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Sample records for molecular motor kif3

  1. Molecular characterization of a KIF3B-like kinesin gene in the testis of Octopus tankahkeei (Cephalopoda, Octopus).

    PubMed

    Dang, Ran; Zhu, Jun-Quan; Tan, Fu-Qing; Wang, Wei; Zhou, Hong; Yang, Wan-Xi

    2012-05-01

    KIF3B is known for maintaining and assembling cilia and flagellum. To date, the function of KIF3B and its relationship with KIF3A during spermiogenesis in the cephalopod Octopus tankahkeei remains unknown. In the present study, we characterized a gene encoding a homologue of rat KIF3B in the O. tankahkeei testis and examined its temporal and spatial expression pattern during spermiogenesis. The cDNA of KIF3B was obtained with degenerate and RACE PCR and the distribution pattern of ot-kif3b were observed with RT-PCR. The morphological development during spermiogenesis was illustrated by histological and transmission electron microscopy and mRNA expression of ot-kif3b was observed by in situ hybridization. The 2,365 nucleotides cDNA consisted of a 102 bp 5' untranslated region (UTR), a 2,208 bp open reading frame (ORF) encoding a protein of 736 amino acids, and a 55 bp 3' UTR. Multiple alignments revealed that the putative Ot-KIF3B shared 68, 68, 69, 68, and 67% identity with that of Homo sapiens, Mus musculus, Gallus gallus, Danio rerio, and Xenopus laevis, respectively, along with high identities with Ot-KIF3A in fundamental structures. Ot-kif3b transcripts appeared gradually in early spermatids, increased in intermediate spermatids and maximized in drastically remodeled and final spermatids. The kif3b gene is identified and its expression pattern is demonstrated for the first time in O. tankahkeei. Compared to ot-kif3a reported by our laboratory before, our data suggested that the putative heterodimeric motor proteins Ot-KIF3A/B may be involved in intraspermatic transport and might contribute to structural changes during spermiogenesis.

  2. KIF3C and KIF3A Form a Novel Neuronal Heteromeric Kinesin That Associates with Membrane Vesicles

    PubMed Central

    Muresan, Virgil; Abramson, Tatiana; Lyass, Asya; Winter, Dirk; Porro, Elena; Hong, Filbert; Chamberlin, Nancy L.; Schnapp, Bruce J.

    1998-01-01

    We have cloned from rat brain the cDNA encoding an 89,828-Da kinesin-related polypeptide KIF3C that is enriched in brain, retina, and lung. Immunocytochemistry of hippocampal neurons in culture shows that KIF3C is localized to cell bodies, dendrites, and, in lesser amounts, to axons. In subcellular fractionation experiments, KIF3C cofractionates with a distinct population of membrane vesicles. Native KIF3C binds to microtubules in a kinesin-like, nucleotide-dependent manner. KIF3C is most similar to mouse KIF3B and KIF3A, two closely related kinesins that are normally present as a heteromer. In sucrose density gradients, KIF3C sediments at two distinct densities, suggesting that it may be part of two different multimolecular complexes. Immunoprecipitation experiments show that KIF3C is in part associated with KIF3A, but not with KIF3B. Unlike KIF3B, a significant portion of KIF3C is not associated with KIF3A. Consistent with these biochemical properties, the distribution of KIF3C in the CNS has both similarities and differences compared with KIF3A and KIF3B. These results suggest that KIF3C is a vesicle-associated motor that functions both independently and in association with KIF3A. PMID:9487132

  3. Heterotrimeric kinesin-2 (KIF3) mediates transition zone and axoneme formation of mouse photoreceptors.

    PubMed

    Jiang, Li; Wei, Yuxiao; Ronquillo, Cecinio C; Marc, Robert E; Yoder, Bradley K; Frederick, Jeanne M; Baehr, Wolfgang

    2015-05-15

    Anterograde intraflagellar transport (IFT) employing kinesin-2 molecular motors has been implicated in trafficking of photoreceptor outer segment proteins. We generated embryonic retina-specific (prefix "emb") and adult tamoxifen-induced (prefix "tam") deletions of KIF3a and IFT88 in adult mice to study photoreceptor ciliogenesis and protein trafficking. In (emb)Kif3a(-/-) and in (emb)Ift88(-/-) mice, basal bodies failed to extend transition zones (connecting cilia) with outer segments, and visual pigments mistrafficked. In contrast, (tam)Kif3a(-/-) and (tam)Ift88(-/-) photoreceptor axonemes disintegrated slowly post-induction, starting distally, but rhodopsin and cone pigments trafficked normally for more than 2 weeks, a time interval during which the outer segment is completely renewed. The results demonstrate that visual pigments transport to the retinal outer segment despite removal of KIF3 and IFT88, and KIF3-mediated anterograde IFT is responsible for photoreceptor transition zone and axoneme formation. PMID:25825494

  4. Stability and specificity of heterodimer formation for the coiled-coil neck regions of the motor proteins Kif3A and Kif3B: the role of unstructured oppositely charged regions

    PubMed Central

    Chana, M.S.; Tripet, B.P.; Mant, C.T.; Hodges, R.

    2005-01-01

    We investigated the folding, stability, and specificity of dimerization of the neck regions of the kinesin-like proteins Kif3A (residues 356–416) and Kif3B (residues 351–411). We showed that the complementary charged regions found in the hinge regions (which directly follow the neck regions) of these proteins do not adopt any secondary structure in solution. We then explored the ability of the complementary charged regions to specify heterodimer formation for the neck region coiled-coils found in Kif3A and Kif3B. Redox experiments demonstrated that oppositely charged regions specified the formation of a heterodimeric coiled-coil. Denaturation studies with urea demonstrated that the negatively charged region of Kif3A dramatically destabilized its neck coiled-coil (urea1/2 value of 3.9 m compared with 6.7 m for the coiled-coil alone). By comparison, the placement of a positively charged region C-terminal to the neck coiled-coil of Kif3B had little effect on stability (urea1/2 value of 8.2 m compared with 8.8 m for the coiled-coil alone). The pairing of complementary charged regions leads to specific heterodimer formation where the stability of the heterodimeric neck coiled-coil with charged regions had similar stability (urea1/2 value of 7.8 m) to the most stable homodimer (Kif3B) with charged regions (urea1/2 value of 8.0 m) and dramatically more stable than the Kif3A homodimer with charged regions (urea1/2, value of 3.9 m). The heterodimeric coiled-coil with charged extensions has essentially the same stability as the heterodimeric coiled-coil on its own (urea1/2 values of 7.8 and 8.1 m, respectively) suggesting that specificity of heterodimerization is driven by non-specific attraction of the oppositely unstructured charged regions without affecting stability of the heterodimeric coiled-coil. PMID:15705165

  5. Kinesin-2 KIF3AC and KIF3AB Can Drive Long-Range Transport along Microtubules

    PubMed Central

    Guzik-Lendrum, Stephanie; Rank, Katherine C.; Bensel, Brandon M.; Taylor, Keenan C.; Rayment, Ivan; Gilbert, Susan P.

    2015-01-01

    Mammalian KIF3AC is classified as a heterotrimeric kinesin-2 that is best known for organelle transport in neurons, yet in vitro studies to characterize its single molecule behavior are lacking. The results presented show that a KIF3AC motor that includes the native helix α7 sequence for coiled-coil formation is highly processive with run lengths of ∼1.23 μm and matching those exhibited by conventional kinesin-1. This result was unexpected because KIF3AC exhibits the canonical kinesin-2 neck-linker sequence that has been reported to be responsible for shorter run lengths observed for another heterotrimeric kinesin-2, KIF3AB. However, KIF3AB with its native neck linker and helix α7 is also highly processive with run lengths of ∼1.62 μm and exceeding those of KIF3AC and kinesin-1. Loop L11, a component of the microtubule-motor interface and implicated in activating ADP release upon microtubule collision, is significantly extended in KIF3C as compared with other kinesins. A KIF3AC encoding a truncation in KIF3C loop L11 (KIF3ACΔL11) exhibited longer run lengths at ∼1.55 μm than wild-type KIF3AC and were more similar to KIF3AB run lengths, suggesting that L11 also contributes to tuning motor processivity. The steady-state ATPase results show that shortening L11 does not alter kcat, consistent with the observation that single molecule velocities are not affected by this truncation. However, shortening loop L11 of KIF3C significantly increases the microtubule affinity of KIF3ACΔL11, revealing another structural and mechanistic property that can modulate processivity. The results presented provide new, to our knowledge, insights to understand structure-function relationships governing processivity and a better understanding of the potential of KIF3AC for long-distance transport in neurons. PMID:26445448

  6. Critical role for the kinesin KIF3A in the HIV life cycle in primary human macrophages

    PubMed Central

    Gaudin, Raphaël; Cunha de Alencar, Bruna; Jouve, Mabel; Bèrre, Stefano; Le Bouder, Emmanuel; Schindler, Michael; Varthaman, Aditi; Gobert, François-Xavier

    2012-01-01

    Macrophages are long-lived target cells for HIV infection and are considered viral reservoirs. HIV assembly in macrophages occurs in virus-containing compartments (VCCs) in which virions accumulate and are stored. The regulation of the trafficking and release of these VCCs remains unknown. Using high resolution light and electron microscopy of HIV-1–infected primary human macrophages, we show that the spatial distribution of VCCs depended on the microtubule network and that VCC-limiting membrane was closely associated with KIF3A+ microtubules. Silencing KIF3A strongly decreased virus release from HIV-1–infected macrophages, leading to VCC accumulation intracellularly. Time-lapse microscopy further suggested that VCCs and associated KIF3A move together along microtubules. Importantly, KIF3A does not play a role in HIV release from T cells that do not possess VCCs. These results reveal that HIV-1 requires the molecular motor KIF3 to complete its cycle in primary macrophages. Targeting this step may lead to novel strategies to eliminate this viral reservoir. PMID:23091068

  7. Functional Analysis of KIF3A and KIF3B during Spermiogenesis of Chinese Mitten Crab Eriocheir sinensis

    PubMed Central

    Lu, Yang; Wang, Qi; Wang, Da-Hui; Zhou, Hong; Hu, Yan-Jun; Yang, Wan-Xi

    2014-01-01

    Background Spermatogenesis represents the transformation process at the level of cellular development. KIF3A and KIF3B are believed to play some roles in the assembly and maintenance of flagella, intracellular transport of materials including organelles and proteins, and other unknown functions during this process. During spermatogenesis in Eriocheir sinensis, if the sperm shaping machinery is dependent on KIF3A and KIF3B remains unknown. Methodology/Principal Findings The cDNA of KIF3A and KIF3B were obtained by designing degenerate primers, 3′RACE, and 5′RACE. We detected the genetic presence of kif3a and kif3b in the heart, muscle, liver, gill, and testis of E. sinensis through RT-PCR. By western blot analysis, the protein presence of KIF3A and KIF3B in heart, muscle, gill, and testis reflected the content in protein level. Using in situ hybridization and immunofluorescence, we could track the dynamic location of KIF3A and KIF3B during different developmental phases of sperm. KIF3A and KIF3B were found surrounding the nucleus in early spermatids. In intermediate spermatids, these proteins expressed at high levels around the nucleus and extended to the final phase. During the nuclear shaping period, KIF3A and KIF3B reached their maximum in the late spermatids and were located around the nucleus and concentrated in the acrosome to some extent. Conclusions/Significance Our results revealed that KIF3A and KIF3B were involved in the nuclear and cellular morphogenesis at the levels of mRNA and protein. These proteins can potentially facilitate the intracellular transport of organelles, proteins, and other cargoes. The results represent the functions of KIF3A and KIF3B in the spermatogenesis of Crustacea and clarify phylogenetic relationships among the Decapoda. PMID:24870586

  8. Molecular motors

    NASA Astrophysics Data System (ADS)

    Allemand, Jean François Desbiolles, Pierre

    2015-10-01

    How do we move? More precisely, what are the molecular mechanisms that can explain that our muscles, made of very small components can move at a osopic scale? To answer these questions we must introduce molecular motors. Those motors are proteins, or small protein assemblies that, in our cells, transform chemical energy into mechanical work. Then, like we could do for a oscopic motor, used in a car or in a fan, we are going to study the basic behavior of these molecular machines, present what are their energy sources, calculate their power, their yield. If molecular motors are crucial for our oscopic movements, we are going to see that they are also essential to cellular transport and that considering the activity of some enzymes as molecular motors bring some interesting new insights on their activity.

  9. Human kidney anion exchanger 1 interacts with kinesin family member 3B (KIF3B)

    SciTech Connect

    Duangtum, Natapol; Junking, Mutita; Sawasdee, Nunghathai; Cheunsuchon, Boonyarit; Limjindaporn, Thawornchai; Yenchitsomanus, Pa-thai

    2011-09-16

    Highlights: {yields} Impaired trafficking of kAE1 causes distal renal tubular acidosis (dRTA). {yields} The interaction between kAE1 and kinesin family member 3B (KIF3B) is reported. {yields} The co-localization between kAE and KIF3B was detected in human kidney tissues. {yields} A marked reduction of kAE1 on the cell membrane was observed when KIF3B was knockdown. {yields} KFI3B plays an important role in trafficking of kAE1 to the plasma membrane. -- Abstract: Impaired trafficking of human kidney anion exchanger 1 (kAE1) to the basolateral membrane of {alpha}-intercalated cells of the kidney collecting duct leads to the defect of the Cl{sup -}/HCO{sub 3}{sup -} exchange and the failure of proton (H{sup +}) secretion at the apical membrane of these cells, causing distal renal tubular acidosis (dRTA). In the sorting process, kAE1 interacts with AP-1 mu1A, a subunit of AP-1A adaptor complex. However, it is not known whether kAE1 interacts with motor proteins in its trafficking process to the plasma membrane or not. We report here that kAE1 interacts with kinesin family member 3B (KIF3B) in kidney cells and a dileucine motif at the carboxyl terminus of kAE1 contributes to this interaction. We have also demonstrated that kAE1 co-localizes with KIF3B in human kidney tissues and the suppression of endogenous KIF3B in HEK293T cells by small interfering RNA (siRNA) decreases membrane localization of kAE1 but increases its intracellular accumulation. All results suggest that KIF3B is involved in the trafficking of kAE1 to the plasma membrane of human kidney {alpha}-intercalated cells.

  10. Human kidney anion exchanger 1 interacts with kinesin family member 3B (KIF3B).

    PubMed

    Duangtum, Natapol; Junking, Mutita; Sawasdee, Nunghathai; Cheunsuchon, Boonyarit; Limjindaporn, Thawornchai; Yenchitsomanus, Pa-thai

    2011-09-16

    Impaired trafficking of human kidney anion exchanger 1 (kAE1) to the basolateral membrane of α-intercalated cells of the kidney collecting duct leads to the defect of the Cl(-)/HCO(3)(-) exchange and the failure of proton (H(+)) secretion at the apical membrane of these cells, causing distal renal tubular acidosis (dRTA). In the sorting process, kAE1 interacts with AP-1 mu1A, a subunit of AP-1A adaptor complex. However, it is not known whether kAE1 interacts with motor proteins in its trafficking process to the plasma membrane or not. We report here that kAE1 interacts with kinesin family member 3B (KIF3B) in kidney cells and a dileucine motif at the carboxyl terminus of kAE1 contributes to this interaction. We have also demonstrated that kAE1 co-localizes with KIF3B in human kidney tissues and the suppression of endogenous KIF3B in HEK293T cells by small interfering RNA (siRNA) decreases membrane localization of kAE1 but increases its intracellular accumulation. All results suggest that KIF3B is involved in the trafficking of kAE1 to the plasma membrane of human kidney α-intercalated cells. PMID:21871436

  11. Disruption of kif3a results in defective osteoblastic differentiation in dental mesenchymal stem/precursor cells via the Wnt signaling pathway

    PubMed Central

    Jiang, Sicong; Chen, Guoqing; Feng, Lian; Jiang, Zongting; Yu, Mei; Bao, Jinku; Tian, Weidong

    2016-01-01

    The anterograde intraflagellar transport motor protein, kif3a, regulates the integrity of primary cilia and various cellular functions, however, the role of kif3a in dental mesenchymal stem/precursor cell differentiation remains to be fully elucidated. In the present study, the expression of kif3a was knocked down in human dental follicle cells (hDFCs) and human dental pulp cells (hDPCs) using short hairpin RNA. The results of subsequent immunofluorescence revealed that knocking down kif3a resulted in the loss of primary cilia, which led to impairment of substantial mineralization and expression of the differentiation-associated markers, including alkaline phosphatase, Runt-related transcription factor 2, dentin matrix protein 1 and dentin sialophosphoprotein in the hDFCs and hDPCs. The results of reverse transcription-quantitative polymerase chain reaction and western blot analyses showed that the expression levels of Wnt3a-mediated active β-catenin and lymphoid enhancer-binding factor 1 were attenuated, whereas the expression of phosphorylated glycogen synthase kinase 3β was enhanced, in the kif3a-knockdown cells. In addition, exogenous Wnt3a partially rescued osteoblastic differentiation in the hDFCs and hDPCs. These results demonstrated that inhibition of kif3a in the hDFCs and hDPCs disrupted primary cilia formation and/or function, and indicated that kif3a is important in the differentiation of hDFCs and hDPCs through the Wnt pathway. These findings not only enhance current understanding of tooth development and diseases of tooth mineralization, but also indicate possible strategies to regulate mineralization during tooth repair and regeneration. PMID:27432616

  12. Disruption of kif3a results in defective osteoblastic differentiation in dental mesenchymal stem/precursor cells via the Wnt signaling pathway.

    PubMed

    Jiang, Sicong; Chen, Guoqing; Feng, Lian; Jiang, Zongting; Yu, Mei; Bao, Jinku; Tian, Weidong

    2016-09-01

    The anterograde intraflagellar transport motor protein, kif3a, regulates the integrity of primary cilia and various cellular functions, however, the role of kif3a in dental mesenchymal stem/precursor cell differentiation remains to be fully elucidated. In the present study, the expression of kif3a was knocked down in human dental follicle cells (hDFCs) and human dental pulp cells (hDPCs) using short hairpin RNA. The results of subsequent immunofluorescence revealed that knocking down kif3a resulted in the loss of primary cilia, which led to impairment of substantial mineralization and expression of the differentiation‑associated markers, including alkaline phosphatase, Runt‑related transcription factor 2, dentin matrix protein 1 and dentin sialophosphoprotein in the hDFCs and hDPCs. The results of reverse transcription‑quantitative polymerase chain reaction and western blot analyses showed that the expression levels of Wnt3a‑mediated active β‑catenin and lymphoid enhancer‑binding factor 1 were attenuated, whereas the expression of phosphorylated glycogen synthase kinase 3β was enhanced, in the kif3a‑knockdown cells. In addition, exogenous Wnt3a partially rescued osteoblastic differentiation in the hDFCs and hDPCs. These results demonstrated that inhibition of kif3a in the hDFCs and hDPCs disrupted primary cilia formation and/or function, and indicated that kif3a is important in the differentiation of hDFCs and hDPCs through the Wnt pathway. These findings not only enhance current understanding of tooth development and diseases of tooth mineralization, but also indicate possible strategies to regulate mineralization during tooth repair and regeneration. PMID:27432616

  13. Molecular motors: nature's nanomachines.

    PubMed

    Tyreman, M J A; Molloy, J E

    2003-12-01

    Molecular motors are protein-based machines that convert chemical potential energy into mechanical work. This paper aims to introduce the non-specialist reader to molecular motors, in particular, acto-myosin, the prototype system for motor protein studies. These motors produce their driving force from changes in chemical potential arising directly from chemical reactions and are responsible for muscle contraction and a variety of other cell motilities.

  14. Mechanics of molecular motors

    NASA Astrophysics Data System (ADS)

    Visscher, Koen

    2001-03-01

    Molecular motors convert chemical energy into work by mechanisms that researchers are just starting to uncover. We have studied the coupling of chemistry to mechanics for kinesin, a motor protein that moves in a stepwise fashion along microtubules and is energized by the hydrolysis of ATP. Velocities of individual kinesin molecules at varying ATP concentrations and loads were recorded using a molecular force cl& a feedback-driven optical trap, which maintains constant loads on individual moving motor molecules. These measurements showed that kinesin requires only a single ATP molecule per mechanical step, and revealed the load-dependant biochemical transitions in the kinesin cycle where conformational changes are likely to occur. Modeling of the velocity data showed that kinesin mechanochemistry can be characterized by a mechanism that involves a thermally-activated and load-dependent isomerization directly following ATP binding. The model quantitatively accounts for velocity data over a wide range of loads and ATP concentrations, and indicates that movement may be accomplished through two sequential, non-identical, 4-nm sized substeps.

  15. Abnormal photoreceptor outer segment development and early retinal degeneration in kif3a mutant zebrafish.

    PubMed

    Raghupathy, Rakesh K; Zhang, Xun; Alhasani, Reem H; Zhou, Xinzhi; Mullin, Margaret; Reilly, James; Li, Wenchang; Liu, Mugen; Shu, Xinhua

    2016-08-01

    Photoreceptors are highly specialized sensory neurons that possess a modified primary cilium called the outer segment. Photoreceptor outer segment formation and maintenance require highly active protein transport via a process known as intraflagellar transport. Anterograde transport in outer segments is powered by the heterotrimeric kinesin II and coordinated by intraflagellar transport proteins. Here, we describe a new zebrafish model carrying a nonsense mutation in the kinesin II family member 3A (kif3a) gene. Kif3a mutant zebrafish exhibited curved body axes and kidney cysts. Outer segments were not formed in most parts of the mutant retina, and rhodopsin was mislocalized, suggesting KIF3A has a role in rhodopsin trafficking. Both rod and cone photoreceptors degenerated rapidly between 4 and 9 days post fertilization, and electroretinography response was not detected in 7 days post fertilization mutant larvae. Loss of KIF3A in zebrafish also resulted in an intracellular transport defect affecting anterograde but not retrograde transport of organelles. Our results indicate KIF3A plays a conserved role in photoreceptor outer segment formation and intracellular transport. PMID:27470972

  16. Molecular motors: Dynein's gearbox.

    PubMed

    Cross, R A

    2004-05-01

    A new optical trapping study shows that the stepsize of cytoplasmic dynein varies according to the applied force, suggesting that this motor can change gear. Complementary biochemical kinetic work on yeast dynein mutants hints at the allosteric mechanisms involved.

  17. Molecular Motors: A Theorist's Perspective

    NASA Astrophysics Data System (ADS)

    Kolomeisky, Anatoly B.; Fisher, Michael E.

    2007-05-01

    Individual molecular motors, or motor proteins, are enzymatic molecules that convert chemical energy, typically obtained from the hydrolysis of ATP (adenosine triphosphate), into mechanical work and motion. Processive motor proteins, such as kinesin, dynein, and certain myosins, step unidirectionally along linear tracks, specifically microtubules and actin filaments, and play a crucial role in cellular transport processes, organization, and function. In this review some theoretical aspects of motor-protein dynamics are presented in the light of current experimental methods that enable the measurement of the biochemical and biomechanical properties on a single-molecule basis. After a brief discussion of continuum ratchet concepts, we focus on discrete kinetic and stochastic models that yield predictions for the mean velocity, V(F, [ATP], …), and other observables as a function of an imposed load force F, the ATP concentration, and other variables. The combination of appropriate theory with single-molecule observations should help uncover the mechanisms underlying motor-protein function.

  18. Nanotechnology Review: Molecular Electronics to Molecular Motors

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Saini, Subhash (Technical Monitor)

    1998-01-01

    Reviewing the status of current approaches and future projections, as already published in scientific journals and books, the talk will summarize the direction in which computational and experimental nanotechnologies are progressing. Examples of nanotechnological approaches to the concepts of design and simulation of carbon nanotube based molecular electronic and mechanical devices will be presented. The concepts of nanotube based gears and motors will be discussed. The above is a non-technical review talk which covers long term precompetitive basic research in already published material that has been presented before many US scientific meeting audiences.

  19. Molecular motors and their functions in plants

    NASA Technical Reports Server (NTRS)

    Reddy, A. S.

    2001-01-01

    Molecular motors that hydrolyze ATP and use the derived energy to generate force are involved in a variety of diverse cellular functions. Genetic, biochemical, and cellular localization data have implicated motors in a variety of functions such as vesicle and organelle transport, cytoskeleton dynamics, morphogenesis, polarized growth, cell movements, spindle formation, chromosome movement, nuclear fusion, and signal transduction. In non-plant systems three families of molecular motors (kinesins, dyneins, and myosins) have been well characterized. These motors use microtubules (in the case of kinesines and dyneins) or actin filaments (in the case of myosins) as tracks to transport cargo materials intracellularly. During the last decade tremendous progress has been made in understanding the structure and function of various motors in animals. These studies are yielding interesting insights into the functions of molecular motors and the origin of different families of motors. Furthermore, the paradigm that motors bind cargo and move along cytoskeletal tracks does not explain the functions of some of the motors. Relatively little is known about the molecular motors and their roles in plants. In recent years, by using biochemical, cell biological, molecular, and genetic approaches a few molecular motors have been isolated and characterized from plants. These studies indicate that some of the motors in plants have novel features and regulatory mechanisms. The role of molecular motors in plant cell division, cell expansion, cytoplasmic streaming, cell-to-cell communication, membrane trafficking, and morphogenesis is beginning to be understood. Analyses of the Arabidopsis genome sequence database (51% of genome) with conserved motor domains of kinesin and myosin families indicates the presence of a large number (about 40) of molecular motors and the functions of many of these motors remain to be discovered. It is likely that many more motors with novel regulatory

  20. Molecular Motors: Power Strokes Outperform Brownian Ratchets.

    PubMed

    Wagoner, Jason A; Dill, Ken A

    2016-07-01

    Molecular motors convert chemical energy (typically from ATP hydrolysis) to directed motion and mechanical work. Their actions are often described in terms of "Power Stroke" (PS) and "Brownian Ratchet" (BR) mechanisms. Here, we use a transition-state model and stochastic thermodynamics to describe a range of mechanisms ranging from PS to BR. We incorporate this model into Hill's diagrammatic method to develop a comprehensive model of motor processivity that is simple but sufficiently general to capture the full range of behavior observed for molecular motors. We demonstrate that, under all conditions, PS motors are faster, more powerful, and more efficient at constant velocity than BR motors. We show that these differences are very large for simple motors but become inconsequential for complex motors with additional kinetic barrier steps. PMID:27136319

  1. Theoretical Modelling of Synthetic Molecular Motors

    NASA Astrophysics Data System (ADS)

    Barbu, Corina; Sofo, Jorge; Crespi, Vincent

    2004-03-01

    Synthetic molecular motors with sizes of few nanometers offer prospects to control molecular-scale mechanical motion. Motors with electric dipoles designed into their structure can undergo conformational changes in response to an external electric field and thereby, in principle, perform mechanical work. The synthetic rotary motor of our interest consists of a molecular caltrop with a three-legged base for attachment to a substrate and a molecular shaft functionalized with a molecular rotor at the upper end. Both the static dipole and the electric field-induced dipole of the molecular rotor are relevant to producing rotation. Also, the combination of external electrostatic torque and the internal thermal fluctuations must be sufficient to overcome any rotational barriers on experimentally relevant timescales. Density functional theory calculations at the B3LYP/TZV level coupled to analytical modelling reveal the dynamical response of the motor.

  2. KIF3A binds to β-arrestin for suppressing Wnt/β-catenin signalling independently of primary cilia in lung cancer.

    PubMed

    Kim, Minsuh; Suh, Young-Ah; Oh, Ju-Hee; Lee, Bo Ra; Kim, Joon; Jang, Se Jin

    2016-01-01

    Aberrant Wnt/β-catenin signalling is implicated in the progression of several human cancers, including non-small cell lung cancer (NSCLC). However, mutations in Wnt/β-catenin pathway components are uncommon in NSCLC, and their epigenetic control remains unclear. Here, we show that KIF3A, a member of the kinesin-2 family, plays a role in suppressing Wnt/β-catenin signalling in NSCLC cells. KIF3A knockdown increases both β-catenin levels and transcriptional activity with concomitant promotion of malignant potential, such as increased proliferation and migration and upregulation of stemness markers. Because KIF3A binds β-arrestin, KIF3A depletion allows β-arrestin to form a complex with DVL2 and axin, stabilizing β-catenin. Although primary cilia, whose biogenesis requires KIF3A, are thought to restrain the Wnt response, pharmacological inhibition of ciliogenesis failed to increase β-catenin activity in NSCLC cells. A correlation between KIF3A loss and a poorer NSCLC prognosis as well as β-catenin and cyclin D1 upregulation further suggests that KIF3A suppresses Wnt/β-catenin signalling and tumourigenesis in NSCLC. PMID:27596264

  3. KIF3A binds to β-arrestin for suppressing Wnt/β-catenin signalling independently of primary cilia in lung cancer

    NASA Astrophysics Data System (ADS)

    Kim, Minsuh; Suh, Young-Ah; Oh, Ju-Hee; Lee, Bo Ra; Kim, Joon; Jang, Se Jin

    2016-09-01

    Aberrant Wnt/β-catenin signalling is implicated in the progression of several human cancers, including non-small cell lung cancer (NSCLC). However, mutations in Wnt/β-catenin pathway components are uncommon in NSCLC, and their epigenetic control remains unclear. Here, we show that KIF3A, a member of the kinesin-2 family, plays a role in suppressing Wnt/β-catenin signalling in NSCLC cells. KIF3A knockdown increases both β-catenin levels and transcriptional activity with concomitant promotion of malignant potential, such as increased proliferation and migration and upregulation of stemness markers. Because KIF3A binds β-arrestin, KIF3A depletion allows β-arrestin to form a complex with DVL2 and axin, stabilizing β-catenin. Although primary cilia, whose biogenesis requires KIF3A, are thought to restrain the Wnt response, pharmacological inhibition of ciliogenesis failed to increase β-catenin activity in NSCLC cells. A correlation between KIF3A loss and a poorer NSCLC prognosis as well as β-catenin and cyclin D1 upregulation further suggests that KIF3A suppresses Wnt/β-catenin signalling and tumourigenesis in NSCLC.

  4. KIF3A binds to β-arrestin for suppressing Wnt/β-catenin signalling independently of primary cilia in lung cancer

    PubMed Central

    Kim, Minsuh; Suh, Young-Ah; Oh, Ju-Hee; Lee, Bo Ra; Kim, Joon; Jang, Se Jin

    2016-01-01

    Aberrant Wnt/β-catenin signalling is implicated in the progression of several human cancers, including non-small cell lung cancer (NSCLC). However, mutations in Wnt/β-catenin pathway components are uncommon in NSCLC, and their epigenetic control remains unclear. Here, we show that KIF3A, a member of the kinesin-2 family, plays a role in suppressing Wnt/β-catenin signalling in NSCLC cells. KIF3A knockdown increases both β-catenin levels and transcriptional activity with concomitant promotion of malignant potential, such as increased proliferation and migration and upregulation of stemness markers. Because KIF3A binds β-arrestin, KIF3A depletion allows β-arrestin to form a complex with DVL2 and axin, stabilizing β-catenin. Although primary cilia, whose biogenesis requires KIF3A, are thought to restrain the Wnt response, pharmacological inhibition of ciliogenesis failed to increase β-catenin activity in NSCLC cells. A correlation between KIF3A loss and a poorer NSCLC prognosis as well as β-catenin and cyclin D1 upregulation further suggests that KIF3A suppresses Wnt/β-catenin signalling and tumourigenesis in NSCLC. PMID:27596264

  5. Molecular motors: thermodynamics and the random walk.

    PubMed Central

    Thomas, N.; Imafuku, Y.; Tawada, K.

    2001-01-01

    The biochemical cycle of a molecular motor provides the essential link between its thermodynamics and kinetics. The thermodynamics of the cycle determine the motor's ability to perform mechanical work, whilst the kinetics of the cycle govern its stochastic behaviour. We concentrate here on tightly coupled, processive molecular motors, such as kinesin and myosin V, which hydrolyse one molecule of ATP per forward step. Thermodynamics require that, when such a motor pulls against a constant load f, the ratio of the forward and backward products of the rate constants for its cycle is exp [-(DeltaG + u(0)f)/kT], where -DeltaG is the free energy available from ATP hydrolysis and u(0) is the motor's step size. A hypothetical one-state motor can therefore act as a chemically driven ratchet executing a biased random walk. Treating this random walk as a diffusion problem, we calculate the forward velocity v and the diffusion coefficient D and we find that its randomness parameter r is determined solely by thermodynamics. However, real molecular motors pass through several states at each attachment site. They satisfy a modified diffusion equation that follows directly from the rate equations for the biochemical cycle and their effective diffusion coefficient is reduced to D-v(2)tau, where tau is the time-constant for the motor to reach the steady state. Hence, the randomness of multistate motors is reduced compared with the one-state case and can be used for determining tau. Our analysis therefore demonstrates the intimate relationship between the biochemical cycle, the force-velocity relation and the random motion of molecular motors. PMID:11600075

  6. Loss of Glis2/NPHP7 causes kidney epithelial cell senescence and suppresses cyst growth in the Kif3a mouse model of cystic kidney disease.

    PubMed

    Lu, Dongmei; Rauhauser, Alysha; Li, Binghua; Ren, Chongyu; McEnery, Kayla; Zhu, Jili; Chaki, Moumita; Vadnagara, Komal; Elhadi, Sarah; Jetten, Anton M; Igarashi, Peter; Attanasio, Massimo

    2016-06-01

    Enlargement of kidney tubules is a common feature of multiple cystic kidney diseases in humans and mice. However, while some of these pathologies are characterized by cyst expansion and organ enlargement, in others, progressive interstitial fibrosis and kidney atrophy prevail. The Kif3a knockout mouse is an established non-orthologous mouse model of cystic kidney disease. Conditional inactivation of Kif3a in kidney tubular cells results in loss of primary cilia and rapid cyst growth. Conversely, loss of function of the gene GLIS2/NPHP7 causes progressive kidney atrophy, interstitial inflammatory infiltration, and fibrosis. Kif3a null tubular cells have unrestrained proliferation and reduced stabilization of p53 resulting in a loss of cell cycle arrest in the presence of DNA damage. In contrast, loss of Glis2 is associated with activation of checkpoint kinase 1, stabilization of p53, and induction of cell senescence. Interestingly, the cystic phenotype of Kif3a knockout mice is partially rescued by genetic ablation of Glis2 and pharmacological stabilization of p53. Thus, Kif3a is required for cell cycle regulation and the DNA damage response, whereas cell senescence is significantly enhanced in Glis2 null cells. Hence, cell senescence is a central feature in nephronophthisis type 7 and Kif3a is unexpectedly required for efficient DNA damage response and cell cycle arrest. PMID:27181777

  7. Development of an electrically driven molecular motor.

    PubMed

    Murphy, Colin J; Sykes, E Charles H

    2014-10-01

    For molecules to be used as components in molecular machinery, methods are required that couple individual molecules to external energy sources in order to selectively excite motion in a given direction. While significant progress has been made in the construction of synthetic molecular motors powered by light and by chemical reactions, there are few experimental examples of electrically driven molecular motors. To this end, we pioneered the use of a new, stable and tunable molecular rotor system based on surface-bound thioethers to comprehensively study many aspects of molecular rotation. As biological molecular motors often operate at interfaces, our synthetic system is especially amenable to microscopic interrogation as compared to solution-based systems. Using scanning tunneling microscopy (STM) and density functional theory, we studied the rotation of surface-bound thioethers, which can be induced either thermally or by electrons from the STM tip in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. This work culminated in the first experimental demonstration of a single-molecule electric motor, where the electrically driven rotation of a butyl methyl sulfide molecule adsorbed on a copper surface could be directionally biased. The direction and rate of the rotation are related to the chirality of both the molecule and the STM tip (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices.

  8. Unidirectional rotary motion in achiral molecular motors

    NASA Astrophysics Data System (ADS)

    Kistemaker, Jos C. M.; Štacko, Peter; Visser, Johan; Feringa, Ben L.

    2015-11-01

    Control of the direction of motion is an essential feature of biological rotary motors and results from the intrinsic chirality of the amino acids from which the motors are made. In synthetic autonomous light-driven rotary motors, point chirality is transferred to helical chirality, and this governs their unidirectional rotation. However, achieving directional rotary motion in an achiral molecular system in an autonomous fashion remains a fundamental challenge. Here, we report an achiral molecular motor in which the presence of a pseudo-asymmetric carbon atom proved to be sufficient for exclusive autonomous disrotary motion of two appended rotor moieties. Isomerization around the two double bonds enables both rotors to move in the same direction with respect to their surroundings—like wheels on an axle—demonstrating that autonomous unidirectional rotary motion can be achieved in a symmetric system.

