemption. (a) General provisions. If you are an engine manufacturer,...

  14. Will Dress Codes Save the Schools? Teaching Strategy.

    ERIC Educational Resources Information Center

    Alvez, Aggie

    1994-01-01

    Discusses issues related to dress codes, student behavior, and youth gangs. Presents a role-playing activity based on a proposed dress code aimed at gang-related clothing in a secondary school. Includes two student handouts and step-by-step instructional procedures. (CFR)

  15. Civil Behavior, Safe-School Planning, and Dress Codes

    ERIC Educational Resources Information Center

    Studak, Cathryn M.; Workman, Jane E.

    2007-01-01

    This research examined news reports in order to identify incidents that precipitated dress code revisions. News reports were examined within the framework of rules for civil behavior. Using key words "school dress codes" and "violence," LEXIS/NEXIS was used to access 104 articles from 44 U.S. newspapers from December 3, 2004 to December 2, 2005.…

  16. Marine Maternity Dress Uniform Tunic, Skirt, and Slack Technical Report

    DTIC Science & Technology

    2007-11-02

    military apparel items. The Cal Poly Demo produces military items in small quantities and used the Marine Maternity Dress Uniform Tunic , Skirt and Slack as...one of its study subjects. This report includes the findings of the study for the Demo’s Year 3 manufacturing of the Marine Maternity Dress Uniform Tunic , Skirt and Slack.

  17. Inhibition of Pseudomonas aeruginosa biofilm formation on wound dressings

    PubMed Central

    Brandenburg, Kenneth S.; Calderon, Diego F.; Kierski, Patricia R.; Brown, Amanda L.; Shah, Nihar M.; Abbott, Nicholas L.; Schurr, Michael J.; Murphy, Christopher J.; McAnulty, Jonathan F.; Czuprynski, Charles J.

    2016-01-01

    Chronic non-healing skin wounds often contain bacterial biofilms that prevent normal wound healing and closure and present challenges to the use of conventional wound dressings. We investigated inhibition of Pseudomonas aeruginosa biofilm formation, a common pathogen of chronic skin wounds, on a commercially available biological wound dressing. Building upon prior reports, we examined whether the amino acid tryptophan would inhibit P. aeruginosa biofilm formation on the 3-dimensional surface of the biological dressing. Bacterial biomass and biofilm polysaccharides were quantified using crystal violet staining or an enzyme linked lectin, respectively. Bacterial cells and biofilm matrix adherent to the wound dressing were visualized through scanning electron microscopy. D-/L-tryptophan inhibited P. aeruginosa biofilm formation on the wound dressing in a dose dependent manner and was not directly cytotoxic to immortalized human keratinocytes although there was some reduction in cellular metabolism or enzymatic activity. More importantly, D-/L-tryptophan did not impair wound healing in a splinted skin wound murine model. Furthermore, wound closure was improved when D-/L-tryptophan treated wound dressing with P. aeruginosa biofilms were compared with untreated dressings. These findings indicate that tryptophan may prove useful for integration into wound dressings to inhibit biofilm formation and promote wound healing. PMID:26342168

  18. The Role of Dress Codes, Uniforms in Urban Schools.

    ERIC Educational Resources Information Center

    LaPoint, Velma; And Others

    1992-01-01

    In response to problems relating to student appearance, dress, and behavior, most urban schools use various kinds of dress codes or uniforms. African-American youth experience difficulties because of a cultural heritage favoring bold designs and bright colors, efforts to compensate for low socioeconomic status, consumerist exploitation, and…

  19. Fashion as Argument: Nineteenth-Century Dress Reform.

    ERIC Educational Resources Information Center

    Torrens, Kathleen M.

    1999-01-01

    Examines the place of the body in the dress-reform movement, a social movement that focused on fashion as a vehicle for achieving social and political equality. Discusses how fashion became one arena in which definitions of gender were contested. Suggests the dress-reform movement's failure in redefining femininity indicates the depth of…

  20. Umbilical Negative Pressure Dressing for Transumbilical Appendectomy in Childern

    PubMed Central

    Kundu, Neilendu; Guerron, Alfredo D.; Garland, Mary M.; Gaffley, Michaela W. G.; Worley, Sarah; Knight, Colin G.

    2016-01-01

    Background and Objectives: Transumbilical laparoscopic-assisted appendectomy (TULAA) carries a high risk for surgical site infection. We investigated the effect of a bio-occlusive umbilical vacuum dressing on wound infection rates after TULAA for patients with acute appendicitis and compared to it with a conventional 3-port appendectomy with a nonvacuum dressing. Methods: This study was a retrospective chart review of 1377 patients (2–20 years) undergoing laparoscopic appendectomy for acute appendicitis in 2 tertiary care referral centers from January 2007 through December 2012. Twenty-two different operative technique/dressing variations were documented. The 6 technique/dressing groups with >50 patients were assessed, including a total of 1283 patients. Results: The surgical site infection rate of the 220 patients treated with TULAA and application of an umbilical vacuum dressing with dry gauze is 1.8% (95% CI, 0.0–10.3%). This compares to an infection rate of 4.1% (95% CI, 1.3–10.5%) in 97 patients with dry dressing without vacuum. In the 395 patients who received an umbilical vacuum dressing with gauze and bacitracin, the surgical site infection rate was found to be 4.3% (95% CI, 2.7–6.8%). Conclusions: Application of an umbilical negative-pressure dressing with dry gauze lowers the rate of umbilical site infections in patients undergoing transumbilical laparoscopic-assisted appendectomy for acute appendicitis. PMID:27807398

  1. Uniforms and Dress-Code Policies. ERIC Digest Number 148.

    ERIC Educational Resources Information Center

    Lumsden, Linda

    This digest examines schools' dress-code policies and discusses the legal considerations and research findings about the effects of such changes. Most revisions to dress codes involve the use of uniforms, typically as a way to curb school violence and create a positive learning environment. A recent survey of secondary school principals found that…

  2. DRESS Syndrome Following Levofloxacin Exposure With Positive Patch-test.

    PubMed

    Charfi, Ons; Lakhoua, Ghozlane; Sahnoun, Rim; Badri, Talel; Daghfous, Riadh; El Aidli, Sihem; Kastalli, Sarah; Zaïem, Ahmed

    2015-01-01

    Drug rash with eosinophilia and systemic symptoms (DRESS syndrome) in a severe cutaneous drug reaction, which can be life threatening. Levofloxacin has not been reported in literature as a causative drug. We are presenting an exceptional case of levofloxacin-induced DRESS without eosinophilia and with positive patch-tests to levofloxacin.

  3. Identification of Workplace Dress by Low-Income Job Seekers

    ERIC Educational Resources Information Center

    Saiki, Diana

    2013-01-01

    The author examined how low-income job seekers participating in a workplace dress program identified traditional business and business casual dress. Seventy low-income job seekers identified clothing items as traditional business (e.g., suits, ties), similar to identifications made by professionals and image consultants in previous literature.…

  4. Dressing Techniques for Children Who Have Cerebral Palsy.

    ERIC Educational Resources Information Center

    Klein, Marsha Dunn

    This pamphlet offers general rules and specific suggestions for people who are dressing children with cerebral palsy. Common dressing problems are examined, such as the child becoming stiff, crossing the legs, or curling the toes, and possible solutions are outlined step-by-step and accompanied by illustrations. Guidelines are also provided for…

  5. Moral Crisis in Higher Institutions and the Dress Code Phenomenon

    ERIC Educational Resources Information Center

    Fayokun, K. O.; Adedeji, S. O.; Oyebade, S. A.

    2009-01-01

    This article reviewed the case of indecent dressing among the youth of today especially on the universities campuses, which has forced the authorities of those institutions to enact dress codes to stem the tide and restore high moral standards, integrity and decency. Whether this bid was successful or not was another thing which was a function of…

  6. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  7. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  8. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  9. The Dewetting Transition and The Hydrophobic Effect.

    SciTech Connect

    Choudhury, Niharendu; Pettitt, Bernard M.

    2007-03-27

    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. A molecular-level description of the behavior of water in hydrophobic spaces is presented in terms of the coupled effects of solute size and atomic solute-solvent interactions. For model solutes with surface areas near those of protein contacts, we identify three different regions of solute-water interaction to be associated with three distinctly different structural characteristics of water in the intersolute region: dry, oscillating, and wet. A first orderlike phase transition is confirmed from the wet to dry state bridged by a narrow region with liquid-vapor oscillations in the intersolute region as the strength of the solute-water attractive dispersion interaction decreases. We demonstrate that the recent idea that cavitation in the intersolute region of nanoscopic solutes is preceded by the formation of a vapor layer around an individual solute is not the general case. The appearance of density waves pulled up around and outside of a nanoscopic plate occurs at lower interaction strengths than are required to obtain a wet state between such plates. We further show that chemically reasonable estimates of the interaction strength lead to a microscopically wet state and a hydrophobic interaction characterized by traps and barriers to association and not by vacuum induced collapse.

  10. Single water entropy: hydrophobic crossover and application to drug binding.

    PubMed

    Sasikala, Wilbee D; Mukherjee, Arnab

    2014-09-11

    Entropy of water plays an important role in both chemical and biological processes e.g. hydrophobic effect, molecular recognition etc. Here we use a new approach to calculate translational and rotational entropy of the individual water molecules around different hydrophobic and charged solutes. We show that for small hydrophobic solutes, the translational and rotational entropies of each water molecule increase as a function of its distance from the solute reaching finally to a constant bulk value. As the size of the solute increases (0.746 nm), the behavior of the translational entropy is opposite; water molecules closest to the solute have higher entropy that reduces with distance from the solute. This indicates that there is a crossover in translational entropy of water molecules around hydrophobic solutes from negative to positive values as the size of the solute is increased. Rotational entropy of water molecules around hydrophobic solutes for all sizes increases with distance from the solute, indicating the absence of crossover in rotational entropy. This makes the crossover in total entropy (translation + rotation) of water molecule happen at much larger size (>1.5 nm) for hydrophobic solutes. Translational entropy of single water molecule scales logarithmically (Str(QH) = C + kB ln V), with the volume V obtained from the ellipsoid of inertia. We further discuss the origin of higher entropy of water around water and show the possibility of recovering the entropy loss of some hypothetical solutes. The results obtained are helpful to understand water entropy behavior around various hydrophobic and charged environments within biomolecules. Finally, we show how our approach can be used to calculate the entropy of the individual water molecules in a protein cavity that may be replaced during ligand binding.

  11. A new postoperative otoplasty dressing technique using cyanoacrylate tissue adhesives.

    PubMed

    Vetter, Miriam; Foehn, Matthias; Wedler, Volker

    2010-04-01

    There are many techniques for cosmetic surgery of the ears and also many different procedures for postoperative treatment. The postoperative dressing is described as important for a successful outcome. We present our method of postoperative dressing in the form of liquid bonding. Cyanoacrylate tissue adhesives as liquid bonding agents are used for fixation of the pinna at the mastoid area. After 10-14 days the bonding can be easily removed. No huge dressings, tapes, or plasters are necessary. The patients are satisfied with the light dressing; they do not feel ashamed to appear in public. We have found this dressing technique to be simple and economical, especially because of the use of the bonding for skin closure before. It can be used after otoplasty with an anterior or a posterior approach.

  12. Dressed State Description of Bichromatic Forces

    NASA Astrophysics Data System (ADS)

    Metcalf, H. J.

    1998-05-01

    In the usual scheme of laser cooling both the force and the dissipation arise from the incoherent sequence of absorption followed by spontaneous emission. By contrast, the bichromatic force derives from a carefully orchestrated sequence of absorptions followed by stimulated emissions that are equivalent to a series of Landau-Zener transitions between dressed states. The magnitude is F ~= hbar k Ω_R/π instead of hbar k γ/2, where ΩR is the Rabi frequency, so this unsaturable force can easily be 10 to 100 times larger than hbar k γ/2. For atoms moving at v >> γ/k in a standing wave, its two counterpropagating components are Doppler shifted by ± kv, and each of the customary pairs of dressed states of slowly moving atoms (i.e., v ~ γ/k) is transformed into a ladder of levels separated by hbar kv >> hbar γ. If the amplitude of each standing wave component is modulated by beats arising because each contains two frequencies, Landau-Zener transitions can drive the atom-field system up this ladder very efficiently, thereby transferring atomic kinetic energy to the light field. Sisyphus cooling and the MOT characterize multilevel atoms in a monochromatic field. It appears that there may be a comparable plethora of new phenomena for two level atoms in bichromatic fields. Recently there was a dramatic demonstration of bichromatic deceleration of an atomic beam(J. Söding et al., Phys. Rev. Lett. 78) 1420 (1997).

  13. Hydrophobic pocket targeting probes for enteroviruses

    NASA Astrophysics Data System (ADS)

    Martikainen, Mari; Salorinne, Kirsi; Lahtinen, Tanja; Malola, Sami; Permi, Perttu; Häkkinen, Hannu; Marjomäki, Varpu

    2015-10-01

    Visualization and tracking of viruses without compromising their functionality is crucial in order to understand virus targeting to cells and tissues, and to understand the subsequent subcellular steps leading to virus uncoating and replication. Enteroviruses are important human pathogens causing a vast number of acute infections, and are also suggested to contribute to the development of chronic diseases like type I diabetes. Here, we demonstrate a novel method to target site-specifically the hydrophobic pocket of enteroviruses. A probe, a derivative of Pleconaril, was developed and conjugated to various labels that enabled the visualization of enteroviruses under light and electron microscopes. The probe mildly stabilized the virus particle by increasing the melting temperature by 1-3 degrees, and caused a delay in the uncoating of the virus in the cellular endosomes, but could not however inhibit the receptor binding, cellular entry or infectivity of the virus. The hydrophobic pocket binding moiety of the probe was shown to bind to echovirus 1 particle by STD and tr-NOESY NMR methods. Furthermore, binding to echovirus 1 and Coxsackievirus A9, and to a lesser extent to Coxsackie virus B3 was verified by using a gold nanocluster labeled probe by TEM analysis. Molecular modelling suggested that the probe fits the hydrophobic pockets of EV1 and CVA9, but not of CVB3 as expected, correlating well with the variations in the infectivity and stability of the virus particles. EV1 conjugated to the fluorescent dye labeled probe was efficiently internalized into the cells. The virus-fluorescent probe conjugate accumulated in the cytoplasmic endosomes and caused infection starting from 6 hours onwards. Remarkably, before and during the time of replication, the fluorescent probe was seen to leak from the virus-positive endosomes and thus separate from the capsid proteins that were left in the endosomes. These results suggest that, like the physiological hydrophobic content

  14. Recent experimental advances on hydrophobic interactions at solid/water and fluid/water interfaces.

    PubMed

    Zeng, Hongbo; Shi, Chen; Huang, Jun; Li, Lin; Liu, Guangyi; Zhong, Hong

    2015-03-15

    Hydrophobic effects play important roles in a wide range of natural phenomena and engineering processes such as coalescence of oil droplets in water, air flotation of mineral particles, and folding and assembly of proteins and biomembranes. In this work, the authors highlight recent experimental attempts to reveal the physical origin of hydrophobic effects by directly quantifying the hydrophobic interaction on both solid/water and fluid/water interfaces using state-of-art nanomechanical techniques such as surface forces apparatus and atomic force microscopy (AFM). For solid hydrophobic surfaces of different hydrophobicity, the range of hydrophobic interaction was reported to vary from ∼10 to >100 nm. With various characterization techniques, the very long-ranged attraction (>100 nm) has been demonstrated to be mainly attributed to nonhydrophobic interaction mechanisms such as pre-existing nanobubbles and molecular rearrangement. By ruling out these factors, intrinsic hydrophobic interaction was measured to follow an exponential law with decay length of 1-2 nm with effective range less than 20 nm. On the other hand, hydrophobic interaction measured at fluid interfaces using AFM droplet/bubble probe technique was found to decay with a much shorter length of ∼0.3 nm. This discrepancy of measured decay lengths is proposed to be attributed to inherent physical distinction between solid and fluid interfaces, which impacts the structure of interface-adjacent water molecules. Direct measurement of hydrophobic interaction on a broader range of interfaces and characterization of interfacial water molecular structure using spectroscopic techniques are anticipated to help unravel the origin of this rigidity-related mismatch of hydrophobic interaction and hold promise to uncover the physical nature of hydrophobic effects. With improved understanding of hydrophobic interaction, intrinsic interaction mechanisms of many biological and chemical pathways can be better

  15. Hydrophobic effect at aqueous interfaces

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew

    2005-01-01

    Conceptual basis for hydrophobic effects in bulk water and at aqueous interfaces have similar conceptual basis but often manifests itself differently. Using a wide range of computer simulations as the basis, I will review different forms of hydrophobic effects at a variety of interfaces starting from simple liquid-vapor and water-oil interfaces and progressing to water-membrane interfaces. I will start with discussing how water is organized at different interfaces, stressing both similarities and differences. The main thread is that, as in the bulk liquid, hydrophobic effects have profound influence on conformational equilibria and organization of both small molecules and macromolecules, but the result of this influence is quite different. Specifically, it will be shown that many small, but not necessarily amphiphilic molecules tend to accumulate at the interface and, and this tendency will be explained. Furthermore, I will show that many short peptides that are disordered in water spontaneously fold into well-defined structures in the interfacial environment. Biological implications of this self-organizing effect will be discussed.

  16. Predicting Enzyme Adsorption to Lignin Films by Calculating Enzyme Surface Hydrophobicity*

    PubMed Central

    Sammond, Deanne W.; Yarbrough, John M.; Mansfield, Elisabeth; Bomble, Yannick J.; Hobdey, Sarah E.; Decker, Stephen R.; Taylor, Larry E.; Resch, Michael G.; Bozell, Joseph J.; Himmel, Michael E.; Vinzant, Todd B.; Crowley, Michael F.

    2014-01-01

    The inhibitory action of lignin on cellulase cocktails is a major challenge to the biological saccharification of plant cell wall polysaccharides. Although the mechanism remains unclear, hydrophobic interactions between enzymes and lignin are hypothesized to drive adsorption. Here we evaluate the role of hydrophobic interactions in enzyme-lignin binding. The hydrophobicity of the enzyme surface was quantified using an estimation of the clustering of nonpolar atoms, identifying potential interaction sites. The adsorption of enzymes to lignin surfaces, measured using the quartz crystal microbalance, correlates to the hydrophobic cluster scores. Further, these results suggest a minimum hydrophobic cluster size for a protein to preferentially adsorb to lignin. The impact of electrostatic contribution was ruled out by comparing the isoelectric point (pI) values to the adsorption of proteins to lignin surfaces. These results demonstrate the ability to predict enzyme-lignin adsorption and could potentially be used to design improved cellulase cocktails, thus lowering the overall cost of biofuel production. PMID:24876380

  17. Hydrophobic-Core Microcapsules and Their Formation

    NASA Technical Reports Server (NTRS)

    Calle, Luz M. (Inventor); Li, Wenyan (Inventor); Buhrow, Jerry W. (Inventor); Jolley, Scott T. (Inventor)

    2016-01-01

    Hydrophobic-core microcapsules and methods of their formation are provided. A hydrophobic-core microcapsule may include a shell that encapsulates a hydrophobic substance with a core substance, such as dye, corrosion indicator, corrosion inhibitor, and/or healing agent, dissolved or dispersed therein. The hydrophobic-core microcapsules may be formed from an emulsion having hydrophobic-phase droplets, e.g., containing the core substance and shell-forming compound, dispersed in a hydrophilic phase. The shells of the microcapsules may be capable of being broken down in response to being contacted by an alkali, e.g., produced during corrosion, contacting the shell.

  18. A Dressing Solution for Burn Wounds: Antibacterial and Low-Adherent Wound Dressings

    NASA Astrophysics Data System (ADS)

    Pu, Tianyun

    Considering the infection and second trauma caused by dressing changes, development of antibacterial and low-adherent wound dressings is urgently needed. Silver ion is a widely used antimicrobial agent, but its cytotoxicity remains a problem. In this study, low-adherent PAM (polyacrylamide) hydrogel incorporated with less toxic AgNP (silver nanoparticle), was immobilized onto PET (poly(ethylene terephthalate)) substrates by an IPN (interpenetrating polymer network) method. The modified PET is effectively antibacterial and the surface is significantly less adherent than untreated PET. However, silver-resistant bacteria become a potential problem. Thus, ionic 5,5-dimethylhydantoin (DMH) analogues containing either a quaternary ammonium moiety or a phosphonate functional group were designed and synthesized. The DMH analogues were converted to antibacterial N-chloramine counterparts through chlorination to serve as potential alternatives to AgNP. The N-chloramine with a structural cation exhibited distinctly enhanced antibacterial functions both in solution and after immobilization on fabrics.

  19. Protease Inhibition by Oleic Acid Transfer From Chronic Wound Dressings to Albumin

    SciTech Connect

    Edwards, J. V.; Howley, Phyllis; Davis, Rachel M.; Mashchak, Andrew D.; Goheen, Steven C.

    2007-08-01

    High elastase and cathepsin G activities have been observed in chronic wounds. These levels can inhibit healing through degradation of growth factors, cytokines, and extracellular matrix proteins. Oleic acid (18:1) is a non-toxic elastase inhibitor with some potential for redressing the imbalance of elastase activity found in chronic wounds. Cotton wound dressing material was characterized as a transfer carrier for affinity uptake of 18:1 by albumin under conditions mimicking chronic wounds. 18:1-treated cotton was examined for its ability to bind and release the fatty acid in the presence of albumin. The mechanism of 18:1 uptake from cotton and binding by albumin was examined with both intact dressings and cotton fiber-designed chromatography. Raman spectra of the albumin-18:1 complexes under liquid-liquid equilibrium conditions revealed fully saturated albumin-18:1 complexes with a 1:1 weight ratio of albumin:18:1. Cotton chromatography under liquid-solid equilibrium conditions revealed oleic acid transfer from cotton to albumin at 27 mole equivalents of 18:1 per mole albumin. Cotton was contrasted with hydrogel, and hydrocolloid wound dressing for its comparative ability to lower elastase activity. Each dressing material evaluated was found to release 18:1 in the presence of albumin with significant inhibition of elastase activity. The 18:1-formulated wound dressings lowered elastase activity in a dose dependent manner in the order cotton gauze > hydrogel > hydrocolloid. In contrast the cationic serine protease Cathepsin G was inihibited by 18:1 within a narrow range of 18:1-cotton formulations. Four per cent Albumin solutions were most effective in binding cotton bound-18:1. However, 2% albumin was sufficient to transfer quantities of 18:1 necessary to achieve a significant elastase-lowering effect. Formulations with 128 mg 18:1/g cotton gauze had equivalent elastase lowering with 1 - 4% albumin. 18:1 bound to cotton wound dressings may have promise in the

  20. Microbiological spoilage of mayonnaise and salad dressings.

    PubMed

    Kurtzman, C P; Rogers, R; Hesseltine, C W

    1971-05-01

    Saccharomyces bailii was isolated from two-thirds of the spoiled mayonnaise and salad dressing samples examined. Most of the rest were spoiled by Lactobacillus fructivorans. However, one sample contained large numbers of both S. bailii and L. plantarum. Two of the spoiled samples also contained small numbers of bacilli. Bacillus subtilis, B. pumilis, B. polymyxa, B. megaterium, and B. licheniformis were found in one sample and B. subtilis and B. pumilis in another. Small numbers of B. subtilis and B. licheniformis were also present in one unspoiled sample. Several media were evaluated for the isolation of L. fructivorans. S. bailii and L. fructivorans vigorously fermented glucose. The concentration of glucose in the spoiled samples ranged from 0 to 38.5 g/kg and from 1.3 to 17.8 g/kg for the unspoiled samples.

  1. Toxicity assessment of nanosilver wound dressing in Wistar rat.

    PubMed

    Bidgoli, Sepideh Arbabi; Mahdavi, Moujan; Rezayat, Seyed Mahdi; Korani, Mitra; Amani, Amir; Ziarati, Parisa

    2013-05-07

    Antibiotic resistance to microorganisms is one of the major problems faced in the field of wound care in burns patients. Silver nanoparticles have come up as potent antimicrobial agent and are being evaluated in diverse medical applications ranging from silver based dressings to silver coated medical devices. We aimed in present study to test the release of nanosilver from nanosilver wound dressing and compare the dermal and systemic toxicity of nanosilver dressings in a repeated dose (21 days) model. Under general anesthesia, a limited standard 2nd degree burns were provided on the back of each rat in all treatment, negative control (simple dressing) and 5% silver nitrate groups, each contained 5 male wistar rats. According to the analysis made by atomic absorption spectrometry, the wound dressings released 0.599 ± 0.083 ppm of nanosilver during first 24 hrs of study. Daily observations were recoded and wounds were covered with new dressings each 24 hrs. Burn healing was observed in nanosilver wound dressing group in shorter time periods than the control groups. In toxicity assessment, this dressing didn't cause any hematological and histopathological abnormalities in treatment group but biochemical studies showed significant rise of plasma transaminase (ALT) at the endpoint (21 days) of the study (P=0.027). Portal mononuclear lymphoid and polymorphonuclear leukocyte infiltrations in three to four adjacent foci were recognized around the central hepatic vein in treatment group. Mild hepatotoxic effects of nanosilver wound dressing in wistar rat emphasize the necessity of more studies on toxicity potentials of low dose nanosilver by dermal applications.