  9. Molecular propellers and tunneling-driven motors

    NASA Astrophysics Data System (ADS)

    Vukovic, Lela; Wang, Boyang; Kral, Petr

    2008-03-01

    We design molecular propellers with carbon nanotube rotors and aromatic blades that allow selective pumping of hydrophobic and hydrophilic liquids [1]. Our molecular dynamics studies show that the pumping efficiency strongly depends on the chemistry of the liquid-blade interface. We also discuss several prototypes of highly efficient molecular motors driven by electron tunneling that could drive such rotary molecular machines [2]. These systems might pump liquids and provide motility at the nanoscale. [1] B. Wang and P. Kr'al, Phys. Rev. Lett. 98, 266102 (2007). [2] L. Vukovic, B. Wang and P. Kr'al, submitted.

  10. Mechanoregulation of molecular motors in flagella

    NASA Astrophysics Data System (ADS)

    Gadelha, Hermes

    2014-11-01

    Molecular motors are nano-biological machines responsible for exerting forces that drive movement in living organisms, from cargo transport to cell division and motility. Interestingly, despite the inherent complexity of many interacting motors, order and structure may arise naturally, as exemplified by the harmonic, self-organized undulatory motion of the flagellum. The real mechanisms behind this collective spontaneous oscillation are still unknown, and it is challenging task to measure experimentally the molecular motor dynamics within the flagellar structure in real time. In this talk we will explore different competing hypotheses that are capable of generating flagellar bending waves that ``resemble'' in-vitro observations, emphasizing the need for further mathematical analysis and model validation. It also highlight that this is a fertile and challenging area of inter-disciplinary research for applied mathematicians and demonstrates the importance of future observational and theoretical studies in understanding the underlying mechanics of these motile cell appendages.

  11. Thermodynamics and kinetics of molecular motors.

    PubMed

    Astumian, R Dean

    2010-06-01

    Molecular motors are first and foremost molecules, governed by the laws of chemistry rather than of mechanics. The dynamical behavior of motors based on chemical principles can be described as a random walk on a network of states. A key insight is that any molecular motor in solution explores all possible motions and configurations at thermodynamic equilibrium. By using input energy and chemical design to prevent motion that is not wanted, what is left behind is the motion that is desired. This review is focused on two-headed motors such as kinesin and Myosin V that move on a polymeric track. By use of microscopic reversibility, it is shown that the ratio between the number of forward steps and the number of backward steps in any sufficiently long time period does not directly depend on the mechanical properties of the linker between the two heads. Instead, this ratio is governed by the relative chemical specificity of the heads in the front-versus-rear position for the fuel, adenosine triphosphate and its products, adenosine diphosphate and inorganic phosphate. These insights have been key factors in the design of biologically inspired synthetic molecular walkers constructed out of DNA or out of small organic molecules.

  12. Chromatin maintenance by a molecular motor protein

    PubMed Central

    Sung, Myong-Hee; Misteli, Tom

    2011-01-01

    The kinesin motor protein KIF4 performs essential functions in mitosis. Like other mitotic kinesins, loss of KIF4 causes spindle defects, aneuploidy, genomic instability and ultimately tumor formation. However, KIF4 is unique among molecular motors in that it resides in the cell nucleus throughout interphase, suggesting a non-mitotic function as well. Here we identify a novel cellular function for a molecular motor protein by demonstrating that KIF4 acts as a modulator of large-scale chromatin architecture during interphase. KIF4 binds globally to chromatin and its absence leads to chromatin decondensation and loss of heterochromatin domains. KIF4-dependent chromatin decondensation has functional consequences by causing replication defects and global mis-regulation of gene expression programs. KIF4 exerts its function in chromatin architecture via regulation of ADP-ribosylation of core and linker histones and by physical interaction and recruitment of chromatin assembly proteins during S-phase. These observations document a novel function for a molecular motor protein in establishment and maintenance of higher order chromatin structure. PMID:22130187

  13. Asymmetric Synthesis of First Generation Molecular Motors

    PubMed Central

    2014-01-01

    A general enantioselective route to functionalized first generation molecular motors is described. An enantioselective protonation of the silyl enol ethers of indanones by a Au(I)BINAP complex sets the stage for a highly diastereoselective McMurry coupling as a second enhancement step for enantiomeric excess. In this way various functionalized overcrowded alkenes could be synthesized in good yields (up to 78%) and good to excellent enantiomeric excess (85% ee–>98% ee) values. PMID:25079823

  14. Statistical kinetics of processive molecular motors

    NASA Astrophysics Data System (ADS)

    Schnitzer, Mark Jacob

    1999-10-01

    We describe new theoretical and experimental tools for studying biological motor proteins at the single molecule scale. These tools enable measurements of molecular fuel economies, thereby providing insight into the pathways for conversion of biochemical energy into mechanical work. Kinesin is an ATP-dependent motor that moves processively along microtubules in discrete steps of 8 nm. How many molecules of ATP are hydrolysed per step? To determine this coupling ratio, we develop a fluctuation analysis, which relates the variance in records of mechanical displacement to the number of rate-limiting biochemical transitions in the engine cycle. Using fluctuation analysis and optical trapping interferometry, we determine that near zero load, single molecules of kinesin hydrolyse one ATP nucleotide per 8-nm step. To study kinesin behavior under load, we use a molecular force clamp, capable of maintaining constant loads on single kinesin motors moving processively. Analysis of records of motion under variable ATP concentrations and loads reveals that kinesin is a `tightly- coupled' motor, maintaining the 1:1 coupling ratio up to loads of ~ 5 pN. Moreover, a Michaelis-Menten analysis of velocity shows that the kinesin cycle contains at least two load- dependent transitions. The rate of one of these transitions affects ATP affinity, while the other does not. Therefore, the kinesin stall force must depend on the ATP concentration, as is demonstrated experimentally. These findings rule out existing theoretical models of kinesin motility. We develop a simple theoretical formalism describing a tightly-coupled mechanism for movement. This `energy-landscape' formalism quantitatively accounts for motile properties of RNA polymerase (RNAP), the enzyme that transcribes DNA into RNA. The shapes of RNAP force-velocity curves indicate that biochemical steps limiting transcription rates at low loads do not generate movement. Modeling suggests that high loads may halt RNAP by promoting a

  15. Excited state dynamics & optical control of molecular motors

    NASA Astrophysics Data System (ADS)

    Wiley, Ted; Sension, Roseanne

    2014-03-01

    Chiral overcrowded alkenes are likely candidates for light driven rotary molecular motors. At their core, these molecular motors are based on the chromophore stilbene, undergoing ultrafast cis/trans photoisomerization about their central double bond. Unlike stilbene, the photochemistry of molecular motors proceeds in one direction only. This unidirectional rotation is a result of helicity in the molecule induced by steric hindrance. However, the steric hindrance which ensures unidirectional excited state rotation, has the unfortunate consequence of producing large ground state barriers which dramatically decrease the overall rate of rotation. These molecular scale ultrafast motors have only recently been studied by ultrafast spectroscopy. Our lab has studied the photochemistry and photophysics of a ``first generation'' molecular motor with UV-visible transient absorption spectroscopy. We hope to use optical pulse shaping to enhance the efficiency and turnover rate of these molecular motors.

  16. Exact dynamic properties of molecular motors

    NASA Astrophysics Data System (ADS)

    Boon, N. J.; Hoyle, R. B.

    2012-08-01

    Molecular motors play important roles within a biological cell, performing functions such as intracellular transport and gene transcription. Recent experimental work suggests that there are many plausible biochemical mechanisms that molecules such as myosin-V could use to achieve motion. To account for the abundance of possible discrete-stochastic frameworks that can arise when modeling molecular motor walks, a generalized and straightforward graphical method for calculating their dynamic properties is presented. It allows the calculation of the velocity, dispersion, and randomness ratio for any proposed system through analysis of its structure. This article extends work of King and Altman ["A schematic method of deriving the rate laws of enzyme-catalyzed reactions," J. Phys. Chem. 60, 1375-1378 (1956)], 10.1021/j150544a010 on networks of enzymatic reactions by calculating additional dynamic properties for spatially hopping systems. Results for n-state systems are presented: single chain, parallel pathway, divided pathway, and divided pathway with a chain. A novel technique for combining multiple system architectures coupled at a reference state is also demonstrated. Four-state examples illustrate the effectiveness and simplicity of these methods.

  17. Theoretical Analysis of Dynamic Processes for Interacting Molecular Motors

    PubMed Central

    Teimouri, Hamid; Kolomeisky, Anatoly B.; Mehrabiani, Kareem

    2015-01-01

    Biological transport is supported by collective dynamics of enzymatic molecules that are called motor proteins or molecular motors. Experiments suggest that motor proteins interact locally via short-range potentials. We investigate the fundamental role of these interactions by analyzing a new class of totally asymmetric exclusion processes where interactions are accounted for in a thermodynamically consistent fashion. It allows us to connect explicitly microscopic features of motor proteins with their collective dynamic properties. Theoretical analysis that combines various mean-field calculations and computer simulations suggests that dynamic properties of molecular motors strongly depend on interactions, and correlations are stronger for interacting motor proteins. Surprisingly, it is found that there is an optimal strength of interactions (weak repulsion) that leads to a maximal particle flux. It is also argued that molecular motors transport is more sensitive to attractive interactions. Applications of these results for kinesin motor proteins are discussed. PMID:25688287

  18. Kinesin-2 Family Motors in the Unusual Photoreceptor Cilium

    PubMed Central

    Malicki, Jarema; Besharse, Joseph C.

    2012-01-01

    This review focuses on recent advances in the understanding of kinesin-2 family motors in vertebrate photoreceptor development. Zebrafish photoreceptors develop by the 3rd day of embryogenesis, making it possible to study mutant phenotypes without the use of conditional alleles. Recent work using a zebrafish kif3b mutant allele validates the concept that the heterotrimeric kinesin II motor is generally required for ciliogenesis. In zebrafish photoreceptors, however, loss of kif3b function delays but does not block cilium formation. This is thought to occur because both kif3b or kif3c can dimerize with kif3a and function redundantly. The second ciliary kinesin thought to function in photoreceptor cells is kif17. Prior work has shown that either morpholino knockdown of this gene or the overexpression of its dominant negative form can reduce or delay photoreceptor cilium development without any evident impact on ciliogenesis in general. This has led to the idea that kif17 may play an important role only in some specialized cilium types, such the one in photoreceptor cells. In a recently identified kif17 mutant, however, photoreceptor outer segments are formed by 5 dpf and an obvious delay of outer segment formation is seen only at the earliest stage analyzed (3 dpf). This work suggests that kif17 plays a significant role mainly at an early stage of photoreceptor development. Taken together, these studies lead to an intriguing concept that as they differentiate photoreceptors alter their kinesin repertoire. PMID:23123805

  19. Thermodynamics and kinetics of a molecular motor ensemble.

    PubMed

    Baker, J E; Thomas, D D

    2000-10-01

    If, contrary to conventional models of muscle, it is assumed that molecular forces equilibrate among rather than within molecular motors, an equation of state and an expression for energy output can be obtained for a near-equilibrium, coworking ensemble of molecular motors. These equations predict clear, testable relationships between motor structure, motor biochemistry, and ensemble motor function, and we discuss these relationships in the context of various experimental studies. In this model, net work by molecular motors is performed with the relaxation of a near-equilibrium intermediate step in a motor-catalyzed reaction. The free energy available for work is localized to this step, and the rate at which this free energy is transferred to work is accelerated by the free energy of a motor-catalyzed reaction. This thermodynamic model implicitly deals with a motile cell system as a dynamic network (not a rigid lattice) of molecular motors within which the mechanochemistry of one motor influences and is influenced by the mechanochemistry of other motors in the ensemble. PMID:11023881

  20. Thermodynamics and kinetics of a molecular motor ensemble.

    PubMed Central

    Baker, J E; Thomas, D D

    2000-01-01

    If, contrary to conventional models of muscle, it is assumed that molecular forces equilibrate among rather than within molecular motors, an equation of state and an expression for energy output can be obtained for a near-equilibrium, coworking ensemble of molecular motors. These equations predict clear, testable relationships between motor structure, motor biochemistry, and ensemble motor function, and we discuss these relationships in the context of various experimental studies. In this model, net work by molecular motors is performed with the relaxation of a near-equilibrium intermediate step in a motor-catalyzed reaction. The free energy available for work is localized to this step, and the rate at which this free energy is transferred to work is accelerated by the free energy of a motor-catalyzed reaction. This thermodynamic model implicitly deals with a motile cell system as a dynamic network (not a rigid lattice) of molecular motors within which the mechanochemistry of one motor influences and is influenced by the mechanochemistry of other motors in the ensemble. PMID:11023881

  1. Cytoskeleton Molecular Motors: Structures and Their Functions in Neuron

    PubMed Central

    Xiao, Qingpin; Hu, Xiaohui; Wei, Zhiyi; Tam, Kin Yip

    2016-01-01

    Cells make use of molecular motors to transport small molecules, macromolecules and cellular organelles to target region to execute biological functions, which is utmost important for polarized cells, such as neurons. In particular, cytoskeleton motors play fundamental roles in neuron polarization, extension, shape and neurotransmission. Cytoskeleton motors comprise of myosin, kinesin and cytoplasmic dynein. F-actin filaments act as myosin track, while kinesin and cytoplasmic dynein move on microtubules. Cytoskeleton motors work together to build a highly polarized and regulated system in neuronal cells via different molecular mechanisms and functional regulations. This review discusses the structures and working mechanisms of the cytoskeleton motors in neurons. PMID:27570482

  2. Energy Conversion by Molecular Motors Coupled to Nucleotide Hydrolysis

    NASA Astrophysics Data System (ADS)

    Lipowsky, Reinhard; Liepelt, Steffen; Valleriani, Angelo

    2009-06-01

    Recent theoretical work on the energy conversion by molecular motors coupled to nucleotide hydrolysis is reviewed. The most abundant nucleotide is provided by adenosine triphosphate (ATP) which is cleaved into adenosine diphosphate (ADP) and inorganic phosphate. The motors have several catalytic domains (or active sites), each of which can be empty or occupied by ATP or ADP. The chemical composition of all catalytic domains defines distinct nucleotide states of the motor which form a discrete state space. Each of these motor states is connected to several other states via chemical transitions. For stepping motors such as kinesin, which walk along cytoskeletal filaments, some motor states are also connected by mechanical transitions, during which the motor is displaced along the filament and able to perform mechanical work. The different motor states together with the possible chemical and mechanical transitions provide a network representation for the chemomechanical coupling of the motor molecule. The stochastic motor dynamics on these networks exhibits several distinct motor cycles, which represent the dominant pathways for different regimes of nucleotide concentrations and load force. For the kinesin motor, the competition of two such cycles determines the stall force, at which the motor velocity vanishes and the motor reverses its direction of motion. In general, kinesin is found to be governed by the competition of three distinct chemomechanical cycles. The corresponding network representation provides a unified description for all motor properties that have been determined by single molecule experiments.

  3. Physical mechanisms of biological molecular motors

    NASA Astrophysics Data System (ADS)

    Miller, John H., Jr.; Vajrala, Vijayanand; Infante, Hans L.; Claycomb, James R.; Palanisami, Akilan; Fang, Jie; Mercier, George T.

    2009-03-01

    Biological motors generally fall into two categories: (1) those that convert chemical into mechanical energy via hydrolysis of a nucleoside triphosphate, usually adenosine triphosphate, regarded as life's chemical currency of energy and (2) membrane bound motors driven directly by an ion gradient and/or membrane potential. Here we argue that electrostatic interactions play a vital role for both types of motors and, therefore, the tools of physics can greatly contribute to understanding biological motors.

  4. Kif3a controls murine nephron number via GLI3 repressor, cell survival, and gene expression in a lineage-specific manner.

    PubMed

    Chi, Lijun; Galtseva, Alevtina; Chen, Lin; Mo, Rong; Hui, Chi-Chung; Rosenblum, Norman D

    2013-01-01

    The primary cilium is required during early embryo patterning, epithelial tubulogenesis, and growth factor-dependent signal transduction. The requirement for primary cilia during renal epithelial-mesenchymal tissue interactions that give rise to nephrons is undefined. Here, we used Cre-mediated recombination to generate mice with Kif3a deficiency targeted to the ureteric and/or metanephric mesenchyme cell lineages in the embryonic kidney. Gradual loss of primary cilia in either lineage leads to a phenotype of reduced nephron number. Remarkably, in addition to cyst formation, loss of primary cilia in the ureteric epithelial cell leads to decreased expression of Wnt11 and Ret and reduced ureteric branching. Constitutive expression of GLI3 repressor (Gli3(Δ699/+) ) rescues these abnormalities. In embryonic metanephric mesenchyme cells, Kif3a deficiency limits survival of nephrogenic progenitor cells and expression of genes required for nephron formation. Together, our data demonstrate that Kif3a controls nephron number via distinct cell lineage-specific mechanisms.

  5. Motor Proteins and Molecular Motors: How to Operate Machines at Nanoscale

    PubMed Central

    Kolomeisky, Anatoly B.

    2013-01-01

    Several classes of biological molecules that transform chemical energy into mechanical work are known as motor proteins or molecular motors. These nanometer-sized machines operate in noisy stochastic isothermal environment, strongly supporting fundamental cellular processes such as transfer of genetic information, transport, organization and functioning. In last two decades motor proteins have become a subject of intense research efforts that were aimed to uncover fundamental principles and mechanisms of molecular motors dynamics. In this review, we critically discuss a recent progress in experimental and theoretical studies on motor proteins. Our focus is on analyzing fundamental concepts and ideas that have been utilized for explaining non-equilibrium nature and mechanisms of molecular motors. PMID:24100357

  6. Distinct Transport Regimes for Two Elastically Coupled Molecular Motors

    NASA Astrophysics Data System (ADS)

    Berger, Florian; Keller, Corina; Klumpp, Stefan; Lipowsky, Reinhard

    2012-05-01

    Cooperative cargo transport by two molecular motors involves an elastic motor-motor coupling, which can reduce the motors’ velocity and/or enhance their unbinding from the filament. We show theoretically that these interference effects lead, in general, to four distinct transport regimes. In addition to a weak coupling regime, kinesin and dynein motors are found to exhibit a strong coupling and an enhanced unbinding regime, whereas myosin motors are predicted to attain a reduced velocity regime. All of these regimes, which we derive by explicit calculations and general time scale arguments, can be explored experimentally by varying the elastic coupling strength.

  7. Helicases as molecular motors: An insight

    NASA Astrophysics Data System (ADS)

    Tuteja, Narendra; Tuteja, Renu

    2006-12-01

    Helicases are one of the smallest motors of biological system, which harness the chemical free energy of ATP hydrolysis to catalyze the opening of energetically stable duplex nucleic acids and thereby are involved in almost all aspect of nucleic acid metabolism including replication, repair, recombination, transcription, translation, and ribosome biogenesis. Basically, they break the hydrogen bonding between the duplex helix and translocate unidirectionally along the bound strand. Mostly all the helicases contain some conserved signature motifs, which act as an engine to power the unwinding. After the discovery of the first prokaryotic DNA helicase from Escherichia coli bacteria in 1976 and the first eukaryotic one from the lily plant in 1978, many more (>100) have been isolated. All the helicases share some common properties, including nucleic acid binding, NTP hydrolysis and unwinding of the duplex. Many helicases have been crystallized and their structures have revealed an underlying common structural fold for their function. The defects in helicases gene have also been reported to be responsible for variety of human genetic disorders, which can lead to cancer, premature aging or mental retardation. Recently, a new role of a helicase in abiotic stress signaling in plant has been discovered. Overall, helicases act as essential molecular tools for cellular machinery and help in maintaining the integrity of genome. Here an overview of helicases has been covered which includes history, biochemical assay, properties, classification, role in human disease and mechanism of unwinding and translocation.

  8. Quantum dynamics of light-driven chiral molecular motors.

    PubMed

    Yamaki, Masahiro; Nakayama, Shin-ichiro; Hoki, Kunihito; Kono, Hirohiko; Fujimura, Yuichi

    2009-03-21

    The results of theoretical studies on quantum dynamics of light-driven molecular motors with internal rotation are presented. Characteristic features of chiral motors driven by a non-helical, linearly polarized electric field of light are explained on the basis of symmetry argument. The rotational potential of the chiral motor is characterized by a ratchet form. The asymmetric potential determines the directional motion: the rotational direction is toward the gentle slope of the asymmetric potential. This direction is called the intuitive direction. To confirm the unidirectional rotational motion, results of quantum dynamical calculations of randomly-oriented molecular motors are presented. A theoretical design of the smallest light-driven molecular machine is presented. The smallest chiral molecular machine has an optically driven engine and a running propeller on its body. The mechanisms of transmission of driving forces from the engine to the propeller are elucidated by using a quantum dynamical treatment. The results provide a principle for control of optically-driven molecular bevel gears. Temperature effects are discussed using the density operator formalism. An effective method for ultrafast control of rotational motions in any desired direction is presented with the help of a quantum control theory. In this method, visible or UV light pulses are applied to drive the motor via an electronic excited state. A method for driving a large molecular motor consisting of an aromatic hydrocarbon is presented. The molecular motor is operated by interactions between the induced dipole of the molecular motor and the electric field of light pulses. PMID:19290336

  9. Fluctuation theorem for the flashing ratchet model of molecular motors

    NASA Astrophysics Data System (ADS)

    Lacoste, D.; Mallick, K.

    2009-08-01

    Molecular motors convert chemical energy derived from the hydrolysis of adenosine triphosphate (ATP) into mechanical energy. A well-studied model of a molecular motor is the flashing ratchet model. We show that this model exhibits a fluctuation relation known as the Gallavotti-Cohen symmetry. Our study highlights the fact that the symmetry is present only if the chemical and mechanical degrees of freedom are both included in the description.

  10. How molecular motors shape the flagellar beat

    PubMed Central

    Riedel-Kruse, Ingmar H.; Hilfinger, Andreas; Howard, Jonathon; Jülicher, Frank

    2007-01-01

    Cilia and eukaryotic flagella are slender cellular appendages whose regular beating propels cells and microorganisms through aqueous media. The beat is an oscillating pattern of propagating bends generated by dynein motor proteins. A key open question is how the activity of the motors is coordinated in space and time. To elucidate the nature of this coordination we inferred the mechanical properties of the motors by analyzing the shape of beating sperm: Steadily beating bull sperm were imaged and their shapes were measured with high precision using a Fourier averaging technique. Comparing our experimental data with wave forms calculated for different scenarios of motor coordination we found that only the scenario of interdoublet sliding regulating motor activity gives rise to satisfactory fits. We propose that the microscopic origin of such “sliding control” is the load dependent detachment rate of motors. Agreement between observed and calculated wave forms was obtained only if significant sliding between microtubules occurred at the base. This suggests a novel mechanism by which changes in basal compliance could reverse the direction of beat propagation. We conclude that the flagellar beat patterns are determined by an interplay of the basal properties of the axoneme and the mechanical feedback of dynein motors. PMID:19404446

  11. Molecular motors: a traffic cop within?

    PubMed Central

    Welte, M. A.; Gross, S. P.

    2008-01-01

    Intracellular transport along microtubules is often bidirectional, employing multiple plus- and minus-end directed motors. How cells regulate such transport in time and space is a fundamental but unsolved question in cell biology. A recent paper presents a new modeling approach to predict how much of transport can be understood just from our knowledge of the motors involved. The model can generate strikingly complex patterns of motion, mimicking key aspects of cargo transport in vivo. Previous studies had inferred that plus-end motors on bidirectional cargoes are usually turned off when the minus-end motors are engaged (and vice versa). In the model, such motor coordination can arise from motors competing in a tug-of-war, without help from additional regulators. This new theoretical framework should stimulate much research that will help unravel whether regulation of intracellular transport is dominated by higher-order control mechanisms or is achieved simply by tuning basic properties of the motors themselves. PMID:19404428

  12. Molecular motor traffic: From biological nanomachines to macroscopic transport

    NASA Astrophysics Data System (ADS)

    Lipowsky, Reinhard; Chai, Yan; Klumpp, Stefan; Liepelt, Steffen; Müller, Melanie J. I.

    2006-12-01

    All cells of animals and plants contain complex transport systems based on molecular motors which walk along cytoskeletal filaments. These motors are rather small and have a size of 20-100 nm but are able to pull vesicles, organelles and other types of cargo over large distances, from micrometers up to meters. There are several families of motors: kinesins, dyneins, and myosins. Most of these motors have two heads which are used as legs and perform discrete steps along the filaments. Several aspects of the motor behavior will be discussed: motor cycles of two-headed motors; walks of single motors or cargo particles which consist of directed movements interrupted by random, diffusive motion; cargo transport through tube-like compartments; active diffusion of cargo particles in slab-like compartments; cooperative transport of cargo by several motors which may be uni- or bi-directional; and systems with many interacting motors that exhibit traffic jams, self-organized density and flux patterns, and traffic phase transitions far from equilibrium. It is necessary to understand these traffic phenomena in a quantitative manner in order to construct and optimize biomimetic transport systems based on motors and filaments with many possible applications in bioengineering, pharmacology, and medicine.

  13. Towards synthetic molecular motors: a model elastic-network study

    NASA Astrophysics Data System (ADS)

    Sarkar, Amartya; Flechsig, Holger; Mikhailov, Alexander S.

    2016-04-01

    Protein molecular motors play a fundamental role in biological cells and development of their synthetic counterparts is a major challenge. Here, we show how a model motor system with the operation mechanism resembling that of muscle myosin can be designed at the concept level, without addressing the implementation aspects. The model is constructed as an elastic network, similar to the coarse-grained descriptions used for real proteins. We show by numerical simulations that the designed synthetic motor can operate as a deterministic or Brownian ratchet and that there is a continuous transition between such two regimes. The motor operation under external load, approaching the stall condition, is also analysed.

  14. REVIEW ARTICLE: The physics of biological molecular motors

    NASA Astrophysics Data System (ADS)

    Thomas, N.; Thornhill, R. A.

    1998-02-01

    Molecular motors are the fundamental agents of movement in living organisms. A prime example is the actomyosin motor that powers muscle contraction. We illustrate the remarkable physics of this motor using a simplified three-state model, in which a myosin cross-bridge attaches to an actin filament, tilts over and then detaches. This `cross-bridge cycle', driven by ATP hydrolysis, is similar to a thermodynamic cycle, except that the molecular system is stochastic. Random transitions in the cycle therefore produce tension fluctuations, which have recently been observed in single-molecule experiments. Furthermore, since the rate constants for attachment and tilting depend on the elastic energy in the cross-bridge spring, the molecular motor is a highly nonlinear mechanical system. A bias tension `stretch activates' the motor, and it then develops the remarkable property of `negative viscosity', which allows it to perform as a self-sustained mechanical oscillator. However, when a series of attachment sites is available, the motor operates instead as a ratchet, pulling the actin filament rapidly forwards against a light load, whilst a heavy load pulls the filament only very slowly in the opposite direction. Similar ideas may apply to the dynein-tubulin motor that powers cilia and flagella and the kinesin-tubulin motor used in intracellular transport.

  15. Molecular crowding creates traffic jams of kinesin motors on microtubules

    PubMed Central

    Leduc, Cécile; Padberg-Gehle, Kathrin; Varga, Vladimír; Helbing, Dirk; Diez, Stefan; Howard, Jonathon

    2012-01-01

    Despite the crowdedness of the interior of cells, microtubule-based motor proteins are able to deliver cargoes rapidly and reliably throughout the cytoplasm. We hypothesize that motor proteins may be adapted to operate in crowded environments by having molecular properties that prevent them from forming traffic jams. To test this hypothesis, we reconstituted high-density traffic of purified kinesin-8 motor protein, a highly processive motor with long end-residency time, along microtubules in a total internal-reflection fluorescence microscopy assay. We found that traffic jams, characterized by an abrupt increase in the density of motors with an associated abrupt decrease in motor speed, form even in the absence of other obstructing proteins. To determine the molecular properties that lead to jamming, we altered the concentration of motors, their processivity, and their rate of dissociation from microtubule ends. Traffic jams occurred when the motor density exceeded a critical value (density-induced jams) or when motor dissociation from the microtubule ends was so slow that it resulted in a pileup (bottleneck-induced jams). Through comparison of our experimental results with theoretical models and stochastic simulations, we characterized in detail under which conditions density- and bottleneck-induced traffic jams form or do not form. Our results indicate that transport kinesins, such as kinesin-1, may be evolutionarily adapted to avoid the formation of traffic jams by moving only with moderate processivity and dissociating rapidly from microtubule ends. PMID:22431622

  16. Cooperative behavior of molecular motors: Cargo transport and traffic phenomena

    NASA Astrophysics Data System (ADS)

    Lipowsky, Reinhard; Beeg, Janina; Dimova, Rumiana; Klumpp, Stefan; Müller, Melanie J. I.

    2010-01-01

    All eukaryotic cells including those of our own body contain complex transport systems based on molecular motors which walk along cytoskeletal filaments. These motors are rather small and make discrete mechanical steps with a step size of the order of 10 nm but are able to pull cargo particles over much larger distances, from micrometers up to meters. In vivo, the intracellular cargos include large membrane-bounded organelles, smaller vesicles, a subset of mRNAs, cytoskeletal filaments, and various protein building blocks, which are transported between different cell compartments. This cargo transport is usually performed by teams of motors. If all motors belong to the same molecular species, the cooperative action of the motors leads to uni-directional transport with a strongly increased run length and with a characteristic force dependence of the velocity distributions. If two antagonistic teams of motors pull on the same cargo particle, they perform a stochastic tug-of-war, which is characterized by a subtle force balance between the two motor teams and leads to several distinct patterns of bi-directional transport. So far, all experimental observations on bi-directional transport are consistent with such a tug-of-war. If many motors and/or cargo particles are transported along the filaments, one encounters various traffic phenomena. Depending on their mutual interactions and the compartment geometry, the motors form various spatio-temporal patterns such as traffic jams, and undergo nonequilibrium phase transitions between different patterns of transport.

  17. A Programmable Optical Angle Clamp for Rotary Molecular Motors

    PubMed Central

    Pilizota, Teuta; Bilyard, Thomas; Bai, Fan; Futai, Masamitsu; Hosokawa, Hiroyuki; Berry, Richard M.

    2007-01-01

    Optical tweezers are widely used for experimental investigation of linear molecular motors. The rates and force dependence of steps in the mechanochemical cycle of linear motors have been probed giving detailed insight into motor mechanisms. With similar goals in mind for rotary molecular motors we present here an optical trapping system designed as an angle clamp to study the bacterial flagellar motor and F1-ATPase. The trap position was controlled by a digital signal processing board and a host computer via acousto-optic deflectors, the motor position via a three-dimensional piezoelectric stage and the motor angle using a pair of polystyrene beads as a handle for the optical trap. Bead-pair angles were detected using back focal plane interferometry with a resolution of up to 1°, and controlled using a feedback algorithm with a precision of up to 2° and a bandwidth of up to 1.6 kHz. Details of the optical trap, algorithm, and alignment procedures are given. Preliminary data showing angular control of F1-ATPase and angular and speed control of the bacterial flagellar motor are presented. PMID:17434937

  18. Electro-magnetic free energy transduction by molecular motors

    NASA Astrophysics Data System (ADS)

    Yakovlev, V. V.

    2009-02-01

    It is generally accepted that molecular motors are utilizing the chemical energy of adenosine triphosphate (ATP) hydrolysis to convert it to the mechanical energy. A set of preliminary data demonstrates that the periodic electric field can induce transport as well, thus providing the energy to the molecular system.

  19. Engineering controllable bidirectional molecular motors based on myosin

    NASA Astrophysics Data System (ADS)

    Chen, Lu; Nakamura, Muneaki; Schindler, Tony D.; Parker, David; Bryant, Zev

    2012-04-01

    Cytoskeletal motors drive the transport of organelles and molecular cargoes within cells and have potential applications in molecular detection and diagnostic devices. Engineering molecular motors with controllable properties will allow selective perturbation of mechanical processes in living cells and provide optimized device components for tasks such as molecular sorting and directed assembly. Biological motors have previously been modified by introducing activation/deactivation switches that respond to metal ions and other signals. Here, we show that myosin motors can be engineered to reversibly change their direction of motion in response to a calcium signal. Building on previous protein engineering studies and guided by a structural model for the redirected power stroke of myosin VI, we have constructed bidirectional myosins through the rigid recombination of structural modules. The performance of the motors was confirmed using gliding filament assays and single fluorophore tracking. Our strategy, in which external signals trigger changes in the geometry and mechanics of myosin lever arms, should make it possible to achieve spatiotemporal control over a range of motor properties including processivity, stride size and branchpoint turning.

  20. Single rotating molecule-machines: nanovehicles and molecular motors.

    PubMed

    Rapenne, Gwénaël; Joachim, Christian

    2014-01-01

    In the last decade many molecular machines with controlled molecular motions have been synthesized. In the present review chapter we will present and discuss our contribution to the field, in particular through some examples of rotating molecular machines that have been designed, synthesized, and studied in our group. After starting by explaining why it is so important to study such machines as single molecules, we will focus on two families of molecular machines, nanovehicles and molecular motors. The first members of the nanovehicle family are molecules with two triptycenes as wheels: the axle and the wheelbarrow. Then come the four-wheel nanocars. Since triptycene wheels are not very mobile on metallic surfaces, alternative wheels with a bowl-shape structure have also been synthesized and studied on surfaces. The molecular motors are built around ruthenium organometallic centers and have a piano-stool geometry with peripheric ferrocenyl groups.

  1. Single rotating molecule-machines: nanovehicles and molecular motors.

    PubMed

    Rapenne, Gwénaël; Joachim, Christian

    2014-01-01

    In the last decade many molecular machines with controlled molecular motions have been synthesized. In the present review chapter we will present and discuss our contribution to the field, in particular through some examples of rotating molecular machines that have been designed, synthesized, and studied in our group. After starting by explaining why it is so important to study such machines as single molecules, we will focus on two families of molecular machines, nanovehicles and molecular motors. The first members of the nanovehicle family are molecules with two triptycenes as wheels: the axle and the wheelbarrow. Then come the four-wheel nanocars. Since triptycene wheels are not very mobile on metallic surfaces, alternative wheels with a bowl-shape structure have also been synthesized and studied on surfaces. The molecular motors are built around ruthenium organometallic centers and have a piano-stool geometry with peripheric ferrocenyl groups. PMID:24563010

  2. Automating the search of molecular motor templates by evolutionary methods.

    PubMed

    Fernández, Jose D; Vico, Francisco J

    2011-11-01

    Biological molecular motors are nanoscale devices capable of transforming chemical energy into mechanical work, which are being researched in many scientific disciplines. From a computational point of view, the characteristics and dynamics of these motors are studied at multiple time scales, ranging from very detailed and complex molecular dynamics simulations spanning a few microseconds, to extremely simple and coarse-grained theoretical models of their working cycles. However, this research is performed only in the (relatively few) instances known from molecular biology. In this work, results from elastic network analysis and behaviour-finding methods are applied to explore a subset of the configuration space of template molecular structures that are able to transform chemical energy into directed movement, for a fixed instance of working cycle. While using methods based on elastic networks limits the scope of our results, it enables the implementation of computationally lightweight methods, in a way that evolutionary search techniques can be applied to discover novel molecular motor templates. The results show that molecular motion can be attained from a variety of structural configurations, when a functional working cycle is provided. Additionally, these methods enable a new computational way to test hypotheses about molecular motors.

  3. Controlled Rotation and Manipulation of Individual Molecular Motors

    NASA Astrophysics Data System (ADS)

    Kersell, Heath; Perera, U. G. E.; Ample, F.; Zhang, Y.; Vives, G.; Echeverria, J.; Grisolia, M.; Rapenne, G.; Joachim, C.; Hla, S.-W.

    2015-03-01

    The design of artificial molecular machines often takes inspiration from macroscopic machines, but the parallels between the two are frequently only superficial because many molecular machines are governed by quantum processes. Previously, chemically and light driven rotary molecular motors have been developed. For electrically driven motors, tunneling electrons from the tip of a scanning tunneling microscope (STM) have been used to drive rotation in a simple rotor into a single direction and to move a wheeled molecule across a surface. Here, we show that a single standalone molecular motor adsorbed on a gold surface can be made to rotate in a clockwise or counterclockwise direction [1] by selective inelastic electron tunneling through different sub-units of the motor. Our motor is composed of a tripodal stator for vertical positioning, a five-arm rotator for controlled rotations, and a Ru atomic ball bearing connecting the static and rotational parts. The directional rotation originates from saw-tooth-like rotational potentials, which are determined by the internal molecular structure and are independent of the surface adsorption site. This project is supported by the US DOE, BES grant: DE-FG02-02ER46012.

  4. Energetics and efficiency of a molecular motor model

    NASA Astrophysics Data System (ADS)

    Fogedby, Hans C.; Svane, Axel

    2013-12-01

    The energetics and efficiency of a linear molecular motor model proposed by Mogilner et al are analyzed from an analytical point of view. The model, which is based on protein friction with a track, is described by coupled Langevin equations for the motion in combination with coupled master equations for the ATP hydrolysis. Here the energetics and efficiency of the motor are addressed using a many body scheme with focus on the efficiency at maximum power (EMP). It is found that the EMP is reduced from about 10% in a heuristic description of the motor to about 1 per mille when incorporating the full motor dynamics, owing to the strong dissipation associated with the motor action.