  2. Characterizing hydrophobicity of interfaces by using cavity formation, solute binding, and water correlations

    PubMed Central

    Godawat, Rahul; Jamadagni, Sumanth N.; Garde, Shekhar

    2009-01-01

    Hydrophobicity is often characterized macroscopically by the droplet contact angle. Molecular signatures of hydrophobicity have, however, remained elusive. Successful theories predict a drying transition leading to a vapor-like region near large hard-sphere solutes and interfaces. Adding attractions wets the interface with local density increasing with attractions. Here we present extensive molecular simulation studies of hydration of realistic surfaces with a wide range of chemistries from hydrophobic (−CF3, −CH3) to hydrophilic (−OH, −CONH2). We show that the water density near weakly attractive hydrophobic surfaces (e.g., −CF3) can be bulk-like or larger, and provides a poor quantification of surface hydrophobicity. In contrast, the probability of cavity formation or the free energy of binding of hydrophobic solutes to interfaces correlates quantitatively with the macroscopic wetting properties and serves as an excellent signature of hydrophobicity. Specifically, the probability of cavity formation is enhanced in the vicinity of hydrophobic surfaces, and water–water correlations correspondingly display characteristics similar to those near a vapor–liquid interface. Hydrophilic surfaces suppress cavity formation and reduce the water–water correlation length. Our results suggest a potentially robust approach for characterizing hydrophobicity of more complex and heterogeneous surfaces of proteins and biomolecules, and other nanoscopic objects. PMID:19706896

  3. Triple-mode squeezing with dressed six-wave mixing

    PubMed Central

    Wen, Feng; Li, Zepei; Zhang, Yiqi; Gao, Hong; Che, Junling; Che, Junling; Abdulkhaleq, Hasan; Zhang, Yanpeng; Wang, Hongxing

    2016-01-01

    The theory of proof-of-principle triple-mode squeezing is proposed via spontaneous parametric six-wave mixing process in an atomic-cavity coupled system. Special attention is focused on the role of dressed state and nonlinear gain on triple-mode squeezing process. Using the dressed state theory, we find that optical squeezing and Autler-Towns splitting of cavity mode can be realized with nonlinear gain, while the efficiency and the location of maximum squeezing point can be effectively shaped by dressed state in atomic ensemble. Our proposal can find applications in multi-channel communication and multi-channel quantum imaging. PMID:27169878

  4. Searching for pathways involving dressed states in optimal control theory.

    PubMed

    von den Hoff, Philipp; Kowalewski, Markus; de Vivie-Riedle, Regina

    2011-01-01

    Selective population of dressed states has been proposed as an alternative control pathway in molecular reaction dynamics [Wollenhaupt et al., J. Photochem. Photobiol. A: Chem., 2006, 180, 248]. In this article we investigate if, and under which conditions, this strong field pathway is included in the search space of optimal control theory. For our calculations we used the proposed example of the potassium dimer, in which the different target states can be reached via dressed states by resonant transition. Especially, we investigate whether the optimization algorithm is able to find the route involving the dressed states although the target state lies out of resonance in the bare state picture.

  5. A Prospective Randomized Study to Compare the Effectiveness of Honey Dressing vs. Povidone Iodine Dressing in Chronic Wound Healing.

    PubMed

    Gulati, Sonia; Qureshi, Ashia; Srivastava, Anurag; Kataria, Kamal; Kumar, Pratik; Ji, Acharya Balakrishna

    2014-06-01

    To compare the healing of chronic wounds with honey dressing vs. Povidone iodine dressing in adult subjects with chronic wounds of ≥6 weeks of duration, attending wound care clinic in Surgical Out Patient Department of All India Institute of Medical Sciences, Surgical Out Patient Department of Jai Prakash Narayan Apex Trauma center, New Delhi. Forty five subjects were randomized into two groups i.e., Honey & Povidone iodine dressing group. Dressing was done on alternate day basis for 6 weeks of followup period. Main outcome measure was complete healing at 6 weeks. Wound healing status was assessed at 2 weekly intervals till 6 weeks. Seven out of 22 subjects in honey treated group achieved complete healing as compared to none out of 20 subjects in Povidone iodine treated group. There was a significant decrease in the wound surface area, pain score & increase in comfort score in Honey dressing group in comparison to the Povidone Iodine group at 0.05 level of significance. Honey dressing is highly effective in achieving healing in chronic wounds as compared to Povidone iodine dressing.

  6. Research on the 2-axis cup-wheel dressing technology of arc-diamond grinding wheel

    NASA Astrophysics Data System (ADS)

    Chang, X. L.; Wu, H. Y.; Peng, Y. F.

    2014-08-01

    The precision dressing of arc-diamond wheel is very hard, expensive and time-consuming because of the super-hard diamond particles and complicated geometrical shape. This paper aims to investigate the cup-wheel dressing technology to realize the high-efficiency regeneration of the arc-diamond wheel. A two-axis cup-wheel dressing technique for precision dressing arc-diamond wheel was suggested and tested. The dressing mechanism of 2-axis cup-wheel was studied. The dressing algorithm and error compensation method were further investigated to improve the dressing precision and efficiency. The experimental results show that the 2-axis cup-wheel dressing technique is valid and applicable to realize the precision dressing of arc-diamond wheel. The machined optical surface condition was apparently improved with the cup-wheel dressed diamond wheel and even became much better when the error compensation algorithm was performed on the arc-diamond wheel.

  7. Is Br2 hydration hydrophobic?

    NASA Astrophysics Data System (ADS)

    Alcaraz-Torres, A.; Gamboa-Suárez, A.; Bernal-Uruchurtu, M. I.

    2017-02-01

    The spectroscopic properties of bromine in aqueous systems suggest it can behave as either hydrophilic or hydrophobic solute. In small water clusters, the halogen bond and the hydrogen-halogen interaction are responsible for its specific way of binding. In water hydrates, it is efficiently hosted by two different cages forming the crystal structure and it has been frequently assumed that there is little or no interaction between the guest and the host. Bromine in liquid solution poses a challenging question due to its non-negligible solubility and the large blue shift measured in its absorption spectra. Using a refined semi-empirical force field, PM3-PIF, we performed a Born-Oppenheimer molecular dynamics study of bromine in liquid water. Here we present a detailed study in which we retrieved the most representative hydration structures in terms of the most frequent positions around bromine and the most common water orientations. Albeit being an approximate description of the total hydration phenomenon, it captures the contribution of the leading molecular interactions in form of the recurrent structures. Our findings confirm that the spectroscopic signature is mainly caused by the closest neighbors. The dynamics of the whole first hydration shell strongly suggests that the external molecules in that structure effectively isolate the bulk from the presence of bromine. The solvation structure fluctuates from a hydrophilic to a hydrophobic-like environment along the studied trajectory.

  8. Preparation of hydrophobic organic aeorgels

    DOEpatents

    Baumann, Theodore F.; Satcher, Jr., Joe H.; Gash, Alexander E.

    2007-11-06

    Synthetic methods for the preparation of hydrophobic organics aerogels. One method involves the sol-gel polymerization of 1,3-dimethoxybenzene or 1,3,5-trimethoxybenzene with formaldehyde in non-aqueous solvents. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be dried using either supercritical solvent extraction to generate the new organic aerogels or air dried to produce an xerogel. Other methods involve the sol-gel polymerization of 1,3,5 trihydroxy benzene (phloroglucinol) or 1,3 dihydroxy benzene (resorcinol) and various aldehydes in non-aqueous solvents. These methods use a procedure analogous to the one-step base and two-step base/acid catalyzed polycondensation of phloroglucinol and formaldehyde, but the base catalyst used is triethylamine. These methods can be applied to a variety of other sol-gel precursors and solvent systems. These hydrophobic organics aerogels have numerous application potentials in the field of material absorbers and water-proof insulation.

  9. Preparation of hydrophobic organic aeorgels

    DOEpatents

    Baumann, Theodore F.; Satcher, Jr., Joe H.; Gash, Alexander E.

    2004-10-19

    Synthetic methods for the preparation of hydrophobic organics aerogels. One method involves the sol-gel polymerization of 1,3-dimethoxybenzene or 1,3,5-trimethoxybenzene with formaldehyde in non-aqueous solvents. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be dried using either supercritical solvent extraction to generate the new organic aerogels or air dried to produce an xerogel. Other methods involve the sol-gel polymerization of 1,3,5 trihydroxy benzene (phloroglucinol) or 1,3 dihydroxy benzene (resorcinol) and various aldehydes in non-aqueous solvents. These methods use a procedure analogous to the one-step base and two-step base/acid catalyzed polycondensation of phloroglucinol and formaldehyde, but the base catalyst used is triethylamine. These methods can be applied to a variety of other sol-gel precursors and solvent systems. These hydrophobic organics aerogels have numerous application potentials in the field of material absorbers and water-proof insulation.

  10. 9. View to west of Tropic Dressing Room (typical). ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. View to west of Tropic Dressing Room (typical). - Natick Research & Development Laboratories, Climatic Chambers Building, U.S. Army Natick Research, Development & Engineering Center (NRDEC), Natick, Middlesex County, MA

  11. Standardized Dress: Where Angels (and School Boards) Fear to Tread.

    ERIC Educational Resources Information Center

    Cain, Bonny

    2002-01-01

    Tells efforts by Pearland Independent School District (Texas) school board and superintendent to adopt a standardized dress code, an effort that led to student and community opposition and controversy. Describes lessons learned. (PKP)

  12. Shifted-action expansion and applicability of dressed diagrammatic schemes

    NASA Astrophysics Data System (ADS)

    Rossi, Riccardo; Werner, Félix; Prokof'ev, Nikolay; Svistunov, Boris

    2016-04-01

    While bare diagrammatic series are merely Taylor expansions in powers of interaction strength, dressed diagrammatic series, built on fully or partially dressed lines and vertices, are usually constructed by reordering the bare diagrams, which is an a priori unjustified manipulation, and can even lead to convergence to an unphysical result [E. Kozik, M. Ferrero, and A. Georges, Phys. Rev. Lett. 114, 156402 (2015), 10.1103/PhysRevLett.114.156402]. Here we show that for a broad class of partially dressed diagrammatic schemes, there exists an action S(ξ ) depending analytically on an auxiliary complex parameter ξ , such that the Taylor expansion in ξ of correlation functions reproduces the original diagrammatic series. The resulting applicability conditions are similar to the bare case. For fully dressed skeleton diagrammatics, analyticity of S(ξ ) is not granted, and we formulate a sufficient condition for converging to the correct result.

  13. Efficacy of commercial dressings in managing malodorous wounds.

    PubMed

    Lee, Gillian; Anand, Subhash C; Rajendran, S; Walker, Ian

    This paper investigates a novel in vitro method of ascertaining quantitative comparative data on a selection of commercial available odour absorbent wound dressing. The aim of this study is to determine and evaluate quantitative desirable data on the efficiency of odour absorbency along with other comparable physical characteristics of commercial odour absorbent dressings. This study is a part of an ongoing research programme into the design and development of novel odour absorbent dressings for managing malodorous wounds. The study also includes the development of a controlled in vitro test method that simulates a more realistic situation. A selection of commercially available activated charcoal dressings were analysed and tested, and comparative evaluation was carried out and discussed.

  14. Evaluation of Biatain Soft-Hold foam dressing.

    PubMed

    Vogensen, Hanne

    Foam dressing products were introduced in the 1970s and quickly became accepted in clinical practice due to a wide range of benefits. Today, various foam dressings are available on the market. They can appear rather similar, but may well have different performance characteristics. A well-established product is Biatain foam dressing, which was introduced in 1998 and quickly became popular due to its superior exudate management properties. The aim of this article is to describe a recent innovation in the Biatain dressing range, Biatain Soft-Hold (Coloplast A/S), and summarize some of the evidence that supports it. The new product feature consists of a soft and skin-friendly adherent layer covering less than 50% of the foam surface, thus providing a third hand in application and atraumatic removal while maintaining superior exudate management.

  15. 3. INTERIOR VIEW OF PARTITIONS IN DRESSING ROOM; INTERIOR HALLWAY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. INTERIOR VIEW OF PARTITIONS IN DRESSING ROOM; INTERIOR HALLWAY FOR HYDROTHERAPY AREA AT RIGHT - Fort McCoy, Building No. T-1054, South side of South Tenth Avenue, Block 10, Sparta, Monroe County, WI

  16. 12. VIEW, LOOKING SOUTH FROM LEFT TO RIGHT, SHOWING DRESSING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. VIEW, LOOKING SOUTH FROM LEFT TO RIGHT, SHOWING DRESSING FROM AND WORK/CHAMBER ROOM - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  17. Novel wound dressing based on nanofibrous PHBV-keratin mats.

    PubMed

    Yuan, Jiang; Geng, Jia; Xing, Zhicai; Shim, Kyoung-Jin; Han, Insook; Kim, Jung-Chul; Kang, Inn-Kyu; Shen, Jian

    2015-09-01

    Keratin is an important protein used for wound healing and tissue recovery. In this study, keratin was first extracted from raw materials and chemically modified to obtain stable keratin (m-keratin). The raw and m-keratin were examined by Raman spectroscopy. The molecular weight of the m-keratin was analysed by SDS-PAGE. The m-keratin was then blended with poly(hydroxybutylate-co-hydroxyvalerate) (PHBV) and electrospun to afford nanofibrous mats. These mats were characterized by field emission scanning electron microscopy (FE-SEM), electron spectroscopy for chemical analysis (ESCA) and atomic force microscopy (AFM). From the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) data, it was found that introduction of keratin enhanced cell proliferation. From wound-healing test and histological examination results, it was shown that the composite mats accelerated wound recovery remarkably as compared to the PHBV control. It was concluded that PHBV-keratin may be a good candidate as a wound dressing.

  18. Natural and synthetic polymers for wounds and burns dressing.

    PubMed

    Mogoşanu, George Dan; Grumezescu, Alexandru Mihai

    2014-03-25

    In the last years, health care professionals faced with an increasing number of patients suffering from wounds and burns difficult to treat and heal. During the wound healing process, the dressing protects the injury and contributes to the recovery of dermal and epidermal tissues. Because their biocompatibility, biodegradability and similarity to macromolecules recognized by the human body, some natural polymers such as polysaccharides (alginates, chitin, chitosan, heparin, chondroitin), proteoglycans and proteins (collagen, gelatin, fibrin, keratin, silk fibroin, eggshell membrane) are extensively used in wounds and burns management. Obtained by electrospinning technique, some synthetic polymers like biomimetic extracellular matrix micro/nanoscale fibers based on polyglycolic acid, polylactic acid, polyacrylic acid, poly-ɛ-caprolactone, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, exhibit in vivo and in vitro wound healing properties and enhance re-epithelialization. They provide an optimal microenvironment for cell proliferation, migration and differentiation, due to their biocompatibility, biodegradability, peculiar structure and good mechanical properties. Thus, synthetic polymers are used also in regenerative medicine for cartilage, bone, vascular, nerve and ligament repair and restoration. Biocompatible with fibroblasts and keratinocytes, tissue engineered skin is indicated for regeneration and remodeling of human epidermis and wound healing improving the treatment of severe skin defects or partial-thickness burn injuries.

  19. Behavior of aqueous solutions in hydrophobic confinement studied using molecular simulations

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit

    Biological processes, such as formation of cell membranes, vesicles and folding of protein molecules, entail formation of a predominantly hydrophobic interior devoid of water. These processes occur in crowded aqueous environments comprising of amino acids, carbohydrates, ionic species, protein molecules, etc. Kinetics of these processes involve drying of hydrophobic pockets. Previous studies reveal that the kinetics of evaporation of water in hydrophobic confinement significantly slow down as the confinement gap increases. Presumably, the constituents of aqueous environment in biological systems modulate the kinetics of evaporation of confined water. In this work, we employ forward flux sampling in molecular dynamics simulations to study the role of solutes at different concentrations in modulating the kinetics and mechanism of evaporation of water under hydrophobic confinement. The results of these simulations will be useful for understanding optimum conditions for protein folding and other biological self-assembly processes.

  20. DEVELOPMENT OF A NEXT-GENERATION ANTIMICROBIAL WOUND DRESSING.

    PubMed

    Metcalf, Daniel; Parsons, David; Bowler, I Philip

    2016-03-01

    Delayed wound healing due to infection is a burden on healthcare systems, and the patient and caregiver alike. An emerging factor in infection and delayed healing is the presence development of biofilm in wounds. Biofilm is communities of microorganisms, protected by an extracellular matrix of slime in the wound, which can tolerate host defences and applied antimicrobials such as antibiotics or antimicrobial dressings. A growing evidence base exists suggesting that biofilm exists in a majority of chronic wounds, and can be a precursor to infection while causing delayed healing itself. In vivo models have demonstrated that the inflammatory, granulation and epithelialization processes of normal wound healing are impaired by biofilm presence. The challenge in the development of a new antimicrobial wound dressing was to make standard antimicrobial agents more effective against biofilm, and this was answered following extensive biofilm research and testing. A combination of metal chelator, surfactant and pH control displayed highly synergistic anti-biofilm action with 1.2% ionic silver in a carboxymethylcellulose dressing. Its effectiveness was challenged and proven in complex in vitro and in vivo wound biofilm models, followed by clinical safety and performance demonstrations in a 42-patient study and 113 clinical evaluations. Post-market surveillance was conducted on the commercially available dressing, and in a 112-case evaluation, the dressing was shown to effectively manage exudate and suspected biofilm while shifting difficult-to-heal wounds onto healing trajectories, after an average of 4 weeks of new dressing use in otherwise standard wound care protocols. This was accompanied by a low frequency of dressing related adverse events. In a second evaluation, clinical signs of infection and wound dimension data, before and after the evaluations, were also available. Following an average of 5.4 weeks of dressing use, all signs of clinical infection were reduced, from

  1. Expulsion of ions from hydrophobic hydration shells.

    PubMed

    Rankin, Blake M; Ben-Amotz, Dor

    2013-06-19

    Raman spectroscopy is combined with multivariate curve resolution to quantify interactions between ions and molecular hydrophobic groups in water. The molecular solutes in this study all have similar structures, with a trimethyl hydrophobic domain and a polar or charged headgroup. Our results imply that aqueous sodium and fluoride ions are strongly expelled from the first hydration shells of the hydrophobic (methyl) groups, while iodide ions are found to enter the hydrophobic hydration shell, to an extent that depends on the methyl group partial charge. However, our quantitative estimates of the corresponding ion binding equilibrium constants indicate that the iodide concentration in the first hydrophobic hydration shell is generally lower than that in the surrounding bulk water, and so an iodide ion cannot be viewed as having a true affinity for the molecular hydrophobic interface, but rather is less strongly expelled from such an interface than fluoride.

  2. Characterisation of nanomaterial hydrophobicity using engineered surfaces

    NASA Astrophysics Data System (ADS)

    Desmet, Cloé; Valsesia, Andrea; Oddo, Arianna; Ceccone, Giacomo; Spampinato, Valentina; Rossi, François; Colpo, Pascal

    2017-03-01

    Characterisation of engineered nanomaterials (NMs) is of outmost importance for the assessment of the potential risks arising from their extensive use. NMs display indeed a large variety of physico-chemical properties that drastically affect their interaction with biological systems. Among them, hydrophobicity is an important property that is nevertheless only slightly covered by the current physico-chemical characterisation techniques. In this work, we developed a method for the direct characterisation of NM hydrophobicity. The determination of the nanomaterial hydrophobic character is carried out by the direct measurement of the affinity of the NMs for different collectors. Each collector is an engineered surface designed in order to present specific surface charge and hydrophobicity degrees. Being thus characterised by a combination of surface energy components, the collectors enable the NM immobilisation with surface coverage in relation to their hydrophobicity. The experimental results are explained by using the extended DLVO theory, which takes into account the hydrophobic forces acting between NMs and collectors.

  3. Exploratory Development of an Ultra-Fast-Curing Wound Dressing

    DTIC Science & Technology

    1989-11-30

    mwv’eri if neceswey ". idientify by block number) eare developing a drug -dispensing field dermal dressing. The dermal dressing, which can be easily applied...polyurethane oligomer which is designed to cure at room temperature and Oelivers drugs on a controlled, sustainedI and highly reproducible basis.i I 20...3 ITASK I .......................................... 5 A. OPTIMIZE DISPERSION OF THE DRUGS ........ 5 B 5. UTILIZE MORE POTENT DRUGS

  4. 5. GENERAL VIEW OF HOG DRESSING AREA ON LEVEL 4; ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. GENERAL VIEW OF HOG DRESSING AREA ON LEVEL 4; LOOKING WEST; WORKERS STOOD ON RAISED PLATFORMS TO EVISCERATE AND WASH CARCASSES; EXPANDED STEEL GRATING PROVIDED NON-SLIP WORKING SURFACE; STAINLESS-STEEL BAFFLES BETWEEN PLATFORMS HELPED TO CONTAIN STEAM AND WATER SPRAY; METAL TROUGHS BELOW PLATFORMS AND CONCRETE GUTTERS IN FLOOR HELPED CHANNEL WASTE WATER TO DRAINS - Rath Packing Company, Hog Dressing Building, Sycamore Street between Elm & Eighteenth Streets, Waterloo, Black Hawk County, IA

  5. Radio-frequency dressing of multiple Feshbach resonances

    NASA Astrophysics Data System (ADS)

    Kaufman, A. M.; Anderson, R. P.; Hanna, Thomas M.; Tiesinga, E.; Julienne, P. S.; Hall, D. S.

    2009-11-01

    We demonstrate and theoretically analyze the dressing of several proximate Feshbach resonances in R87b using radio-frequency (rf) radiation. We present accurate measurements and characterizations of the resonances, and the dramatic changes in scattering properties that can arise through the rf dressing. Our scattering theory analysis yields quantitative agreement with the experimental data. We also present a simple interpretation of our results in terms of rf-coupled bound states interacting with the collision threshold.

  6. Painful dressing changes for chronic wounds: assessment and management.

    PubMed

    Solowiej, Kazia; Upton, Dominic

    Wound pain can arise from the wound itself, continuing wound treatment and anticipatory pain, which occurs in some patients as a consequence of negative experiences of care. Specifically, pain caused by the removal and application of dressings has been identified as a major contributor to wound pain, from both patient and health professional perspectives. This article reviews literature on the impact of pain at dressing change, and provides practical suggestions for assessment and management of pain during wound care.

  7. Field-dressed orbitals in strong-field molecular ionization

    NASA Astrophysics Data System (ADS)

    Siemering, Robert; Njoya, Oumarou; Weinacht, Thomas; de Vivie-Riedle, Regina

    2015-10-01

    We demonstrate the importance of considering the shape of field-dressed molecular orbitals in interpreting angle-dependent measures of strong-field ionization from excited states. Our calculations of angle-dependent ionization for three homologous polyatomic molecules with very similar valence orbitals show that one has to take into account the shape of the field-dressed orbitals rather than the field-free orbitals in order to rationalize the experimental measurements.

  8. Dressing Wear Time after Breast Reconstruction: A Randomized Clinical Trial

    PubMed Central

    Paiva, Luiz Francisley; Fonseca, Fernando Elias Martins; Cabral, Isaías Vieira; Pinto, Natália Lana Larcher; Juliano, Yara

    2016-01-01

    Background The evidence to support dressing standards for breast surgery wounds is empiric and scarce. Objective This two-arm randomized clinical trial was designed to assess the effect of dressing wear time on surgical site infection (SSI) rates, skin colonization and patient perceptions. Methods A total of 200 breast cancer patients undergoing breast reconstruction were prospectively enrolled. Patients were randomly allocated to group I (dressing removed on the first postoperative day, n = 100) or group II (dressing removed on the sixth postoperative day, n = 100). SSIs were defined and classified according to criteria from the Centers for Disease Control and Prevention. Samples collected before placing the dressing and after 1 day (group I) and 6 days (both groups) were cultured for skin colonization assessments. Patients preferences and perceptions with regard to safety, comfort and convenience were recorded and analyzed. Results A total of 186 patients completed the follow-up. The global SSI rate was 4.5%. Six patients in group I and three in group II had SSI (p = 0.497). Before dressing, the groups were similar with regard to skin colonization. At the sixth day, there was a higher colonization by coagulase-negative staphylococci in group I (p<0.0001). Patients preferred to keep dressing for six days (p<0.0001), and considered this a safer choice (p<0.05). Conclusions Despite group I had a higher skin colonization by coagulase-negative staphylococci on the sixth postoperative day, there was no difference in SSI rates. Patients preferred keeping dressing for six days and considered it a safer choice. Trial Registration ClinicalTrials.gov NCT01148823 PMID:27911904

  9. [DRESS in intensive care unit: a challenging diagnosis and treatment].

    PubMed

    Derlon, V; Audibert, G; Barbaud, A; Mertes, P M

    2014-12-01

    Drug reaction with eosinophilia ans systemic symptoms (DRESS) is a severe medication-induced adverse reaction, which can threaten patient's life. Clinical symptoms and organ failures present wide variability. Furthermore, the latency period is long, so that diagnosis could be a real challenge in the intensive care unit. We report the case of a woman developing a DRESS after neurosurgery complicated by a nosocomial infection.

  10. Repulsive effects of hydrophobic diamond thin films on biomolecule detection

    NASA Astrophysics Data System (ADS)

    Ruslinda, A. Rahim; Ishiyama, Y.; Penmatsa, V.; Ibori, S.; Kawarada, H.

    2015-02-01

    The repulsive effect of hydrophobic diamond thin film on biomolecule detection, such as single-nucleotide polymorphisms and human immunodeficiency virus type 1 trans-activator of transcription peptide protein detection, was investigated using a mixture of a fluorine-, amine-, and hydrogen-terminated diamond surfaces. These chemical modifications lead to the formation of a surface that effectively resists the nonspecific adsorption of proteins and other biomolecules. The effect of fluorine plasma treatment on elemental composition was also investigated via X-ray photoelectron spectroscopy (XPS). XPS results revealed a fluorocarbon layer on the diamond thin films. The contact angle measurement results indicated that the fluorine-treated diamond thin films were highly hydrophobic with a surface energy value of ∼25 mN/m.