  5. Molecular motors are stymied by microtubule lattice defects

    NASA Astrophysics Data System (ADS)

    Gramlich, Michael

    2014-03-01

    The microtubule surface provides the tracks that molecular motors use to transport cargo throughout the cell. Much like any surface lattice, the microtubule surface may have surface defects such as dislocations or step edges caused by missing tubulin dimers or shifts in the number of protofilaments, respectively. It is an open question as to how microtubule lattice defects affect molecular motors walking along microtubule surfaces. We used the kinesin-1 motor that walks along a single protofilament and has a short step size of only 8 nm to test how lattice defects affect transport. We created microtubule lattice defects by end-to-end annealing microtubules with different protofilament numbers and differential fluorescence labeling, creating a transition in microtubule radius at the annealed site that is directly visualizable. Surprisingly, we observed that kinesin-1 motors are significantly inhibited by protofilament shift defects. GFP-tagged kinesin-1 motors detach at the defect site during at least 70% of encounters with the defect. We find end-to-end annealed microtubules without the additional change in protofilament number at the defect site inhibit at least 50% of kinesin-1 motors at the defect, suggesting that the process of end-to-end annealing creates defects within the lattice. Our results imply that defects within the microtubule lattice can inhibit motility, and must be corrected. Our work sheds light on the biological importance of removing and correcting lattice defects, an activity known to occur by multiple methods in cells.

  6. Remote control of molecular motors using light-activated gearshifting

    NASA Astrophysics Data System (ADS)

    Bryant, Zev

    2013-03-01

    Engineering molecular motors with dynamically controllable properties will allow selective perturbation of mechanical processes in vivo and provide sophisticated components for directed nanoscale transport in vitro. We previously constructed myosin motors that respond to a change in [Ca++] by reversing their direction of motion along the polarized actin filament. To expand the potential applications of controllable molecular motors, we have now developed myosins that shift gears in response to blue light illumination. Light is a versatile control signal that can be readily modulated in time and space, and is generally orthogonal to cellular signaling. Using structure-guided protein engineering, we have incorporated LOV photoreceptor domains into the lever arms of chimeric myosins, resulting in motors that robustly speed up, slow down, or switch directions upon illumination. These genetically encoded motors should be directly deployable inside living cells. Our successful designs include constructs based on two different myosin classes, and we show that optical velocity control can be implemented in motors that move at microns/sec speeds, enabling practical biological and bioengineering applications.

  7. Control of rotor motion in a light-driven molecular motor: towards a molecular gearbox.

    PubMed

    Ter Wiel, Matthijs K J; van Delden, Richard A; Meetsma, Auke; Feringa, Ben L

    2005-11-21

    Controlled intramolecular movement and coupling of motor and rotor functions is exerted by this new molecular device. The rate of rotation of the rotor part of the molecule can be adjusted by alteration of the conformation of the motor part of the molecule. For all states of the motor part, different rates of rotation were measured for the rotor part. Conversion between the four propeller orientations was achieved by irradiation and heating.

  8. Time-dependent motor properties of multipedal molecular spiders

    NASA Astrophysics Data System (ADS)

    Samii, Laleh; Blab, Gerhard A.; Bromley, Elizabeth H. C.; Linke, Heiner; Curmi, Paul M. G.; Zuckermann, Martin J.; Forde, Nancy R.

    2011-09-01

    Molecular spiders are synthetic biomolecular walkers that use the asymmetry resulting from cleavage of their tracks to bias the direction of their stepping motion. Using Monte Carlo simulations that implement the Gillespie algorithm, we investigate the dependence of the biased motion of molecular spiders, along with binding time and processivity, on tunable experimental parameters, such as number of legs, span between the legs, and unbinding rate of a leg from a substrate site. We find that an increase in the number of legs increases the spiders’ processivity and binding time but not their mean velocity. However, we can increase the mean velocity of spiders with simultaneous tuning of the span and the unbinding rate of a spider leg from a substrate site. To study the efficiency of molecular spiders, we introduce a time-dependent expression for the thermodynamic efficiency of a molecular motor, allowing us to account for the behavior of spider populations as a function of time. Based on this definition, we find that spiders exhibit transient motor function over time scales of many hours and have a maximum efficiency on the order of 1%, weak compared to other types of molecular motors.

  9. Molecular rotors and motors: recent advances and future challenges.

    PubMed

    Michl, Josef; Sykes, E Charles H

    2009-05-26

    At the "Molecular Rotors and Motors" symposium of the Spring 2009 ACS National Meeting in Salt Lake City (March 22-26), a diverse mix of talks addressed many current issues in the field. Speakers described topics that varied from single-molecule rotors and nanomachines to exquisite synthetic approaches toward building functional materials and mathematical and computational methods aimed at uncovering design opportunities and highlighting the fundamental limitations of molecular motors. While the realization of building useful nanomachines remains far off, a general consensus abounded that investigating biological systems and understanding the implications of the laws of thermodynamics and quantum mechanics for the behavior of nanostructures will help drive important advances in the quest for molecular machinery. Molecular rotors were demonstrated to have practical applications as probes for microviscosity, and many speakers presented experimental studies that indicated that highly directed translation and rotation of individual molecules, as well as interacting dipolar arrays, are just around the corner. While this Nano Focus is not intended to be a comprehensive review of the subject, it will focus on several key advances that were presented at the ACS meeting and highlight future challenges for the field of molecular rotors and motors. PMID:19845364

  10. Myosin-I molecular motors at a glance.

    PubMed

    McIntosh, Betsy B; Ostap, E Michael

    2016-07-15

    Myosin-I molecular motors are proposed to play various cellular roles related to membrane dynamics and trafficking. In this Cell Science at a Glance article and the accompanying poster, we review and illustrate the proposed cellular functions of metazoan myosin-I molecular motors by examining the structural, biochemical, mechanical and cell biological evidence for their proposed molecular roles. We highlight evidence for the roles of myosin-I isoforms in regulating membrane tension and actin architecture, powering plasma membrane and organelle deformation, participating in membrane trafficking, and functioning as a tension-sensitive dock or tether. Collectively, myosin-I motors have been implicated in increasingly complex cellular phenomena, yet how a single isoform accomplishes multiple types of molecular functions is still an active area of investigation. To fully understand the underlying physiology, it is now essential to piece together different approaches of biological investigation. This article will appeal to investigators who study immunology, metabolic diseases, endosomal trafficking, cell motility, cancer and kidney disease, and to those who are interested in how cellular membranes are coupled to the underlying actin cytoskeleton in a variety of different applications. PMID:27401928

  11. Biased motion and molecular motor properties of bipedal spiders

    NASA Astrophysics Data System (ADS)

    Samii, Laleh; Linke, Heiner; Zuckermann, Martin J.; Forde, Nancy R.

    2010-02-01

    Molecular spiders are synthetic molecular motors featuring multiple legs that each can interact with a substrate through binding and cleavage. Experimental studies suggest the motion of the spider in a matrix is biased toward uncleaved substrates and that spider properties such as processivity can be altered by changing the binding strength of the legs to substrate [R. Pei, S. K. Taylor, D. Stefanovic, S. Rudchenko, T. E. Mitchell, and M. N. Stojanovic, J. Am. Chem. Soc. 128, 12693 (2006)]. We investigate the origin of biased motion and molecular motor properties of bipedal spiders using Monte Carlo simulations. Our simulations combine a realistic chemical kinetic model, hand-over-hand or inchworm modes of stepping, and the use of a one-dimensional track. We find that stronger binding to substrate, cleavage and spider detachment from the track are contributing mechanisms to population bias. We investigate the contributions of stepping mechanism to speed, randomness parameter, processivity, coupling, and efficiency, and comment on how these molecular motor properties can be altered by changing experimentally tunable kinetic parameters.

  12. ATOMIC AND MOLECULAR PHYSICS: Modelling of a DNA packaging motor

    NASA Astrophysics Data System (ADS)

    Qian, Jun; Xie, Ping; Xue, Xiao-Guang; Wang, Peng-Ye

    2009-11-01

    During the assembly of many viruses, a powerful molecular motor packages the genome into a preassembled capsid. The Bacillus subtilis phage phi29 is an excellent model system to investigate the DNA packaging mechanism because of its highly efficient in vitro DNA packaging activity and the development of a single-molecule packaging assay. Here we make use of structural and biochemical experimental data to build a physical model of DNA packaging by the phi29 DNA packaging motor. Based on the model, various dynamic behaviours such as the packaging rate, pause frequency and slip frequency under different ATP concentrations, ADP concentrations, external loads as well as capsid fillings are studied by using Monte Carlo simulation. Good agreement is obtained between the simulated and available experimental results. Moreover, we make testable predictions that should guide future experiments related to motor function.

  13. Rotary molecular motion at the nanoscale: motors, propellers, wheels

    NASA Astrophysics Data System (ADS)

    Vukovic, Lela; Wang, Boyang; Kral, Petr

    2009-03-01

    We describe by molecular dynamics simulations nanoscale systems that could realize rotary motion. First, we study molecular propellers formed by carbon nanotube rotors with attached aromatic blades [1]. We show that these propellers could pump different types of liquids, and their pumping efficiency strongly depends on the chemistry of the (hydrophobic or hydrophilic) liquid-blade interface. We also investigate nanoscopic wheels with hydrophobic surfaces that show rolling activity on water when driven. Finally, we model efficient molecular motors driven by electron tunneling, which could drive rotary molecular systems [2]. [3pt] [1] B. Wang and P. Kr'al, . Rev. Lett. 98, 266102 (2007).[0pt] [2] B. Wang, L. Vukovic and P. Kr'al, Phys. Rev. Lett. 101, 186808 (2008).

  14. Chemical and thermal modulation of molecular motor activities

    NASA Astrophysics Data System (ADS)

    Hong, Weili

    Molecular motors of kinesin and dynein families are responsible for various intracellular activities, from long distance movement of organelles, vesicles, protein complexes, and mRNAs to powering mitotic processes. They can take nanometer steps using chemical energy from the hydrolysis of ATP (adenosine triphosphate), and their dysfunction is involved in many neurodegenerative diseases that require long distance transport of cargos. Here I report on the study of the properties of molecular motors at a single-molecule level using optical trappings. I first studied the inhibition properties of kinesin motors by marine natural compound adociasulfates. I showed that adociasulfates compete with microtubules for binding to kinesins and thus inhibit kinesins' activity. Although adociasulfates are a strong inhibitor for all kinesin members, they show a much higher inhibition effect for conventional kinesins than for mitotic kinesins. Thus adociasulfates can be used to specifically inhibit conventional kinesins. By comparing the inhibition of kinesins by two structurally similar adociasulfates, one can see that the negatively charged sulfate residue of adociasulfates can be replaced by other negative residues and thus make it possible for adociasulfate-derived compounds to be more cell permeable. Kinesins and dyneins move cargos towards opposite directions along a microtubule. Cargos with both kinesins and dyneins attached often move bidirectionally due to undergoing a tug-of-war between the oppositely moving kinesin and dynein motors. Here I studied the effect of temperature on microtubule-based kinesin and dynein motor transport. While kinesins' and dyneins' velocities are closely matched above 15 °C, below this temperature the dyneins' velocity decreases much faster than the kinesins'. The kinesins' and dyneins' forces do not measurably change with temperature. The results suggest that temperature has significant effects on bidirectional transport and can be used to

  15. Microtubules and associated molecular motors in Neurospora crassa.

    PubMed

    Mouriño-Pérez, Rosa Reyna; Riquelme, Meritxell; Callejas-Negrete, Olga Alicia; Galván-Mendoza, José Iván

    2016-01-01

    The cytoskeleton provides structure, shape and movement to various cells. Microtubules (MTs) are tubular structures made of α and β-tubulin heterodimers organized in 13 protofilaments, forming a hollow cylinder. A vast group of MT-associated proteins determines the function, behavior and interaction of the MTs with other cellular components. Among these proteins, molecular motors such as the dynein-dynactin complex and kinesin superfamily play roles in MT organization and organelle transport. This article focuses on the MT cytoskeleton and associated molecular motors in the filamentous fungus Neurospora crassa In addition to reviewing current available information for this fungus and contrasting it with knowledge of other fungal species, we present new experimental results that support the role of dynein, dynactin and conventional kinesin in MT organization, dynamics and transport of subcellular structures (nuclei and secretory vesicles). In wild type hyphae of N. crassa, cytoplasmic MTs are arranged longitudinally along hyphae and display a helical curvature. They interlace with one another to form a network throughout the cytoplasm. N. crassa dynein and dynactin mutants have a scant and disorganized MT cytoskeleton, an erratic and reduced Spitzenkörper (Spk) and distorted hyphal morphology. In contrast, hyphae of mutants with defective conventional kinesin exhibit only minor disruptions in MT and Spk organization. Although nuclear positioning is affected in all mutants, the MT-associated motor proteins are not major contributors to nuclear movement during hyphal growth. Cytoplasmic bulk flow is the vehicle for nuclear displacement in growing hyphal regions of N. crassa Motors are involved in nuclei saltatory movements in both retrograde or anterograde direction. In the dynein and kinesin mutants, micro and macrovesicles can reach the Spk, although growth is slightly impaired and the Spk displays an erratic path. Hyphal growth requires MTs, and their associated

  16. Optical Traps to Study Properties of Molecular Motors

    PubMed Central

    Spudich, James A.; Rice, Sarah E.; Rock, Ronald S.; Purcell, Thomas J.; Warrick, Hans M.

    2016-01-01

    In vitro motility assays enabled the analysis of coupling between ATP hydrolysis and movement of myosin along actin filaments or kinesin along microtubules. Single-molecule assays using laser trapping have been used to obtain more detailed information about kinesins, myosins, and processive DNA enzymes. The combination of in vitro motility assays with laser-trap measurements has revealed detailed dynamic structural changes associated with the ATPase cycle. This article describes the use of optical traps to study processive and nonprocessive molecular motor proteins, focusing on the design of the instrument and the assays to characterize motility. PMID:22046048

  17. Optical traps to study properties of molecular motors.

    PubMed

    Spudich, James A; Rice, Sarah E; Rock, Ronald S; Purcell, Thomas J; Warrick, Hans M

    2011-11-01

    In vitro motility assays enabled the analysis of coupling between ATP hydrolysis and movement of myosin along actin filaments or kinesin along microtubules. Single-molecule assays using laser trapping have been used to obtain more detailed information about kinesins, myosins, and processive DNA enzymes. The combination of in vitro motility assays with laser-trap measurements has revealed detailed dynamic structural changes associated with the ATPase cycle. This article describes the use of optical traps to study processive and nonprocessive molecular motor proteins, focusing on the design of the instrument and the assays to characterize motility.

  18. Relation between cooperative molecular motors and active Brownian particles.

    PubMed

    Touya, Clément; Schwalger, Tilo; Lindner, Benjamin

    2011-05-01

    Active Brownian particles (ABPs), obeying a nonlinear Langevin equation with speed-dependent drift and noise amplitude, are well-known models used to describe self-propelled motion in biology. In this paper we study a model describing the stochastic dynamics of a group of coupled molecular motors (CMMs). Using two independent numerical methods, one based on the stationary velocity distribution of the motors and the other one on the local increments (also known as the Kramers-Moyal coefficients) of the velocity, we establish a connection between the CMM and the ABP models. The parameters extracted for the ABP via the two methods show good agreement for both symmetric and asymmetric cases and are independent of N, the number of motors, provided that N is not too small. This indicates that one can indeed describe the CMM problem with a simpler ABP model. However, the power spectrum of velocity fluctuations in the CMM model reveals a peak at a finite frequency, a peak which is absent in the velocity spectrum of the ABP model. This implies richer dynamic features of the CMM model which cannot be captured by an ABP model.

  19. Actin-based motility propelled by molecular motors

    NASA Astrophysics Data System (ADS)

    Upadyayula, Sai Pramod; Rangarajan, Murali

    2012-09-01

    Actin-based motility of Listeria monocytogenes propelled by filament end-tracking molecular motors has been simulated. Such systems may act as potential nanoscale actuators and shuttles useful in sorting and sensing biomolecules. Filaments are modeled as three-dimensional elastic springs distributed on one end of the capsule and persistently attached to the motile bacterial surface through an end-tracking motor complex. Filament distribution is random, and monomer concentration decreases linearly as a function of position on the bacterial surface. Filament growth rate increases with monomer concentration but decreases with the extent of compression. The growing filaments exert push-pull forces on the bacterial surface. In addition to forces, torques arise due to two factors—distribution of motors on the bacterial surface, and coupling of torsion upon growth due to the right-handed helicity of F-actin—causing the motile object to undergo simultaneous translation and rotation. The trajectory of the bacterium is simulated by performing a force and torque balance on the bacterium. All simulations use a fixed value of torsion. Simulations show strong alignment of the filaments and the long axis of the bacterium along the direction of motion. In the absence of torsion, the bacterial surface essentially moves along the direction of the long axis. When a small amount of the torsion is applied to the bacterial surface, the bacterium is seen to move in right-handed helical trajectories, consistent with experimental observations.

  20. External forces influence the elastic coupling effects during cargo transport by molecular motors.

    PubMed

    Berger, Florian; Keller, Corina; Klumpp, Stefan; Lipowsky, Reinhard

    2015-02-01

    Cellular transport is achieved by the cooperative action of molecular motors which are elastically linked to a common cargo. When the motors pull on the cargo at the same time, they experience fluctuating elastic strain forces induced by the stepping of the other motors. These elastic coupling forces can influence the motors' stepping and unbinding behavior and thereby the ability to transport cargos. Based on a generic single motor description, we introduce a framework that explains the response of two identical molecular motors to a constant external force. In particular, we relate the single motor parameters, the coupling strength and the external load force to the dynamics of the motor pair. We derive four distinct transport regimes and determine how the crossover lines between the regimes depend on the load force. Our description of the overall cargo dynamics takes into account relaxational displacements of the cargo caused by the unbinding of one motor. For large forces and weak elastic coupling these back-shifts dominate the displacements. To develop an intuitive understanding about motor cooperativity during cargo transport, we introduce a time scale for load sharing. This time scale allows us to predict how the regulation of single motor parameters influences the cooperativity. As an example, we show that up-regulating the single motor processivity enhances load sharing of the motor pair.

  1. Intra-cellular traffic: bio-molecular motors on filamentary tracks

    NASA Astrophysics Data System (ADS)

    Chowdhury, D.; Basu, A.; Garai, A.; Greulich, P.; Nishinari, K.; Schadschneider, A.; Tripathi, T.

    2008-08-01

    Molecular motors are macromolecular complexes which use some form of input energy to perform mechanical work. The filamentary tracks, on which these motors move, are made of either proteins (e.g., microtubules) or nucleic acids (DNA or RNA). Often, many such motors move simultaneously on the same track and their collective properties have superficial similarities with vehicular traffic on highways. The models we have developed provide "unified" description: in the low-density limit, a model captures the transport properties of a single motor while, at higher densities the same model accounts for the collective spatio-temporal organization of interacting motors. By drawing analogy with vehicular traffic, we have introduced novel quantities for characterizing the nature of the spatio-temporal organization of molecular motors on their tracks. We show how the traffic-like intracellular collective phenomena depend on the mechano-chemistry of the corresponding individual motors.

  2. Simulation studies of self-organization of microtubules and molecular motors.

    SciTech Connect

    Jian, Z.; Karpeev, D.; Aranson, I. S.; Bates, P. W.; Michigan State Univ.

    2008-05-01

    We perform Monte Carlo type simulation studies of self-organization of microtubules interacting with molecular motors. We model microtubules as stiff polar rods of equal length exhibiting anisotropic diffusion in the plane. The molecular motors are implicitly introduced by specifying certain probabilistic collision rules resulting in realignment of the rods. This approximation of the complicated microtubule-motor interaction by a simple instant collision allows us to bypass the 'computational bottlenecks' associated with the details of the diffusion and the dynamics of motors and the reorientation of microtubules. Consequently, we are able to perform simulations of large ensembles of microtubules and motors on a very large time scale. This simple model reproduces all important phenomenology observed in in vitro experiments: Formation of vortices for low motor density and raylike asters and bundles for higher motor density.

  3. Simulation studies of self-organization of microtubules and molecular motors

    NASA Astrophysics Data System (ADS)

    Jia, Zhiyuan; Karpeev, Dmitry; Aranson, Igor S.; Bates, Peter W.

    2008-05-01

    We perform Monte Carlo type simulation studies of self-organization of microtubules interacting with molecular motors. We model microtubules as stiff polar rods of equal length exhibiting anisotropic diffusion in the plane. The molecular motors are implicitly introduced by specifying certain probabilistic collision rules resulting in realignment of the rods. This approximation of the complicated microtubule-motor interaction by a simple instant collision allows us to bypass the “computational bottlenecks” associated with the details of the diffusion and the dynamics of motors and the reorientation of microtubules. Consequently, we are able to perform simulations of large ensembles of microtubules and motors on a very large time scale. This simple model reproduces all important phenomenology observed in in vitro experiments: Formation of vortices for low motor density and raylike asters and bundles for higher motor density.

  4. The stochastic model of F1-ATPase molecular motor functioning

    NASA Astrophysics Data System (ADS)

    Pogrebnaya, Aleksandra F.; Romanovsky, Yury M.; Tikhonov, Aleksander N.

    2004-05-01

    This work is devoted to the study of the energy characteristics of the F1ATPase-substrate complex. The results of calculations of the electrostatic energy in the enzyme-substrate complex are presented in the first part. In calculations, we take into account the electrostatic interactions between the charged groups of the substrate (MgATP) and reaction products (MgADP and Pi) and charged amino acid residues of the α3β3γ complex that correspond to various conformations of the enzyme. The hydrolysis of ATP in the catalytic site leads to coordinated conformational changes in α, β subunits and to ordered rotation of γ subunit located in the center of F1ATPase complex. The calculations show that the energetically favorable process involving MgATP binding at the catalytic site in the "open" conformation initiates γ subunit rotation followed by the hydrolysis in the other (tight) catalytic site. In the second part, we propose the simplest stochastic model describing the ordered rotation of γ subunit (the rotor of F1-ATPase molecular motor). In the model we take into account the electrostatic interaction using the results of the previous calculations. We employ experimentally obtained dynamic parameters. The model takes into account the thermal fluctuations of the bath and the random processes of the substrate binding and the escape of the reaction products.

  5. Chemomechanical Coupling of Molecular Motors: Thermodynamics, Network Representations, and Balance Conditions

    NASA Astrophysics Data System (ADS)

    Lipowsky, Reinhard; Liepelt, Steffen

    2008-01-01

    Molecular motors are considered that convert the chemical energy released from the hydrolysis of adenosine triphosphate (ATP) into mechanical work. Such a motor represents a small system that is coupled to a heat reservoir, a work reservoir, and particle reservoirs for ATP, adenosine diphosphate (ADP), and inorganic phosphate (P). The discrete state space of the motor is defined in terms of the chemical composition of its catalytic domains. Each motor state represents an ensemble of molecular conformations that are thermally equilibrated. The motor states together with the possible transitions between neighboring states define a network representation of the motor. The motor dynamics is described by a continuous-time Markov process (or master equation) on this network. The consistency between thermodynamics and network dynamics implies (i) local and nonlocal balance conditions for the transition rates of the motor and (ii) an underlying landscape of internal energies for the motor states. The local balance conditions can be interpreted in terms of constrained equilibria between neighboring motor states; the nonlocal balance conditions pinpoint chemical and/or mechanical nonequilibrium.

  6. From the Cover: Cooperative extraction of membrane nanotubes by molecular motors

    NASA Astrophysics Data System (ADS)

    Leduc, Cécile; Campàs, Otger; Zeldovich, Konstantin B.; Roux, Aurélien; Jolimaitre, Pascale; Bourel-Bonnet, Line; Goud, Bruno; Joanny, Jean-François; Bassereau, Patricia; Prost, Jacques

    2004-12-01

    In eukaryotic cells, nanotubes represent a substantial fraction of transport intermediates between organelles. They are extracted from membranes by molecular motors walking along microtubules. We previously showed that kinesins fixed on giant unilamellar vesicles in contact with microtubules are sufficient to form nanotubes in vitro. Motors were attached to the membrane through beads, thus facilitating cooperative effects. Koster et al. [Koster, G., VanDuijn, M., Hofs, B. & Dogterom, M. (2003) Proc. Natl. Acad. Sci. USA 100, 15583-15588] proposed that motors could dynamically cluster at the tip of tubes when they are individually attached to the membrane. We demonstrate, in a recently designed experimental system, the existence of an accumulation of motors allowing tube extraction. We determine the motor density along a tube by using fluorescence intensity measurements. We also perform a theoretical analysis describing the dynamics of motors and tube growth. The only adjustable parameter is the motor binding rate onto microtubules, which we measure to be 4.7 ± 2.4 s-1. In addition, we quantitatively determine, for a given membrane tension, the existence of a threshold in motor density on the vesicle above which nanotubes can be formed. We find that the number of motors pulling a tube can range from four at threshold to a few tens away from it. The threshold in motor density (or in membrane tension at constant motor density) could be important for the understanding of membrane traffic regulation in cells. giant unilamellar vesicle | intracellular transport | kinesin | membrane tubule | traffic jam

  7. Enhanced Diffusion of Molecular Motors in the Presence of Adenosine Triphosphate and External Force

    NASA Astrophysics Data System (ADS)

    Shinagawa, Ryota; Sasaki, Kazuo

    2016-06-01

    The diffusion of a molecular motor in the presence of a constant external force is considered on the basis of a simple theoretical model. The motor is represented by a Brownian particle moving in a series of parabolic potentials placed periodically on a line, and the potential is switched stochastically from one parabola to another by a chemical reaction, which corresponds to the hydrolysis or synthesis of adenosine triphosphate (ATP) in motor proteins. It is found that the diffusion coefficient as a function of the force exhibits peaks. The mechanism of this diffusion enhancement and the possibility of observing it in F1-ATPase, a biological rotary motor, are discussed.

  8. Computational Design of a Family of Light-Driven Rotary Molecular Motors with Improved Quantum Efficiency.

    PubMed

    Nikiforov, Alexander; Gamez, Jose A; Thiel, Walter; Filatov, Michael

    2016-01-01

    Two new light-driven molecular rotary motors based on the N-alkylated indanylidene benzopyrrole frameworks are proposed and studied using quantum chemical calculations and nonadiabatic molecular dynamics simulations. These new motors perform pure axial rotation, and the photochemical steps of the rotary cycle are dominated by the fast bond-length-alternation motion that enables ultrafast access to the S1/S0 intersection. The new motors are predicted to display a quantum efficiency higher than that of the currently available synthetic all-hydrocarbon motors. Remarkably, the quantum efficiency is not governed by the topography (peaked versus sloped) of the minimum-energy conical intersection, whereas the S1 decay time depends on the topography as well as on the energy of the intersection relative to the S1 minimum. It is the axial chirality (helicity), rather than the point chirality, that controls the sense of rotation of the motor. PMID:26670164

  9. Computational Design of a Family of Light-Driven Rotary Molecular Motors with Improved Quantum Efficiency.

    PubMed

    Nikiforov, Alexander; Gamez, Jose A; Thiel, Walter; Filatov, Michael

    2016-01-01

    Two new light-driven molecular rotary motors based on the N-alkylated indanylidene benzopyrrole frameworks are proposed and studied using quantum chemical calculations and nonadiabatic molecular dynamics simulations. These new motors perform pure axial rotation, and the photochemical steps of the rotary cycle are dominated by the fast bond-length-alternation motion that enables ultrafast access to the S1/S0 intersection. The new motors are predicted to display a quantum efficiency higher than that of the currently available synthetic all-hydrocarbon motors. Remarkably, the quantum efficiency is not governed by the topography (peaked versus sloped) of the minimum-energy conical intersection, whereas the S1 decay time depends on the topography as well as on the energy of the intersection relative to the S1 minimum. It is the axial chirality (helicity), rather than the point chirality, that controls the sense of rotation of the motor.

  10. Kinetic mechanism of DNA translocation by the RSC molecular motor.

    PubMed

    Eastlund, Allen; Malik, Shuja Shafi; Fischer, Christopher J

    2013-04-15

    ATP-dependent nucleosome repositioning by chromatin remodeling enzymes requires the translocation of these enzymes along the nucleosomal DNA. Using a fluorescence stopped-flow assay we monitored DNA translocation by a minimal RSC motor and through global analysis of these time courses we have determined that this motor has a macroscopic translocation rate of 2.9 bp/s with a step size of 1.24 bp. From the complementary quantitative analysis of the associated time courses of ATP consumption during DNA translocation we have determined that this motor has an efficiency of 3.0 ATP/bp, which is slightly less that the efficiency observed for several genetically related DNA helicases and which likely results from random pausing by the motor during translocation. Nevertheless, this motor is able to exert enough force during translocation to displace streptavidin from biotinylated DNA. Taken together these results are the necessary first step for quantifying both the role of DNA translocation in nucleosome repositioning by RSC and the efficiency at which RSC couples ATP binding and hydrolysis to nucleosome repositioning.

  11. Pattern Formations in Polymer-Molecular Motor Networks

    NASA Astrophysics Data System (ADS)

    Smith, David; Humphrey, David; Duggan, Cynthia; Käs, Josef

    2001-03-01

    In previous studies with the microtubule-kinesin system, organized patterns such as asters and rotating vortices have been seen (Nedelec et al, Nature 1997), which were of a dynamic nature and dependent on active motors. A similar system was constructed using actin and myosin, which displays similar patterns, however, with drastically different dynamics. These patterns arise independent of the initial amount of immediate use energy (in the form of ATP), assembling only upon the near exhaustion of available ATP. Further studies have clearly shown that in fact these patterns are not dependent upon the motor activity of the myosin but its propensity to serve as a cross-linking element in an actin network, with the motor activity serving to prevent the arising of order in the system. We believe the dynamic differences inherent between the two polymer-motor systems studied lies primarily in the structural nature of the motor complexes, with the kinesin complex ordering the system by pushing multiple filaments in a parallel direction, and the myosin complexes disordering the system by pushing filaments in an antiparallel manner.

  12. Differential screening of mutated SOD1 transgenic mice reveals early up-regulation of a fast axonal transport component in spinal cord motor neurons.

    PubMed

    Dupuis, L; de Tapia, M; René, F; Lutz-Bucher, B; Gordon, J W; Mercken, L; Pradier, L; Loeffler, J P

    2000-08-01

    In the present study we analyze the molecular mechanisms underlying motor neuron degeneration in familial amyotrophic lateral sclerosis (FALS). For this, we used a transgenic mouse model expressing the Cu/Zn superoxide dismutase (SOD1) gene with a Gly(86) to Arg (G86R) mutation equivalent to that found in a subset of human FALS. Using an optimized suppression subtractive hybridization method, a cDNA specifically up-regulated during the asymptomatic phase in the lumbar spinal cord of G86R mice was identified by sequence analysis as the KIF3-associated protein (KAP3), a regulator of fast axonal transport. RT-PCR analysis revealed that KAP3 induction was an early event arising long before axonal degeneration. Immunohistochemical studies further revealed that KAP3 protein predominantly accumulates in large motor neurons of the ventral spinal cord. We further demonstrated that KAP3 up-regulation occurs independent of any change in the other components of the kinesin II complex. However, since the ubiquitous KIF1A motor is up-regulated, our results show an early and complex rearrangement of the fast axonal transport machinery in the course of FALS pathology.

  13. Intrinsic irreversibility limits the efficiency of multidimensional molecular motors.

    PubMed

    Jack, M W; Tumlin, C

    2016-05-01

    We consider the efficiency limits of Brownian motors able to extract work from the temperature difference between reservoirs or from external thermodynamic forces. These systems can operate in a variety of modes, including as isothermal engines, heat engines, refrigerators, and heat pumps. We derive analytical results showing that certain classes of multidimensional Brownian motor, including the Smoluchowski-Feynman ratchet, are unable to attain perfect efficiency (Carnot efficiency for heat engines). This demonstrates the presence of intrinsic irreversibilities in their operating mechanism. We present numerical simulations showing that in some cases the loss process that limits efficiency is associated with vortices in the probability current.

  14. Intrinsic irreversibility limits the efficiency of multidimensional molecular motors

    NASA Astrophysics Data System (ADS)

    Jack, M. W.; Tumlin, C.

    2016-05-01

    We consider the efficiency limits of Brownian motors able to extract work from the temperature difference between reservoirs or from external thermodynamic forces. These systems can operate in a variety of modes, including as isothermal engines, heat engines, refrigerators, and heat pumps. We derive analytical results showing that certain classes of multidimensional Brownian motor, including the Smoluchowski-Feynman ratchet, are unable to attain perfect efficiency (Carnot efficiency for heat engines). This demonstrates the presence of intrinsic irreversibilities in their operating mechanism. We present numerical simulations showing that in some cases the loss process that limits efficiency is associated with vortices in the probability current.

  15. Intrinsic irreversibility limits the efficiency of multidimensional molecular motors.

    PubMed

    Jack, M W; Tumlin, C

    2016-05-01

    We consider the efficiency limits of Brownian motors able to extract work from the temperature difference between reservoirs or from external thermodynamic forces. These systems can operate in a variety of modes, including as isothermal engines, heat engines, refrigerators, and heat pumps. We derive analytical results showing that certain classes of multidimensional Brownian motor, including the Smoluchowski-Feynman ratchet, are unable to attain perfect efficiency (Carnot efficiency for heat engines). This demonstrates the presence of intrinsic irreversibilities in their operating mechanism. We present numerical simulations showing that in some cases the loss process that limits efficiency is associated with vortices in the probability current. PMID:27300832

  16. A molecular brake, not a clutch, stops the Rhodobacter sphaeroides flagellar motor

    PubMed Central

    Pilizota, Teuta; Brown, Mostyn T.; Leake, Mark C.; Branch, Richard W.; Berry, Richard M.; Armitage, Judith P.

    2009-01-01

    Many bacterial species swim by employing ion-driven molecular motors that power the rotation of helical filaments. Signals are transmitted to the motor from the external environment via the chemotaxis pathway. In bidirectional motors, the binding of phosphorylated CheY (CheY-P) to the motor is presumed to instigate conformational changes that result in a different rotor-stator interface, resulting in rotation in the alternative direction. Controlling when this switch occurs enables bacteria to accumulate in areas favorable for their survival. Unlike most species that swim with bidirectional motors, Rhodobacter sphaeroides employs a single stop-start flagellar motor. Here, we asked, how does the binding of CheY-P stop the motor in R. sphaeroides—using a clutch or a brake? By applying external force with viscous flow or optical tweezers, we show that the R. sphaeroides motor is stopped using a brake. The motor stops at 27–28 discrete angles, locked in place by a relatively high torque, approximately 2–3 times its stall torque. PMID:19571004

  17. How molecular motors work in the crowded environment of living cells: coexistence and efficiency of normal and anomalous transport.

    PubMed

    Goychuk, Igor; Kharchenko, Vasyl O; Metzler, Ralf

    2014-01-01

    Recent experiments reveal both passive subdiffusion of various nanoparticles and anomalous active transport of such particles by molecular motors in the molecularly crowded environment of living biological cells. Passive and active microrheology reveals that the origin of this anomalous dynamics is due to the viscoelasticity of the intracellular fluid. How do molecular motors perform in such a highly viscous, dissipative environment? Can we explain the observed co-existence of the anomalous transport of relatively large particles of 100 to 500 nm in size by kinesin motors with the normal transport of smaller particles by the same molecular motors? What is the efficiency of molecular motors in the anomalous transport regime? Here we answer these seemingly conflicting questions and consistently explain experimental findings in a generalization of the well-known continuous diffusion model for molecular motors with two conformational states in which viscoelastic effects are included.

  18. Interplay between crosslinkers and dynamic molecular motor-induced instabilities in the moderation of biopolymer organization

    NASA Astrophysics Data System (ADS)

    Smith, David; Humphrey, David; Ziebert, Falko; Zimmermann, Walter; Käs, Josef

    2006-03-01

    Structure and function of biological cells rely on the highly-dynamic self-organization of protein filaments to an intracellular cytoskeleton responsive to mechanical and chemical stimuli. While dissolving these complex cellular structures through Brownian motion is inherently slow (tens of minutes), changes in the activity of the molecular motor myosin II cause rapid order-disorder transitions within 1-2 minutes in reconstituted cytoskeletal actin networks. When motor-induced filament sliding decreases, actin network structure rapidly and reversibly self-organizes into various assemblies triggered by a nonlinear instability. Modulation of static crosslinker concentrations allow for a wide phase space of order ranging from nematics to compact asters & dense packing of motor-filament clusters. The observed isothermal transitions between disorder and self-organization illustrate that molecular motors can substantially contribute to dynamic cellular organization.

  19. Influence of molecular motors on the motion of particles in viscoelastic media.

    PubMed

    Bouzat, Sebastián

    2014-06-01

    We study theoretically and by numerical simulations the motion of particles driven by molecular motors in a viscoelastic medium representing the cell cytoplasm. For this, we consider a generalized Langevin equation coupled to a stochastic stepping dynamics for the motors that takes into account the action of each motor separately. In the absence of motors, the model produces subdiffusive motion of particles characterized by a power-law scaling of the mean square displacement versus the lag time as t^{α}, with 0<α<1, similar to that observed in cells. Our results show how the action of the motors can induce a transition to a superdiffusive regime at large lag times with the characteristics of those found in experiments reported in the literature. We also show that at small lag times, the motors can act as static crosslinkers that slow down the natural subdiffusive transport. An analysis of previously reported experimental data in the relevant time scales provides evidence of this phenomenon. Finally, we study the effect of a harmonic potential representing an optical trap, and we show a way to approach to a macroscopic description of the active transport in cells. This last point stresses the relevance of the molecular motors for generating not only directed motion to specific targets, but also fast diffusivelike random motion.

  20. Stepping and Crowding of Molecular Motors: Statistical Kinetics from an Exclusion Process Perspective

    PubMed Central

    Ciandrini, Luca; Romano, M. Carmen; Parmeggiani, Andrea

    2014-01-01

    Motor enzymes are remarkable molecular machines that use the energy derived from the hydrolysis of a nucleoside triphosphate to generate mechanical movement, achieved through different steps that constitute their kinetic cycle. These macromolecules, nowadays investigated with advanced experimental techniques to unveil their molecular mechanisms and the properties of their kinetic cycles, are implicated in many biological processes, ranging from biopolymerization (e.g., RNA polymerases and ribosomes) to intracellular transport (motor proteins such as kinesins or dyneins). Although the kinetics of individual motors is well studied on both theoretical and experimental grounds, the repercussions of their stepping cycle on the collective dynamics still remains unclear. Advances in this direction will improve our comprehension of transport process in the natural intracellular medium, where processive motor enzymes might operate in crowded conditions. In this work, we therefore extend contemporary statistical kinetic analysis to study collective transport phenomena of motors in terms of lattice gas models belonging to the exclusion process class. Via numerical simulations, we show how to interpret and use the randomness calculated from single particle trajectories in crowded conditions. Importantly, we also show that time fluctuations and non-Poissonian behavior are intrinsically related to spatial correlations and the emergence of large, but finite, clusters of comoving motors. The properties unveiled by our analysis have important biological implications on the collective transport characteristics of processive motor enzymes in crowded conditions. PMID:25185553

  1. Stepping and crowding of molecular motors: statistical kinetics from an exclusion process perspective.

    PubMed

    Ciandrini, Luca; Romano, M Carmen; Parmeggiani, Andrea

    2014-09-01

    Motor enzymes are remarkable molecular machines that use the energy derived from the hydrolysis of a nucleoside triphosphate to generate mechanical movement, achieved through different steps that constitute their kinetic cycle. These macromolecules, nowadays investigated with advanced experimental techniques to unveil their molecular mechanisms and the properties of their kinetic cycles, are implicated in many biological processes, ranging from biopolymerization (e.g., RNA polymerases and ribosomes) to intracellular transport (motor proteins such as kinesins or dyneins). Although the kinetics of individual motors is well studied on both theoretical and experimental grounds, the repercussions of their stepping cycle on the collective dynamics still remains unclear. Advances in this direction will improve our comprehension of transport process in the natural intracellular medium, where processive motor enzymes might operate in crowded conditions. In this work, we therefore extend contemporary statistical kinetic analysis to study collective transport phenomena of motors in terms of lattice gas models belonging to the exclusion process class. Via numerical simulations, we show how to interpret and use the randomness calculated from single particle trajectories in crowded conditions. Importantly, we also show that time fluctuations and non-Poissonian behavior are intrinsically related to spatial correlations and the emergence of large, but finite, clusters of comoving motors. The properties unveiled by our analysis have important biological implications on the collective transport characteristics of processive motor enzymes in crowded conditions.

  2. Self-organization of waves and pulse trains by molecular motors in cellular protrusions

    PubMed Central

    Yochelis, A.; Ebrahim, S.; Millis, B.; Cui, R.; Kachar, B.; Naoz, M.; Gov, N. S.

    2015-01-01

    Actin-based cellular protrusions are an ubiquitous feature of cells, performing a variety of critical functions ranging from cell-cell communication to cell motility. The formation and maintenance of these protrusions relies on the transport of proteins via myosin motors, to the protrusion tip. While tip-directed motion leads to accumulation of motors (and their molecular cargo) at the protrusion tip, it is observed that motors also form rearward moving, periodic and isolated aggregates. The origins and mechanisms of these aggregates, and whether they are important for the recycling of motors, remain open puzzles. Motivated by novel myosin-XV experiments, a mass conserving reaction-diffusion-advection model is proposed. The model incorporates a non-linear cooperative interaction between motors, which converts them between an active and an inactive state. Specifically, the type of aggregate formed (traveling waves or pulse-trains) is linked to the kinetics of motors at the protrusion tip which is introduced by a boundary condition. These pattern selection mechanisms are found not only to qualitatively agree with empirical observations but open new vistas to the transport phenomena by molecular motors in general. PMID:26335545

  3. Influence of molecular motors on the motion of particles in viscoelastic media.

    PubMed

    Bouzat, Sebastián

    2014-06-01

    We study theoretically and by numerical simulations the motion of particles driven by molecular motors in a viscoelastic medium representing the cell cytoplasm. For this, we consider a generalized Langevin equation coupled to a stochastic stepping dynamics for the motors that takes into account the action of each motor separately. In the absence of motors, the model produces subdiffusive motion of particles characterized by a power-law scaling of the mean square displacement versus the lag time as t^{α}, with 0<α<1, similar to that observed in cells. Our results show how the action of the motors can induce a transition to a superdiffusive regime at large lag times with the characteristics of those found in experiments reported in the literature. We also show that at small lag times, the motors can act as static crosslinkers that slow down the natural subdiffusive transport. An analysis of previously reported experimental data in the relevant time scales provides evidence of this phenomenon. Finally, we study the effect of a harmonic potential representing an optical trap, and we show a way to approach to a macroscopic description of the active transport in cells. This last point stresses the relevance of the molecular motors for generating not only directed motion to specific targets, but also fast diffusivelike random motion. PMID:25019814

  4. Self-organization of waves and pulse trains by molecular motors in cellular protrusions.

    PubMed

    Yochelis, A; Ebrahim, S; Millis, B; Cui, R; Kachar, B; Naoz, M; Gov, N S

    2015-01-01

    Actin-based cellular protrusions are an ubiquitous feature of cells, performing a variety of critical functions ranging from cell-cell communication to cell motility. The formation and maintenance of these protrusions relies on the transport of proteins via myosin motors, to the protrusion tip. While tip-directed motion leads to accumulation of motors (and their molecular cargo) at the protrusion tip, it is observed that motors also form rearward moving, periodic and isolated aggregates. The origins and mechanisms of these aggregates, and whether they are important for the recycling of motors, remain open puzzles. Motivated by novel myosin-XV experiments, a mass conserving reaction-diffusion-advection model is proposed. The model incorporates a non-linear cooperative interaction between motors, which converts them between an active and an inactive state. Specifically, the type of aggregate formed (traveling waves or pulse-trains) is linked to the kinetics of motors at the protrusion tip which is introduced by a boundary condition. These pattern selection mechanisms are found not only to qualitatively agree with empirical observations but open new vistas to the transport phenomena by molecular motors in general. PMID:26335545

  5. Reversing the direction in a light-driven rotary molecular motor

    NASA Astrophysics Data System (ADS)

    Ruangsupapichat, Nopporn; Pollard, Michael M.; Harutyunyan, Syuzanna R.; Feringa, Ben L.

    2011-01-01

    Biological rotary motors can alter their mechanical function by changing the direction of rotary motion. Achieving a similar reversal of direction of rotation in artificial molecular motors presents a fundamental stereochemical challenge: how to change from clockwise to anticlockwise motion without compromising the autonomous unidirectional rotary behaviour of the system. A new molecular motor with multilevel control of rotary motion is reported here, in which the direction of light-powered rotation can be reversed by base-catalysed epimerization. The key steps are deprotonation and reprotonation of the photochemically generated less-stable isomers during the 360° unidirectional rotary cycle, with complete inversion of the configuration at the stereogenic centre. The ability to change directionality is an essential step towards mechanical molecular systems with adaptive functional behaviour.

  6. Ultra-fast force-clamp laser trapping of single molecular motors and DNA binding proteins

    NASA Astrophysics Data System (ADS)

    Capitanio, Marco; Monico, Carina; Vanzi, Francesco; Pavone, Francesco S.

    2013-09-01

    Forces play a fundamental role in a wide array of biological processes, regulating enzymatic activity, kinetics of molecular bonds, and molecular motors mechanics. Single molecule force spectroscopy techniques have enabled the investigation of such processes, but they are inadequate to probe short-lived (millisecond and sub-millisecond) molecular complexes. We developed an ultrafast force-clamp spectroscopy technique that uses a dual trap configuration to apply constant loads to a single intermittently interacting biological polymer and a binding protein. Our system displays a delay of only ˜10 μs between formation of the molecular bond and application of the force and is capable of detecting interactions as short as 100 μs. The force-clamp configuration in which our assay operates allows direct measurements of load-dependence of lifetimes of single molecular bonds. Moreover, conformational changes of single proteins and molecular motors can be recorded with sub-nanometer accuracy and few tens of microseconds of temporal resolution. We demonstrate our technique on molecular motors, using myosin II from fast skeletal muscle and on protein-DNA interaction, specifically on Lactose repressor (LacI). The apparatus is stabilized to less than 1 nm with both passive and active stabilization, allowing resolving specific binding regions along the actin filament and DNA molecule. Our technique extends single-molecule force-clamp spectroscopy to molecular complexes that have been inaccessible up to now, opening new perspectives for the investigation of the effects of forces on biological processes.

  7. Molecular motors that digest their track to rectify Brownian motion: processive movement of exonuclease enzymes.

    PubMed

    Xie, Ping

    2009-09-16

    A general model is presented for the processive movement of molecular motors such as λ-exonuclease, RecJ and exonuclease I that use digestion of a DNA track to rectify Brownian motion along this track. Using this model, the translocation dynamics of these molecular motors is studied. The sequence-dependent pausing of λ-exonuclease, which results from a site-specific high affinity DNA interaction, is also studied. The theoretical results are consistent with available experimental data. Moreover, the model is used to predict the lifetime distribution and force dependence of these paused states.

  8. Molecular shuttles based on motor proteins: active transport in synthetic environments.

    PubMed

    Hess, H; Vogel, V

    2001-11-01

    Active transport in cells, utilizing molecular motors like kinesin and myosin, provides the inspiration for the integration of active transport into synthetic devices. Hybrid devices, employing motor proteins in a synthetic environment, are the first prototypes of molecular shuttles. Here the basic characteristics of motor proteins are discussed from an engineering point of view, and the experiments aimed at incorporating motor proteins, such as myosins and kinesins, into devices are reviewed. The key problems for the construction of a molecular shuttle are: guiding the direction of motion, controlling the speed, and loading and unloading of cargo. Various techniques, relying on surface topography and chemistry as well as flow fields and electric fields, have been developed to guide the movement of molecular shuttles on surfaces. The control of ATP concentration, acting as a fuel supply, can serve as a means to control the speed of movement. The loading process requires the coupling of cargo to the shuttle, ideally by a strong and specific link. Applications of molecular shuttles can be envisioned, e.g. in the field of nano-electro-mechanical systems (NEMS), where scaling laws favor active transport over fluid flow, and in the bottom-up assembly of novel materials.

  9. Structured attachment of bacterial molecular motors for defined microflow induction

    NASA Astrophysics Data System (ADS)

    Woerdemann, Mike; Hörner, Florian; Denz, Cornelia

    2014-01-01

    Bacterial rotational motor complexes that propel flagellated bacteria possess unique properties like their size of a few nanometres and the ability of selfreproduction that have led to various exciting applications including biohybrid nano-machines. One mandatory prerequisite to utilize bacterial nano motors in fluid applications is the ability to transfer force and torque to the fluid, which usually can be achieved by attachment of the bacterial cell to adequate surfaces. Additionally, for optimal transfer of force or torque, precise control of the position down to the single cell level is of utmost importance. Based on a PIV (particle image velocimetry) evaluation of the induced flow of single bacteria,we propose and demonstrate attachment of arbitrary patterns of motile bacterial cells in a fast light-based two-step process for the first time to our knowledge. First, these cells are pre-structured by holographic optical tweezers and then attached to a homogeneous, polystyrene-coated surface. In contrast to the few approaches that have been implemented up to now and which rely on pre-structured surfaces, our scheme allows for precise control on a single bacterium level, is versatile, interactive and has low requirements with respect to the surface preparation.

  10. Assembly of bipolar microtubule structures by passive cross-linkers and molecular motors

    NASA Astrophysics Data System (ADS)

    Johann, D.; Goswami, D.; Kruse, K.

    2016-06-01

    During cell division, sister chromatids are segregated by the mitotic spindle, a bipolar assembly of interdigitating antiparallel polar filaments called microtubules. The spindle contains the midzone, a stable region of overlapping antiparallel microtubules, that is essential for maintaining bipolarity. Although a lot is known about the molecular players involved, the mechanism underlying midzone formation and maintenance is still poorly understood. We study the interaction of polar filaments that are cross-linked by molecular motors moving directionally and by passive cross-linkers diffusing along microtubules. Using a particle-based stochastic model, we find that the interplay of motors and passive cross-linkers can generate a stable finite overlap between a pair of antiparallel polar filaments. We develop a mean-field theory to study this mechanism in detail and investigate the influence of steric interactions between motors and passive cross-linkers on the overlap dynamics. In the presence of interspecies steric interactions, passive cross-linkers mimic the behavior of molecular motors and stable finite overlaps are generated even for non-cross-linking motors. Finally, we develop a mean-field theory for a bundle of aligned polar filaments and show that they can self-organize into a spindlelike pattern. Our work suggests possible ways as to how cells can generate spindle midzones and control their extensions.

  11. Force Generation by Molecular-Motor-Powered Microtubule Bundles; Implications for Neuronal Polarization and Growth

    PubMed Central

    Jakobs, Maximilian; Franze, Kristian; Zemel, Assaf

    2015-01-01

    The heavily cross-linked microtubule (MT) bundles found in neuronal processes play a central role in the initiation, growth and maturation of axons and dendrites; however, a quantitative understanding of their mechanical function is still lacking. We here developed computer simulations to investigate the dynamics of force generation in 1D bundles of MTs that are cross-linked and powered by molecular motors. The motion of filaments and the forces they exert are investigated as a function of the motor type (unipolar or bipolar), MT density and length, applied load, and motor connectivity. We demonstrate that only unipolar motors (e.g., kinesin-1) can provide the driving force for bundle expansion, while bipolar motors (e.g., kinesin-5) oppose it. The force generation capacity of the bundles is shown to depend sharply on the fraction of unipolar motors due to a percolation transition that must occur in the bundle. Scaling laws between bundle length, force, MT length and motor fraction are presented. In addition, we investigate the dynamics of growth in the presence of a constant influx of MTs. Beyond a short equilibration period, the bundles grow linearly in time. In this growth regime, the bundle extends as one mass forward with most filaments sliding with the growth velocity. The growth velocity is shown to be dictated by the inward flux of MTs, to inversely scale with the load and to be independent of the free velocity of the motors. These findings provide important molecular-level insights into the mechanical function of the MT cytoskeleton in normal axon growth and regeneration after injury. PMID:26617489

  12. Macroscopic contraction of a gel induced by the integrated motion of light-driven molecular motors

    NASA Astrophysics Data System (ADS)

    Li, Quan; Fuks, Gad; Moulin, Emilie; Maaloum, Mounir; Rawiso, Michel; Kulic, Igor; Foy, Justin T.; Giuseppone, Nicolas

    2015-02-01

    Making molecular machines that can be useful in the macroscopic world is a challenging long-term goal of nanoscience. Inspired by the protein machinery found in biological systems, and based on the theoretical understanding of the physics of motion at the nanoscale, organic chemists have developed a number of molecules that can produce work by contraction or rotation when triggered by various external chemical or physical stimuli. In particular, basic molecular switches that commute between at least two thermodynamic minima and more advanced molecular motors that behave as dissipative units working far from equilibrium when fuelled with external energy have been reported. However, despite recent progress, the ultimate challenge of coordinating individual molecular motors in a continuous mechanical process that can have a measurable effect at the macroscale has remained elusive. Here, we show that by integrating light-driven unidirectional molecular rotors as reticulating units in a polymer gel, it is possible to amplify their individual motions to achieve macroscopic contraction of the material. Our system uses the incoming light to operate under far-from-equilibrium conditions, and the work produced by the motor in the photostationary state is used to twist the entangled polymer chains up to the collapse of the gel. Our design could be a starting point to integrate nanomotors in metastable materials to store energy and eventually to convert it.

  13. Measuring the number and spacing of molecular motors propelling a gliding microtubule

    NASA Astrophysics Data System (ADS)

    Fallesen, Todd L.; Macosko, Jed C.; Holzwarth, G.

    2011-01-01

    The molecular motor gliding assay, in which a microtubule or other filament moves across a surface coated with motors, has provided much insight into how molecular motors work. The kinesin-microtubule system is also a strong candidate for the job of nanoparticle transporter in nanotechnology devices. In most cases, several motors transport each filament. Each motor serves both to bind the microtubule to a stationary surface and to propel the microtubule along the surface. By applying a uniform transverse force of 4-19 pN to a superparamagnetic bead attached to the trailing end of the microtubule, we have measured the distance d between binding points (motors). The average value of d was determined as a function of motor surface density σ. The measurements agree well with the scaling model of Duke, Holy, and Liebler, which predicts that ~σ-2/5 if 0.05⩽σ⩽20μm-2 [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.74.330 74, 330 (1995)]. The distribution of d fits an extension of the model. The radius of curvature of a microtubule bent at a binding point by the force of the magnetic bead was ≈1 μm, 5000-fold smaller than the radius of curvature of microtubules subjected only to thermal forces. This is evidence that at these points of high bending stress, generated by the force on the magnetic bead, the microtubule is in the more flexible state of a two-state model of microtubule bending proposed by Heussinger, Schüller, and Frey [Phys. Rev. EPLEEE81063-651X10.1103/PhysRevE.81.021904 81, 021904 (2010)].

  14. Memory, bias, and correlations in bidirectional transport of molecular-motor-driven cargoes

    NASA Astrophysics Data System (ADS)

    Bhat, Deepak; Gopalakrishnan, Manoj

    2013-10-01

    Molecular motors are specialized proteins that perform active, directed transport of cellular cargoes on cytoskeletal filaments. In many cases, cargo motion powered by motor proteins is found to be bidirectional, and may be viewed as a biased random walk with fast unidirectional runs interspersed with slow tug-of-war states. The statistical properties of this walk are not known in detail, and here, we study memory and bias, as well as directional correlations between successive runs in bidirectional transport. We show, based on a study of the direction-reversal probabilities of the cargo using a purely stochastic (tug-of-war) model, that bidirectional motion of cellular cargoes is, in general, a correlated random walk. In particular, while the motion of a cargo driven by two oppositely pulling motors is a Markovian random walk, memory of direction appears when multiple motors haul the cargo in one or both directions. In the latter case, the Markovian nature of the underlying single-motor processes is hidden by internal transitions between degenerate run and pause states of the cargo. Interestingly, memory is found to be a nonmonotonic function of the number of motors. Stochastic numerical simulations of the tug-of-war model support our mathematical results and extend them to biologically relevant situations.

  15. Asymptotic analysis of microtubule-based transport by multiple identical molecular motors.

    PubMed

    McKinley, Scott A; Athreya, Avanti; Fricks, John; Kramer, Peter R

    2012-07-21

    We describe a system of stochastic differential equations (SDEs) which model the interaction between processive molecular motors, such as kinesin and dynein, and the biomolecular cargo they tow as part of microtubule-based intracellular transport. We show that the classical experimental environment fits within a parameter regime which is qualitatively distinct from conditions one expects to find in living cells. Through an asymptotic analysis of our system of SDEs, we develop a means for applying in vitro observations of the nonlinear response by motors to forces induced on the attached cargo to make analytical predictions for two parameter regimes that have thus far eluded direct experimental observation: (1) highly viscous in vivo transport and (2) dynamics when multiple identical motors are attached to the cargo and microtubule.

  16. Towards artificial molecular motor-based electroactive/photoactive biomimetic muscles

    NASA Astrophysics Data System (ADS)

    Huang, Tony Jun

    2007-04-01

    Artificial molecular motors have recently attracted considerable interest from the nanoscience and nanoengineering community. These molecular-scale systems utilize a 'bottom-up' technology centered around the design and manipulation of molecular assemblies, and are potentially capable of delivering efficient actuations at dramatically reduced length scales when compared to traditional microscale actuators. When stimulated by light, electricity, or chemical reagents, a group of artificial molecular motors called bistable rotaxanes - which are composed of mutually recognizable and intercommunicating ring and dumbbell-shaped components - experience relative internal motions of their components just like the moving parts of macroscopic machines. Bistable rotaxanes' ability to precisely and cooperatively control mechanical motions at the molecular level reveals the potential of engineering systems that operate with the same elegance, efficiency, and complexity as biological motors function within the human body. We are in a process of developing a new class of bistable rotaxane-based electroactive/photoactive biomimetic muscles with unprecedented performance (strain: 40-60%, operating frequency: up to 1 MHz, energy density: ~50 J/cm 3, multi-stimuli: chemical, electricity, light). As a substantial step towards this longterm objective, we have proven, for the first time, that rotaxanes are mechanically switchable in condensed phases on solid substrates. We have further developed a rotaxane-powered microcantilever actuator utilizing an integrated approach that combines "bottom-up" assembly of molecular functionality with "top-down" micro/nano fabrication. By harnessing the nanoscale mechanical motion from artificial molecular machines and eliciting a nanomechanical response in a microscale device, this system mimics natural skeletal muscle and provides a key component for the development of nanoelectromechanical system (NEMS).

  17. Structural and Molecular Basis for Coordination in a Viral DNA Packaging Motor

    PubMed Central

    Reyes-Aldrete, Emilio; Sherman, Michael B.; Woodson, Michael; Atz, Rockney; Grimes, Shelley; Jardine, Paul J.; Morais, Marc C.

    2016-01-01

    SUMMARY Ring NTPases are a class of ubiquitous molecular motors involved in basic biological partitioning processes. dsDNA viruses encode ring ATPases that translocate their genomes to near-crystalline densities within pre-assembled viral capsids. Here, X-ray crystallography, cryoEM, and biochemical analyses of the dsDNA packaging motor in bacteriophage phi29 show how individual subunits are arranged in a pentameric ATPase ring, and suggest how their activities are coordinated to translocate dsDNA. The resulting pseudo-atomic structure of the motor and accompanying functional analyses show how ATP is bound in the ATPase active site; identify two DNA contacts, including a potential DNA translocating loop; demonstrate that a trans-acting arginine finger is involved in coordinating hydrolysis around the ring; and suggest a functional coupling between the arginine finger and the DNA translocating loop. The ability to visualize the motor in action illuminates how the different motor components interact with each other and with their DNA substrate. PMID:26904950

  18. A unified phenomenological analysis of the experimental velocity curves in molecular motors.

    PubMed

    Ciudad, Aleix; Sancho, J M

    2008-06-14

    We present a unified phenomenological kinetic framework to analyze the experimental data of several motor proteins (either linear or rotatory). This formalism allows us to discriminate the characteristic times of most relevant subprocesses. Explicitly, internal mechanical as well as chemical times are taken into account and joined together in a full-cycle time where effusion, diffusion and chemical rates, viscoelastic friction, and overdamped motion are considered. This approach clarifies the most relevant mechanisms in a particular motor by using the available experimental data of velocity versus external load and substrate concentration. We apply our analysis to three real molecular motors for which enough experimental data are available: the bacterial flagellar motor [Yoshiyuki et al., J. Mol. Biol. 377, 1043 (2003)], conventional kinesin (kinesin-1) [Block et al., Proc. Natl. Acad. Sci. U.S.A. 100, 2351 (2003)], and a RAN polymerase [Abbondanzieril, Nature (London) 438, 460 (2003)]. Moreover, the mechanism of stalling a motor is revised and split into two different concepts (mechanical and chemical stalling) that shed light to the understanding of backstepping in kinesin-1.

  19. Physical aspects of the structure and function of helicases as rotary molecular motors

    SciTech Connect

    Pikin, S. A.

    2009-11-15

    Helicases were shown to have common physical properties with rotary molecular motors, such as F{sub 0}F{sub 1}-ATP synthase and type I restriction-modification (RM) enzymes. The necessary conditions for action of molecular motors are chirality, the presence of the C{sub 2} (or lower) symmetry axis within rather large atomic groups, and polarization properties. The estimates were made for the material parameters of helicases, which translocate DNA due to moving chiral kinks without DNA cleavage and are characterized by higher viscosity, low mobility, and smaller chiral kinetic coefficients than type II RM enzymes. This paper discusses the efficiency of helicases with opposite polarities that drive DNA translocation in opposite directions.

  20. Allosteric Regulation of the Rotational Speed in a Light-Driven Molecular Motor

    PubMed Central

    2016-01-01

    The rotational speed of an overcrowded alkene-based molecular rotary motor, having an integrated 4,5-diazafluorenyl coordination motif, can be regulated allosterically via the binding of metal ions. DFT calculations have been used to predict the relative speed of rotation of three different (i.e., zinc, palladium, and platinum) metal dichloride complexes. The photochemical and thermal isomerization behavior of these complexes has been studied in detail using UV–vis and 1H NMR spectroscopy. Our results confirm that metal coordination induces a contraction of the diazafluorenyl lower half, resulting in a reduction of the steric hindrance in the “fjord” region of the molecule, which causes an increase of the rotational speed. Importantly, metal complexation can be accomplished in situ and is found to be reversible upon the addition of a competing ligand. Consequently, the rotational behavior of these molecular motors can be dynamically controlled with chemical additives. PMID:27669358

  1. How molecular motors extract order from chaos (a key issues review).

    PubMed

    Hoffmann, Peter M

    2016-03-01

    Molecular motors are the workhorses of living cells. Seemingly by 'magic', these molecules are able to complete purposeful tasks while being immersed in a sea of thermal chaos. Here, we review the current understanding of how these machines work, present simple models based on thermal ratchets, discuss implications for statistical physics, and provide an overview of ongoing research in this important and fascinating field of study. PMID:26863000

  2. How molecular motors extract order from chaos (a key issues review)

    NASA Astrophysics Data System (ADS)

    Hoffmann, Peter M.

    2016-03-01

    Molecular motors are the workhorses of living cells. Seemingly by ‘magic’, these molecules are able to complete purposeful tasks while being immersed in a sea of thermal chaos. Here, we review the current understanding of how these machines work, present simple models based on thermal ratchets, discuss implications for statistical physics, and provide an overview of ongoing research in this important and fascinating field of study.

  3. Magnetic capture from blood rescues molecular motor function in diagnostic nanodevices

    PubMed Central

    2013-01-01

    Background Introduction of effective point-of-care devices for use in medical diagnostics is part of strategies to combat accelerating health-care costs. Molecular motor driven nanodevices have unique potentials in this regard due to unprecedented level of miniaturization and independence of external pumps. However motor function has been found to be inhibited by body fluids. Results We report here that a unique procedure, combining separation steps that rely on antibody-antigen interactions, magnetic forces applied to magnetic nanoparticles (MPs) and the specificity of the actomyosin bond, can circumvent the deleterious effects of body fluids (e.g. blood serum). The procedure encompasses the following steps: (i) capture of analyte molecules from serum by MP-antibody conjugates, (ii) pelleting of MP-antibody-analyte complexes, using a magnetic field, followed by exchange of serum for optimized biological buffer, (iii) mixing of MP-antibody-analyte complexes with actin filaments conjugated with same polyclonal antibodies as the magnetic nanoparticles. This causes complex formation: MP-antibody-analyte-antibody-actin, and magnetic separation is used to enrich the complexes. Finally (iv) the complexes are introduced into a nanodevice for specific binding via actin filaments to surface adsorbed molecular motors (heavy meromyosin). The number of actin filaments bound to the motors in the latter step was significantly increased above the control value if protein analyte (50–60 nM) was present in serum (in step i) suggesting appreciable formation and enrichment of the MP-antibody-analyte-antibody-actin complexes. Furthermore, addition of ATP demonstrated maintained heavy meromyosin driven propulsion of actin filaments showing that the serum induced inhibition was alleviated. Detailed analysis of the procedure i-iv, using fluorescence microscopy and spectroscopy identified main targets for future optimization. Conclusion The results demonstrate a promising approach for

  4. Stochastic dynamics of small ensembles of non-processive molecular motors: The parallel cluster model

    NASA Astrophysics Data System (ADS)

    Erdmann, Thorsten; Albert, Philipp J.; Schwarz, Ulrich S.

    2013-11-01

    Non-processive molecular motors have to work together in ensembles in order to generate appreciable levels of force or movement. In skeletal muscle, for example, hundreds of myosin II molecules cooperate in thick filaments. In non-muscle cells, by contrast, small groups with few tens of non-muscle myosin II motors contribute to essential cellular processes such as transport, shape changes, or mechanosensing. Here we introduce a detailed and analytically tractable model for this important situation. Using a three-state crossbridge model for the myosin II motor cycle and exploiting the assumptions of fast power stroke kinetics and equal load sharing between motors in equivalent states, we reduce the stochastic reaction network to a one-step master equation for the binding and unbinding dynamics (parallel cluster model) and derive the rules for ensemble movement. We find that for constant external load, ensemble dynamics is strongly shaped by the catch bond character of myosin II, which leads to an increase of the fraction of bound motors under load and thus to firm attachment even for small ensembles. This adaptation to load results in a concave force-velocity relation described by a Hill relation. For external load provided by a linear spring, myosin II ensembles dynamically adjust themselves towards an isometric state with constant average position and load. The dynamics of the ensembles is now determined mainly by the distribution of motors over the different kinds of bound states. For increasing stiffness of the external spring, there is a sharp transition beyond which myosin II can no longer perform the power stroke. Slow unbinding from the pre-power-stroke state protects the ensembles against detachment.

  5. Stochastic dynamics of small ensembles of non-processive molecular motors: The parallel cluster model

    SciTech Connect

    Erdmann, Thorsten; Albert, Philipp J.; Schwarz, Ulrich S.

    2013-11-07

    Non-processive molecular motors have to work together in ensembles in order to generate appreciable levels of force or movement. In skeletal muscle, for example, hundreds of myosin II molecules cooperate in thick filaments. In non-muscle cells, by contrast, small groups with few tens of non-muscle myosin II motors contribute to essential cellular processes such as transport, shape changes, or mechanosensing. Here we introduce a detailed and analytically tractable model for this important situation. Using a three-state crossbridge model for the myosin II motor cycle and exploiting the assumptions of fast power stroke kinetics and equal load sharing between motors in equivalent states, we reduce the stochastic reaction network to a one-step master equation for the binding and unbinding dynamics (parallel cluster model) and derive the rules for ensemble movement. We find that for constant external load, ensemble dynamics is strongly shaped by the catch bond character of myosin II, which leads to an increase of the fraction of bound motors under load and thus to firm attachment even for small ensembles. This adaptation to load results in a concave force-velocity relation described by a Hill relation. For external load provided by a linear spring, myosin II ensembles dynamically adjust themselves towards an isometric state with constant average position and load. The dynamics of the ensembles is now determined mainly by the distribution of motors over the different kinds of bound states. For increasing stiffness of the external spring, there is a sharp transition beyond which myosin II can no longer perform the power stroke. Slow unbinding from the pre-power-stroke state protects the ensembles against detachment.

  6. Molecular interactions and residues involved in force generation in the T4 viral DNA packaging motor.

    PubMed

    Migliori, Amy D; Smith, Douglas E; Arya, Gaurav

    2014-12-12

    Many viruses utilize molecular motors to package their genomes into preformed capsids. A striking feature of these motors is their ability to generate large forces to drive DNA translocation against entropic, electrostatic, and bending forces resisting DNA confinement. A model based on recently resolved structures of the bacteriophage T4 motor protein gp17 suggests that this motor generates large forces by undergoing a conformational change from an extended to a compact state. This transition is proposed to be driven by electrostatic interactions between complementarily charged residues across the interface between the N- and C-terminal domains of gp17. Here we use atomistic molecular dynamics simulations to investigate in detail the molecular interactions and residues involved in such a compaction transition of gp17. We find that although electrostatic interactions between charged residues contribute significantly to the overall free energy change of compaction, interactions mediated by the uncharged residues are equally if not more important. We identify five charged residues and six uncharged residues at the interface that play a dominant role in the compaction transition and also reveal salt bridging, van der Waals, and solvent hydrogen-bonding interactions mediated by these residues in stabilizing the compact form of gp17. The formation of a salt bridge between Glu309 and Arg494 is found to be particularly crucial, consistent with experiments showing complete abrogation in packaging upon Glu309Lys mutation. The computed contributions of several other residues are also found to correlate well with single-molecule measurements of impairments in DNA translocation activity caused by site-directed mutations. PMID:25311860

  7. Application of quasi-steady state methods to molecular motor transport on microtubules in fungal hyphae.

    PubMed

    Dauvergne, Duncan; Edelstein-Keshet, Leah

    2015-08-21

    We consider bidirectional transport of cargo by molecular motors dynein and kinesin that walk along microtubules, and/or diffuse in the cell. The motors compete to transport cargo in opposite directions with respect to microtubule polarity (towards the plus or minus end of the microtubule). In recent work, Gou et al. (2014) used a hierarchical set of models, each consisting of continuum transport equations to track the evolution of motors and their cargo (early endosomes) in the specific case of the fungus Ustilago maydis. We complement their work using a framework of quasi-steady state analysis developed by Newby and Bressloff (2010) and Bressloff and Newby (2013) to reduce the models to an approximating steady state Fokker-Plank equation. This analysis allows us to find analytic approximations to the steady state solutions in many cases where the full models are not easily solved. Consequently, we can make predictions about parameter dependence of the resulting spatial distributions. We also characterize the overall rates of bulk transport and diffusion, and how these are related to state transition parameters, motor speeds, microtubule polarity distribution, and specific assumptions made.

  8. Improved Hidden Markov Models for Molecular Motors, Part 2: Extensions and Application to Experimental Data

    PubMed Central

    Syed, Sheyum; Müllner, Fiona E.; Selvin, Paul R.; Sigworth, Fred J.

    2010-01-01

    Unbiased interpretation of noisy single molecular motor recordings remains a challenging task. To address this issue, we have developed robust algorithms based on hidden Markov models (HMMs) of motor proteins. The basic algorithm, called variable-stepsize HMM (VS-HMM), was introduced in the previous article. It improves on currently available Markov-model based techniques by allowing for arbitrary distributions of step sizes, and shows excellent convergence properties for the characterization of staircase motor timecourses in the presence of large measurement noise. In this article, we extend the VS-HMM framework for better performance with experimental data. The extended algorithm, variable-stepsize integrating-detector HMM (VSI-HMM) better models the data-acquisition process, and accounts for random baseline drifts. Further, as an extension, maximum a posteriori estimation is provided. When used as a blind step detector, the VSI-HMM outperforms conventional step detectors. The fidelity of the VSI-HMM is tested with simulations and is applied to in vitro myosin V data where a small 10 nm population of steps is identified. It is also applied to an in vivo recording of melanosome motion, where strong evidence is found for repeated, bidirectional steps smaller than 8 nm in size, implying that multiple motors simultaneously carry the cargo. PMID:21112294

  9. Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching.

    PubMed

    Lee, Lawrence K; Ginsburg, Michael A; Crovace, Claudia; Donohoe, Mhairi; Stock, Daniela

    2010-08-19

    The flagellar motor drives the rotation of flagellar filaments at hundreds of revolutions per second, efficiently propelling bacteria through viscous media. The motor uses the potential energy from an electrochemical gradient of cations across the cytoplasmic membrane to generate torque. A rapid switch from anticlockwise to clockwise rotation determines whether a bacterium runs smoothly forward or tumbles to change its trajectory. A protein called FliG forms a ring in the rotor of the flagellar motor that is involved in the generation of torque through an interaction with the cation-channel-forming stator subunit MotA. FliG has been suggested to adopt distinct conformations that induce switching but these structural changes and the molecular mechanism of switching are unknown. Here we report the molecular structure of the full-length FliG protein, identify conformational changes that are involved in rotational switching and uncover the structural basis for the formation of the FliG torque ring. This allows us to propose a model of the complete ring and switching mechanism in which conformational changes in FliG reverse the electrostatic charges involved in torque generation. PMID:20676082

  10. Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching

    SciTech Connect

    Lee, Lawrence K.; Ginsburg, Michael A.; Crovace, Claudia; Donohoe, Mhairi; Stock, Daniela

    2010-09-13

    The flagellar motor drives the rotation of flagellar filaments at hundreds of revolutions per second, efficiently propelling bacteria through viscous media. The motor uses the potential energy from an electrochemical gradient of cations across the cytoplasmic membrane to generate torque. A rapid switch from anticlockwise to clockwise rotation determines whether a bacterium runs smoothly forward or tumbles to change its trajectory. A protein called FliG forms a ring in the rotor of the flagellar motor that is involved in the generation of torque through an interaction with the cation-channel-forming stator subunit MotA. FliG has been suggested to adopt distinct conformations that induce switching but these structural changes and the molecular mechanism of switching are unknown. Here we report the molecular structure of the full-length FliG protein, identify conformational changes that are involved in rotational switching and uncover the structural basis for the formation of the FliG torque ring. This allows us to propose a model of the complete ring and switching mechanism in which conformational changes in FliG reverse the electrostatic charges involved in torque generation.