  11. Cotton and Protein Interactions

    SciTech Connect

    Goheen, Steven C.; Edwards, J. V.; Rayburn, Alfred R.; Gaither, Kari A.; Castro, Nathan J.

    2006-06-30

    The adsorbent properties of important wound fluid proteins and cotton cellulose are reviewed. This review focuses on the adsorption of albumin to cotton-based wound dressings and some chemically modified derivatives targeted for chronic wounds. Adsorption of elastase in the presence of albumin was examined as a model to understand the interactive properties of these wound fluid components with cotton fibers. In the chronic non-healing wound, elastase appears to be over-expressed, and it digests tissue and growth factors, interfering with the normal healing process. Albumin is the most prevalent protein in wound fluid, and in highly to moderately exudative wounds, it may bind significantly to the fibers of wound dressings. Thus, the relative binding properties of both elastase and albumin to wound dressing fibers are of interest in the design of more effective wound dressings. The present work examines the binding of albumin to two different derivatives of cotton, and quantifies the elastase binding to the same derivatives following exposure of albumin to the fiber surface. An HPLC adsorption technique was employed coupled with a colorimetric enzyme assay to quantify the relative binding properties of albumin and elastase to cotton. The results of wound protein binding are discussed in relation to the porosity and surface chemistry interactions of cotton and wound proteins. Studies are directed to understanding the implications of protein adsorption phenomena in terms of fiber-protein models that have implications for rationally designing dressings for chronic wounds.

  12. How specific halide adsorption varies hydrophobic interactions.

    PubMed

    Stock, Philipp; Müller, Melanie; Utzig, Thomas; Valtiner, Markus

    2016-03-11

    Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.

  13. Application of wound dressings in dermatology laser procedures

    NASA Astrophysics Data System (ADS)

    Hetzel, Fred W.; Chen, Qun; Hoskins, Greg

    1995-05-01

    High powered lasers have been used in dermatological procedures such as tattoo removal. This use is associated with a potential, biological hazard of high speed tissue particles from the laser field. It has been proposed that by applying a clear dermatological would dressing directly over the laser treatment site, it may be possible to completely trap the potentially airborne tissue particles from the procedure. Some important questions must be addressed prior to the implementation of such a technique. While the use of a wound dressing may significantly reduce the airborne materials during the laser procedures, new problems may arise: 1 . The wound dressing or some of its components may absorb excessive amount of light energy. This would result in a very localized temperature rise which may be harmful to the patient; 2. The smooth surface of the wound dressing material could induce specular reflection of the incident laser beam, thus introducing a laser hazard to the staff and patient. To address these possible problems, we studied a series of ClearSite Wound Dressings which have been reportedly tested for such laser procedures. The objective of the studies were, to determine if the use of ClearSite in conjunction with laser procedures poses a possible hazard to either the patient or to the Operating Room personnel, and to determine the effect of the ClearSite dressing on the optical characteristics of the light beam. The latter includes light absorption and transmittance for various wavelengths.

  14. Biomedical evaluation of a novel nitrogen oxides releasing wound dressing.

    PubMed

    Dave, Rachna N; Joshi, Hiren M; Venugopalan, Vayalam P

    2012-12-01

    Chronic wounds are a major cause for both suffering and economical losses. Management of chronic non-healing wounds requires multipronged approach. They are polymicrobial and agonizing for the patient due to associated pain. Moist dressing providing antimicrobial action is a highly desirable chronic wound management option. Here we report a hydrogel based dressing that possesses the antimicrobial properties of acidified sodium nitrite and the homeostatic property of a hydrogel. The dressing was developed by combining citric acid cross-linked cotton gauze and sodium nitrite loaded gelatin. The cotton gauze was cross-linked with citric acid by pad-dry-curing in presence of nano-titania catalyst. The cotton gauze-gelatin hydrogel combination was gamma-irradiated and freeze-dried. At the time of application, the freeze-dried dressing is wetted by sodium nitrite solution. The dressing has a fluid uptake ability of 90 % (w/v) and the water vapour evaporation rate was estimated to be 2,809 ± 20 g/m(2)/day. The dressing showed significant antimicrobial activity against both planktonic and biofilm forms and was effective during consecutive re-uses. Cytotoxicity study showed inhibition of fibroblasts, but to a lesser extent than clinically administered concentrations of antiseptic like povidone iodine. Storage at 37 °C over a 3 month period resulted in no significant loss of its antimicrobial activity.

  15. Method for making nanoporous hydrophobic coatings

    DOEpatents

    Fan, Hongyou; Sun, Zaicheng

    2013-04-23

    A simple coating method is used to form nanoporous hydrophobic films that can be used as optical coatings. The method uses evaporation-induced self-assembly of materials. The coating method starts with a homogeneous solution comprising a hydrophobic polymer and a surfactant polymer in a selective solvent. The solution is coated onto a substrate. The surfactant polymer forms micelles with the hydrophobic polymer residing in the particle core when the coating is dried. The surfactant polymer can be dissolved and selectively removed from the separated phases by washing with a polar solvent to form the nanoporous hydrophobic film.

  16. The physical origin of hydrophobic effects

    NASA Astrophysics Data System (ADS)

    Sun, Qiang

    2017-03-01

    From the structural studies on water and air/water interface, hydration free energy is derived, and used to investigate the origin of hydrophobic effects. As a solute is dissolved into water, hydration free energy increases, and is divided into initial and hydrophobic solvation processes. In the initial process, hydration free energy is dominated by hydrogen bonding in interfacial water (topmost water layer at solute/water interface). For hydrophobic process, hydration free energy is related to the hydrogen bonding in bulk and interfacial water. Therefore, hydrophobic effects originate from the structural competition between hydrogen bonding in bulk water and that in interfacial water.

  17. The brain's dress code: How The Dress allows to decode the neuronal pathway of an optical illusion.

    PubMed

    Schlaffke, Lara; Golisch, Anne; Haag, Lauren M; Lenz, Melanie; Heba, Stefanie; Lissek, Silke; Schmidt-Wilcke, Tobias; Eysel, Ulf T; Tegenthoff, Martin

    2015-12-01

    Optical illusions have broadened our understanding of the brain's role in visual perception. A modern day optical illusion emerged from a posted photo of a striped dress, which some perceived as white and gold and others as blue and black. Here we show, using functional magnetic resonance imaging (fMRI), that those who perceive The Dress as white/gold have higher activation in response to the image of The Dress in brain regions critically involved in higher cognition (frontal and parietal brain areas). These results are consistent with theories of top-down modulation and present a neural signature associated with the differences in perceiving The Dress as white/gold or blue/black. Furthermore the results support recent psychophysiological data on this phenomenon and provide a fundamental building block to study interindividual differences in visual processing.

  18. Membrane penetration of Sendai virus glycoproteins during the early stages of fusion with liposomes as determined by hydrophobic photoaffinity labeling

    SciTech Connect

    Novick, S.L.; Hoekstra, D.

    1988-10-01

    The hydrophobic photoaffinity label 3-(trifluoromethyl)-3-(m-(/sup 125/I)iodophenyl)diazirine was used to label Sendai virus proteins during fusion with cardiolipin and phosphatidylserine liposomes. Preferential labeling of the viral fusion protein during the initial stages of fusion demonstrated that this protein interacts with the hydrophobic core of the target membrane as an initiating event of virus-liposome fusion. Labeling showed time, temperature, and pH dependence consistent with earlier fluorescent measurements of fusion kinetics. The present method provides conclusive evidence supporting the hypothesis that hydrophobic interaction of the fusion protein with the target bilayer is an initial event in the fusion mechanism of viral membranes.

  19. Role of the lid hydrophobicity pattern in pancreatic lipase activity.

    PubMed

    Thomas, Annick; Allouche, Maya; Basyn, Frédéric; Brasseur, Robert; Kerfelec, Brigitte

    2005-12-02

    Pancreatic lipase is a soluble globular protein that must undergo structural modifications before it can hydrolyze oil droplets coated with bile salts. The binding of colipase and movement of the lipase lid open access to the active site. Mechanisms triggering lid mobility are unclear. The *KNILSQIVDIDGI* fragment of the lid of the human pancreatic lipase is predicted by molecular modeling to be a tilted peptide. Tilted peptides are hydrophobicity motifs involved in membrane fusion and more globally in perturbations of hydrophobic/hydrophilic interfaces. Analysis of this lid fragment predicts no clear consensus of secondary structure that suggests that its structure is not strongly sequence determined and could vary with environment. Point mutations were designed to modify the hydrophobicity profile of the [240-252] fragment and their consequences on the lipase-mediated catalysis were tested. Two mutants, in which the tilted peptide motif was lost, also have poor activity on bile salt-coated oil droplets and cannot be reactivated by colipase. Conversely, one mutant in which a different tilted peptide is created retains colipase dependence. These results suggest that the tilted hydrophobicity pattern of the [240-252] fragment is neither important for colipase binding to lipase, nor for interfacial binding but is important to trigger the maximal catalytic efficiency of lipase in the presence of bile salt.

  20. Hydrophobic coatings for MEMS applications

    NASA Astrophysics Data System (ADS)

    Doms, M.; Feindt, H.; Kuipers, W. J.; Shewtanasoontorn, D.; Matar, A. S.; Brinkhues, S.; Welton, R. H.; Mueller, J.

    2008-05-01

    Different kinds of thin-film coatings were investigated with regard to their applicability as hydrophobic coatings for MEMS. The films were deposited onto silicon and borosilicate glass substrates by spincoating of Dyneon™ PTFE and PFA, plasmapolymerization of HMDS-N and C4F8 as well as liquid-phase and vapor-phase coating of SAMs from DDMS, FDTS, FOTS and Geleste Aquaphobe™ CM. The layer properties were analyzed using profilometry, FTIR, SEM and contact angle measurements. Furthermore, the adhesion of the layers to the substrates was determined in an acetone ultrasonic bath. The influence of various deposition process parameters on the properties of the films was investigated. As these layers can be used in microfluidic systems, as water-repellent layers and as anti-stiction coatings, they are suited for versatile fields of application.

  1. Comparison between Free and Immobilized Ion Effects on Hydrophobic Interactions: A Molecular Dynamics Study.

    PubMed

    Huang, Kai; Gast, Sebastian; Ma, C Derek; Abbott, Nicholas L; Szlufarska, Izabela

    2015-10-15

    Fundamental studies of the effect of specific ions on hydrophobic interactions are driven by the need to understand phenomena such as hydrophobically driven self-assembly or protein folding. Using β-peptide-inspired nanorods, we investigate the effects of both free ions (dissolved salts) and proximally immobilized ions on hydrophobic interactions. We find that the free ion effect is correlated with the water density fluctuation near a nonpolar molecular surface, showing that such fluctuation can be an indicator of hydrophobic interactions in the case of solution additives. In the case of immobilized ion, our results demonstrate that hydrophobic interactions can be switched on and off by choosing different spatial arrangements of proximal ions on a nanorod. For globally amphiphilic nanorods, we find that the magnitude of the interaction can be further tuned using proximal ions with varying ionic sizes. In general, univalent proximal anions are found to weaken hydrophobic interactions. This is in contrast to the effect of free ions, which according to our simulations strengthen hydrophobic interactions. In addition, immobilized anions of increasing ionic size do not follow the same ordering (Hofmeister-like ranking) as free ions when it comes to their impact on hydrophobic interactions. The immobilized ion effect is not simply correlated with the water density fluctuation near the nonpolar side of the amphiphilic nanorod. We propose a molecular picture that explains the contrasting effects of immobilized versus free ions.

  2. Dehydration-Driven Solvent Exposure of Hydrophobic Surfaces as a Driving Force in Peptide Folding

    SciTech Connect

    Daidone, Isabella; Ulmschneider, Martin; DiNola, Alfredo; Amadei, Andrea; Smith, Jeremy C

    2007-09-01

    Recent work has shown that the nature of hydration of pure hydrophobic surfaces changes with the length scale considered: water hydrogen-bonding networks adapt to small exposed hydrophobic species, hydrating or 'wetting' them at relatively high densities, whereas larger hydrophobic areas are 'dewetted' [Chandler D (2005), Nature 29:640-647]. Here we determine whether this effect is also present in peptides by examining the folding of a {beta}-hairpin (the 14-residue amyloidogenic prion protein H1 peptide), using microsecond time-scale molecular dynamics simulations. Two simulation models are compared, one explicitly including the water molecules, which may thus adapt locally to peptide configurations, and the other using a popular continuum approximation, the generalized Born/surface area implicit solvent model. The results obtained show that, in explicit solvent, peptide conformers with high solvent-accessible hydrophobic surface area indeed also have low hydration density around hydrophobic residues, whereas a concomitant higher hydration density around hydrophilic residues is observed. This dewetting effect stabilizes the fully folded {beta}-hairpin state found experimentally. In contrast, the implicit solvent model destabilizes the fully folded hairpin, tending to cluster hydrophobic residues regardless of the size of the exposed hydrophobic surface. Furthermore, the rate of the conformational transitions in the implicit solvent simulation is almost doubled with respect to that of the explicit solvent. The results suggest that dehydration-driven solvent exposure of hydrophobic surfaces may be a significant factor determining peptide conformational equilibria.