  11. Molecular motor-induced instabilities and cross linkers determine biopolymer organization.

    SciTech Connect

    Smith, D.; Ziebert, F.; Humphrey, D.; Duggan, C.; Steinbeck, M.; Zimmermann, W.; Kas, J.; Materials Science Division; Univ. of Leipzig; Univ. of Texas at Austin; Univ. Bayreuth

    2007-01-01

    All eukaryotic cells rely on the active self-organization of protein filaments to form a responsive intracellular cytoskeleton. The necessity of motility and reaction to stimuli additionally requires pathways that quickly and reversibly change cytoskeletal organization. While thermally driven order-disorder transitions are, from the viewpoint of physics, the most obvious method for controlling states of organization, the timescales necessary for effective cellular dynamics would require temperatures exceeding the physiologically viable temperature range. We report a mechanism whereby the molecular motor myosin II can cause near-instantaneous order-disorder transitions in reconstituted cytoskeletal actin solutions. When motor-induced filament sliding diminishes, the actin network structure rapidly and reversibly self-organizes into various assemblies. Addition of stable cross linkers was found to alter the architectures of ordered assemblies. These isothermal transitions between dynamic disorder and self-assembled ordered states illustrate that the interplay between passive crosslinking and molecular motor activity plays a substantial role in dynamic cellular organization.

  12. Discrete Step Sizes of Molecular Motors Lead to Bimodal Non-Gaussian Velocity Distributions under Force

    NASA Astrophysics Data System (ADS)

    Vu, Huong T.; Chakrabarti, Shaon; Hinczewski, Michael; Thirumalai, D.

    2016-08-01

    Fluctuations in the physical properties of biological machines are inextricably linked to their functions. Distributions of run lengths and velocities of processive molecular motors, like kinesin-1, are accessible through single-molecule techniques, but rigorous theoretical models for these probabilities are lacking. Here, we derive exact analytic results for a kinetic model to predict the resistive force (F )-dependent velocity [P (v )] and run length [P (n )] distribution functions of generic finitely processive molecular motors. Our theory quantitatively explains the zero force kinesin-1 data for both P (n ) and P (v ) using the detachment rate as the only parameter. In addition, we predict the F dependence of these quantities. At nonzero F , P (v ) is non-Gaussian and is bimodal with peaks at positive and negative values of v , which is due to the discrete step size of kinesin-1. Although the predictions are based on analyses of kinesin-1 data, our results are general and should hold for any processive motor, which walks on a track by taking discrete steps.

  13. Mechanochemical coupling of the motion of molecular motors to ATP hydrolysis.

    PubMed Central

    Astumian, R D; Bier, M

    1996-01-01

    The typical biochemical paradigm for coupling between hydrolysis of ATP and the performance of chemical or mechanical work involves a well-defined sequence of events (a kinetic mechanism) with a fixed stoichiometry between the number of ATP molecules hydrolyzed and the turnover of the output reaction. Recent experiments show, however, that such a deterministic picture of coupling may not be adequate to explain observed behavior of molecular motor proteins in the presence of applied forces. Here we present a general model in which the binding of ATP and release of ADP serve to modulate the binding energy of a motor protein as it travels along a biopolymer backbone. The mechanism is loosely coupled--the average number of ATPs hydrolyzed to cause a single step from one binding site to the next depends strongly on the magnitude of an applied force and on the effective viscous drag force. The statistical mechanical perspective described here offers insight into how local anisotrophy along the "track" for a molecular motor, combined with an energy-releasing chemical reaction to provide a source of nonequilibrium fluctuations, can lead to macroscopic motion. Images Scheme 1 FIGURE 1 PMID:8789082

  14. Discrete Step Sizes of Molecular Motors Lead to Bimodal Non-Gaussian Velocity Distributions under Force.

    PubMed

    Vu, Huong T; Chakrabarti, Shaon; Hinczewski, Michael; Thirumalai, D

    2016-08-12

    Fluctuations in the physical properties of biological machines are inextricably linked to their functions. Distributions of run lengths and velocities of processive molecular motors, like kinesin-1, are accessible through single-molecule techniques, but rigorous theoretical models for these probabilities are lacking. Here, we derive exact analytic results for a kinetic model to predict the resistive force (F)-dependent velocity [P(v)] and run length [P(n)] distribution functions of generic finitely processive molecular motors. Our theory quantitatively explains the zero force kinesin-1 data for both P(n) and P(v) using the detachment rate as the only parameter. In addition, we predict the F dependence of these quantities. At nonzero F, P(v) is non-Gaussian and is bimodal with peaks at positive and negative values of v, which is due to the discrete step size of kinesin-1. Although the predictions are based on analyses of kinesin-1 data, our results are general and should hold for any processive motor, which walks on a track by taking discrete steps. PMID:27564000

  15. Carbon Nanotube Based Molecular Electronics and Motors: A View from Classical and Quantum Dynamics Simulations

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Saini, Subhash (Technical Monitor)

    1998-01-01

    The tubular forms of fullerenes popularly known as carbon nanotubes are experimentally produced as single-, multiwall, and rope configurations. The nanotubes and nanoropes have shown to exhibit unusual mechanical and electronic properties. The single wall nanotubes exhibit both semiconducting and metallic behavior. In short undefected lengths they are the known strongest fibers which are unbreakable even when bent in half. Grown in ropes their tensile strength is approximately 100 times greater than steel at only one sixth the weight. Employing large scale classical and quantum molecular dynamics simulations we will explore the use of carbon nanotubes and carbon nanotube junctions in 2-, 3-, and 4-point molecular electronic device components, dynamic strength characterization for compressive, bending and torsional strains, and chemical functionalization for possible use in a nanoscale molecular motor. The above is an unclassified material produced for non-competitive basic research in the nanotechnology area.

  16. Thermal fluctuation statistics in a molecular motor described by a multidimensional master equation

    NASA Astrophysics Data System (ADS)

    Challis, K. J.; Jack, M. W.

    2013-12-01

    We present a theoretical investigation of thermal fluctuation statistics in a molecular motor. Energy transfer in the motor is described using a multidimensional discrete master equation with nearest-neighbor hopping. In this theory, energy transfer leads to statistical correlations between thermal fluctuations in different degrees of freedom. For long times, the energy transfer is a multivariate diffusion process with constant drift and diffusion. The fluctuations and drift align in the strong-coupling limit enabling a one-dimensional description along the coupled coordinate. We derive formal expressions for the probability distribution and simulate single trajectories of the system in the near- and far-from-equilibrium limits both for strong and weak coupling. Our results show that the hopping statistics provide an opportunity to distinguish different operating regimes.

  17. Kinetics and chemomechanical properties of the F1-ATPase molecular motor

    NASA Astrophysics Data System (ADS)

    Liu, Ming S.; Todd, B. D.; Sadus, Richard J.

    2003-06-01

    F1-ATPase hydrolyzes ATP into ADP and Pi and converts chemical energy into mechanical rotation with exceptionally high efficiency. This energy-transducing molecular motor increasingly attracts interest for its unique cellular functions and promising application in nanobiotechnology. To better understand the chemomechanics of rotation and loading dynamics of F1-ATPase, we propose a computational model based on enzyme kinetics and Langevin dynamics. We show that the torsional energy and stepwise rotation can be regulated by a series of near-equilibrium reactions when nucleotides bind or unbind, as well as characterized by an effective "ratchet" drag coefficient and a fitting chemomechanic coefficient. For the case of driving an actin filament, the theoretical load-rotation profile is analyzed and comparison with experimental data indicates reasonable agreement. The chemomechanics described in this work is of fundamental importance to all ATP-fueled motor proteins.

  18. Operation mechanism of rotary molecular motor F1 probed by single-molecule techniques

    NASA Astrophysics Data System (ADS)

    Iino, Ryota

    2013-03-01

    F1 is a rotary motor protein. Three catalytic β - subunitsinthestator 33ring are torque generators, and rotate the rotor γ-subunit by sequential and cooperative conformational changes coupled with adenosine triphosphate (ATP) hydrolysis reaction. F1 shows remarkable performances such as rotation rate faster than 10,000 rpm, high reversibility and efficiency in chemo-mechanical energy conversion. I will introduce basic characteristics of F1 revealed by single-molecule imaging and manipulation techniques based on optical microscopy and high-speed atomic force microscopy. I will also discuss the possible operation mechanism behind the F1, along with structurally-related hexameric ATPases, also mentioning the possibility of generating hybrid molecular motors.

  19. Molecular genetics of myosin motors in Arabidopsis. Final report, July 1, 1992--June 30, 1996

    SciTech Connect

    Schiefelbein, J.

    1997-02-01

    The normal growth and development of plant cells depends on the precise organization and distribution of the cellular contents. The basic goal of this investigation was to define a group of the molecules that are involved in organizing and transporting plant cell components. Based largely on studies of animal and fungal cells, one of the molecules thought to be involved in intracellular trafficking in plants is the actin-based motor protein myosin. Therefore, the major aim of this study was to isolate and analyze plant genes encoding myosin proteins. The plant of choice for these experiments was Arabidopsis thaliana, which offers numerous advantages for molecular genetics research.

  20. Fast axonal transport of the proteasome complex depends on membrane interaction and molecular motor function.

    PubMed

    Otero, Maria G; Alloatti, Matías; Cromberg, Lucas E; Almenar-Queralt, Angels; Encalada, Sandra E; Pozo Devoto, Victorio M; Bruno, Luciana; Goldstein, Lawrence S B; Falzone, Tomás L

    2014-04-01

    Protein degradation by the ubiquitin-proteasome system in neurons depends on the correct delivery of the proteasome complex. In neurodegenerative diseases, aggregation and accumulation of proteins in axons link transport defects with degradation impairments; however, the transport properties of proteasomes remain unknown. Here, using in vivo experiments, we reveal the fast anterograde transport of assembled and functional 26S proteasome complexes. A high-resolution tracking system to follow fluorescent proteasomes revealed three types of motion: actively driven proteasome axonal transport, diffusive behavior in a viscoelastic axonema and proteasome-confined motion. We show that active proteasome transport depends on motor function because knockdown of the KIF5B motor subunit resulted in impairment of the anterograde proteasome flux and the density of segmental velocities. Finally, we reveal that neuronal proteasomes interact with intracellular membranes and identify the coordinated transport of fluorescent proteasomes with synaptic precursor vesicles, Golgi-derived vesicles, lysosomes and mitochondria. Taken together, our results reveal fast axonal transport as a new mechanism of proteasome delivery that depends on membrane cargo 'hitch-hiking' and the function of molecular motors. We further hypothesize that defects in proteasome transport could promote abnormal protein clearance in neurodegenerative diseases.

  1. Affinity of molecular interactions in the bacteriophage φ29 DNA packaging motor

    PubMed Central

    Robinson, Mark A.; Wood, Jonathan P.A.; Capaldi, Stephanie A.; Baron, Andrew J.; Gell, Christopher; Smith, D. Alastair; Stonehouse, Nicola J.

    2006-01-01

    DNA packaging in the bacteriophage φ29 involves a molecular motor with protein and RNA components, including interactions between the viral connector protein and molecules of pRNA, both of which form multimeric complexes. Data are presented to demonstrate the higher order assembly of pRNA together with the affinity of pRNA:pRNA and pRNA:connector interactions, which are used to propose a model for motor function. In solution, pRNA can form dimeric and trimeric multimers in a magnesium-dependent manner, with dissociation constants for multimerization in the micromolar range. pRNA:connector binding is also facilitated by the presence of magnesium ions, with a nanomolar apparent dissociation constant for the interaction. From studies with a mutant pRNA, it appears that multimerization of pRNA is not essential for connector binding and it is likely that connector protein is involved in the stabilization of higher order RNA multimers. It is proposed that magnesium ions may promote conformational change that facilitate pRNA:connector interactions, essential for motor function. PMID:16714447

  2. Affinity of molecular interactions in the bacteriophage phi29 DNA packaging motor.

    PubMed

    Robinson, Mark A; Wood, Jonathan P A; Capaldi, Stephanie A; Baron, Andrew J; Gell, Christopher; Smith, D Alastair; Stonehouse, Nicola J

    2006-01-01

    DNA packaging in the bacteriophage phi29 involves a molecular motor with protein and RNA components, including interactions between the viral connector protein and molecules of pRNA, both of which form multimeric complexes. Data are presented to demonstrate the higher order assembly of pRNA together with the affinity of pRNA:pRNA and pRNA:connector interactions, which are used to propose a model for motor function. In solution, pRNA can form dimeric and trimeric multimers in a magnesium-dependent manner, with dissociation constants for multimerization in the micromolar range. pRNA:connector binding is also facilitated by the presence of magnesium ions, with a nanomolar apparent dissociation constant for the interaction. From studies with a mutant pRNA, it appears that multimerization of pRNA is not essential for connector binding and it is likely that connector protein is involved in the stabilization of higher order RNA multimers. It is proposed that magnesium ions may promote conformational change that facilitate pRNA:connector interactions, essential for motor function.

  3. A chemically powered unidirectional rotary molecular motor based on a palladium redox cycle

    NASA Astrophysics Data System (ADS)

    Collins, Beatrice S. L.; Kistemaker, Jos C. M.; Otten, Edwin; Feringa, Ben L.

    2016-09-01

    The conversion of chemical energy to drive directional motion at the molecular level allows biological systems, ranging from subcellular components to whole organisms, to perform a myriad of dynamic functions and respond to changes in the environment. Directional movement has been demonstrated in artificial molecular systems, but the fundamental motif of unidirectional rotary motion along a single-bond rotary axle induced by metal-catalysed transformation of chemical fuels has not been realized, and the challenge is to couple the metal-centred redox processes to stepwise changes in conformation to arrive at a full unidirectional rotary cycle. Here, we present the design of an organopalladium-based motor and the experimental demonstration of a 360° unidirectional rotary cycle using simple chemical fuels. Exploiting fundamental reactivity principles in organometallic chemistry enables control of directional rotation and offers the potential of harnessing the wealth of opportunities offered by transition-metal-based catalytic conversions to drive motion and dynamic functions.

  4. Mouse Myosin-19 Is a Plus-end-directed, High-duty Ratio Molecular Motor*

    PubMed Central

    Lu, Zekuan; Ma, Xiao-Nan; Zhang, Hai-Man; Ji, Huan-Hong; Ding, Hao; Zhang, Jie; Luo, Dan; Sun, Yujie; Li, Xiang-dong

    2014-01-01

    Class XIX myosin (Myo19) is a vertebrate-specific unconventional myosin, responsible for the transport of mitochondria. To characterize biochemical properties of Myo19, we prepared recombinant mouse Myo19-truncated constructs containing the motor domain and the IQ motifs using the baculovirus/Sf9 expression system. We identified regulatory light chain (RLC) of smooth muscle/non-muscle myosin-2 as the light chain of Myo19. The actin-activated ATPase activity and the actin-gliding velocity of Myo19-truncated constructs were about one-third and one-sixth as those of myosin-5a, respectively. The apparent affinity of Myo19 to actin was about the same as that of myosin-5a. The RLCs bound to Myo19 could be phosphorylated by myosin light chain kinase, but this phosphorylation had little effect on the actin-activated ATPase activity and the actin-gliding activity of Myo19-truncated constructs. Using dual fluorescence-labeled actin filaments, we determined that Myo19 is a plus-end-directed molecular motor. We found that, similar to that of the high-duty ratio myosin, such as myosin-5a, ADP release rate was comparable with the maximal actin-activated ATPase activity of Myo19, indicating that ADP release is a rate-limiting step for the ATPase cycle of acto-Myo19. ADP strongly inhibited the actin-activated ATPase activity and actin-gliding activity of Myo19-truncated constructs. Based on the above results, we concluded that Myo19 is a high-duty ratio molecular motor moving to the plus-end of the actin filament. PMID:24825904

  5. Molecular dissection of the photoreceptor ribbon synapse: physical interaction of Bassoon and RIBEYE is essential for the assembly of the ribbon complex.

    PubMed

    tom Dieck, Susanne; Altrock, Wilko D; Kessels, Michael M; Qualmann, Britta; Regus, Hanna; Brauner, Dana; Fejtová, Anna; Bracko, Oliver; Gundelfinger, Eckart D; Brandstätter, Johann H

    2005-02-28

    The ribbon complex of retinal photoreceptor synapses represents a specialization of the cytomatrix at the active zone (CAZ) present at conventional synapses. In mice deficient for the CAZ protein Bassoon, ribbons are not anchored to the presynaptic membrane but float freely in the cytoplasm. Exploiting this phenotype, we dissected the molecular structure of the photoreceptor ribbon complex. Identifiable CAZ proteins segregate into two compartments at the ribbon: a ribbon-associated compartment including Piccolo, RIBEYE, CtBP1/BARS, RIM1, and the motor protein KIF3A, and an active zone compartment including RIM2, Munc13-1, a Ca2+ channel alpha1 subunit, and ERC2/CAST1. A direct interaction between the ribbon-specific protein RIBEYE and Bassoon seems to link the two compartments and is responsible for the physical integrity of the photoreceptor ribbon complex. Finally, we found the RIBEYE homologue CtBP1 at ribbon and conventional synapses, suggesting a novel role for the CtBP/BARS family in the molecular assembly and function of central nervous system synapses.

  6. A QTAIM and stress tensor investigation of the torsion path of a light-driven fluorene molecular rotary motor.

    PubMed

    Hu, Ming Xing; Xu, Tianlv; Momen, Roya; Huan, Guo; Kirk, Steven R; Jenkins, Samantha; Filatov, Michael

    2016-11-01

    The utility of the QTAIM/stress tensor analysis method for characterizing the photoisomerization of light driven molecular rotary machines is investigated on the example of the torsion path in fluorene molecular motor. The scalar and vector descriptors of QTAIM/stress tensor reveal additional information on the bonding interactions between the rotating units of the motor, which cannot be obtained from the analysis of the ground and excited state potential energy surfaces. The topological features of the fluorene motor molecular graph display that, upon the photoexcitation a certain increase in the torsional stiffness of the rotating bond can be attributed to the increasing topological stability of the rotor carbon atom attached to the rotation axle. The established variations in the torsional stiffness of the rotating bond may cause transfer of certain fraction of the torsional energy to other internal degrees of freedom, such as the pyramidalization distortion. © 2016 Wiley Periodicals, Inc. PMID:27671359

  7. Synthetic Molecular Motors: Thermal N Inversion and Directional Photoinduced C=N Bond Rotation of Camphorquinone Imines.

    PubMed

    Greb, Lutz; Eichhöfer, Andreas; Lehn, Jean-Marie

    2015-11-23

    The thermal and photochemical E/Z isomerization of camphorquinone-derived imines was studied by a combination of kinetic, structural, and computational methods. The thermal isomerization proceeds by linear N inversion, whereas the photoinduced process occurs through C=N bond rotation with preferred directionality as a result of diastereoisomerism. Thereby, these imines are arguably the simplest example of synthetic molecular motors. The generality of the orthogonal trajectories of the thermal and photochemical pathways allows for the postulation that every suitable chiral imine qualifies, in principle, as a molecular motor driven by light or heat.

  8. Elastic properties of dynein motor domain obtained from all-atom molecular dynamics simulations

    PubMed Central

    Kamiya, Narutoshi; Mashimo, Tadaaki; Takano, Yu; Kon, Takahide; Kurisu, Genji; Nakamura, Haruki

    2016-01-01

    Dyneins are large microtubule motor proteins that convert ATP energy to mechanical power. High-resolution crystal structures of ADP-bound cytoplasmic dynein have revealed the organization of the motor domain, comprising the AAA+ ring, the linker, the stalk/strut and the C sequence. Recently, the ADP.vanadate-bound structure, which is similar to the ATP hydrolysis transition state, revealed how the structure of dynein changes upon ATP binding. Although both the ADP- and ATP-bound state structures have been resolved, the dynamic properties at the atomic level remain unclear. In this work, we built two models named ‘the ADP model’ and ‘the ATP model’, where ADP and ATP are bound to AAA1 in the AAA+ ring, respectively, to observe the initial procedure of the structural change from the unprimed to the primed state. We performed 200-ns molecular dynamics simulations for both models and compared their structures and dynamics. The motions of the stalk, consisting of a long coiled coil with a microtubule-binding domain, significantly differed between the two models. The elastic properties of the stalk were analyzed and compared with the experimental results. PMID:27334455

  9. Elastic properties of dynein motor domain obtained from all-atom molecular dynamics simulations.

    PubMed

    Kamiya, Narutoshi; Mashimo, Tadaaki; Takano, Yu; Kon, Takahide; Kurisu, Genji; Nakamura, Haruki

    2016-08-01

    Dyneins are large microtubule motor proteins that convert ATP energy to mechanical power. High-resolution crystal structures of ADP-bound cytoplasmic dynein have revealed the organization of the motor domain, comprising the AAA(+) ring, the linker, the stalk/strut and the C sequence. Recently, the ADP.vanadate-bound structure, which is similar to the ATP hydrolysis transition state, revealed how the structure of dynein changes upon ATP binding. Although both the ADP- and ATP-bound state structures have been resolved, the dynamic properties at the atomic level remain unclear. In this work, we built two models named 'the ADP model' and 'the ATP model', where ADP and ATP are bound to AAA1 in the AAA(+) ring, respectively, to observe the initial procedure of the structural change from the unprimed to the primed state. We performed 200-ns molecular dynamics simulations for both models and compared their structures and dynamics. The motions of the stalk, consisting of a long coiled coil with a microtubule-binding domain, significantly differed between the two models. The elastic properties of the stalk were analyzed and compared with the experimental results. PMID:27334455

  10. Reaction-diffusion-advection approach to spatially localized treadmilling aggregates of molecular motors

    NASA Astrophysics Data System (ADS)

    Yochelis, Arik; Bar-On, Tomer; Gov, Nir S.

    2016-04-01

    Unconventional myosins belong to a class of molecular motors that walk processively inside cellular protrusions towards the tips, on top of actin filament. Surprisingly, in addition, they also form retrograde moving self-organized aggregates. The qualitative properties of these aggregates are recapitulated by a mass conserving reaction-diffusion-advection model and admit two distinct families of modes: traveling waves and pulse trains. Unlike the traveling waves that are generated by a linear instability, pulses are nonlinear structures that propagate on top of linearly stable uniform backgrounds. Asymptotic analysis of isolated pulses via a simplified reaction-diffusion-advection variant on large periodic domains, allows to draw qualitative trends for pulse properties, such as the amplitude, width, and propagation speed. The results agree well with numerical integrations and are related to available empirical observations.

  11. Specific Transformation of Assembly with Actin Filaments and Molecular Motors in a Cell-Sized Self-Emerged Liposome

    NASA Astrophysics Data System (ADS)

    Takiguchi, Kingo; Negishi, Makiko; Tanaka-Takiguchi, Yohko; Hayashi, Masahito; Yoshikawa, Kenichi

    2014-12-01

    Eukaryotes, by the same combination of cytoskeleton and molecular motor, for example actin filament and myosin, can generate a variety of movements. For this diversity, the organization of biological machineries caused by the confinement and/or crowding effects of internal living cells, may play very important roles.

  12. The Utilization of Sensori-motor Experiences for Introducing Young Pupils to Molecular Motion: A Report of a Pilot Study.

    ERIC Educational Resources Information Center

    Hadzigeorgiou, Yannis

    2002-01-01

    Does a sensori-motor experience help a physics student understand the movement of molecules in solids, liquids, and gases? Students aged 9-10 were given either traditional demonstrations of solids, liquids, and gases and the variation of molecular motion with temperature (iconic presentation), or they were involved in physical activities as they…

  13. Parallel computation with molecular-motor-propelled agents in nanofabricated networks.

    PubMed

    Nicolau, Dan V; Lard, Mercy; Korten, Till; van Delft, Falco C M J M; Persson, Malin; Bengtsson, Elina; Månsson, Alf; Diez, Stefan; Linke, Heiner; Nicolau, Dan V

    2016-03-01

    The combinatorial nature of many important mathematical problems, including nondeterministic-polynomial-time (NP)-complete problems, places a severe limitation on the problem size that can be solved with conventional, sequentially operating electronic computers. There have been significant efforts in conceiving parallel-computation approaches in the past, for example: DNA computation, quantum computation, and microfluidics-based computation. However, these approaches have not proven, so far, to be scalable and practical from a fabrication and operational perspective. Here, we report the foundations of an alternative parallel-computation system in which a given combinatorial problem is encoded into a graphical, modular network that is embedded in a nanofabricated planar device. Exploring the network in a parallel fashion using a large number of independent, molecular-motor-propelled agents then solves the mathematical problem. This approach uses orders of magnitude less energy than conventional computers, thus addressing issues related to power consumption and heat dissipation. We provide a proof-of-concept demonstration of such a device by solving, in a parallel fashion, the small instance {2, 5, 9} of the subset sum problem, which is a benchmark NP-complete problem. Finally, we discuss the technical advances necessary to make our system scalable with presently available technology.

  14. Physics of transport and traffic phenomena in biology: from molecular motors and cells to organisms

    NASA Astrophysics Data System (ADS)

    Chowdhury, Debashish; Schadschneider, Andreas; Nishinari, Katsuhiro

    2005-12-01

    Traffic-like collective movements are observed at almost all levels of biological systems. Molecular motor proteins like, for example, kinesin and dynein, which are the vehicles of almost all intra-cellular transport in eukaryotic cells, sometimes encounter traffic jam that manifests as a disease of the organism. Similarly, traffic jam of collagenase MMP-1, which moves on the collagen fibrils of the extracellular matrix of vertebrates, has also been observed in recent experiments. Novel efforts have been made to utilize some uni-cellular organisms as “micro-transporters”. Traffic-like movements of social insects like ants and termites on trails are, perhaps, more familiar in our everyday life. Experimental, theoretical and computational investigations in the last few years have led to a deeper understanding of the generic or common physical principles involved in these phenomena. In this review we critically examine the current status of our understanding, expose the limitations of the existing methods, mention open challenging questions and speculate on the possible future directions of research in this interdisciplinary area where physics meets not only chemistry and biology but also (nano-)technology.

  15. Selective cell-surface labeling of the molecular motor protein prestin

    PubMed Central

    McGuire, Ryan M.; Silberg, Jonathan J.; Pereira, Fred A.; Raphael, Robert M.

    2011-01-01

    Prestin, a multipass transmembrane protein whose N- an C-termini are localized to the cytoplasm, must be trafficked to the plasma membrane to fulfill its cellular function as a molecular motor. One challenge in studying prestin sequence-function relationships within living cells is separating the effects of amino acid substitutions on prestin trafficking, plasma membrane localization and function. To develop an approach for directly assessing prestin levels at the plasma membrane, we have investigated whether fusion of prestin to a single pass transmembrane protein results in a functional fusion protein with a surface-exposed N-terminal tag that can be detected in living cells. We find that fusion of the biotin-acceptor peptide (BAP) and transmembrane domain of the platelet-derived growth factor receptor (PDGFR) to the N-terminus of prestin-GFP yields a membrane protein that can be metabolically-labeled with biotin, trafficked to the plasma membrane, and selectively detected at the plasma membrane using fluorescently-tagged streptavidin. Furthermore, we show that the addition of a surface detectable tag and a single-pass transmembrane domain to prestin does not disrupt its voltage-sensitive activity. PMID:21651892

  16. Parallel computation with molecular-motor-propelled agents in nanofabricated networks

    PubMed Central

    Nicolau, Dan V.; Lard, Mercy; Korten, Till; van Delft, Falco C. M. J. M.; Persson, Malin; Bengtsson, Elina; Månsson, Alf; Diez, Stefan; Linke, Heiner; Nicolau, Dan V.

    2016-01-01

    The combinatorial nature of many important mathematical problems, including nondeterministic-polynomial-time (NP)-complete problems, places a severe limitation on the problem size that can be solved with conventional, sequentially operating electronic computers. There have been significant efforts in conceiving parallel-computation approaches in the past, for example: DNA computation, quantum computation, and microfluidics-based computation. However, these approaches have not proven, so far, to be scalable and practical from a fabrication and operational perspective. Here, we report the foundations of an alternative parallel-computation system in which a given combinatorial problem is encoded into a graphical, modular network that is embedded in a nanofabricated planar device. Exploring the network in a parallel fashion using a large number of independent, molecular-motor-propelled agents then solves the mathematical problem. This approach uses orders of magnitude less energy than conventional computers, thus addressing issues related to power consumption and heat dissipation. We provide a proof-of-concept demonstration of such a device by solving, in a parallel fashion, the small instance {2, 5, 9} of the subset sum problem, which is a benchmark NP-complete problem. Finally, we discuss the technical advances necessary to make our system scalable with presently available technology. PMID:26903637

  17. Parallel computation with molecular-motor-propelled agents in nanofabricated networks.

    PubMed

    Nicolau, Dan V; Lard, Mercy; Korten, Till; van Delft, Falco C M J M; Persson, Malin; Bengtsson, Elina; Månsson, Alf; Diez, Stefan; Linke, Heiner; Nicolau, Dan V

    2016-03-01

    The combinatorial nature of many important mathematical problems, including nondeterministic-polynomial-time (NP)-complete problems, places a severe limitation on the problem size that can be solved with conventional, sequentially operating electronic computers. There have been significant efforts in conceiving parallel-computation approaches in the past, for example: DNA computation, quantum computation, and microfluidics-based computation. However, these approaches have not proven, so far, to be scalable and practical from a fabrication and operational perspective. Here, we report the foundations of an alternative parallel-computation system in which a given combinatorial problem is encoded into a graphical, modular network that is embedded in a nanofabricated planar device. Exploring the network in a parallel fashion using a large number of independent, molecular-motor-propelled agents then solves the mathematical problem. This approach uses orders of magnitude less energy than conventional computers, thus addressing issues related to power consumption and heat dissipation. We provide a proof-of-concept demonstration of such a device by solving, in a parallel fashion, the small instance {2, 5, 9} of the subset sum problem, which is a benchmark NP-complete problem. Finally, we discuss the technical advances necessary to make our system scalable with presently available technology. PMID:26903637

  18. Covalent Immobilization of Microtubules on Glass Surfaces for Molecular Motor Force Measurements and Other Single-Molecule Assays

    PubMed Central

    Nicholas, Matthew P.; Rao, Lu; Gennerich, Arne

    2014-01-01

    Rigid attachment of microtubules (MTs) to glass cover slip surfaces is a prerequisite for a variety of microscopy experiments in which MTs are used as substrates for MT-associated proteins, such as the molecular motors kinesin and cytoplasmic dynein. We present an MT-surface coupling protocol in which aminosilanized glass is formylated using the cross-linker glutaraldehyde, fluorescence-labeled MTs are covalently attached, and the surface is passivated with highly pure beta-casein. The technique presented here yields rigid MT immobilization while simultaneously blocking the remaining glass surface against nonspecific binding by polystyrene optical trapping microspheres. This surface chemistry is straightforward and relatively cheap and uses a minimum of specialized equipment or hazardous reagents. These methods provide a foundation for a variety of optical tweezers experiments with MT-associated molecular motors and may also be useful in other assays requiring surface-immobilized proteins. PMID:24633798

  19. Covalent immobilization of microtubules on glass surfaces for molecular motor force measurements and other single-molecule assays.

    PubMed

    Nicholas, Matthew P; Rao, Lu; Gennerich, Arne

    2014-01-01

    Rigid attachment of microtubules (MTs) to glass cover slip surfaces is a prerequisite for a variety of microscopy experiments in which MTs are used as substrates for MT-associated proteins, such as the molecular motors kinesin and cytoplasmic dynein. We present an MT-surface coupling protocol in which aminosilanized glass is formylated using the cross-linker glutaraldehyde, fluorescence-labeled MTs are covalently attached, and the surface is passivated with highly pure beta-casein. The technique presented here yields rigid MT immobilization while simultaneously blocking the remaining glass surface against nonspecific binding by polystyrene optical trapping microspheres. This surface chemistry is straightforward and relatively cheap and uses a minimum of specialized equipment or hazardous reagents. These methods provide a foundation for a variety of optical tweezers experiments with MT-associated molecular motors and may also be useful in other assays requiring surface-immobilized proteins. PMID:24633798

  20. Molecular dynamics simulations of the rotary motor F(0) under external electric fields across the membrane.

    PubMed

    Lin, Yang-Shan; Lin, Jung-Hsin; Chang, Chien-Cheng

    2010-03-17

    The membrane-bound component F(0), which is a major component of the F(0)F(1)-ATP synthase, works as a rotary motor and plays a central role in driving the F(1) component to transform chemiosmotic energy into ATP synthesis. We conducted molecular dynamics simulations of b(2)-free F(0) in a 1-palmitoyl-2-oleoyl-phosphatidylcholine lipid bilayer for tens of nanoseconds with two different protonation states of the cAsp-61 residue at the interface of the a-c complex in the absence of electric fields and under electric fields of +/-0.03 V/nm across the membrane. To our surprise, we observed that the upper half of the N-terminal helix of the c(1) subunit rotated about its axis clockwise by 30 degrees . An energetic analysis revealed that the electrostatic repulsion between this N-terminal helix and subunit c(12) was a major contributor to the observed rotation. A correlation map analysis indicated that the correlated motions of residues in the interface of the a-c complex were significantly reduced by external electric fields. The deuterium order parameter (S(CD)) profile calculated by averaging all the lipids in the F(0)-bound bilayer was not very different from that of the pure bilayer system, in agreement with recent (2)H solid-state NMR experiments. However, by delineating the lipid properties according to their vicinity to F(0), we found that the S(CD) profiles of different lipid shells were prominently different. Lipids close to F(0) formed a more ordered structure. Similarly, the lateral diffusion of lipids on the membrane surface also followed a shell-dependent behavior. The lipids in the proximity of F(0) exhibited very significantly reduced diffusional motion. The numerical value of S(CD) was anticorrelated with that of the diffusion coefficient, i.e., the more ordered lipid structures led to slower lipid diffusion. Our findings will help elucidate the dynamics of F(0) depending on the protonation state and electric field, and may also shed some light on the

  1. Kinetic modeling of molecular motors: pause model and parameter determination from single-molecule experiments

    NASA Astrophysics Data System (ADS)

    Morin, José A.; Ibarra, Borja; Cao, Francisco J.

    2016-05-01

    Single-molecule manipulation experiments of molecular motors provide essential information about the rate and conformational changes of the steps of the reaction located along the manipulation coordinate. This information is not always sufficient to define a particular kinetic cycle. Recent single-molecule experiments with optical tweezers showed that the DNA unwinding activity of a Phi29 DNA polymerase mutant presents a complex pause behavior, which includes short and long pauses. Here we show that different kinetic models, considering different connections between the active and the pause states, can explain the experimental pause behavior. Both the two independent pause model and the two connected pause model are able to describe the pause behavior of a mutated Phi29 DNA polymerase observed in an optical tweezers single-molecule experiment. For the two independent pause model all parameters are fixed by the observed data, while for the more general two connected pause model there is a range of values of the parameters compatible with the observed data (which can be expressed in terms of two of the rates and their force dependencies). This general model includes models with indirect entry and exit to the long-pause state, and also models with cycling in both directions. Additionally, assuming that detailed balance is verified, which forbids cycling, this reduces the ranges of the values of the parameters (which can then be expressed in terms of one rate and its force dependency). The resulting model interpolates between the independent pause model and the indirect entry and exit to the long-pause state model

  2. Prokaryotic and eukaryotic DNA helicases. Essential molecular motor proteins for cellular machinery.

    PubMed

    Tuteja, Narendra; Tuteja, Renu

    2004-05-01

    DNA helicases are ubiquitous molecular motor proteins which harness the chemical free energy of ATP hydrolysis to catalyze the unwinding of energetically stable duplex DNA, and thus play important roles in nearly all aspects of nucleic acid metabolism, including replication, repair, recombination, and transcription. They break the hydrogen bonds between the duplex helix and move unidirectionally along the bound strand. All helicases are also translocases and DNA-dependent ATPases. Most contain conserved helicase motifs that act as an engine to power DNA unwinding. All DNA helicases share some common properties, including nucleic acid binding, NTP binding and hydrolysis, and unwinding of duplex DNA in the 3' to 5' or 5' to 3' direction. The minichromosome maintenance (Mcm) protein complex (Mcm4/6/7) provides a DNA-unwinding function at the origin of replication in all eukaryotes and may act as a licensing factor for DNA replication. The RecQ family of helicases is highly conserved from bacteria to humans and is required for the maintenance of genome integrity. They have also been implicated in a variety of human genetic disorders. Since the discovery of the first DNA helicase in Escherichia coli in 1976, and the first eukaryotic one in the lily in 1978, a large number of these enzymes have been isolated from both prokaryotic and eukaryotic systems, and the number is still growing. In this review we cover the historical background of DNA helicases, helicase assays, biochemical properties, prokaryotic and eukaryotic DNA helicases including Mcm proteins and the RecQ family of helicases. The properties of most of the known DNA helicases from prokaryotic and eukaryotic systems, including viruses and bacteriophages, are summarized in tables.