  3. Effects of the osmolyte TMAO (Trimethylamine-N-oxide) on aqueous hydrophobic contact-pair interactions.

    PubMed

    Macdonald, Ryan D; Khajehpour, Mazdak

    2013-12-31

    Osmolytes are small, soluble organic molecules produced by living organisms for maintaining cell volume. These molecules have also been shown to have significant effects on the stability of proteins. Perhaps one of the most studied osmolytes is Trimethylamine-N-oxide (TMAO). Thermodynamic studies of the effects of TMAO on proteins have shown that this molecule is a strong stabilizer of the protein folded state, thus being able to counteract the effects of protein denaturants such as urea and guanidine hydrochloride. Most studies of TMAO effects on bio-molecular stability have until now been focused on how the osmolyte reduces the solubility of polypeptide backbones, while the effects of TMAO on hydrophobic interactions are still not well understood. In fact, there are few experimental data measuring the effect of TMAO on hydrophobic interactions. This work studies phenyl and alkyl contact pairs as model hydrophobic contact pairs. The formation of these contact pairs is monitored using fluorescence, i.e., through the quenching of phenol fluorescence by carboxylate ions; and a methodology is developed to isolate hydrophobic contributions from other interactions. The data demonstrate that the addition of TMAO to the aqueous solvent destabilizes hydrophobic contact pairs formed between alkyl and phenyl moieties. In other words, TMAO acts as a "denaturant" for hydrophobic interactions.

  4. Interplay between the hydrophobic effect and dipole interactions in peptide aggregation at interfaces.

    PubMed

    Ganesan, Sai J; Matysiak, Silvina

    2016-01-28

    Protein misfolding is an intrinsic property of polypeptides, and misfolded conformations have a propensity to aggregate. In the past decade, the development of various coarse-grained models for proteins has provided key insights into the driving forces in folding and aggregation. We recently developed a low resolution Water Explicit Polarizable PROtein coarse-grained Model (WEPPROM) by adding oppositely charged dummy particles inside protein backbone beads. With this model, we were able to achieve significant α/β secondary structure content, without any added bias. We now extend the model to study peptide aggregation at hydrophobic-hydrophilic interfaces and draw comparisons to aggregation in explicit water solvent. Elastin-like octapeptides (GV)4 are used as a model system for this study. A condensation-ordering mechanism of aggregation is observed in water. Our results suggest that backbone interpeptide dipolar interactions, not hydrophobicity, plays a more significant role in fibril-like peptide aggregation. We observe a cooperative effect in hydrogen bonding or dipolar interactions, with an increase in aggregate size in water and at interfaces. Based on this cooperative effect, we provide a potential explanation for the observed nucleus size in peptide aggregation pathways. The presence of a hydrophobic-hydrophilic interface increases both (a) order of aggregates formed, and (b) rate of the aggregation process. Without dipolar particles, peptide aggregation is not observed at the hydrophilic-hydrophobic interface. Thus, the presence of dipoles, not hydrophobicity, plays a key role in aggregation observed at hydrophobic interfaces.

  5. Composite, nanostructured, super-hydrophobic material

    DOEpatents

    D'Urso, Brian R.; Simpson, John T.

    2007-08-21

    A hydrophobic disordered composite material having a protrusive surface feature includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite material having an etched surface wherein the protrusive phase protrudes from the surface to form a protrusive surface feature, the protrusive feature being hydrophobic.

  6. Hydrophobic Silsesquioxane Nanoparticles and Nanocomposite Surfaces (POSTPRINT)

    DTIC Science & Technology

    2006-05-04

    Fluorinated Polyhedral Oligomeric Silsesquioxanes are hydrophobic nanoparticles. One compound, FD8T8, is ultrahydrophobic, possessing a water contact ... angle of 154 deg. This is believed to be the most hydrophobic and lowest surface tension crystalline substance known. Analysis of the x-ray crystal

  7. Why are water-hydrophobic interfaces charged?

    PubMed

    Kudin, Konstantin N; Car, Roberto

    2008-03-26

    We report ab initio molecular dynamics simulations of hydroxide and hydronium ions near a hydrophobic interface, indicating that both ions behave like amphiphilic surfactants that stick to a hydrophobic hydrocarbon surface with their hydrophobic side. We show that this behavior originates from the asymmetry of the molecular charge distribution which makes one end of the ions strongly hydrophobic while the other end is even more hydrophilic than the regular water (H2O) molecules. The effect is more pronounced for the hydroxide than for the hydronium. Our results are consistent with several experimental observations and explain why hydrophobic surfaces in contact with water acquire a net negative charge, a phenomenon that has important implications for biology and polymer science.

  8. Structural and energetic consequences of mutations in a solvated hydrophobic cavity

    NASA Technical Reports Server (NTRS)

    Adamek, D. H.; Guerrero, L.; Blaber, M.; Caspar, D. L. D.

    2005-01-01

    The structural and energetic consequences of modifications to the hydrophobic cavity of interleukin 1-beta (IL-1beta) are described. Previous reports demonstrated that the entirely hydrophobic cavity of IL-1beta contains positionally disordered water. To gain a better understanding of the nature of this cavity and the water therein, a number of mutant proteins were constructed by site-directed mutagenesis, designed to result in altered hydrophobicity of the cavity. These mutations involve the replacement of specific phenylalanine residues, which circumscribe the cavity, with tyrosine, tryptophan, leucine and isoleucine. Using differential scanning calorimetry to determine the relative stabilities of the wild-type and mutant proteins, we found all of the mutants to be destabilizing. X-ray crystallography was used to identify the structural consequences of the mutations. No clear correlation between the hydrophobicities of the specific side-chains introduced and the resulting stabilities was found.

  9. Superficial Burn Wound Healing with Intermittent Negative Pressure Wound Therapy Under Limited Access and Conventional Dressings

    PubMed Central

    Honnegowda, Thittamaranahalli Muguregowda; Padmanabha Udupa, Echalasara Govindarama; Rao, Pragna; Kumar, Pramod; Singh, Rekha

    2016-01-01

    BACKGROUND Thermal injury is associated with several biochemical and histopathological alteration in tissue. Analysis of these objective parameters in research and clinical field are common to determine healing rate of burn wound. Negative pressure wound therapy has been achieved wide success in treating chronic wounds. This study determines superficial burn wound healing with intermittent negative pressure wound therapy under limited access and conventional dressings METHODS A total 50 patients were randomised into two equal groups: limited access and conventional dressing groups. Selective biochemical parameters such as hydroxyproline, hexosamine, total protein, and antioxidants, malondialdhyde (MDA), wound surface pH, matrix metalloproteinase-2 (MMP-2), and nitric oxide (NO) were measured in the granulation tissue. Histopathologically, necrotic tissue, amount of inflammatory infiltrate, angiogenesis and extracellular matrix deposition (ECM) were studied to determine wound healing under intermittent negative pressure. RESULTS Patients treated with limited access have shown significant increase in the mean hydroxyproline, hexosamine, total protein, reduced glutathione (GSH), glutathione peroxidase (GPx), and decrease in MDA, MMP-2, wound surface pH, and NO. Histopathologic study showed that there was a significant difference after 10 days of treatment between limited access vs conventional dressing group, Median (Q1, Q3)=3 (2, 4.25) vs 2 (1.75, 4). CONCLUSION Limited access was shown to exert its beneficial effects on wound healing by increasing ground substance, antioxidants and reducing MMP-2 activity, MDA, NO and providing optimal pH, decreasing necrotic tissue, amount of inflammatory infiltrate, increasing ECM deposition and angiogenesis. PMID:27853690

  10. Application of VitaVallis dressing for infected wounds

    NASA Astrophysics Data System (ADS)

    Kirilova, N. V.; Fomenko, A. N.; Korovin, M. S.

    2015-11-01

    Today there is a growing demand for safe and efficient antimicrobial dressings for infected wound treatment. The antimicrobial sorption material for VitaVallis dressings was produced by one-stage oxidation of aluminum nanopowder in water in the presence of fibrous acetylcellulose matrix. Scanning electron microscopy revealed that the material is made up of fibers of diameter 1.5-3.0 µm with adhered agglomerated alumina nanosheets. An antimicrobial study revealed a high inhibitory effect of VitaVallis against the growth of gram-negative (E.coli, P. aeruginosa) and gram-positive (S. aureus) strains. The antimicrobial activity of the dressing against microbial pathogens on the wound surface was demonstrated in in vivo experiments on male rats. The dressing was also tested on volunteer patients. The testing showed reduction of the wound healing period, accelerated cleaning of the infected wound and enhanced tissue regeneration in the wound. The results demonstrate that the VitaVallis dressing can be used for the treatment of deep infected wounds.

  11. Application of VitaVallis dressing for infected wounds

    SciTech Connect

    Kirilova, N. V. Fomenko, A. N. Korovin, M. S.

    2015-11-17

    Today there is a growing demand for safe and efficient antimicrobial dressings for infected wound treatment. The antimicrobial sorption material for VitaVallis dressings was produced by one-stage oxidation of aluminum nanopowder in water in the presence of fibrous acetylcellulose matrix. Scanning electron microscopy revealed that the material is made up of fibers of diameter 1.5–3.0 µm with adhered agglomerated alumina nanosheets. An antimicrobial study revealed a high inhibitory effect of VitaVallis against the growth of gram-negative (E.coli, P. aeruginosa) and gram-positive (S. aureus) strains. The antimicrobial activity of the dressing against microbial pathogens on the wound surface was demonstrated in in vivo experiments on male rats. The dressing was also tested on volunteer patients. The testing showed reduction of the wound healing period, accelerated cleaning of the infected wound and enhanced tissue regeneration in the wound. The results demonstrate that the VitaVallis dressing can be used for the treatment of deep infected wounds.

  12. Transient absorption spectra of the laser-dressed hydrogen atom

    NASA Astrophysics Data System (ADS)

    Murakami, Mitsuko; Chu, Shih-I.

    2013-10-01

    We present a theoretical study of transient absorption spectra of laser-dressed hydrogen atoms, based on numerical solutions of the time-dependent Schrödinger equation. The timing of absorption is controlled by the delay between an extreme ultra violet (XUV) pulse and an infrared (IR) laser field. The XUV pulse is isolated and several hundred attoseconds in duration, which acts as a pump to drive the ground-state electron to excited p states. The subsequent interaction with the IR field produces dressed states, which manifest as sidebands between the 1s-np absorption spectra separated by one IR-photon energy. We demonstrate that the population of dressed states is maximized when the timing of the XUV pulse coincides with the zero crossing of the IR field, and that their energies can be manipulated in a subcycle time scale by adding a chirp to the IR field. An alternative perspective to the problem is to think of the XUV pulse as a probe to detect the dynamical ac Stark shifts. Our results indicate that the accidental degeneracy of the hydrogen excited states is removed while they are dressed by the IR field, leading to large ac Stark shifts. Furthermore, we observe the Autler-Townes doublets for the n=2 and 3 levels using the 656 nm dressing field, but their separation does not agree with the prediction by the conventional three-level model that neglects the dynamical ac Stark shifts.

  13. Spectroscopic signatures of dressed Rydberg-Rydberg interactions in Sr

    NASA Astrophysics Data System (ADS)

    Mukherjee, Rick; Hazzard, Kaden

    2015-05-01

    Ultracold Rydberg-dressed atoms exhibit strong, long-range interactions that can potentially create exotic phases of matter and entangled states that are useful in quantum computation and metrology. Rydberg-dressed atoms are obtained by off-resonantly admixing a Rydberg state | R > into a long-lived electronic state, often the ground state. As a tool to observe dressed Rydberg interactions, we theoretically consider a spectroscopic method that relies on strontium's unique long-lived (~ 23 μ s) electronic excited state 3P1. Specifically, we consider an effective two level system: the electronic ground state | G > and the Rydberg dressed state | D > = | 3 P1 > + ɛ | R > with ɛ << 1 . Using spin language to describe this two level system, our proposed Ramsey scheme rotates the spins by angle θ, allows the atoms to interact for a time t, and then measures the final spin vector. Our calculation is exact and includes experimental complications, such as dissipation and pulse timing errors. Excitingly, the dependence of the spin vector on time and θ can be used to experimentally measure the strength and power law dependence of the dressed Rydberg atom interaction.