  3. The molecular motor F-ATP synthase is targeted by the tumoricidal protein HAMLET.

    PubMed

    Ho, James; Sielaff, Hendrik; Nadeem, Aftab; Svanborg, Catharina; Grüber, Gerhard

    2015-05-22

    HAMLET (human alpha-lactalbumin made lethal to tumor cells) interacts with multiple tumor cell compartments, affecting cell morphology, metabolism, proteasome function, chromatin structure and viability. This study investigated if these diverse effects of HAMLET might be caused, in part, by a direct effect on the ATP synthase and a resulting reduction in cellular ATP levels. A dose-dependent reduction in cellular ATP levels was detected in A549 lung carcinoma cells, and by confocal microscopy, co-localization of HAMLET with the nucleotide-binding subunits α (non-catalytic) and β (catalytic) of the energy converting F1F0 ATP synthase was detected. As shown by fluorescence correlation spectroscopy, HAMLET binds to the F1 domain of the F1F0 ATP synthase with a dissociation constant (KD) of 20.5μM. Increasing concentrations of the tumoricidal protein HAMLET added to the enzymatically active α3β3γ complex of the F-ATP synthase lowered its ATPase activity, demonstrating that HAMLET binding to the F-ATP synthase effects the catalysis of this molecular motor. Single-molecule analysis was applied to study HAMLET-α3β3γ complex interaction. Whereas the α3β3γ complex of the F-ATP synthase rotated in a counterclockwise direction with a mean rotational rate of 3.8±0.7s(-1), no rotation could be observed in the presence of bound HAMLET. Our findings suggest that direct effects of HAMLET on the F-ATP synthase may inhibit ATP-dependent cellular processes. PMID:25681694

  4. The molecular motor F-ATP synthase is targeted by the tumoricidal protein HAMLET.

    PubMed

    Ho, James; Sielaff, Hendrik; Nadeem, Aftab; Svanborg, Catharina; Grüber, Gerhard

    2015-05-22

    HAMLET (human alpha-lactalbumin made lethal to tumor cells) interacts with multiple tumor cell compartments, affecting cell morphology, metabolism, proteasome function, chromatin structure and viability. This study investigated if these diverse effects of HAMLET might be caused, in part, by a direct effect on the ATP synthase and a resulting reduction in cellular ATP levels. A dose-dependent reduction in cellular ATP levels was detected in A549 lung carcinoma cells, and by confocal microscopy, co-localization of HAMLET with the nucleotide-binding subunits α (non-catalytic) and β (catalytic) of the energy converting F1F0 ATP synthase was detected. As shown by fluorescence correlation spectroscopy, HAMLET binds to the F1 domain of the F1F0 ATP synthase with a dissociation constant (KD) of 20.5μM. Increasing concentrations of the tumoricidal protein HAMLET added to the enzymatically active α3β3γ complex of the F-ATP synthase lowered its ATPase activity, demonstrating that HAMLET binding to the F-ATP synthase effects the catalysis of this molecular motor. Single-molecule analysis was applied to study HAMLET-α3β3γ complex interaction. Whereas the α3β3γ complex of the F-ATP synthase rotated in a counterclockwise direction with a mean rotational rate of 3.8±0.7s(-1), no rotation could be observed in the presence of bound HAMLET. Our findings suggest that direct effects of HAMLET on the F-ATP synthase may inhibit ATP-dependent cellular processes.

  5. Selective cell-surface labeling of the molecular motor protein prestin

    SciTech Connect

    McGuire, Ryan M.; Silberg, Jonathan J.; Pereira, Fred A.; Raphael, Robert M.

    2011-06-24

    Highlights: {yields} Trafficking to the plasma membrane is required for prestin function. {yields} Biotin acceptor peptide (BAP) was fused to prestin through a transmembrane domain. {yields} BAP-prestin can be metabolically labeled with biotin in HEK293 cells. {yields} Biotin-BAP-prestin allows for selective imaging of fully trafficked prestin. {yields} The biotin-BAP-prestin displays voltage-sensitive activity. -- Abstract: Prestin, a multipass transmembrane protein whose N- and C-termini are localized to the cytoplasm, must be trafficked to the plasma membrane to fulfill its cellular function as a molecular motor. One challenge in studying prestin sequence-function relationships within living cells is separating the effects of amino acid substitutions on prestin trafficking, plasma membrane localization and function. To develop an approach for directly assessing prestin levels at the plasma membrane, we have investigated whether fusion of prestin to a single pass transmembrane protein results in a functional fusion protein with a surface-exposed N-terminal tag that can be detected in living cells. We find that fusion of the biotin-acceptor peptide (BAP) and transmembrane domain of the platelet-derived growth factor receptor (PDGFR) to the N-terminus of prestin-GFP yields a membrane protein that can be metabolically-labeled with biotin, trafficked to the plasma membrane, and selectively detected at the plasma membrane using fluorescently-tagged streptavidin. Furthermore, we show that the addition of a surface detectable tag and a single-pass transmembrane domain to prestin does not disrupt its voltage-sensitive activity.

  6. A simple statistical approach to the boyer model of the molecular motor adenosine triphosphatase

    SciTech Connect

    Loginov, E. B. Pikin, S. A.

    2006-03-15

    A physical description of the F{sub 0}F{sub 1} adenosine triphosphatase as a rotating motor is proposed. The catalytic center and the ion-conducting membrane are considered within the classical Boyer model for the rotor and the catalytic parts of the motor, thereby allowing application of a simple three-pole model, which decreases the number of parameters significantly. The stochastic character of the processes occurring in motors is described by the Fokker-Planck equations. Various dependences of the rotation speed on the degree of excitation, localization of excitations, and the amplitude of the potential are reported.

  7. Mechanical Operation and Intersubunit Coordination of Ring-Shaped Molecular Motors: Insights from Single-Molecule Studies

    PubMed Central

    Liu, Shixin; Chistol, Gheorghe; Bustamante, Carlos

    2014-01-01

    Ring NTPases represent a large and diverse group of proteins that couple their nucleotide hydrolysis activity to a mechanical task involving force generation and some type of transport process in the cell. Because of their shape, these enzymes often operate as gates that separate distinct cellular compartments to control and regulate the passage of chemical species across them. In this manner, ions and small molecules are moved across membranes, biopolymer substrates are segregated between cells or moved into confined spaces, double-stranded nucleic acids are separated into single strands to provide access to the genetic information, and polypeptides are unfolded and processed for recycling. Here we review the recent advances in the characterization of these motors using single-molecule manipulation and detection approaches. We describe the various mechanisms by which ring motors convert chemical energy to mechanical force or torque and coordinate the activities of individual subunits that constitute the ring. We also examine how single-molecule studies have contributed to a better understanding of the structural elements involved in motor-substrate interaction, mechanochemical coupling, and intersubunit coordination. Finally, we discuss how these molecular motors tailor their operation—often through regulation by other cofactors—to suit their unique biological functions. PMID:24806916

  8. Towards a molecular understanding of the apicomplexan actin motor: on a road to novel targets for malaria remedies?

    SciTech Connect

    Kumpula, Esa-Pekka; Kursula, Inari

    2015-04-16

    In this review, current structural understanding of the apicomplexan glideosome and actin regulation is described. Apicomplexan parasites are the causative agents of notorious human and animal diseases that give rise to considerable human suffering and economic losses worldwide. The most prominent parasites of this phylum are the malaria-causing Plasmodium species, which are widespread in tropical and subtropical regions, and Toxoplasma gondii, which infects one third of the world’s population. These parasites share a common form of gliding motility which relies on an actin–myosin motor. The components of this motor and the actin-regulatory proteins in Apicomplexa have unique features compared with all other eukaryotes. This, together with the crucial roles of these proteins, makes them attractive targets for structure-based drug design. In recent years, several structures of glideosome components, in particular of actins and actin regulators from apicomplexan parasites, have been determined, which will hopefully soon allow the creation of a complete molecular picture of the parasite actin–myosin motor and its regulatory machinery. Here, current knowledge of the function of this motor is reviewed from a structural perspective.

  9. A rotary molecular motor that can work at near 100% efficiency.

    PubMed Central

    Kinosita, K; Yasuda, R; Noji, H; Adachi, K

    2000-01-01

    A single molecule of F1-ATPase is by itself a rotary motor in which a central gamma-subunit rotates against a surrounding cylinder made of alpha3beta3-subunits. Driven by the three betas that sequentially hydrolyse ATP, the motor rotates in discrete 120 degree steps, as demonstrated in video images of the movement of an actin filament bound, as a marker, to the central gamma-subunit. Over a broad range of load (hydrodynamic friction against the rotating actin filament) and speed, the F1 motor produces a constant torque of ca. 40 pN nm. The work done in a 120 degree step, or the work per ATP molecule, is thus ca. 80 pN nm. In cells, the free energy of ATP hydrolysis is ca. 90 pN nm per ATP molecule, suggesting that the F1 motor can work at near 100% efficiency. We confirmed in vitro that F1 indeed does ca. 80 pN nm of work under the condition where the free energy per ATP is 90 pN nm. The high efficiency may be related to the fully reversible nature of the F1 motor: the ATP synthase, of which F1 is a part, is considered to synthesize ATP from ADP and phosphate by reverse rotation of the F1 motor. Possible mechanisms of F1 rotation are discussed. PMID:10836501

  10. An exact approach for studying cargo transport by an ensemble of molecular motors

    PubMed Central

    2013-01-01

    Background Intracellular transport is crucial for many cellular processes where a large fraction of the cargo is transferred by motor-proteins over a network of microtubules. Malfunctions in the transport mechanism underlie a number of medical maladies. Existing methods for studying how motor-proteins coordinate the transfer of a shared cargo over a microtubule are either analytical or are based on Monte-Carlo simulations. Approaches that yield analytical results, while providing unique insights into transport mechanism, make simplifying assumptions, where a detailed characterization of important transport modalities is difficult to reach. On the other hand, Monte-Carlo based simulations can incorporate detailed characteristics of the transport mechanism; however, the quality of the results depend on the number and quality of simulation runs used in arriving at results. Here, for example, it is difficult to simulate and study rare-events that can trigger abnormalities in transport. Results In this article, a semi-analytical methodology that determines the probability distribution function of motor-protein behavior in an exact manner is developed. The method utilizes a finite-dimensional projection of the underlying infinite-dimensional Markov model, which retains the Markov property, and enables the detailed and exact determination of motor configurations, from which meaningful inferences on transport characteristics of the original model can be derived. Conclusions Under this novel probabilistic approach new insights about the mechanisms of action of these proteins are found, suggesting hypothesis about their behavior and driving the design and realization of new experiments. The advantages provided in accuracy and efficiency make it possible to detect rare events in the motor protein dynamics, that could otherwise pass undetected using standard simulation methods. In this respect, the model has allowed to provide a possible explanation for possible mechanisms

  11. On the possibility to accelerate the thermal isomerizations of overcrowded alkene-based rotary molecular motors with electron-donating or electron-withdrawing substituents.

    PubMed

    Oruganti, Baswanth; Durbeej, Bo

    2016-09-01

    We employ computational methods to investigate the possibility of using electron-donating or electron-withdrawing substituents to reduce the free-energy barriers of the thermal isomerizations that limit the rotational frequencies achievable by synthetic overcrowded alkene-based molecular motors. Choosing as reference systems one of the fastest motors known to date and two variants thereof, we consider six new motors obtained by introducing electron-donating methoxy and dimethylamino or electron-withdrawing nitro and cyano substituents in conjugation with the central olefinic bond connecting the two (stator and rotator) motor halves. Performing density functional theory calculations, we then show that electron-donating (but not electron-withdrawing) groups at the stator are able to reduce the already small barriers of the reference motors by up to 18 kJ mol(-1). This result outlines a possible strategy for improving the rotational frequencies of motors of this kind. Furthermore, exploring the origin of the catalytic effect, it is found that electron-donating groups exert a favorable steric influence on the thermal isomerizations, which is not manifested by electron-withdrawing groups. This finding suggests a new mechanism for controlling the critical steric interactions of these motors. Graphical Abstract The introduction of electron-donating groups in one of the fastest rotary molecular motors known to date is found to reduce the free-energy barriers of the thermal steps that limit the rotational frequencies by up to 18 kJ mol(-1). PMID:27553304

  12. High bandwidth optical force clamp for investigation of molecular motor motion

    NASA Astrophysics Data System (ADS)

    Roychowdhury, Subhrajit; Aggarwal, Tanuj; Salapaka, Srinivasa; Salapaka, Murti V.

    2013-10-01

    Use of optical tweezers for load force regulation on processive motors has yielded significant insights into intracellular transport mechanisms. The methodology developed in this letter circumvents the limitations of existing active force clamps with the use of experimentally determined models for various components of the optical tweezing system, thus making it possible to probe motor proteins at higher speeds. This paradigm also allows for real-time step estimation for step sizes as small as 8 nm with dwell time of 5 ms or higher without sacrificing force regulation.

  13. Using electrical and optical tweezers to facilitate studies of molecular motors.

    PubMed

    Arsenault, Mark E; Sun, Yujie; Bau, Haim H; Goldman, Yale E

    2009-06-28

    Dielectrophoresis was used to stretch and suspend actin filaments across a trench etched between two electrodes patterned on a glass slide. Optical tweezers were used to bring a motor protein-coated bead into close proximity to a pre-selected, suspended actin filament, facilitating the attachment of the myosin-coated bead to the filament. The clearance beneath the filament allowed the bead to move freely along and around its filamentous track, unhindered by solid surfaces. Using defocused images, the three-dimensional position of the bead was tracked as a function of time to obtain its trajectory. Experiments were carried out with myosin V and myosin X. Both motor proteins followed left-handed helical paths with the myosin X motor exhibiting a shorter pitch than the myosin V. The combined use of electrostatic and optical tweezers facilitates the preparation of motility assays with suspended tracks. Variants of this technique will enable higher complexity experiments in vitro to better understand the behavior of motors in cells. PMID:19506758

  14. Identification of molecular motors in the Woods Hole squid, Loligo pealei: an expressed sequence tag approach.

    PubMed

    DeGiorgis, Joseph A; Cavaliere, Kimberly R; Burbach, J Peter H

    2011-10-01

    The squid giant axon and synapse are unique systems for studying neuronal function. While a few nucleotide and amino acid sequences have been obtained from squid, large scale genetic and proteomic information is lacking. We have been particularly interested in motors present in axons and their roles in transport processes. Here, to obtain genetic data and to identify motors expressed in squid, we initiated an expressed sequence tag project by single-pass sequencing mRNAs isolated from the stellate ganglia of the Woods Hole Squid, Loligo pealei. A total of 22,689 high quality expressed sequence tag (EST) sequences were obtained and subjected to basic local alignment search tool analysis. Seventy six percent of these sequences matched genes in the National Center for Bioinformatics databases. By CAP3 analysis this library contained 2459 contigs and 7568 singletons. Mining for motors successfully identified six kinesins, six myosins, a single dynein heavy chain, as well as components of the dynactin complex, and motor light chains and accessory proteins. This initiative demonstrates that EST projects represent an effective approach to obtain sequences of interest.

  15. Cloning, expression, and characterization of a novel molecular motor, Leishmania myosin-XXI.

    PubMed

    Batters, Christopher; Woodall, Katy A; Toseland, Christopher P; Hundschell, Christian; Veigel, Claudia

    2012-08-10

    The genome of the Leishmania parasite contains two classes of myosin. Myosin-XXI, seemingly the only myosin isoform expressed in the protozoan parasite, has been detected in both the promastigote and amastigote stages of the Leishmania life cycle. It has been suggested to perform a variety of functions, including roles in membrane anchorage, but also long-range directed movements of cargo. However, nothing is known about the biochemical or mechanical properties of this motor. Here we designed and expressed various myosin-XXI constructs using a baculovirus expression system. Both full-length (amino acids 1-1051) and minimal motor domain constructs (amino acids 1-800) featured actin-activated ATPase activity. Myosin-XXI was soluble when expressed either with or without calmodulin. In the presence of calcium (pCa 4.1) the full-length motor could bind a single calmodulin at its neck domain (probably amino acids 809-823). Calmodulin binding was required for motility but not for ATPase activity. Once bound, calmodulin remained stably attached independent of calcium concentration (pCa 3-7). In gliding filament assays, myosin-XXI moved actin filaments at ∼15 nm/s, insensitive to both salt (25-1000 mm KCl) and calcium concentrations (pCa 3-7). Calmodulin binding to the neck domain might be involved in regulating the motility of the myosin-XXI motor for its various cellular functions in the different stages of the Leishmania parasite life cycle. PMID:22718767

  16. Forced desorption of semiflexible polymers, adsorbed and driven by molecular motors.

    PubMed

    Chaudhuri, Abhishek; Chaudhuri, Debasish

    2016-02-21

    We formulate and characterize a model to describe the dynamics of semiflexible polymers in the presence of activity due to motor proteins attached irreversibly to a substrate, and a transverse pulling force acting on one end of the filament. The stochastic binding-unbinding of the motor proteins and their ability to move along the polymer generate active forces. As the pulling force reaches a threshold value, the polymer eventually desorbs from the substrate. Performing underdamped Langevin dynamics simulation of the polymer, and with stochastic motor activity, we obtain desorption phase diagrams. The correlation time for fluctuations in the desorbed fraction increases as one approaches complete desorption, captured quantitatively by a power law spectral density. We present theoretical analysis of the phase diagram using mean field approximations in the weakly bending limit of the polymer and performing linear stability analysis. This predicts an increase in the desorption force with the polymer bending rigidity, active velocity and processivity of the motor proteins to capture the main features of the simulation results. PMID:26750537

  17. Torque, chemistry and efficiency in molecular motors: a study of the rotary-chemical coupling in F1-ATPase.

    PubMed

    Mukherjee, Shayantani; Bora, Ram Prasad; Warshel, Arieh

    2015-11-01

    Detailed understanding of the action of biological molecular machines must overcome the challenge of gaining a clear knowledge of the corresponding free-energy landscape. An example for this is the elucidation of the nature of converting chemical energy to torque and work in the rotary molecular motor of F1-ATPase. A major part of the challenge involves understanding the rotary-chemical coupling from a non-phenomenological structure/energy description. Here we focused on using a coarse-grained model of F1-ATPase to generate a structure-based free-energy landscape of the rotary-chemical process of the whole system. In particular, we concentrated on exploring the possible impact of the position of the catalytic dwell on the efficiency and torque generation of the molecular machine. It was found that the experimentally observed torque can be reproduced with landscapes that have different positions for the catalytic dwell on the rotary-chemical surface. Thus, although the catalysis is undeniably required for torque generation, the experimentally observed position of the catalytic dwell at 80° might not have a clear advantage for the force generation by F1-ATPase. This further implies that the rotary-chemical couplings in these biological motors are quite robust and their efficiencies do not depend explicitly on the position of the catalytic dwells. Rather, the specific positioning of the dwells with respect to the rotational angle is a characteristic arising due to the structural construct of the molecular machine and might not bear any clear connection to the thermodynamic efficiency for the system.

  18. Torque, chemistry and efficiency in molecular motors: a study of the rotary-chemical coupling in F1-ATPase.

    PubMed

    Mukherjee, Shayantani; Bora, Ram Prasad; Warshel, Arieh

    2015-11-01

    Detailed understanding of the action of biological molecular machines must overcome the challenge of gaining a clear knowledge of the corresponding free-energy landscape. An example for this is the elucidation of the nature of converting chemical energy to torque and work in the rotary molecular motor of F1-ATPase. A major part of the challenge involves understanding the rotary-chemical coupling from a non-phenomenological structure/energy description. Here we focused on using a coarse-grained model of F1-ATPase to generate a structure-based free-energy landscape of the rotary-chemical process of the whole system. In particular, we concentrated on exploring the possible impact of the position of the catalytic dwell on the efficiency and torque generation of the molecular machine. It was found that the experimentally observed torque can be reproduced with landscapes that have different positions for the catalytic dwell on the rotary-chemical surface. Thus, although the catalysis is undeniably required for torque generation, the experimentally observed position of the catalytic dwell at 80° might not have a clear advantage for the force generation by F1-ATPase. This further implies that the rotary-chemical couplings in these biological motors are quite robust and their efficiencies do not depend explicitly on the position of the catalytic dwells. Rather, the specific positioning of the dwells with respect to the rotational angle is a characteristic arising due to the structural construct of the molecular machine and might not bear any clear connection to the thermodynamic efficiency for the system. PMID:26537397

  19. A modified active Brownian dynamics model using asymmetric energy conversion and its application to the molecular motor system.

    PubMed

    Park, Pyeong Jun; Lee, Kong-Ju-Bock

    2013-06-01

    We consider a modified energy depot model in the overdamped limit using an asymmetric energy conversion rate, which consists of linear and quadratic terms in an active particle's velocity. In order to analyze our model, we adopt a system of molecular motors on a microtubule and employ a flashing ratchet potential synchronized to a stochastic energy supply. By performing an active Brownian dynamics simulation, we investigate effects of the active force, thermal noise, external load, and energy-supply rate. Our model yields the stepping and stalling behaviors of the conventional molecular motor. The active force is found to facilitate the forwardly processive stepping motion, while the thermal noise reduces the stall force by enhancing relatively the backward stepping motion under external loads. The stall force in our model decreases as the energy-supply rate is decreased. Hence, assuming the Michaelis-Menten relation between the energy-supply rate and the an ATP concentration, our model describes ATP-dependent stall force in contrast to kinesin-1.

  20. Testing a structural model for viral DNA packaging motor function by optical tweezers measurements, site directed mutagenesis, and molecular dynamics calculations

    NASA Astrophysics Data System (ADS)

    Keller, Nicholas A.; Migliori, Amy D.; Arya, Gaurav; Rao, Venigalla B.; Smith, Douglas E.

    2013-09-01

    Many double-stranded DNA viruses employ a molecular motor to package DNA into preformed capsid shells. Based on structures of phage T4 motor proteins determined by X-ray crystallography and cryo-electron microscopy, Rao, Rossmann and coworkers recently proposed a structural model for motor function. They proposed that DNA is ratcheted by a large conformational change driven by electrostatic interactions between charged residues at an interface between two globular domains of the motor protein. We have conducted experiments to test this model by studying the effect on packaging under applied load of site-directed changes altering these residues. We observe significant impairment of packaging activity including reductions in packaging rate, percent time packaging, and time active under high load. We show that these measured impairments correlate well with alterations in free energies associated with the conformational change predicted by molecular dynamics simulations.

  1. Ensemble velocity of non-processive molecular motors with multiple chemical states

    PubMed Central

    Vilfan, Andrej

    2014-01-01

    We study the ensemble velocity of non-processive motor proteins, described with multiple chemical states. In particular, we discuss the velocity as a function of ATP concentration. Even a simple model which neglects the strain dependence of transition rates, reverse transition rates and nonlinearities in the elasticity can show interesting functional dependencies, which deviate significantly from the frequently assumed Michaelis–Menten form. We discuss how the order of events in the duty cycle can be inferred from the measured dependence. The model also predicts the possibility of velocity reversal at a certain ATP concentration if the duty cycle contains several conformational changes of opposite directionalities. PMID:25485083

  2. Hereditary motor and sensory neuropathies: Understanding molecular pathogenesis could lead to future treatment strategies.

    PubMed

    Jerath, Nivedita U; Shy, Michael E

    2015-04-01

    Inherited peripheral neuropathies, like many other degenerative disorders, have been challenging to treat. At this point, there is little specific therapy for the inherited neuropathies other than genetic counseling as well as symptomatic treatment and rehabilitation. In the past, ascorbic acid, progesterone antagonists, and subcutaneous neurotrophin-3 (NT3) injections have demonstrated improvement in animal models of CMT 1A, the most common inherited neuropathy, but have failed to translate any effect in humans. Given the difficulty in treatment, it is important to understand the molecular pathogenesis of hereditary neuropathies in order to strategize potential future therapies. The hereditary neuropathies are in an era of molecular insight and over the past 20 years, more than 78 subtypes of Charcot Marie Tooth disease (CMT) have been identified and extensively studied to understand the biological pathways in greater detail. Next generation molecular sequencing has also improved the diagnosis as well as the understanding of CMT. A greater understanding of the molecular pathways will help pave the way to future therapeutics of CMT. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis. PMID:25108281

  3. Visible-Light-Driven Photoisomerization and Increased Rotation Speed of a Molecular Motor Acting as a Ligand in a Ruthenium(II) Complex.

    PubMed

    Wezenberg, Sander J; Chen, Kuang-Yen; Feringa, Ben L

    2015-09-21

    Toward the development of visible-light-driven molecular rotary motors, an overcrowded alkene-based ligand and the corresponding ruthenium(II) complex is presented. In our design, a 4,5-diazafluorenyl coordination motif is directly integrated into the motor function. The photochemical and thermal isomerization behavior has been studied by UV/Vis and NMR spectroscopy. Upon coordination to a Ru(II) bipyridine complex, the photoisomerization process can be driven by visible (λmax = 450 nm) instead of UV light and furthermore, a large increase of the speed of rotation is noted. DFT calculations point to a contraction of the diazafluorenyl lower half upon metal-coordination resulting in reduced steric hindrance in the "fjord region" of the molecule. Consequently, it is shown that metal-ligand interactions can play an important role in the adjustment of both photophysical and thermodynamic properties of molecular motors.

  4. INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Monte—Carlo Simulation of Multiple-Molecular-Motor Transport

    NASA Astrophysics Data System (ADS)

    Wang, Zi-Qing; Wang, Guo-Dong; Shen, Wei-Bo

    2010-10-01

    Multimotor transport is studied by Monte-Carlo simulation with consideration of motor detachment from the filament. Our work shows, in the case of low load, the velocity of multi-motor system can decrease or increase with increasing motor numbers depending on the single motor force-velocity curve. The stall force and run-length reduced greatly compared to other models. Especially in the case of low ATP concentrations, the stall force of multi motor transport even smaller than the single motor's stall force.

  5. From Computational Photobiology to the Design of Vibrationally Coherent Molecular Devices and Motors

    NASA Astrophysics Data System (ADS)

    Olivucci, Massimo

    2014-03-01

    In the past multi-configurational quantum chemical computations coupled with molecular mechanics force fields have been employed to investigate spectroscopic, thermal and photochemical properties of visual pigments. Here we show how the same computational technology can nowadays be used to design, characterize and ultimately, prepare light-driven molecular switches which mimics the photophysics of the visual pigment bovine rhodopsin (Rh). When embedded in the protein cavity the chromophore of Rh undergoes an ultrafast and coherent photoisomerization. In order to design a synthetic chromophore displaying similar properties in common solvents, we recently focused on indanylidene-pyrroline (NAIP) systems. We found that these systems display light-induced ground state coherent vibrational motion similar to the one detected in Rh. Semi-classical trajectories provide a mechanistic description of the structural changes associated to the observed coherent motion which is shown to be ultimately due to periodic changes in the π-conjugation.

  6. Engineering of a novel Ca{sup 2+}-regulated kinesin molecular motor using a calmodulin dimer linker

    SciTech Connect

    Shishido, Hideki; Maruta, Shinsaku

    2012-06-29

    Highlights: Black-Right-Pointing-Pointer Engineered kinesin-M13 and calmodulin involving single cysteine were prepared. Black-Right-Pointing-Pointer CaM mutant was cross-linked to dimer by bifunctional thiol reactive reagent. Black-Right-Pointing-Pointer Kinesin-M13 was dimerized via CaM dimer in the presence of calcium. Black-Right-Pointing-Pointer Function of the engineered kinesin was regulated by a Ca{sup 2+}-calmodulin dimer linker. -- Abstract: The kinesin-microtubule system holds great promise as a molecular shuttle device within biochips. However, one current barrier is that such shuttles do not have 'on-off' control of their movement. Here we report the development of a novel molecular motor powered by an accelerator and brake system, using a kinesin monomer and a calmodulin (CaM) dimer. The kinesin monomer, K355, was fused with a CaM target peptide (M13 peptide) at the C-terminal part of the neck region (K355-M13). We also prepared CaM dimers using CaM mutants (Q3C), (R86C), or (A147C) and crosslinkers that react with cysteine residues. Following induction of K355-M13 dimerization with CaM dimers, we measured K355-M13 motility and found that it can be reversibly regulated in a Ca{sup 2+}-dependent manner. We also found that velocities of K355-M13 varied depending on the type and crosslink position of the CaM dimer used; crosslink length also had a moderate effect on motility. These results suggest Ca{sup 2+}-dependent dimerization of K355-M13 could be used as a novel molecular shuttle, equipped with an accelerator and brake system, for biochip applications.

  7. Molecular mapping of movement-associated areas in the avian brain: a motor theory for vocal learning origin.

    PubMed

    Feenders, Gesa; Liedvogel, Miriam; Rivas, Miriam; Zapka, Manuela; Horita, Haruhito; Hara, Erina; Wada, Kazuhiro; Mouritsen, Henrik; Jarvis, Erich D

    2008-03-12

    Vocal learning is a critical behavioral substrate for spoken human language. It is a rare trait found in three distantly related groups of birds-songbirds, hummingbirds, and parrots. These avian groups have remarkably similar systems of cerebral vocal nuclei for the control of learned vocalizations that are not found in their more closely related vocal non-learning relatives. These findings led to the hypothesis that brain pathways for vocal learning in different groups evolved independently from a common ancestor but under pre-existing constraints. Here, we suggest one constraint, a pre-existing system for movement control. Using behavioral molecular mapping, we discovered that in songbirds, parrots, and hummingbirds, all cerebral vocal learning nuclei are adjacent to discrete brain areas active during limb and body movements. Similar to the relationships between vocal nuclei activation and singing, activation in the adjacent areas correlated with the amount of movement performed and was independent of auditory and visual input. These same movement-associated brain areas were also present in female songbirds that do not learn vocalizations and have atrophied cerebral vocal nuclei, and in ring doves that are vocal non-learners and do not have cerebral vocal nuclei. A compilation of previous neural tracing experiments in songbirds suggests that the movement-associated areas are connected in a network that is in parallel with the adjacent vocal learning system. This study is the first global mapping that we are aware for movement-associated areas of the avian cerebrum and it indicates that brain systems that control vocal learning in distantly related birds are directly adjacent to brain systems involved in movement control. Based upon these findings, we propose a motor theory for the origin of vocal learning, this being that the brain areas specialized for vocal learning in vocal learners evolved as a specialization of a pre-existing motor pathway that controls

  8. Molecular mapping of movement-associated areas in the avian brain: a motor theory for vocal learning origin.

    PubMed

    Feenders, Gesa; Liedvogel, Miriam; Rivas, Miriam; Zapka, Manuela; Horita, Haruhito; Hara, Erina; Wada, Kazuhiro; Mouritsen, Henrik; Jarvis, Erich D

    2008-01-01

    Vocal learning is a critical behavioral substrate for spoken human language. It is a rare trait found in three distantly related groups of birds-songbirds, hummingbirds, and parrots. These avian groups have remarkably similar systems of cerebral vocal nuclei for the control of learned vocalizations that are not found in their more closely related vocal non-learning relatives. These findings led to the hypothesis that brain pathways for vocal learning in different groups evolved independently from a common ancestor but under pre-existing constraints. Here, we suggest one constraint, a pre-existing system for movement control. Using behavioral molecular mapping, we discovered that in songbirds, parrots, and hummingbirds, all cerebral vocal learning nuclei are adjacent to discrete brain areas active during limb and body movements. Similar to the relationships between vocal nuclei activation and singing, activation in the adjacent areas correlated with the amount of movement performed and was independent of auditory and visual input. These same movement-associated brain areas were also present in female songbirds that do not learn vocalizations and have atrophied cerebral vocal nuclei, and in ring doves that are vocal non-learners and do not have cerebral vocal nuclei. A compilation of previous neural tracing experiments in songbirds suggests that the movement-associated areas are connected in a network that is in parallel with the adjacent vocal learning system. This study is the first global mapping that we are aware for movement-associated areas of the avian cerebrum and it indicates that brain systems that control vocal learning in distantly related birds are directly adjacent to brain systems involved in movement control. Based upon these findings, we propose a motor theory for the origin of vocal learning, this being that the brain areas specialized for vocal learning in vocal learners evolved as a specialization of a pre-existing motor pathway that controls

  9. Physics in cell biology: on the physics of biopolymers and molecular motors.

    PubMed

    Frey, Erwin

    2002-03-12

    "What is Life?" is the title of a book by Erwin Schrödinger, first published in 1944. This book is a bold attempt to try to understand some of the wonders of life in terms of physics, in particular statistical mechanics. Since the publication of this visionary book, we have seen a revolution in molecular biology complemented by the development of new physical tools like single-molecule spectroscopy. The goal of this article is to highlight some examples where physics can contribute to questions in cell biology. One might hope that through interdisciplinary research one can get closer to answering Schrödinger's fundamental question.

  10. M(o)TOR of aging: MTOR as a universal molecular hypothalamus.

    PubMed

    Blagosklonny, Mikhail V

    2013-07-01

    A recent ground-breaking publication described hypothalamus-driven programmatic aging. As a Russian proverb goes "everything new is well-forgotten old". In 1958, Dilman proposed that aging and its related diseases are programmed by the hypothalamus. This theory, supported by beautiful experiments, remained unnoticed just to be re-discovered recently. Yet, it does not explain all manifestations of aging. And would organism age without hypothalamus? Do sensing pathways such as MTOR (mechanistic Target of Rapamycin) and IKK-beta play a role of a "molecular hypothalamus" in every cell? Are hypothalamus-driven alterations simply a part of quasi-programmed aging manifested by hyperfunction and secondary signal-resistance? Here are some answers.

  11. Taking a molecular motor for a spin: helicase mechanism studied by spin labeling and PELDOR

    PubMed Central

    Constantinescu-Aruxandei, Diana; Petrovic-Stojanovska, Biljana; Schiemann, Olav; Naismith, James H.; White, Malcolm F.

    2016-01-01

    The complex molecular motions central to the functions of helicases have long attracted attention. Protein crystallography has provided transformative insights into these dynamic conformational changes, however important questions about the true nature of helicase configurations during the catalytic cycle remain. Using pulsed EPR (PELDOR or DEER) to measure interdomain distances in solution, we have examined two representative helicases: PcrA from superfamily 1 and XPD from superfamily 2. The data show that PcrA is a dynamic structure with domain movements that correlate with particular functional states, confirming and extending the information gleaned from crystal structures and other techniques. XPD in contrast is shown to be a rigid protein with almost no conformational changes resulting from nucleotide or DNA binding, which is well described by static crystal structures. Our results highlight the complimentary nature of PELDOR to crystallography and the power of its precision in understanding the conformational changes relevant to helicase function. PMID:26657627

  12. Taking a molecular motor for a spin: helicase mechanism studied by spin labeling and PELDOR.

    PubMed

    Constantinescu-Aruxandei, Diana; Petrovic-Stojanovska, Biljana; Schiemann, Olav; Naismith, James H; White, Malcolm F

    2016-01-29

    The complex molecular motions central to the functions of helicases have long attracted attention. Protein crystallography has provided transformative insights into these dynamic conformational changes, however important questions about the true nature of helicase configurations during the catalytic cycle remain. Using pulsed EPR (PELDOR or DEER) to measure interdomain distances in solution, we have examined two representative helicases: PcrA from superfamily 1 and XPD from superfamily 2. The data show that PcrA is a dynamic structure with domain movements that correlate with particular functional states, confirming and extending the information gleaned from crystal structures and other techniques. XPD in contrast is shown to be a rigid protein with almost no conformational changes resulting from nucleotide or DNA binding, which is well described by static crystal structures. Our results highlight the complimentary nature of PELDOR to crystallography and the power of its precision in understanding the conformational changes relevant to helicase function. PMID:26657627

  13. Converting conformational changes to electrostatic energy in molecular motors: The energetics of ATP synthase

    NASA Astrophysics Data System (ADS)

    Trajbl, Marek; Shurki, Avital; Warshel, Arieh

    2003-12-01

    F1-ATPase is the catalytic component of the ATP synthase molecular machine responsible for most of the uphill synthesis of ATP in living systems. The enormous advances in biochemical and structural studies of this machine provide an opportunity for detailed understanding of the nature of its rotary mechanism. However, further quantitative progress in this direction requires development of reliable ways of translating the observed structural changes to the corresponding energies. This requirement is particularly challenging because we are dealing with a large system that couples major structural changes with a chemical process. The present work provides such a structure-function correlation by using the linear response approximation to describe the rotary mechanism. This approach allows one to evaluate the energy of transitions between different conformational states by considering only the changes in the corresponding electrostatic energies of the ligands. The relevant energetics are also obtained by calculating the linear response approximation-based free energies of transferring the ligands from water to the different sites of F1-ATPase in their different conformational states. We also use the empirical valence bond approach to evaluate the actual free-energy profile for the ATP synthesis in the different conformational states of the system. Integrating the information from the different approaches provides a semiquantitative structure-function correlation for F1-ATPase. It is found that the conformational changes are converted to changes in the electrostatic interaction between the protein and its ligands, which drives the ATP synthesis.