  14. Phase behavior of a lattice hydrophobic oligomer in explicit water.

    PubMed

    Romero-Vargas Castrillón, Santiago; Matysiak, Silvina; Stillinger, Frank H; Rossky, Peter J; Debenedetti, Pablo G

    2012-08-09

    We investigate the thermodynamics of hydrophobic oligomer collapse using a water-explicit, three-dimensional lattice model. The model captures several aspects of protein thermodynamics, including the emergence of cold- and thermal-unfolding, as well as unfolding at high solvent density (a phenomenon akin to pressure-induced denaturation). We show that over a range of conditions spanning a ≈14% increase in solvent density, the oligomer transforms into a compact, strongly water-penetrated conformation at low temperature. This contrasts with thermal unfolding at high temperature, where the system "denatures" into an extended random coil conformation. We report a phase diagram for hydrophobic collapse that correctly captures qualitative aspects of cold and thermal unfolding at low to intermediate solvent densities.

  15. Quantification of hydrophobic interaction affinity of colloids

    NASA Astrophysics Data System (ADS)

    Saini, G.; Nasholm, N.; Wood, B. D.

    2009-12-01

    Colloids play an important role in a wide variety of disciplines, including water and wastewater treatment, subsurface transport of metals and organic contaminants, migration of fines in oil reservoirs, biocolloid (virus and bacteria) transport in subsurface, and are integral to laboratory transport studies. Although the role of hydrophobicity in adhesion and transport of colloids, particularly bacteria, is well known; there is scarcity of literature regarding hydrophobicity measurement of non-bacterial colloids and other micron-sized particles. Here we detail an experimental approach based on differential partitioning of colloids between two liquid phases (hydrocarbon and buffer) as a measure of the hydrophobic interaction affinity of colloids. This assay, known as Microbial adhesion to hydrocarbons or MATH, is frequently used in microbiology and bacteriology for quantifying the hydrophobicity of microbes. Monodispersed colloids and particles, with sizes ranging from 1 micron to 33 micron, were used for the experiments. A range of hydrophobicity values were observed for different particles. The hydrophobicity results are also verified against water contact angle measurements of these particles. This liquid-liquid partitioning assay is quick, easy-to-perform and requires minimal instrumentation. Estimation of the hydrophobic interaction affinity of colloids would lead to a better understanding of their adhesion to different surfaces and subsequent transport in porous media.

  16. DRESS syndrome and thrombotic thrombocytopaenic purpura: are they related?

    PubMed Central

    Sandouk, Zahrae; Alirhayim, Zaid; Khoulani, Dania; Hassan, Syed

    2012-01-01

    A middle-aged man diagnosed with a drug reaction with eosinophilia and systemic symptom (DRESS) syndrome, secondary to phenytoin use, subsequently developed thrombotic thrombocytopaenic purpura. The patient improved with steroids and plasmapheresis. Their diagnosis can be challenging, and an early recognition and treatment are critical owing to their high mortality rates. Both diseases are thought to be of an autoimmune origin, and a potential relationship between them led to the consideration of the DRESS syndrome as an aetiology for thrombotic thrombocytopaenic purpura in this case. We concluded that two possibilities exist: some type of antibody developed during the clinical presentation of DRESS syndrome and subsequently resulted in an inhibition of a disintegrin and metalloproteinase with a thrombospondin type-1 motif, member 13 (ADAMTS13) leading to thrombotic thrombocytopaenic purpura, or perhaps this patient's autoimmune predisposition to thrombotic thrombocytopaenic purpura contributed to the drug reaction. PMID:23152183

  17. Expanding Dress Code Requirements in the Doctor of Pharmacy Program.

    PubMed

    Naughton, Cynthia A; Schweiger, Teresa A; Angelo, Lauren B; Lea Bonner, C; Dhing, Conrad W; Farley, Joel F

    2016-06-25

    Although the use of a professional dress code is standard practice across colleges and schools of pharmacy during introductory and advanced pharmacy practice experiences, requiring professional attire is not applied consistently during the didactic portion of students' education. There are arguments for and against the adoption of a professional dress code throughout the entire doctor of pharmacy program, including the classroom setting. Given uncertainty regarding the potential benefits and challenges that may arise from adopting a professional dress code in the didactic portion of a student pharmacist's education, it is perhaps not surprising that programs adopt disparate policies regarding its use. This exploration was conducted as part of a series of debates held in conjunction with the American Association of Colleges of Pharmacy's (AACP) Academic Leadership Fellows Program (ALFP) and was presented at the 2015 AACP Interim Meeting on February 7, 2015.

  18. [Skin reaction to carbamazepine or DRESS syndrome: a case presentation].

    PubMed

    Cabrera Fundora, Emigdio Jesús; Cabrera Osorio, Yuliet; Cabrera Osorio, Claudia

    2016-02-25

    Carbamazepine is a frequently used drug that can produce adverse reactions like vertigo, somnolence and severe skin reactions like Drug Rash with Eosinophilia and Systemic Symptoms Syndrome (DRESS Syndrome). This syndrome is characterized by a late-appearing, slow-progressing cutaneous eruption accompanied by atypical lymphocytes, eosinophilia, and systemic symptoms such as fever, lymphadenopathy, hepatic compromise, and renal dysfunction that can be severe enough to cause death. We present a case that aims to highlight the importance of an early diagnosis of DRESS syndrome to adjust therapy and improve survival. The patient is a female patient prescribed carbamazepine for trigeminal neuralgia who presented with skin lesions, which were initially attributed to a hypersensitivity reaction. The lesions worsened in spite of treatment and systemic symptoms ensued. A diagnosis of DRESS syndrome was proposed and steroid treatment was initiated with rapid improvement.

  19. Role of dressed-state interference in electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Khan, Sumanta; Bharti, Vineet; Natarajan, Vasant

    2016-12-01

    Electromagnetically induced transparency (EIT) in three-level systems uses a strong control laser on one transition to modify the absorption of a weak probe laser on a second transition. The control laser creates dressed states whose decay pathways show interference. We study the role of dressed-state interference in causing EIT in the three types of three-level systems-lambda (Λ), ladder (Ξ), and vee (V). In order to get realistic values for the linewidths of the energy levels involved, we consider appropriate hyperfine levels of 87Rb. For such realistic systems, we find that dressed-state interference causes probe absorption-given by the imaginary part of the susceptibility-to go to zero in a Λ system, but plays a negligible role in Ξ and V systems.

  20. The Efficacy of Gelam Honey Dressing towards Excisional Wound Healing.

    PubMed

    Tan, Mui Koon; Hasan Adli, Durriyyah Sharifah; Tumiran, Mohd Amzari; Abdulla, Mahmood Ameen; Yusoff, Kamaruddin Mohd

    2012-01-01

    Honey is one of the oldest substances used in wound management. Efficacy of Gelam honey in wound healing was evaluated in this paper. Sprague-Dawley rats were randomly divided into four groups of 24 rats each (untreated group, saline group, Intrasite Gel group, and Gelam honey group) with 2 cm by 2 cm full thickness, excisional wound created on neck area. Wounds were dressed topically according to groups. Rats were sacrificed on days 1, 5, 10, and 15 of treatments. Wounds were then processed for macroscopic and histological observations. Gelam-honey-dressed wounds healed earlier (day 13) than untreated and saline treated groups, as did wounds treated with Intrasite Gel. Honey-treated wounds exhibited less scab and only thin scar formations. Histological features demonstrated positive effects of Gelam honey on the wounds. This paper showed that Gelam honey dressing on excisional wound accelerated the process of wound healing.

  1. Bedazzled: A Blue and Black Ship, Dressed to Deceive

    PubMed Central

    2015-01-01

    The blue and black dress that “melted the Internet” is thought to have done so because its perceived color depended on people using different prior assumptions about discounting the illuminant. However, this is not the first monochromatic object to have confused the public. For a brief period during WWI, RMS Mauretania was dressed in (dazzle) camouflage shades of blue and black/grey, yet she is sometimes depicted by artists, modelers, and historians in a much showier dress of red, blue, yellow, green, and black. I raise the possibility that this originates from a case of public deception deriving from the momentary misperception of a playful artist who neglected to discount the illuminant, propagating the most (perhaps only) successful application of dazzle camouflage known. PMID:28299171

  2. Medicare Payment: Surgical Dressings and Topical Wound Care Products.

    PubMed

    Schaum, Kathleen D

    2014-08-01

    Medicare patients' access to surgical dressings and topical wound care products is greatly influenced by the Medicare payment system that exists in each site of care. Qualified healthcare professionals should consider these payment systems, as well as the medical necessity for surgical dressings and topical wound care products. Scientists and manufacturers should also consider these payment systems, in addition to the Food and Drug Administration requirements for clearance or approval, when they are developing new surgical dressings and topical wound care products. Due to the importance of the Medicare payment systems, this article reviews the Medicare payment systems in acute care hospitals, long-term acute care hospitals, skilled nursing facilities, home health agencies, durable medical equipment suppliers, hospital-based outpatient wound care departments, and qualified healthcare professional offices.

  3. Medicare Payment: Surgical Dressings and Topical Wound Care Products

    PubMed Central

    Schaum, Kathleen D.

    2014-01-01

    Medicare patients' access to surgical dressings and topical wound care products is greatly influenced by the Medicare payment system that exists in each site of care. Qualified healthcare professionals should consider these payment systems, as well as the medical necessity for surgical dressings and topical wound care products. Scientists and manufacturers should also consider these payment systems, in addition to the Food and Drug Administration requirements for clearance or approval, when they are developing new surgical dressings and topical wound care products. Due to the importance of the Medicare payment systems, this article reviews the Medicare payment systems in acute care hospitals, long-term acute care hospitals, skilled nursing facilities, home health agencies, durable medical equipment suppliers, hospital-based outpatient wound care departments, and qualified healthcare professional offices. PMID:25126477

  4. Trap losses induced by Rydberg dressing of cold atomic gases

    NASA Astrophysics Data System (ADS)

    Aman, J. A.; Desalvo, B. J.; Dunning, F. B.; Killian, T. C.

    2015-05-01

    The near-resonant dressing of ultracold strontium gases and BECs contained in an optical dipole trap (ODT) with the n = 303S1 Rydberg state is investigated as a function of the effective two-photon Rabi frequency, detuning, and dressing time. The measurements demonstrate that, even when well detuned from resonance, such dressing can lead to a rapid decrease in the ground-state atom population in the ODT. This decrease is attributed to Rydberg atom excitation which can lead to direct escape from the trap and/or population of very-long-lived metastable states. The large Rydberg atom production rates are explained using a reaction model in which the initial excitation of a Rydberg atom triggers the excitation of neighboring atoms leading to rapid avalanche-like growth in the Rydberg population. Research supported by the AFOSR, the NSF and the Robert A Welch Foundation.

  5. Expanding Dress Code Requirements in the Doctor of Pharmacy Program

    PubMed Central

    Schweiger, Teresa A.; Angelo, Lauren B.; Lea Bonner, C.; Dhing, Conrad W.; Farley, Joel F.

    2016-01-01

    Although the use of a professional dress code is standard practice across colleges and schools of pharmacy during introductory and advanced pharmacy practice experiences, requiring professional attire is not applied consistently during the didactic portion of students’ education. There are arguments for and against the adoption of a professional dress code throughout the entire doctor of pharmacy program, including the classroom setting. Given uncertainty regarding the potential benefits and challenges that may arise from adopting a professional dress code in the didactic portion of a student pharmacist’s education, it is perhaps not surprising that programs adopt disparate policies regarding its use. This exploration was conducted as part of a series of debates held in conjunction with the American Association of Colleges of Pharmacy’s (AACP) Academic Leadership Fellows Program (ALFP) and was presented at the 2015 AACP Interim Meeting on February 7, 2015. PMID:27402977

  6. Ice adhesion on super-hydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Kulinich, S. A.; Farzaneh, M.

    2009-06-01

    In this study, ice adhesion strength on flat hydrophobic and rough super-hydrophobic coatings with similar surface chemistry (based on same fluoropolymer) is compared. Glaze ice, similar to naturally accreted, was prepared on the surfaces by spraying super-cooled water microdroplets at subzero temperature. Ice adhesion was evaluated by spinning the samples at constantly increasing speed until ice delamination occurred. Super-hydrophobic surfaces with different contact angle hysteresis were tested, clearly showing that the latter, along with the contact angle, also influences the ice-solid adhesion strength.

  7. Super-hydrophobic fluorine containing aerogels

    DOEpatents

    Coronado, Paul R.; Poco, John F.; Hrubesh, Lawrence W.

    2007-05-01

    An aerogel material with surfaces containing fluorine atoms which exhibits exceptional hydrophobicity, or the ability to repel liquid water. Hydrophobic aerogels are efficient absorbers of solvents from water. Solvents miscible with water are separated from it because the solvents are more volatile than water and they enter the porous aerogel as a vapor across the liquid water/solid interface. Solvents that are immisicble with water are separated from it by selectively wetting the aerogel. The hydrophobic property is achieved by formulating the aerogel using fluorine containing molecules either directly by addition in the sol-gel process, or by treating a standard dried aerogel using the vapor of fluorine containing molecules.

  8. Effect of dressing choice on outcomes after hip and knee arthroplasty: a literature review.

    PubMed

    Tustanowski, J

    2009-11-01

    Selecting the right dressing for these wounds can prevent blistering, maceration and the risk of infection. Ideally, the dressing should be permeable, waterproof, transparent, absorbent and flexible enough to withstand joint movement.

  9. The effect of ethanol and heat on the functional hydrophobicity of casein micelles.

    PubMed

    Trejo, R; Harte, F

    2010-06-01

    Milk proteins are very important ingredients to the food industry. As new uses and applications for these proteins are developed, it becomes more important to understand their physicochemical properties when they are subjected to different treatments. It has been reported that casein micelles dissociate when heated in the presence of ethanol. The changes to the hydrophobicity of milk proteins during that process were evaluated by using the fluorescent hydrophobic probe 1-anilinonaphthalene-8-sulfonic acid (ANS). Raw skim milk, pasteurized skim milk, and whey protein isolate samples with ethanol concentrations of 0 to 60% (vol/vol) were heated from 20 to 60 degrees C. The fluorescence of the samples with and without the addition of ANS was measured at an excitation wavelength of 390 nm and an emission wavelength of 400 to 500 nm. The results showed a decrease in the extrinsic fluorescence of the samples as the ethanol concentration and temperature increased, indicating competitive inhibition of the ANS-hydrophobic site interaction by ethanol. This inhibition was further enhanced by the addition of heat. This resulted in a reduction in the functional hydrophobicity of the milk proteins as ethanol rendered the hydrophobic sites unavailable for interaction.

  10. Sericin-binded-deprotenized natural rubber film containing chitin whiskers as elasto-gel dressing.

    PubMed

    Watthanaphanit, Anyarat; Rujiravanit, Ratana

    2017-03-18

    Here, we aims to demonstrate a simple concept in biomaterials design by using natural resources solely as raw materials to fabricate elastic wound care dressing. Elasto-gel films comprise of silk sericin (SRC), natural rubber (NR), and chitin whisker (CTW) were developed. A glue-like protein SRC found in silk cocoons is beneficial for the treatment of wounds due to its superior skin moisturizing ability. However, the pure SRC film is generally difficult to be fabricated because of its weak structural feature. This limitation was overcome by using NR as a binder which consecutively rendered elasticity and strength of the films. CTW was chosen as another component to promote ability of the films for tissue restoration. Before the film formation, protein in the natural rubber latex (NRL) was removed to avoid allergic and cytotoxic problems. The enzyme-treated NR/SRC (ETNR/SRC) films having different blend compositions were fabricated by solution casting technique. The highest amount of the SRC to gain an easy to handle ETNR/SRC film was 30%. The ETNR/SRC/CTW films having 20% SRC were fabricated and studied in comparison. Essential properties of the films as elastic wound care dressings were investigated and effect of the materials chemistry on the observed properties were discussed.

  11. Hydrophobic interactions increase attachment of gum Arabic- and PVP-coated Ag nanoparticles to hydrophobic surfaces.

    PubMed

    Song, Jee Eun; Phenrat, Tanapon; Marinakos, Stella; Xiao, Yao; Liu, Jie; Wiesner, Mark R; Tilton, Robert D; Lowry, Gregory V

    2011-07-15

    A fundamental understanding of attachment of surface-coated nanoparticles (NPs) is essential to predict the distribution and potential risks of NPs in the environment. Column deposition studies were used to examine the effect of surface-coating hydrophobicity on NP attachment to collector surfaces in mixtures with varying ratios of octadecylichlorosilane (OTS)-coated (hydrophobic) glass beads and clean silica (hydrophilic) glass beads. Silver nanoparticles (AgNPs) coated with organic coatings of varying hydrophobicity, including citrate, polyvinylpyrrolidone (PVP), and gum arabic (GA), were used. The attachment efficiencies of GA and PVP AgNPs increased by 2- and 4-fold, respectively, for OTS-coated glass beads compared to clean glass beads. Citrate AgNPs showed no substantial change in attachment efficiency for hydrophobic compared to hydrophilic surfaces. The attachment efficiency of PVP-, GA-, and citrate-coated AgNPs to hydrophobic collector surfaces correlated with the relative hydrophobicity of the coatings. The differences in the observed attachment efficiencies among AgNPs could not be explained by classical DLVO, suggesting that hydrophobic interactions between AgNPs and OTS-coated glass beads were responsible for the increase in attachment of surface-coated AgNPs with greater hydrophobicity. This study indicates that the overall attachment efficiency of AgNPs will be influenced by the hydrophobicity of the NP coating and the fraction of hydrophobic surfaces in the environment.

  12. Effects of Hydrophobic Macromolecular Crowders on Amyloid β (16–22) Aggregation

    PubMed Central

    Latshaw, David C.; Hall, Carol K.

    2015-01-01

    In Alzheimer’s disease (AD), the amyloid β (Aβ) peptide aggregates in the brain to form progressively larger oligomers, fibrils, and plaques. The aggregation process is strongly influenced by the presence of other macromolecular species, called crowders, that can exert forces on the proteins. One very common attribute of macromolecular crowders is their hydrophobicity. We examined the effect of hydrophobic crowders on protein aggregation by using discontinuous molecular dynamics (DMD) simulations in combination with an intermediate resolution protein model, PRIME20. The systems considered contained 48 Aβ (16–22) peptides and crowders with diameters of 5 Å, 20 Å, and 40 Å, represented by hard spheres or spheres with square-well/square-shoulder interactions, at a crowder volume fraction of ϕ = 0.10. Results show that low levels of crowder hydrophobicity are capable of increasing the fibrillation lag time and high levels of crowder hydrophobicity can fully prevent the formation of fibrils. The types of structures that remain during the final stages of the simulations are summarized in a global phase diagram that shows fibril, disordered oligomer, or β-sheet phases in the space spanned by crowder size and crowder hydrophobicity. In particular, at high levels of hydrophobicity, simulations with 5 Å crowders result in only disordered oligomers and simulations with 40 Å crowders result in only β-sheets. The presence of hydrophobic crowders reduces the antiparallel β-sheet content of fibrils, whereas hard sphere crowders increase it. Finally, strong hydrophobic crowders alter the secondary structure of the Aβ (16–22) monomers, bending them into a shape that is incapable of forming ordered β-sheets or fibrils. These results qualitatively agree with previous theoretical and experimental work. PMID:26153709

  13. Dressed Hard States and Black Hole Soft Hair

    NASA Astrophysics Data System (ADS)

    Mirbabayi, Mehrdad; Porrati, Massimo

    2016-11-01

    A recent, intriguing Letter by Hawking, Perry, and Strominger suggests that soft photons and gravitons can be regarded as black hole hair and may be relevant to the black hole information paradox. In this Letter we make use of factorization theorems for infrared divergences of the S matrix to argue that by appropriately dressing in and out hard states, the soft-quanta-dependent part of the S matrix becomes essentially trivial. The information paradox can be fully formulated in terms of dressed hard states, which do not depend on soft quanta.

  14. Dressed Hard States and Black Hole Soft Hair.

    PubMed

    Mirbabayi, Mehrdad; Porrati, Massimo

    2016-11-18

    A recent, intriguing Letter by Hawking, Perry, and Strominger suggests that soft photons and gravitons can be regarded as black hole hair and may be relevant to the black hole information paradox. In this Letter we make use of factorization theorems for infrared divergences of the S matrix to argue that by appropriately dressing in and out hard states, the soft-quanta-dependent part of the S matrix becomes essentially trivial. The information paradox can be fully formulated in terms of dressed hard states, which do not depend on soft quanta.

  15. Nanomaterials from bacterial cellulose for antimicrobial wound dressing

    NASA Astrophysics Data System (ADS)

    Liyaskina, E.; Revin, V.; Paramonova, E.; Nazarkina, M.; Pestov, N.; Revina, N.; Kolesnikova, S.

    2017-01-01

    Bacterial nanocellulose (BNC) is widely used in biomedical applications. BNC has attracted increasing attention as a novel wound dressing material, but it has no antimicrobial activity. To get over this problem in the present study the BNC was saturated with antibiotic fusidic acid (FA). The subject of the experiment was BNC, produced by bacteria Gluconacetobacter sucrofermentans B-11267. The resulting biocomposites have high antibiotic activity against Staphylococcus aureus and can be used in medicine as a wound dressing. The structure of BNC was analyzed by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR).

  16. Biomaterials based on chitin and chitosan in wound dressing applications.

    PubMed

    Jayakumar, R; Prabaharan, M; Sudheesh Kumar, P T; Nair, S V; Tamura, H

    2011-01-01

    Wound dressing is one of the most promising medical applications for chitin and chitosan. The adhesive nature of chitin and chitosan, together with their antifungal and bactericidal character, and their permeability to oxygen, is a very important property associated with the treatment of wounds and burns. Different derivatives of chitin and chitosan have been prepared for this purpose in the form of hydrogels, fibers, membranes, scaffolds and sponges. The purpose of this review is to take a closer look on the wound dressing applications of biomaterials based on chitin, chitosan and their derivatives in various forms in detail.

  17. Dressed-atom description of the bichromatic force

    SciTech Connect

    Yatsenko, Leonid; Metcalf, Harold

    2004-12-01

    We develop a dressed-atom picture of the bichromatic force in two standing waves using a Floquet approach. It is based on previous work, but the approach allows for an interpretation of the velocity range of the force. It is limited to two-level atoms and one dimension, and the Floquet frequency is the beat between the two bichromatic optical fields. The force is mediated by Landau-Zener transitions between the dressed states of the Floquet Hamiltonian. Related topics have been addressed before in the literature, but not applied to this particular case.

  18. Colloidal silver-based nanogel as nonocclusive dressing for multiple superficial pellet wounds.

    PubMed

    Dharmshaktu, Ganesh Singh; Singhal, Aanshu; Pangtey, Tanuja

    2016-01-01

    A good dressing is mandatory to an uncomplicated wound healing, especially when foreign particles contaminate the wound. Various forms of dressing preparations are available for use and differ in chemical composition and efficacy. Silver has been a known agent with good antimicrobial and healing properties and recent times has seen an upsurge in various silver-based dressing supplements. We describe our report of use and efficacy of a silver nanoparticle- based gel dressing in the healing of multiple superficial firearm pellet wounds.

  19. Hemicellulose dressing versus rayon dressing in the re-epithelialization of split-thickness skin graft donor sites: a multicenter study.

    PubMed

    Ferreira, Lydia M; Blanes, Leila; Gragnani, Alfredo; Veiga, Daniela F; Veiga, Frederico P; Nery, Gilka B; Rocha, Gustavo Henrique H R; Gomes, Heitor C; Rocha, Mario G; Okamoto, Regina

    2009-08-01

    The aim of this study was to compare the effectiveness of a hemicellulose dressing with that of rayon dressing in the healing of split-thickness skin graft donor sites. Twenty-eight patients were selected from five different hospitals and randomized into two groups: hemicellulose dressing group and rayon dressing group. All patients underwent split-thickness skin grafting for various reasons, and the skin graft donor site wounds were covered with hemicellulose dressing (n=14) or rayon dressing (n=14). The donor site was assessed on postoperative days 1, 7, 14, 21, and 28 for hyperemia, pruritus, pain, exudate level, and adherence of the wound dressing. At the 60-day follow-up visit, the donor site was assessed again for pruritus and pain. Touch-pressure, thermal, and pain sensibility tests were performed preoperatively and on postoperative day 60 together with the assessment of color and texture of the re-epithelialized area. In all patients, re-epithelialization was completed between 14 and 21 days after surgery. There were no significant differences between the two groups with regard to pain, hyperemia, pruritus, exudate, and final appearance (color and texture) of the skin graft donor site. The rayon dressing provided significantly better adherence than the hemicellulose dressing, and both dressings showed similar results with regard to the parameters evaluated when used in the treatment of split-thickness skin graft donor sites.

  20. Erosion and flow of hydrophobic granular materials

    NASA Astrophysics Data System (ADS)

    Utter, Brian; Benns, Thomas; Foltz, Benjamin; Mahler, Joseph

    2015-03-01

    We experimentally investigate submerged granular flows of hydrophobic and hydrophilic grains both in a rotating drum geometry and under erosion by a surface water flow. While slurry and suspension flows are common in nature and industry, effects of surface chemistry on flow behavior have received relatively little attention. In the rotating drum, we use varying concentrations of hydrophobic and hydrophilic grains of sand submerged in water rotated at a constant angular velocity. Sequential images of the resulting avalanches are taken and analyzed. High concentrations of hydrophobic grains result in an effectively cohesive interaction between the grains forming aggregates, with aggregate size and repose angle increasing with hydrophobic concentration. However, the formation and nature of the aggregates depends significantly on the presence of air in the system. We present results from a related experiment on erosion by a surface water flow designed to characterize the effects of heterogeneous granular surfaces on channelization and erosion.