  14. Elasticity of a semiflexible filament with a discontinuous tension due to a cross-link or a molecular motor

    NASA Astrophysics Data System (ADS)

    Razbin, Mohammadhosein; Benetatos, Panayotis; Zippelius, Annette

    2016-05-01

    We analyze the stretching elasticity of a wormlike chain with a tension discontinuity resulting from a Hookean spring connecting its backbone to a fixed point. The elasticity of isolated semiflexible filaments has been the subject in a significant body of literature, primarily because of its relevance to the mechanics of biological matter. In real systems, however, these filaments are usually part of supramolecular structures involving cross-linkers or molecular motors, which cause tension discontinuities. Our model is intended as a minimal structural element incorporating such a discontinuity. We obtain analytical results in the weakly bending limit of the filament, concerning its force-extension relation and the response of the two parts in which the filament is divided by the spring. For a small tension discontinuity, the linear response of the filament extension to this discontinuity strongly depends on the external tension. For large external tension f , the spring force contributes a subdominant correction ˜1 /f3 /2 to the well-known ˜1 /√{f } -dependence of the end-to-end extension.

  15. fMRI as a molecular imaging procedure for the functional reorganization of motor systems in chronic stroke.

    PubMed

    Lazaridou, Asimina; Astrakas, Loukas; Mintzopoulos, Dionyssios; Khanchiceh, Azadeh; Singhal, Aneesh; Moskowitz, Michael; Rosen, Bruce; Tzika, Aria

    2013-09-01

    Previous brain imaging studies suggest that stroke alters functional connectivity in motor execution networks. Moreover, current understanding of brain plasticity has led to new approaches in stroke rehabilitation. Recent studies showed a significant role of effective coupling of neuronal activity in the SMA (supplementary motor area) and M1 (primary motor cortex) network for motor outcome in patients after stroke. After a subcortical stroke, functional magnetic resonance imaging (fMRI) during movement reveals cortical reorganization that is associated with the recovery of function. The aim of the present study was to explore connectivity alterations within the motor-related areas combining motor fMRI with a novel MR-compatible hand-induced robotic device (MR_CHIROD) training. Patients completed training at home and underwent serial MR evaluation at baseline and after 8 weeks of training. Training at home consisted of squeezing a gel exercise ball with the paretic hand at ~75% of maximum strength for 1 h/day, 3 days/week. The fMRI analysis revealed alterations in M1, SMA, PMC (premotor cortex) and Cer (cerebellum) in both stroke patients and healthy controls after the training. Findings of the present study suggest that enhancement of SMA activity could benefit M1 dysfunction in stroke survivors. These results also indicate that connectivity alterations between motor areas might assist the counterbalance of a functionally abnormal M1 in chronic stroke survivors and possibly other patients with motor dysfunction.

  16. Controlled Directional Motions of Molecular Vehicles, Rotors, and Motors: From Metallic to Silicon Surfaces, a Strategy to Operate at Higher Temperatures.

    PubMed

    Chérioux, Frédéric; Galangau, Olivier; Palmino, Frank; Rapenne, Gwénaël

    2016-06-17

    In the last decade, many nanomachines with controlled molecular motions have been studied, mainly on metallic surfaces, which are easy to obtain very clean, and are stable over months. However, the studies of mechanical properties of nanomachines are mainly performed at very low temperatures, usually between 5 and 80 K, which prevents any kind of applications. In this Minireview, we will present our strategy to operate at higher temperatures, in particular through the use of semiconducting silicon surfaces. We also review our best achievements in the field through some examples of rotating molecular machines that have been designed, synthesized, and studied in our groups. On metallic surfaces, the nanovehicles are molecules with two or four triptycenes as wheels and the molecular motor is built around a ruthenium organometallic center with a piano-stool geometry and peripheric ferrocenyl groups. On semiconducting silicon surfaces, vehicles are also made from triptycene fragments and the rotor is a pentaphenylbenzene molecule.

  17. Pigment granule translocation in red ovarian chromatophores from the palaemonid shrimp Macrobrachium olfersi (Weigmann, 1836): functional roles for the cytoskeleton and its molecular motors.

    PubMed

    Milograna, Sarah Ribeiro; Ribeiro, Márcia Regina; Baqui, Munira Muhammad Abdel; McNamara, John Campbell

    2014-12-01

    The binding of red pigment concentrating hormone (RPCH) to membrane receptors in crustacean chromatophores triggers Ca²⁺/cGMP signaling cascades that activate cytoskeletal motors, driving pigment granule translocation. We investigate the distributions of microfilaments and microtubules and their associated molecular motors, myosin and dynein, by confocal and transmission electron microscopy, evaluating a functional role for the cytoskeleton in pigment translocation using inhibitors of polymer turnover and motor activity in vitro. Microtubules occupy the chromatophore cell extensions whether the pigment granules are aggregated or dispersed. The inhibition of microtubule turnover by taxol induces pigment aggregation and inhibits re-dispersion. Phalloidin-FITC actin labeling, together with tannic acid fixation and ultrastructural analysis, reveals that microfilaments form networks associated with the pigment granules. Actin polymerization induced by jasplaquinolide strongly inhibits RPCH-induced aggregation, causes spontaneous pigment dispersion, and inhibits pigment re-dispersion. Inhibition of actin polymerization by latrunculin-A completely impedes pigment aggregation and re-dispersion. Confocal immunocytochemistry shows that non-muscle myosin II (NMMII) co-localizes mainly with pigment granules while blebbistatin inhibition of NMMII strongly reduces the RPCH response, also inducing spontaneous pigment dispersion. Myosin II and dynein also co-localize with the pigment granules. Inhibition of dynein ATPase by erythro-9-(2-hydroxy-3-nonyl) adenine induces aggregation, inhibits RPCH-triggered aggregation, and inhibits re-dispersion. Granule aggregation and dispersion depend mainly on microfilament integrity although microtubules may be involved. Both cytoskeletal polymers are functional only when subunit turnover is active. Myosin and dynein may be the molecular motors that drive pigment aggregation. These mechanisms of granule translocation in crustacean

  18. Elements in nucleotide sensing and hydrolysis of the AAA+ disaggregation machine ClpB: a structure-based mechanistic dissection of a molecular motor

    SciTech Connect

    Zeymer, Cathleen Barends, Thomas R. M.; Werbeck, Nicolas D.; Schlichting, Ilme; Reinstein, Jochen

    2014-02-01

    High-resolution crystal structures together with mutational analysis and transient kinetics experiments were utilized to understand nucleotide sensing and the regulation of the ATPase cycle in an AAA+ molecular motor. ATPases of the AAA+ superfamily are large oligomeric molecular machines that remodel their substrates by converting the energy from ATP hydrolysis into mechanical force. This study focuses on the molecular chaperone ClpB, the bacterial homologue of Hsp104, which reactivates aggregated proteins under cellular stress conditions. Based on high-resolution crystal structures in different nucleotide states, mutational analysis and nucleotide-binding kinetics experiments, the ATPase cycle of the C-terminal nucleotide-binding domain (NBD2), one of the motor subunits of this AAA+ disaggregation machine, is dissected mechanistically. The results provide insights into nucleotide sensing, explaining how the conserved sensor 2 motif contributes to the discrimination between ADP and ATP binding. Furthermore, the role of a conserved active-site arginine (Arg621), which controls binding of the essential Mg{sup 2+} ion, is described. Finally, a hypothesis is presented as to how the ATPase activity is regulated by a conformational switch that involves the essential Walker A lysine. In the proposed model, an unusual side-chain conformation of this highly conserved residue stabilizes a catalytically inactive state, thereby avoiding unnecessary ATP hydrolysis.

  19. A Reconsideration of the Link between the Energetics of Water and of ATP Hydrolysis Energy in the Power Strokes of Molecular Motors in Protein Structures

    PubMed Central

    Widdas, Wilfred F.

    2008-01-01

    Mechanical energy from oxygen metabolism by mammalian tissues has been studied since 1837. The production of heat by mechanical work was studied by Fick in about 1860. Prior to Fick’s work, energetics were revised by Joule’s experiments which founded the First Law of Thermodynamics. Fenn in 1923/24 found that frog muscle contractions generated extra heat proportional to the amount of work done in shortening the muscle. This was fully consistent with the Joule, Helmholtz concept used for the First Law of Thermodynamics. The link between the energetics of water and ATP hydrolysis in molecular motors is recommended for reconsideration. PMID:19325829

  20. Optimized efficiency and figure of merit for a tight-coupling molecular motor: their bounds and phase diagrams

    NASA Astrophysics Data System (ADS)

    Bekele, Mulugeta; Nuru, Tadle

    2014-03-01

    We consider a model translational motor that consumes one fuel molecule against a given amount of load at the same physiological temperature. Taking the chemical step to be tightlly coupled to the mechanical step, we derive thermodynamic quantities such as input and output power as well as power efficiency. Using optimization criteria of energy utilization, we determine the motor's optimized efficiency as well as its figure of merit. Bounds and phase daigrams of these quantities are studied. International Science Program, Uppsala University, Uppsala, Sweden.

  1. Functional interactions of VirB11 traffic ATPases with VirB4 and VirD4 molecular motors in type IV secretion systems.

    PubMed

    Ripoll-Rozada, Jorge; Zunzunegui, Sandra; de la Cruz, Fernando; Arechaga, Ignacio; Cabezón, Elena

    2013-09-01

    Pilus biogenesis and substrate transport by type IV secretion systems require energy, which is provided by three molecular motors localized at the base of the secretion channel. One of these motors, VirB11, belongs to the superfamily of traffic ATPases, which includes members of the type II secretion system and the type IV pilus and archaeal flagellar assembly apparatus. Here, we report the functional interactions between TrwD, the VirB11 homolog of the conjugative plasmid R388, and TrwK and TrwB, the motors involved in pilus biogenesis and DNA transport, respectively. Although these interactions remained standing upon replacement of the traffic ATPase by a homolog from a phylogenetically related conjugative system, namely, TraG of plasmid pKM101, this homolog could not replace the TrwD function for DNA transfer. This result suggests that VirB11 works as a switch between pilus biogenesis and DNA transport and reinforces a mechanistic model in which VirB11 proteins act as traffic ATPases by regulating both events in type IV secretion systems.

  2. Different pathways of molecular pathophysiology underlie cognitive and motor tauopathy phenotypes in transgenic models for Alzheimer's disease and frontotemporal lobar degeneration.

    PubMed

    Melis, V; Zabke, C; Stamer, K; Magbagbeolu, M; Schwab, K; Marschall, P; Veh, R W; Bachmann, S; Deiana, S; Moreau, P-H; Davidson, K; Harrington, K A; Rickard, J E; Horsley, D; Garman, R; Mazurkiewicz, M; Niewiadomska, G; Wischik, C M; Harrington, C R; Riedel, G; Theuring, F

    2015-06-01

    A poorly understood feature of the tauopathies is their very different clinical presentations. The frontotemporal lobar degeneration (FTLD) spectrum is dominated by motor and emotional/psychiatric abnormalities, whereas cognitive and memory deficits are prominent in the early stages of Alzheimer's disease (AD). We report two novel mouse models overexpressing different human tau protein constructs. One is a full-length tau carrying a double mutation [P301S/G335D; line 66 (L66)] and the second is a truncated 3-repeat tau fragment which constitutes the bulk of the PHF core in AD corresponding to residues 296-390 fused with a signal sequence targeting it to the endoplasmic reticulum membrane (line 1; L1). L66 has abundant tau pathology widely distributed throughout the brain, with particularly high counts of affected neurons in hippocampus and entorhinal cortex. The pathology is neuroanatomically static and declines with age. Behaviourally, the model is devoid of a higher cognitive phenotype but presents with sensorimotor impairments and motor learning phenotypes. L1 displays a much weaker histopathological phenotype, but shows evidence of neuroanatomical spread and amplification with age that resembles the Braak staging of AD. Behaviourally, the model has minimal motor deficits but shows severe cognitive impairments affecting particularly the rodent equivalent of episodic memory which progresses with advancing age. In both models, tau aggregation can be dissociated from abnormal phosphorylation. The two models make possible the demonstration of two distinct but nevertheless convergent pathways of tau molecular pathogenesis. L1 appears to be useful for modelling the cognitive impairment of AD, whereas L66 appears to be more useful for modelling the motor features of the FTLD spectrum. Differences in clinical presentation of AD-like and FTLD syndromes are therefore likely to be inherent to the respective underlying tauopathy, and are not dependent on presence or absence

  3. Application of molecular modeling to analysis of inhibition of kinesin motor proteins of the BimC subfamily by monastrol and related compounds.

    PubMed

    Bevan, David R; Garst, James F; Osborne, Caroline K; Sims, Angela M

    2005-11-01

    Application of molecular modeling approaches has potential to contribute to rational drug design. These approaches may be especially useful when attempting to elucidate the structural features associated with novel drug targets. In this study, molecular docking and molecular dynamics were applied to studies of inhibition of the human motor protein denoted HsEg5 and other homologues in the BimC subfamily. These proteins are essential for mitosis, so compounds that inhibit their activity may have potential as anticancer therapeutics. The discovery of a small-molecule cell-permeable inhibitor, monastrol, has stimulated research in this area. Interestingly, monastrol is reported to inhibit the human and Xenopus forms of Eg5, but not those from Drosophila and Aspergillus. In this study, homology modeling was used to generate models of the Xenopus, Drosophila, and Aspergillus homologues, using the crystal structure of the human protein in complex with monastrol as a template. A series of known inhibitors was docked into each of the homologues, and the differences in binding energies were consistent with reported experimental data. Molecular dynamics revealed significant changes in the structure of the Aspergillus homologue that may contribute to its relative insensitivity to monastrol and related compounds. PMID:17191952

  4. The role of molecular motors in the mechanics of active gels and the effects of inertia, hydrodynamic interaction and compressibility in passive microrheology

    NASA Astrophysics Data System (ADS)

    Uribe, Andres Cordoba

    The mechanical properties of soft biological materials are essential to their physiological function and cannot easily be duplicated by synthetic materials. The study of the mechanical properties of biological materials has lead to the development of new rheological characterization techniques. In the technique called passive microbead rheology, the positional autocorrelation function of a micron-sized bead embedded in a viscoelastic fluid is used to infer the dynamic modulus of the fluid. Single particle microrheology is limited to fluids were the microstructure is much smaller than the size of the probe bead. To overcome this limitation in two-bead microrheology the cross-correlated thermal motion of pairs of tracer particles is used to determine the dynamic modulus. Here we present a time-domain data analysis methodology and generalized Brownian dynamics simulations to examine the effects of inertia, hydrodynamic interaction, compressibility and non-conservative forces in passive microrheology. A type of biological material that has proven specially challenging to characterize are active gels. They are formed by semiflexible polymer filaments driven by motor proteins that convert chemical energy from the hydrolysis of adenosine triphosphate (ATP) to mechanical work and motion. Active gels perform essential functions in living tissue. Here we introduce a single-chain mean-field model to describe the mechanical properties of active gels. We model the semiflexible filaments as bead-spring chains and the molecular motors are accounted for by using a mean-field approach. The level of description of the model includes the end-to-end length and attachment state of the filaments, and the motor-generated forces, as stochastic state variables which evolve according to a proposed differential Chapman-Kolmogorov equation. The model allows accounting for physics that are not available in models that have been postulated on coarser levels of description. Moreover it allows

  5. On the Functional Role of the {epsilon} Subunit of the Molecular Motor F-Adenosine Triphosphatase in Lipid Membranes of Cells

    SciTech Connect

    Pikin, S. A. Loginov, E. B.

    2010-11-15

    The effect of the e subunit of the molecular motor F-adenosine triphosphatase, which is built into the lipid membrane of a cell, on the dynamics of the rotor ({gamma} subunit), with which this subunit is bound, has been qualitatively considered. It is shown that its structural and conformational features arising during the hydrolysis of 'fuel' adenosine triphosphate (ATP) molecules can be explained by the change in the potential within which the rotor is located. As the numerical calculations showed, at a low ATP concentration, the hydrolysis is accompanied by an unstable rotation of the {gamma} subunit and the related proton current. A model is proposed to describe the interaction between the {epsilon} subunit and the lipid order fluctuations caused by the membrane transition to the gel state. It is demonstrated that the rotor rotations become inhomogeneous when this interaction is enhanced with a decrease in the cell temperature.

  6. Tuning Multiple Motor Travel Via Single Motor Velocity

    PubMed Central

    Xu, Jing; Shu, Zhanyong; King, Stephen J.; Gross, Steven P.

    2012-01-01

    Microtubule-based molecular motors often work in small groups to transport cargos in cells. A key question in understanding transport (and its regulation in vivo) is to identify the sensitivity of multiple-motor-based motion to various single molecule properties. Whereas both single-motor travel distance and microtubule binding rate have been demonstrated to contribute to cargo travel, the role of single-motor velocity is yet to be explored. Here, we recast a previous theoretical study, and make explicit a potential contribution of velocity to cargo travel. We test this possibility experimentally, and demonstrate a strong negative correlation between single-motor velocity and cargo travel for transport driven by two motors. Our study thus discovers a previously unappreciated role of single-motor velocity in regulating multiple-motor transport. PMID:22672518

  7. Chemistry: No turning back for motorized molecules

    NASA Astrophysics Data System (ADS)

    Clayden, Jonathan

    2016-06-01

    Two molecular motors have been developed that use chemical energy to drive rotational motion in a single direction. The findings bring the prospect of devices powered by such motors a tantalizing step closer. See Letter p.235

  8. Lack of serotonin1B receptor expression leads to age-related motor dysfunction, early onset of brain molecular aging and reduced longevity

    PubMed Central

    Sibille, E; Su, J; Leman, S; Le Guisquet, AM; Ibarguen-Vargas, Y; Joeyen-Waldorf, J; Glorioso, C; Tseng, GC; Pezzone, M; Hen, R; Belzung, C

    2008-01-01

    Normal aging of the brain differs from pathological conditions and is associated with increased risk for psychiatric and neurological disorders. In addition to its role in the etiology and treatment of mood disorders, altered serotonin (5-HT) signaling is considered a contributing factor to aging; however, no causative role has been identified in aging. We hypothesized that a deregulation of the 5-HT system would reveal its contribution to age-related processes and investigated behavioral and molecular changes throughout adult life in mice lacking the regulatory presynaptic 5-HT1B receptor (5-HT1BR), a candidate gene for 5-HT-mediated age-related functions. We show that the lack of 5-HT1BR (Htr1bKO mice) induced an early age-related motor decline and resulted in decreased longevity. Analysis of life-long transcriptome changes revealed an early and global shift of the gene expression signature of aging in the brain of Htr1bKO mice. Moreover, molecular changes reached an apparent maximum effect at 18-months in Htr1bKO mice, corresponding to the onset of early death in that group. A comparative analysis with our previous characterization of aging in the human brain revealed a phylogenetic conservation of age-effect from mice to humans, and confirmed the early onset of molecular aging in Htr1bKO mice. Potential mechanisms appear independent of known central mechanisms (Bdnf, inflammation), but may include interactions with previously identified age-related systems (IGF-1, sirtuins). In summary, our findings suggest that the onset of age-related events can be influenced by altered 5-HT function, thus identifying 5-HT as a modulator of brain aging, and suggesting age-related consequences to chronic manipulation of 5-HT. PMID:17420766

  9. Molecular, Physiological, and Motor Performance Defects in DMSXL Mice Carrying >1,000 CTG Repeats from the Human DM1 Locus

    PubMed Central

    Huguet, Aline; Medja, Fadia; Nicole, Annie; Vignaud, Alban; Guiraud-Dogan, Céline; Ferry, Arnaud; Decostre, Valérie; Hogrel, Jean-Yves; Metzger, Friedrich; Hoeflich, Andreas; Baraibar, Martin; Gomes-Pereira, Mário; Puymirat, Jack; Bassez, Guillaume; Furling, Denis; Munnich, Arnold; Gourdon, Geneviève

    2012-01-01

    Myotonic dystrophy type 1 (DM1) is caused by an unstable CTG repeat expansion in the 3′UTR of the DM protein kinase (DMPK) gene. DMPK transcripts carrying CUG expansions form nuclear foci and affect splicing regulation of various RNA transcripts. Furthermore, bidirectional transcription over the DMPK gene and non-conventional RNA translation of repeated transcripts have been described in DM1. It is clear now that this disease may involve multiple pathogenic pathways including changes in gene expression, RNA stability and splicing regulation, protein translation, and micro–RNA metabolism. We previously generated transgenic mice with 45-kb of the DM1 locus and >300 CTG repeats (DM300 mice). After successive breeding and a high level of CTG repeat instability, we obtained transgenic mice carrying >1,000 CTG (DMSXL mice). Here we described for the first time the expression pattern of the DMPK sense transcripts in DMSXL and human tissues. Interestingly, we also demonstrate that DMPK antisense transcripts are expressed in various DMSXL and human tissues, and that both sense and antisense transcripts accumulate in independent nuclear foci that do not co-localize together. Molecular features of DM1-associated RNA toxicity in DMSXL mice (such as foci accumulation and mild missplicing), were associated with high mortality, growth retardation, and muscle defects (abnormal histopathology, reduced muscle strength, and lower motor performances). We have found that lower levels of IGFBP-3 may contribute to DMSXL growth retardation, while increased proteasome activity may affect muscle function. These data demonstrate that the human DM1 locus carrying very large expansions induced a variety of molecular and physiological defects in transgenic mice, reflecting DM1 to a certain extent. As a result, DMSXL mice provide an animal tool to decipher various aspects of the disease mechanisms. In addition, these mice can be used to test the preclinical impact of systemic therapeutic

  10. The Autophagy Receptor TAX1BP1 and the Molecular Motor Myosin VI Are Required for Clearance of Salmonella Typhimurium by Autophagy.

    PubMed

    Tumbarello, David A; Manna, Paul T; Allen, Mark; Bycroft, Mark; Arden, Susan D; Kendrick-Jones, John; Buss, Folma

    2015-10-01

    Autophagy plays a key role during Salmonella infection, by eliminating these pathogens following escape into the cytosol. In this process, selective autophagy receptors, including the myosin VI adaptor proteins optineurin and NDP52, have been shown to recognize cytosolic pathogens. Here, we demonstrate that myosin VI and TAX1BP1 are recruited to ubiquitylated Salmonella and play a key role in xenophagy. The absence of TAX1BP1 causes an accumulation of ubiquitin-positive Salmonella, whereas loss of myosin VI leads to an increase in ubiquitylated and LC3-positive bacteria. Our structural studies demonstrate that the ubiquitin-binding site of TAX1BP1 overlaps with the myosin VI binding site and point mutations in the TAX1BP1 zinc finger domains that affect ubiquitin binding also ablate binding to myosin VI. This mutually exclusive binding and the association of TAX1BP1 with LC3 on the outer limiting membrane of autophagosomes may suggest a molecular mechanism for recruitment of this motor to autophagosomes. The predominant role of TAX1BP1, a paralogue of NDP52, in xenophagy is supported by our evolutionary analysis, which demonstrates that functionally intact NDP52 is missing in Xenopus and mice, whereas TAX1BP1 is expressed in all vertebrates analysed. In summary, this work highlights the importance of TAX1BP1 as a novel autophagy receptor in myosin VI-mediated xenophagy. Our study identifies essential new machinery for the autophagy-dependent clearance of Salmonella typhimurium and suggests modulation of myosin VI motor activity as a potential therapeutic target in cellular immunity.

  11. Motor Starters

    NASA Astrophysics Data System (ADS)

    1986-01-01

    The power factor controller (PFC) was invented by a NASA engineer. It matches voltage with a motor's actual need by sensing shifts in the relationship between voltage and current flow. With the device, power can be trimmed as much as 65%. Intellinet adopted this technology and designed "soft start" and "load-responsive" control modes to start engines gradually and recycle voltage without reducing motor speed. Other features are lower motor heat and faster fault identification.

  12. Stepper motor

    NASA Technical Reports Server (NTRS)

    Dekramer, Cornelis

    1994-01-01

    The purpose of this document is to describe the more commonly used permanent magnet stepper motors for spaceflight. It will discuss the mechanical and electrical aspects of the devices, their torque behavior, those parameters which need to be controlled and measured, and test methods to be employed. It will also discuss torque margins, compare these to the existing margin requirements, and determine the applicability of these requirements. Finally it will attempt to generate a set of requirements which will be used in any stepper motor procurement and will fully characterize the stepper motor behavior in a consistent and repeatable fashion.

  13. Hybrid survival motor neuron genes in patients with autosomal recessive spinal muscular atrophy: New insights into molecular mechanisms responsible for the disease

    SciTech Connect

    Hahnen, E.; Schoenling, J.; Zerres, K.

    1996-11-01

    Spinal muscular atrophy (SMA) is a frequent autosomal recessive neurodegenerative disorder leading to weakness and atrophy of voluntary muscles. The survival motor-neuron gene (SMN), a strong candidate for SMA, is present in two highly homologous copies (telSMN and cenSMN) within the SMA region. Only five nucleotide differences within the region between intron 6 and exon 8 distinguish these homologues. Independent of the severity of the disease, 90%-98% of all SMA patients carry homozygous deletions in telSMN, affecting either exon 7 or both exons 7 and 8. We present the molecular analysis of 42 SMA patients who carry homozygous deletions of telSMN exon 7 but not of exon 8. The question arises whether in these cases the telSMN is truncated upstream of exon 8 or whether hybrid SMN genes exist that are composed of centromeric and telomeric sequences. By a simple PCR-based assay we demonstrate that in each case the remaining telSMN exon 8 is part of a hybrid SMN gene. Sequencing of cloned hybrid SMN genes from seven patients revealed the same composition in all but two patients: the base-pair differences in introns 6 and 7 and exon 7 are of centromeric origin whereas exon 8 is of telomeric origin. Nonetheless, haplotype analysis with polymorphic multicopy markers, Ag1-CA and C212, localized at the 5{prime} end of the SMN genes, suggests different mechanisms of occurrence, unequal rearrangements, and gene conversion involving both copies of the SMN genes. In approximately half of all patients, we identified a consensus haplotype, suggesting a common origin. Interestingly, we identified a putative recombination hot spot represented by recombination-simulating elements (TGGGG and TGAGGT) in exon 8 that is homologous to the human deletion-hot spot consensus sequence in the immunoglobulin switch region, the {alpha}-globin cluster, and the polymerase {alpha} arrest sites. This may explain why independent hybrid SMN genes show identical sequences. 35 refs., 4 figs., 1 tab.

  14. Advanced Motors

    SciTech Connect

    Knoth, Edward A; Chelluri, Bhanumathi; Schumaker, Edward J

    2012-12-14

    vProject Summary Transportation energy usage is predicted to increase substantially by 2020. Hybrid vehicles and fuel cell powered vehicles are destined to become more prominent as fuel prices rise with the demand. Hybrid and fuel cell vehicle platforms are both dependent on high performance electric motors. Electric motors for transportation duty will require sizeable low-speed torque to accelerate the vehicle. As motor speed increases, the torque requirement decreases which results in a nearly constant power motor output. Interior permanent magnet synchronous motors (IPMSM) are well suited for this duty. , , These rotor geometries are configured in straight lines and semi circular arc shapes. These designs are of limited configurations because of the lack of availability of permanent magnets of any other shapes at present. We propose to fabricate rotors via a novel processing approach where we start with magnet powders and compact them into a net shape rotor in a single step. Using this approach, widely different rotor designs can be implemented for efficiency. The current limitation on magnet shape and thickness will be eliminated. This is accomplished by co-filling magnet and soft iron powders at specified locations in intricate shapes using specially designed dies and automatic powder filling station. The process fundamentals for accomplishing occurred under a previous Applied Technology Program titled, Motors and Generators for the 21st Century. New efficient motor designs that are not currently possible (or cost prohibitive) can be accomplished by this approach. Such an approach to motor fabrication opens up a new dimension in motor design. Feasibility Results We were able to optimize a IPMSM rotor to take advantage of the powder co-filling and DMC compaction processing methods. The minimum low speed torque requirement of 5 N-m can be met through an optimized design with magnet material having a Br capability of 0.2 T. This level of magnetic performance can

  15. Motor neglect.

    PubMed Central

    Laplane, D; Degos, J D

    1983-01-01

    Motor neglect is characterised by an underutilisation of one side, without defects of strength, reflexes or sensibility. Twenty cases of frontal, parietal and thalamic lesions causing motor neglect, but all without sensory neglect, are reported. It is proposed that the cerebral structures involved in motor neglect are the same as those for sensory neglect and for the preparation of movement. As in sensory neglect, the multiplicity of the structures concerned suggests that this interconnection is necessary to maintain a sufficient level of activity. Predominance of left sided neglect by right sided lesions suggests that the left hemisphere is dominant for deliberate activity; hemispheric dominance could be applied to sensory neglect where conscious awareness would play the role of deliberate activity. PMID:6842219

  16. Motor learning.

    PubMed

    Wolpert, Daniel M; Flanagan, J Randall

    2010-06-01

    Although learning a motor skill, such as a tennis stroke, feels like a unitary experience, researchers who study motor control and learning break the processes involved into a number of interacting components. These components can be organized into four main groups. First, skilled performance requires the effective and efficient gathering of sensory information, such as deciding where and when to direct one's gaze around the court, and thus an important component of skill acquisition involves learning how best to extract task-relevant information. Second, the performer must learn key features of the task such as the geometry and mechanics of the tennis racket and ball, the properties of the court surface, and how the wind affects the ball's flight. Third, the player needs to set up different classes of control that include predictive and reactive control mechanisms that generate appropriate motor commands to achieve the task goals, as well as compliance control that specifies, for example, the stiffness with which the arm holds the racket. Finally, the successful performer can learn higher-level skills such as anticipating and countering the opponent's strategy and making effective decisions about shot selection. In this Primer we shall consider these components of motor learning using as an example how we learn to play tennis. PMID:20541489

  17. Motor Controllers

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Kollmorgen Corporation's Mermaid II two person submersible is propeller-driven by a system of five DC brushless motors with new electronic controllers that originated in work performed in a NASA/DOE project managed by Lewis Research Center. A key feature of the system is electric commutation rather than mechanical commutation for converting AC current to DC.

  18. Motor learning.

    PubMed

    Wolpert, Daniel M; Flanagan, J Randall

    2010-06-01

    Although learning a motor skill, such as a tennis stroke, feels like a unitary experience, researchers who study motor control and learning break the processes involved into a number of interacting components. These components can be organized into four main groups. First, skilled performance requires the effective and efficient gathering of sensory information, such as deciding where and when to direct one's gaze around the court, and thus an important component of skill acquisition involves learning how best to extract task-relevant information. Second, the performer must learn key features of the task such as the geometry and mechanics of the tennis racket and ball, the properties of the court surface, and how the wind affects the ball's flight. Third, the player needs to set up different classes of control that include predictive and reactive control mechanisms that generate appropriate motor commands to achieve the task goals, as well as compliance control that specifies, for example, the stiffness with which the arm holds the racket. Finally, the successful performer can learn higher-level skills such as anticipating and countering the opponent's strategy and making effective decisions about shot selection. In this Primer we shall consider these components of motor learning using as an example how we learn to play tennis.

  19. Therma motor

    DOEpatents

    Kandarian, R.

    The disclosure is directed to a thermal motor utilizing two tapered prestressed parallel adjacent cylinders lengthwise disposed about one third in a coolant. Heat is applied to contacting portions of the cylinders outside the coolant to cause them to deform and turn. Heat sources such as industrial waste heat, geothermal hot water, solar radiation, etc. can be used.

  20. Motor Neuron Diseases

    MedlinePlus

    ... called upper motor neurons ) are transmitted to nerve cells in the brain stem and spinal cord (called lower motor neurons ) and from them to particular muscles. Upper motor neurons direct the lower motor neurons ...

  1. Motor Neuron Diseases

    MedlinePlus

    ... Enhancing Diversity Find People About NINDS NINDS Motor Neuron Diseases Information Page Condensed from Motor Neuron Diseases ... and Information Publicaciones en Español What are Motor Neuron Diseases? The motor neuron diseases (MNDs) are a ...

  2. Locomotion of chemically powered autonomous nanowire motors

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Li, Longqiu; Li, Tianlong; Zhang, Guangyu; Sun, Qian

    2015-08-01

    Physical insights on the hydrodynamics and locomotion of self-propelled nanowire motor under nonequilibrium steady state are investigated using finite element method in accordance with hybrid molecular dynamics/multiparticle collision dynamics and rigid body dynamics. Nanowire motor is discretized into finite segments, and forces of solvent molecule acting on the motor are assumed to be the sum of forces acting on all segments of the motor. We show that the locomotion of nanowire motor is mainly determined by the imbalance forces acting on the catalytic and noncatalytic segments. The average velocity along the axis increases significantly as a function of time prior to reaching equilibrium. The length of nanowire motor shows negligible effect on the velocity of the motor. Preliminary experimental results are provided to validate the current model.

  3. Kinesin family 17 (osmotic avoidance abnormal-3) is dispensable for photoreceptor morphology and function.

    PubMed

    Jiang, Li; Tam, Beatrice M; Ying, Guoxing; Wu, Sen; Hauswirth, William W; Frederick, Jeanne M; Moritz, Orson L; Baehr, Wolfgang

    2015-12-01

    In Caenorhabditis elegans, homodimeric [kinesin family (KIF) 17, osmotic avoidance abnormal-3 (OSM-3)] and heterotrimeric (KIF3) kinesin-2 motors are required to establish sensory cilia by intraflagellar transport (IFT) where KIF3 and KIF17 cooperate to build the axoneme core and KIF17 builds the distal segments. However, the function of KIF17 in vertebrates is unresolved. We expressed full-length and motorless KIF17 constructs in mouse rod photoreceptors using adeno-associated virus in Xenopus laevis rod photoreceptors using a transgene and in ciliated IMCD3 cells. We found that tagged KIF17 localized along the rod outer segment axoneme when expressed in mouse and X. laevis photoreceptors, whereas KIF3A was restricted to the proximal axoneme. Motorless KIF3A and KIF17 mutants caused photoreceptor degeneration, likely through dominant negative effects on IFT. KIF17 mutant lacking the motor domain translocated to nuclei after exposure of a C-terminal nuclear localization signal. Germ-line deletion of Kif17 in mouse did not affect photoreceptor function. A rod-specific Kif3/Kif17 double knockout mouse demonstrated that KIF17 and KIF3 do not act synergistically and did not prevent rhodopsin trafficking to rod outer segments. In summary, the nematode model of KIF3/KIF17 cooperation apparently does not apply to mouse photoreceptors in which the photosensory cilium is built exclusively by KIF3. PMID:26229057

  4. The heterotrimeric kinesin-2 complex interacts with and regulates GLI protein function

    PubMed Central

    Carpenter, Brandon S.; Barry, Renee L.; Verhey, Kristen J.; Allen, Benjamin L.

    2015-01-01

    ABSTRACT GLI transport to the primary cilium and nucleus is required for proper Hedgehog (HH) signaling; however, the mechanisms that mediate these trafficking events are poorly understood. Kinesin-2 motor proteins regulate ciliary transport of cargo, yet their role in GLI protein function remains unexplored. To examine a role for the heterotrimeric KIF3A–KIF3B–KAP3 kinesin-2 motor complex in regulating GLI activity, we performed a series of structure-function analyses using biochemical, cell signaling and in vivo approaches that define novel specific interactions between GLI proteins and two components of this complex, KAP3 and KIF3A. We find that all three mammalian GLI proteins interact with KAP3 and we map specific interaction sites in both proteins. Furthermore, we find that GLI proteins interact selectively with KIF3A, but not KIF3B, and that GLI interacts synergistically with KAP3 and KIF3A. Using a combination of cell signaling assays and chicken in ovo electroporation, we demonstrate that KAP3 interactions restrict GLI activator function but not GLI repressor function. These data suggest that GLI interactions with KIF3A–KIF3B–KAP3 complexes are essential for proper GLI transcriptional activity. PMID:25588831

  5. The Molecular Motor KIF1A Transports the TrkA Neurotrophin Receptor and Is Essential for Sensory Neuron Survival and Function.

    PubMed

    Tanaka, Yosuke; Niwa, Shinsuke; Dong, Ming; Farkhondeh, Atena; Wang, Li; Zhou, Ruyun; Hirokawa, Nobutaka

    2016-06-15

    KIF1A is a major axonal transport motor protein, but its functional significance remains elusive. Here we show that KIF1A-haploinsufficient mice developed sensory neuropathy. We found progressive loss of TrkA(+) sensory neurons in Kif1a(+/-) dorsal root ganglia (DRGs). Moreover, axonal transport of TrkA was significantly disrupted in Kif1a(+/-) neurons. Live imaging and immunoprecipitation assays revealed that KIF1A bound to TrkA-containing vesicles through the adaptor GTP-Rab3, suggesting that TrkA is a cargo of the KIF1A motor. Physiological measurements revealed a weaker capsaicin response in Kif1a(+/-) DRG neurons. Moreover, these neurons were hyposensitive to nerve growth factor, which could explain the reduced neuronal survival and the functional deficiency of the pain receptor TRPV1. Because phosphatidylinositol 3-kinase (PI3K) signaling significantly rescued these phenotypes and also increased Kif1a mRNA, we propose that KIF1A is essential for the survival and function of sensory neurons because of the TrkA transport and its synergistic support of the NGF/TrkA/PI3K signaling pathway.

  6. Siphon motor

    SciTech Connect

    Bunn, C.H.

    1980-01-01

    A siphon motor comprises the combination of siphon means and generating means for generating electrical energy from a water source located below the generating means and a water discharge at a lower level than the water source. Water rises by siphonic action upward from the water source to a sealed working region maintained under partial vacuum, and descends to the water discharge. The working region contains the generating means. The system has particular utility as a source of power generation in remote locations having a water table within about 30 feet of the ground.

  7. Motor neurons and the sense of place.

    PubMed

    Jessell, Thomas M; Sürmeli, Gülşen; Kelly, John S

    2011-11-01

    Seventy years ago George Romanes began to document the anatomical organization of the spinal motor system, uncovering a multilayered topographic plan that links the clustering and settling position of motor neurons to the spatial arrangement and biomechanical features of limb muscles. To this day, these findings have provided a structural foundation for analysis of the neural control of movement and serve as a guide for studies to explore mechanisms that direct the wiring of spinal motor circuits. In this brief essay we outline the core of Romanes's findings and place them in the context of recent studies that begin to provide insight into molecular programs that assign motor pool position and to resolve how motor neuron position shapes circuit assembly. Romanes's findings reveal how and why neuronal positioning contributes to sensory-motor connectivity and may have relevance to circuit organization in other regions of the central nervous system.

  8. Multifocal Motor Neuropathy

    MedlinePlus

    ... Diversity Find People About NINDS NINDS Multifocal Motor Neuropathy Information Page Table of Contents (click to jump ... done? Clinical Trials Organizations What is Multifocal Motor Neuropathy? Multifocal motor neuropathy is a progressive muscle disorder ...

  9. Neuroplasticity subserving motor skill learning

    PubMed Central

    Dayan, Eran; Cohen, Leonardo G.

    2011-01-01

    Summary Recent years have seen significant progress in our understanding of the neural substrates of motor skill learning. Advances in neuroimaging provide new insight into functional reorganization associated with the acquisition, consolidation and retention of motor skills. Plastic changes involving structural reorganization in gray and white matter architecture that occurs over shorter time periods than previously thought have been documented as well. Data from experimental animals provided crucial information on plausible cellular and molecular substrates contributing to large-scale reorganization underlying skill acquisition in humans. Here, we review findings demonstrating functional and structural plasticity across different spatial and temporal scales that mediate motor skill learning, while identifying converging areas of interest, and possible avenues for future research. PMID:22078504

  10. Engineering molecular machines

    NASA Astrophysics Data System (ADS)

    Erman, Burak

    2016-04-01

    Biological molecular motors use chemical energy, mostly in the form of ATP hydrolysis, and convert it to mechanical energy. Correlated thermal fluctuations are essential for the function of a molecular machine and it is the hydrolysis of ATP that modifies the correlated fluctuations of the system. Correlations are consequences of the molecular architecture of the protein. The idea that synthetic molecular machines may be constructed by designing the proper molecular architecture is challenging. In their paper, Sarkar et al (2016 New J. Phys. 18 043006) propose a synthetic molecular motor based on the coarse grained elastic network model of proteins and show by numerical simulations that motor function is realized, ranging from deterministic to thermal, depending on temperature. This work opens up a new range of possibilities of molecular architecture based engine design.

  11. Motor control for a brushless DC motor

    NASA Technical Reports Server (NTRS)

    Peterson, William J. (Inventor); Faulkner, Dennis T. (Inventor)

    1985-01-01

    This invention relates to a motor control system for a brushless DC motor having an inverter responsively coupled to the motor control system and in power transmitting relationship to the motor. The motor control system includes a motor rotor speed detecting unit that provides a pulsed waveform signal proportional to rotor speed. This pulsed waveform signal is delivered to the inverter to thereby cause an inverter fundamental current waveform output to the motor to be switched at a rate proportional to said rotor speed. In addition, the fundamental current waveform is also pulse width modulated at a rate proportional to the rotor speed. A fundamental current waveform phase advance circuit is controllingly coupled to the inverter. The phase advance circuit is coupled to receive the pulsed waveform signal from the motor rotor speed detecting unit and phase advance the pulsed waveform signal as a predetermined function of motor speed to thereby cause the fundamental current waveform to be advanced and thereby compensate for fundamental current waveform lag due to motor winding reactance which allows the motor to operate at higher speeds than the motor is rated while providing optimal torque and therefore increased efficiency.

  12. Nature's Nanomachines: The Physics of Biomolecular Motors

    SciTech Connect

    Shaevitz, Joshua W.

    2004-10-13

    Molecular motors are tiny protein engines that use the chemical energy stored in a molecular bond to produce a variety of complex movements within biological cells. I will present an overview of these fascinating machines as well as the current technologies used to study them. One specific motor, RNA polymerase, transcribes DNA into messenger RNA, using the energy from nucleotide polymerization to move along a DNA template. Optical traps have been used to visualize these motions with ever increasing precision. I will present optical trapping data that provide evidence of a proofreading mechanism, i.e. a molecular backspace key, used by RNA polymerase to correct mistakes made in the RNA.

  13. Emergence of Motor Circuit Activity

    PubMed Central

    Law, Chris; Paquet, Michel; Kania, Artur

    2014-01-01

    In the developing nervous system, ordered neuronal activity patterns can occur even in the absence of sensory input and to investigate how these arise, we have used the model system of the embryonic chicken spinal motor circuit, focusing on motor neurons of the lateral motor column (LMC). At the earliest stages of their molecular differentiation, we can detect differences between medial and lateral LMC neurons in terms of expression of neurotransmitter receptor subunits, including CHRNA5, CHRNA7, GRIN2A, GRIK1, HTR1A and HTR1B, as well as the KCC2 transporter. Using patch-clamp recordings we also demonstrate that medial and lateral LMC motor neurons have subtly different activity patterns that reflect the differential expression of neurotransmitter receptor subunits. Using a combination of patch-clamp recordings in single neurons and calcium-imaging of motor neuron populations, we demonstrate that inhibition of nicotinic, muscarinic or GABA-ergic activity, has profound effects of motor circuit activity during the initial stages of neuromuscular junction formation. Finally, by analysing the activity of large populations of motor neurons at different developmental stages, we show that the asynchronous, disordered neuronal activity that occurs at early stages of circuit formation develops into organised, synchronous activity evident at the stage of LMC neuron muscle innervation. In light of the considerable diversity of neurotransmitter receptor expression, activity patterns in the LMC are surprisingly similar between neuronal types, however the emergence of patterned activity, in conjunction with the differential expression of transmitter systems likely leads to the development of near-mature patterns of locomotor activity by perinatal ages. PMID:24722186

  14. Synthetic Motors and Nanomachines.

    NASA Astrophysics Data System (ADS)

    Flood, Amar

    2006-03-01

    A bistable and palindromically-constituted [3]rotaxane incorporating two mechanically-mobile rings interlocked around a linear dumbbell component, has been designed to operate like the sarcomeres of skeletal muscle. Contraction and extension occurs when the inter-ring distance of the two rings switch, ideally, between 4.2 and 1.4 nm upon redox stimulation either chemically or electrochemically in the solution phase. When the mobile rings of these artificial molecular muscles are bound onto the tops of gold-coated, micron-scale cantilever beams, their controllable nanometer motions have a chance to be amplified along the long axis of each cantilever. It turns out that ˜6 billion of the self-assembled [3]rotaxanes can bend the cantilevers in a bistable manner concomitant with the cycled addition of redox agents. The extent of bending is commensurate with 10's of pN of force per [3]rotaxane. Recent studies on a set of ``single-shot'' control [2]rotaxanes have provided additional evidence for the origins of the force generation as it arises from a molecule-based electrostatic repulsion energy of about 10 kcal/mol at 300 K. These findings will be presented in terms of the underlying thermodynamics and kinetics that have been utilized extensively to direct the design and synthesis of artificial molecular machines and which may also serve as a guide for the rational design of unidirectional molecular motors.

  15. A microrotary motor powered by bacteria

    NASA Astrophysics Data System (ADS)

    Hiratsuka, Yuichi; Miyata, Makoto; Tada, Tetsuya; Uyeda, Taro Q. P.

    2006-09-01

    Biological molecular motors have a number of unique advantages over artificial motors, including efficient conversion of chemical energy into mechanical work and the potential for self-assembly into larger structures, as is seen in muscle sarcomeres and bacterial and eukaryotic flagella. The development of an appropriate interface between such biological materials and synthetic devices should enable us to realize useful hybrid micromachines. Here we describe a microrotary motor composed of a 20-μm-diameter silicon dioxide rotor driven on a silicon track by the gliding bacterium Mycoplasma mobile. This motor is fueled by glucose and inherits some of the properties normally attributed to living systems. glucose | micro actuator | motor protein | nanobiotechnology | Mycoplasma gliding

  16. Dynamic Concentration of Motors in Microtubule Arrays

    NASA Astrophysics Data System (ADS)

    Nédélec, François; Surrey, Thomas; Maggs, A. C.

    2001-04-01

    We present experimental and theoretical studies of the dynamics of molecular motors in microtubule arrays and asters. By solving a convection-diffusion equation we find that the density profile of motors in a two-dimensional aster is characterized by continuously varying exponents. Simulations are used to verify the assumptions of the continuum model. We observe the concentration profiles of kinesin moving in quasi-two-dimensional artificial asters by fluorescent microscopy and compare with our theoretical results.

  17. Traffic of cytoskeletal motors with disordered attachment rates

    NASA Astrophysics Data System (ADS)

    Grzeschik, H.; Harris, R. J.; Santen, L.

    2010-03-01

    Motivated by experimental results on the interplay between molecular motors and tau proteins, we extend lattice-based models of intracellular transport to include a second species of particle which locally influences the motor-filament attachment rate. We consider various exactly solvable limits of a stochastic multiparticle model before focusing on the low-motor-density regime. Here, an approximate treatment based on the random-walk behavior of single motors gives good quantitative agreement with simulation results for the tau dependence of the motor current. Finally, we discuss the possible physiological implications of our results.

  18. Taking control of the flagellar motor

    NASA Astrophysics Data System (ADS)

    Gauthier, Mathieu; Truchon, Dany; Rainville, Simon

    2008-06-01

    Numerous types of bacteria swim in their environment by rotating long helical filaments. At the base of each filament is a tiny rotary motor called the bacterial flagellar motor. A lot is already known about the structure, assembly and function of this splendid molecular machine of nanoscopic dimensions. Nevertheless many fundamental questions remain open and the study of the flagellar motor is a very exciting area of current research. We are developing an in vitro assay to enable studies of the bacterial flagellar motor in precisely controlled conditions and to gain direct access to the inner components of the motor. We partly squeeze a filamentous E. coli bacterium inside a micropipette, leaving a working flagellar motor outside. We then punch a hole through the cell wall at the end of the bacterium located inside the micropipette using a brief train of ultrashort (~60 fs) laser pulses. This enables us to control the rotation of the motor with an external voltage (for at least 15 minutes). In parallel, new methods to monitor the speed of rotation of the motor in the low load (high speed) regime are being developed using various nanoparticules.

  19. Peripheral facial nerve axotomy in mice causes sprouting of motor axons into perineuronal central white matter: time course and molecular characterization.

    PubMed

    Makwana, Milan; Werner, Alexander; Acosta-Saltos, Alejandro; Gonitel, Roman; Pararajasingam, Abirami; Pararajasingham, Abirami; Ruff, Crystal; Rumajogee, Prakasham; Cuthill, Dan; Galiano, Mathias; Bohatschek, Marion; Wallace, Adam S; Anderson, Patrick N; Mayer, Ulrike; Behrens, Axel; Raivich, Gennadij

    2010-03-01

    Generation of new axonal sprouts plays an important role in neural repair. In the current study, we examined the appearance, composition and effects of gene deletions on intrabrainstem sprouts following peripheral facial nerve axotomy. Axotomy was followed by the appearance of galanin(+) and calcitonin gene-related peptide (CGRP)(+) sprouts peaking at day 14, matching both large, neuropeptide(+) subpopulations of axotomized facial motoneurons, but with CGRP(+) sprouts considerably rarer. Strong immunoreactivity for vesicular acetylcholine transporter (VAChT) and retrogradely transported MiniRuby following its application on freshly cut proximal facial nerve stump confirmed their axotomized motoneuron origin; the sprouts expressed CD44 and alpha7beta1 integrin adhesion molecules and grew apparently unhindered along neighboring central white matter tracts. Quantification of the galanin(+) sprouts revealed a stronger response following cut compared with crush (day 7-14) as well as enhanced sprouting after recut (day 8 + 6 vs. 14; 14 + 8 vs. 22), arguing against delayed appearance of sprouting being the result of the initial phase of reinnervation. Sprouting was strongly diminished in brain Jun-deficient mice but enhanced in alpha7 null animals that showed apparently compensatory up-regulation in beta1, suggesting important regulatory roles for transcription factors and the sprout-associated adhesion molecules. Analysis of inflammatory stimuli revealed a 50% reduction 12-48 hours following systemic endotoxin associated with neural inflammation and a tendency toward more sprouts in TNFR1/2 null mutants (P = 10%) with a reduced inflammatory response, indicating detrimental effects of excessive inflammation. Moreover, the study points to the usefulness of the facial axotomy model in exploring physiological and molecular stimuli regulating central sprouting. PMID:20034058

  20. Directed flux motor

    NASA Technical Reports Server (NTRS)

    Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

    2011-01-01

    A directed flux motor described utilizes the directed magnetic flux of at least one magnet through ferrous material to drive different planetary gear sets to achieve capabilities in six actuated shafts that are grouped three to a side of the motor. The flux motor also utilizes an interwoven magnet configuration which reduces the overall size of the motor. The motor allows for simple changes to modify the torque to speed ratio of the gearing contained within the motor as well as simple configurations for any number of output shafts up to six. The changes allow for improved manufacturability and reliability within the design.

  1. Motor control of fly feeding.

    PubMed

    McKellar, Claire E

    2016-06-01

    Following considerable progress on the molecular and cellular basis of taste perception in fly sensory neurons, the time is now ripe to explore how taste information, integrated with hunger and satiety, undergo a sensorimotor transformation to lead to the motor actions of feeding behavior. I examine what is known of feeding circuitry in adult flies from more than 250 years of work in larger flies and from newer work in Drosophila. I review the anatomy of the proboscis, its muscles and their functions (where known), its motor neurons, interneurons known to receive taste inputs, interneurons that diverge from taste circuitry to provide information to other circuits, interneurons from other circuits that converge on feeding circuits, proprioceptors that influence the motor control of feeding, and sites of integration of hunger and satiety on feeding circuits. In spite of the several neuron types now known, a connected pathway from taste inputs to feeding motor outputs has yet to be found. We are on the threshold of an era where these individual components will be assembled into circuits, revealing how nervous system architecture leads to the control of behavior. PMID:27309215

  2. Chronic motor tic disorder

    MedlinePlus

    Chronic vocal tic disorder; Tic - chronic motor tic disorder ... Chronic motor tic disorder is more common than Tourette syndrome . Chronic tics may be forms of Tourette syndrome. Tics usually start ...

  3. Introduction to ultrasonic motors

    SciTech Connect

    Sashida, Toshiiku; Kenjo, Takashi.

    1993-01-01

    The ultrasonic motor, invented in 1980, utilizes the piezoelectric effect in the ultrasonic frequency range to provide the motive force. (In conventional electric motors the motive force is electromagnetic.) The result is a motor with unusually good low-speed high-torque and power-to-weight characteristics. It has already found applications in camera autofocus mechanisms, medical equipment subject to high magnetic fields, and motorized car accessories. Its applications will increase as designers become more familiar with its unique characteristics. This book is the result of a collaboration between the inventor and an expert in conventional electric motors: the result is an introduction to the general theory presented in a way that links it to conventional motor theory. It will be invaluable both to motor designers and to those who design with and use electric motors as an introduction to this important new invention.

  4. Fine motor control

    MedlinePlus

    ... out the child's developmental age. Children develop fine motor skills over time, by practicing and being taught. To have fine motor control, children need: Awareness and planning Coordination Muscle ...

  5. Smart motor technology

    NASA Technical Reports Server (NTRS)

    Packard, D.; Schmitt, D.

    1984-01-01

    Current spacecraft design relies upon microprocessor control; however, motors usually require extensive additional electronic circuitry to interface with these microprocessor controls. An improved control technique that allows a smart brushless motor to connect directly to a microprocessor control system is described. An actuator with smart motors receives a spacecraft command directly and responds in a closed loop control mode. In fact, two or more smart motors can be controlled for synchronous operation.

  6. Enhanced conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.; Rabo, Jule A.

    1986-01-01

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  7. Enhanced catalyst for conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, P.K.; Rabo, J.A.

    1985-12-03

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C[sub 5][sup +] hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising a SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  8. Enhanced catalyst for conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.; Rabo, Jule A.

    1985-01-01

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  9. Sliding of microtubules by a team of dynein motors: Understanding the effect of spatial distribution of motor tails and mutual exclusion of motor heads on microtubules

    NASA Astrophysics Data System (ADS)

    Singh, Hanumant Pratap; Takshak, Anjneya; Mall, Utkarsh; Kunwar, Ambarish

    2016-06-01

    Molecular motors are natural nanomachines that use the free energy released from ATP hydrolysis to generate mechanical forces. Cytoplasmic dynein motors often work collectively as a team to drive important processes such as axonal growth, proplatelet formation and mitosis, as forces generated by single motors are insufficient. A large team of dynein motors is used to slide cytoskeletal microtubules with respect to one another during the process of proplatelet formation and axonal growth. These motors attach to a cargo microtubule via their tail domains, undergo the process of detachment and reattachment of their head domains on another track microtubule, while sliding the cargo microtubule along the track. Traditional continuum/mean-field approaches used in the past are not ideal for studying the sliding mechanism of microtubules, as they ignore spatial and temporal fluctuations due to different possible distributions of motor tails on cargo filament, as well as binding/unbinding of motors from their track. Therefore, these models cannot be used to address important questions such as how the distribution of motor tails on microtubules, or how the mutual exclusion of motor heads on microtubule tracks affects the sliding velocity of cargo microtubule. To answer these, here we use a computational stochastic model where we model each dynein motor explicitly. In our model, we use both random as well as uniform distributions of dynein motors on cargo microtubule, as well as mutual exclusion of motors on microtubule tracks. We find that sliding velocities are least affected by the distribution of motor tails on microtubules, whereas they are greatly affected by mutual exclusion of motor heads on microtubule tracks. We also find that sliding velocity depends on the length of cargo microtubule if mutual exclusion among motor heads is considered.

  10. The Genetic Engineering of Motor Proteins

    NASA Astrophysics Data System (ADS)

    Hartz, Rachael M.

    Molecular motors are a remarkable feature within living organisms that are responsible for directional mechanical motion, which is driven by adenosine triphosphate (ATP) hydrolysis. Actin-binding molecular motors are of specific interest in the field of nanotechnology as filamentous actin is capable of carrying cargo, such as quantum dots, while it is translocated along a motor coated surface. The binding regions of motor proteins, which are known to interact with actin, such as Myosin, have been thoroughly examined and identified. Rapid genetic engineering of the ATP-hydrolyzing enzyme, adenosine kinase, to incorporate these binding regions is possible through the use of site- directed mutagenesis. The sequences, which were mutated into the ADK wt gene, were incorporated in an unstructured loop region. During the phosphate transfer, the mutants switch between open and closed conformational states. The binding affinity of the sequences to the actin is altered during this conformational switch, thus causing the motor to move along actin filament. The ADK mutants and their interaction with filamentous actin was monitored by an in vitro motility assay. Two different mutants of ADK were found to have retained enzymatic functionality after the mutagenesis as well as function as actin-based motor proteins.

  11. Sticks in honey - Motor-connected Microtubules at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Berman, Rotem S.; Leshansky, Alex; Avron, Joseph E.

    2010-11-01

    It is known that suspensions of microtubules (MTs) and molecular motors spontaneously form ordered asters and vortices. We consider the motion of MTs' assemblages connected by molecular motors at low Reynolds number. The MTs are modeled as rigid sticks and their hydrodynamic interaction with the medium is determined using slender body approximation. The motors are modeled as moving points which provide kinematic constrains for the sticks' motion. The hydrodynamic alignment of a pair of MTs for two possible motor connections is considered: a single head motor connection, in which the motor moves on one of the sticks and carries the other one, and a dual head motor connection whereas the motor advances on both sticks. We further address the formation of an aster from the vortex of inter-connected MTs. The forces the motors need to exert on the MTs in the course of closing the vortex and their dependence on the number of MTs are computed.

  12. MAGNETIC TWEEZERS FOR THE STUDY OF DNA TRACKING MOTORS

    PubMed Central

    Manosas, Maria; Meglio, Adrien; Spiering, Michelle M.; Ding, Fangyuan; Benkovic, Stephen J.; Barre, François-Xavier; Saleh, Omar A.; Allemand, Jean François; Bensimon, David; Croquette, Vincent

    2011-01-01

    Single-molecule manipulation methods have opened a new vista on the study of molecular motors. Here we describe the use of magnetic traps for the investigation of the mechanism of DNA based motors, in particular helicases and translocases. PMID:20627163

  13. Solid propellant motor

    NASA Technical Reports Server (NTRS)

    Shafer, J. I.; Marsh, H. E., Jr. (Inventor)

    1978-01-01

    A case bonded end burning solid propellant rocket motor is described. A propellant with sufficiently low modulus to avoid chamber buckling on cooling from cure and sufficiently high elongation to sustain the stresses induced without cracking is used. The propellant is zone cured within the motor case at high pressures equal to or approaching the pressure at which the motor will operate during combustion. A solid propellant motor with a burning time long enough that its spacecraft would be limited to a maximum acceleration of less than 1 g is provided by one version of the case bonded end burning solid propellant motor of the invention.

  14. Motor/generator

    DOEpatents

    Hickam, Christopher Dale

    2008-05-13

    A motor/generator is provided for connecting between a transmission input shaft and an output shaft of a prime mover. The motor/generator may include a motor/generator housing, a stator mounted to the motor/generator housing, a rotor mounted at least partially within the motor/generator housing and rotatable about a rotor rotation axis, and a transmission-shaft coupler drivingly coupled to the rotor. The transmission-shaft coupler may include a clamp, which may include a base attached to the rotor and a plurality of adjustable jaws.

  15. Piezoceramic Ultrasonic Motor Technology

    SciTech Connect

    Burden, J.S.

    1999-02-24

    The objective of this project was to team Aerotech and AlliedSignal FM and T (AS) to develop a cost-efficient process for small-batch, high performance PZT motor production. Aerotech would acquire the basic process expertise in motor fabrication, assembly, and testing from AS. Together, Aerotech and AS were to identify appropriate process improvements, focusing on raw material quality, manufacturing processes, and durability assessment. Aerotech would then design and build a motor in consultation with AS. Aerotech engineering observed motor manufacturing in the AS piezo lab and worked side by side with AS personnel to build and test a prototype motor to facilitate learning the technology. Using information from AS and hands-on experience with the AS motor drive system enabled Aerotech to design and build its own laboratory drive system to operate motors. The team compiled information to establish a potential piezo motor users' list, and an intellectual property search was conducted to understand current patent and IP (intellectual property) status of motor design. Work was initiated to identify and develop an American source for piezo motor elements; however, due to manpower restraints created by the resignation of the AS Ph.D. ceramist responsible for these tasks, the project schedule slipped. The project was subsequently terminated before significant activities were accomplished. AS did, however, provide Aerotech with contacts in Japanese industry that are willing and capable of supplying them with special design motor elements.

  16. Motorized support jack

    DOEpatents

    Haney, Steven J.; Herron, Donald Joe

    2001-01-01

    A compact, vacuum compatible motorized jack for supporting heavy loads and adjusting their positions is provided. The motorized jack includes: (a) a housing having a base; (b) a first roller device that provides a first slidable surface and that is secured to the base; (c) a second roller device that provides a second slidable surface and that has an upper surface; (d) a wedge that is slidably positioned between the first roller device and the second roller device so that the wedge is in contact with the first slidable surface and the second slidable surface; (e) a motor; and (d) a drive mechanism that connects the motor and the wedge to cause the motor to controllably move the wedge forwards or backwards. Individual motorized jacks can support and lift of an object at an angle. Two or more motorized jacks can provide tip, tilt and vertical position adjustment capabilities.

  17. Motor degradation prediction methods

    SciTech Connect

    Arnold, J.R.; Kelly, J.F.; Delzingaro, M.J.

    1996-12-01

    Motor Operated Valve (MOV) squirrel cage AC motor rotors are susceptible to degradation under certain conditions. Premature failure can result due to high humidity/temperature environments, high running load conditions, extended periods at locked rotor conditions (i.e. > 15 seconds) or exceeding the motor`s duty cycle by frequent starts or multiple valve stroking. Exposure to high heat and moisture due to packing leaks, pressure seal ring leakage or other causes can significantly accelerate the degradation. ComEd and Liberty Technologies have worked together to provide and validate a non-intrusive method using motor power diagnostics to evaluate MOV rotor condition and predict failure. These techniques have provided a quick, low radiation dose method to evaluate inaccessible motors, identify degradation and allow scheduled replacement of motors prior to catastrophic failures.

  18. Motorized support jack

    DOEpatents

    Haney, Steven J.; Herron, Donald Joe

    2003-05-13

    A compact, vacuum compatible motorized jack for supporting heavy loads and adjusting their positions is provided. The motorized jack includes: (a) a housing having a base; (b) a first roller device that provides a first slidable surface and that is secured to the base; (c) a second roller device that provides a second slidable surface and that has an upper surface; (d) a wedge that is slidably positioned between the first roller device and the second roller device so that the wedge is in contact with the first slidable surface and the second slidable surface; (e) a motor; and (d) a drive mechanism that connects the motor and the wedge to cause the motor to controllably move the wedge forwards or backwards. Individual motorized jacks can support and lift of an object at an angle. Two or more motorized jacks can provide tip, tilt and vertical position adjustment capabilities.

  19. Cyclic motor activity; migrating motor complex: 1985.

    PubMed

    Sarna, S K

    1985-10-01

    Most of the gastrointestinal tract and the biliary tract have a cyclic motor activity. The electric counterpart of this motor activity is called cyclic myoelectric activity. A typical motor cycle in the LES, stomach, and small intestine is composed of a quiescent state, followed by progressively increasing amplitude and frequency of contractions culminating in a state of maximal contractile activity. The colonic motor cycle has only the quiescent and the contractile states. In the small intestine, these motor complexes migrate in an aborad direction, and in the colon in both orad and aborad directions. The mechanisms of initiation and migration of these complexes are best understood in the small intestine. Both the initiation and migration of these complexes seem to be controlled by enteric neural mechanisms. The functions of the enteric mechanisms may be modulated by the central nervous system and by circulating endogenous substances. The mechanisms of initiation of these complexes are not completely understood in the rest of the gastrointestinal tract and in the biliary tract. The physiologic function of these motor complexes that occur only after several hours of fast in the upper gastrointestinal tract of nonruminants may be to clean the digestive tract of residual food, secretions, and cellular debris. This function is aided by a coordinated secretion of enzymes, acid, and bicarbonate. In ruminants, phase III activity is associated with the distal propulsion of ingested food. The function of colonic motor complexes that are not coordinated with the cyclic motor activities of the rest of the gastrointestinal tract may be only to move contents back and forth for optimal absorption. PMID:3896912

  20. Dissociating motor cortex from the motor

    PubMed Central

    Schieber, Marc H

    2011-01-01

    Abstract During closed-loop control of a brain–computer interface, neurons in the primary motor cortex can be intensely active even though the subject may be making no detectable movement or muscle contraction. How can neural activity in the primary motor cortex become dissociated from the movements and muscles of the native limb that it normally controls? Here we examine circumstances in which motor cortex activity is known to dissociate from movement – including mental imagery, visuo-motor dissociation and instructed delay. Many such motor cortex neurons may be related to muscle activity only indirectly. Furthermore, the integration of thousands of synaptic inputs by individual α-motoneurons means that under certain circumstances even cortico-motoneuronal cells, which make monosynaptic connections to α-motoneurons, can become dissociated from muscle activity. The natural ability of motor cortex neurons under voluntarily control to become dissociated from bodily movement may underlie the utility of this cortical area for controlling brain–computer interfaces. PMID:22005673

  1. Motor Neurons that Multitask

    PubMed Central

    Goulding, Martyn

    2013-01-01

    Animals use a form of sensory feedback termed proprioception to monitor their body position and modify the motor programs that control movement. In this issue of Neuron, Wen et al. (2012) provide evidence that a subset of motor neurons function as proprioceptors in C. elegans, where B-type motor neurons sense body curvature to control the bending movements that drive forward locomotion. PMID:23177952

  2. Theory of self-assembly of microtubules and motors.

    SciTech Connect

    Aranson, I. S.; Tsimring, L. S.; Materials Science Division; Univ. California at San Diego

    2006-01-01

    We derive a model describing spatiotemporal organization of an array of microtubules interacting via molecular motors. Starting from a stochastic model of inelastic polar rods with a generic anisotropic interaction kernel, we obtain a set of equations for the local rods concentration and orientation. At large enough mean density of rods and concentration of motors, the model describes an orientational instability. We demonstrate that the orientational instability leads to the formation of vortices and (for large density and/or kernel anisotropy) asters seen in recent experiments. We derive the specific form of the interaction kernel from the detailed analysis of microscopic interaction of two filaments mediated by a moving molecular motor and extend our results to include variable motor density and motor attachment to the substrate.

  3. Theory of self-assembly of microtubules and motors

    NASA Astrophysics Data System (ADS)

    Aranson, Igor S.; Tsimring, Lev S.

    2006-09-01

    We derive a model describing spatiotemporal organization of an array of microtubules interacting via molecular motors. Starting from a stochastic model of inelastic polar rods with a generic anisotropic interaction kernel, we obtain a set of equations for the local rods concentration and orientation. At large enough mean density of rods and concentration of motors, the model describes an orientational instability. We demonstrate that the orientational instability leads to the formation of vortices and (for large density and/or kernel anisotropy) asters seen in recent experiments. We derive the specific form of the interaction kernel from the detailed analysis of microscopic interaction of two filaments mediated by a moving molecular motor and extend our results to include variable motor density and motor attachment to the substrate.

  4. Cryogenic Electric Motor Tested

    NASA Technical Reports Server (NTRS)

    Brown, Gerald V.

    2004-01-01

    Technology for pollution-free "electric flight" is being evaluated in a number of NASA Glenn Research Center programs. One approach is to drive propulsive fans or propellers with electric motors powered by fuel cells running on hydrogen. For large transport aircraft, conventional electric motors are far too heavy to be feasible. However, since hydrogen fuel would almost surely be carried as liquid, a propulsive electric motor could be cooled to near liquid hydrogen temperature (-423 F) by using the fuel for cooling before it goes to the fuel cells. Motor windings could be either superconducting or high purity normal copper or aluminum. The electrical resistance of pure metals can drop to 1/100th or less of their room-temperature resistance at liquid hydrogen temperature. In either case, super or normal, much higher current density is possible in motor windings. This leads to more compact motors that are projected to produce 20 hp/lb or more in large sizes, in comparison to on the order of 2 hp/lb for large conventional motors. High power density is the major goal. To support cryogenic motor development, we have designed and built in-house a small motor (7-in. outside diameter) for operation in liquid nitrogen.

  5. Hybrid vehicle motor alignment

    DOEpatents

    Levin, Michael Benjamin

    2001-07-03

    A rotor of an electric motor for a motor vehicle is aligned to an axis of rotation for a crankshaft of an internal combustion engine having an internal combustion engine and an electric motor. A locator is provided on the crankshaft, a piloting tool is located radially by the first locator to the crankshaft. A stator of the electric motor is aligned to a second locator provided on the piloting tool. The stator is secured to the engine block. The rotor is aligned to the crankshaft and secured thereto.

  6. Self-assembly of microtubules and motors

    NASA Astrophysics Data System (ADS)

    Aranson, Igor; Tsimring, Lev

    2005-03-01

    We derive a model describing spatio-temporal assembly of an array of microtubules interacting via molecular motors. Starting from a stochastic model of inelastic polar rods with a generic anisotropic interaction kernel we obtain a set of equations for the local rods concentration and orientation. At large enough mean density of rods and concentration of motors, the model describes orientational instability. We demonstrate that the orientational instability leads to the formation of vortices and (for large density and/or kernel anisotropy) asters seen in recent experiments.

  7. Self-organization of microtubules and motors.

    SciTech Connect

    Aranson, I. S.; Tsimring, L. S.; Materials Science Division; Univ. of California at San Diego

    2006-01-01

    Here we introduce a model for spatio-temporal self-organization of an ensemble of microtubules interacting via molecular motors. Starting from a generic stochastic model of inelastic polar rods with an anisotropic interaction kernel we derive a set of equations for the local rods concentration and orientation. At large enough mean density of rods and concentration of motors, the model describes orientational instability. We demonstrate that the orientational instability leads to the formation of vortices and (for large density and/or kernel anisotropy) asters seen in recent experiments. The corresponding phase diagram of vortexasters transitions is in qualitative agreement with experiment.

  8. Motor efficiency management

    SciTech Connect

    Lobodovsky, K.K. , Penn Valley, CA )

    1994-01-01

    During the 102nd Congress, the Markey Bill, H.R. 2451, was introduced. The bill mandated component efficiency standards for such products as lighting, distribution transformers, and electric A.C. motors. This plan was met with opposition by NEMA and other interested groups. They called for a system approach that would recognize the complex nature of the product involved under the plan. The bill passed by the Energy Power Subcommittee on the theory that the elimination of the least efficient component from the market would ensure that consumers would purchase and use the most efficient products possible. Experience indicates that despite heightened awareness and concern with energy efficiency, the electric motor is either completely neglected or decisions are made on the basis of incomplete information. An on-going analysis of motor performance prevents major breakdown. Performance evaluation of a motor should be done as routinely as it is done on an employee. Both the motor and the employee are equally important. Applied motor maintenance will keep the building or plant running smoothly with minimal stress on the system or downtime because of failure. The Motor Performance Management Process (MPMP) is designed to be the Motor Manager's primary tool to evaluate, measure, and most importantly manage electric motors. MPMP focuses on building a stronger relationship between the Motor Manager and the electric motor employed to perform a task. Specifically, it is a logical, systematic, and structured approach to reduce energy waste. Energy waste reduction is fundamental in becoming more efficient in an increasingly competitive market. The implementation of MPMP is more than a good business practice it is an intelligent management resource.

  9. Heritability of motor control and motor learning

    PubMed Central

    Missitzi, Julia; Gentner, Reinhard; Misitzi, Angelica; Geladas, Nickos; Politis, Panagiotis; Klissouras, Vassilis; Classen, Joseph

    2013-01-01

    Abstract The aim of this study was to elucidate the relative contribution of genes and environment on individual differences in motor control and acquisition of a force control task, in view of recent association studies showing that several candidate polymorphisms may have an effect on them. Forty‐four healthy female twins performed brisk isometric abductions with their right thumb. Force was recorded by a transducer and fed back to the subject on a computer screen. The task was to place the tracing of the peak force in a force window defined between 30% and 40% of the subject's maximum force, as determined beforehand. The initial level of proficiency was defined as the number of attempts reaching the force window criterion within the first 100 trials. The difference between the number of successful trials within the last and the first 100 trials was taken as a measure of motor learning. For motor control, defined by the initial level of proficiency, the intrapair differences in monozygotic (MZ) and dizygotic (DZ) twins were 6.8 ± 7.8 and 13.8 ± 8.4, and the intrapair correlations 0.77 and 0.39, respectively. Heritability was estimated at 0.68. Likewise for motor learning intrapair differences in the increment of the number of successful trials in MZ and DZ twins were 5.4 ± 5.2 and 12.8 ± 7, and the intrapair correlations 0.58 and 0.19. Heritability reached 0.70. The present findings suggest that heredity accounts for a major part of existing differences in motor control and motor learning, but uncertainty remains which gene polymorphisms may be responsible. PMID:24744865

  10. Roles of the orexin system in central motor control.

    PubMed

    Hu, Bo; Yang, Nian; Qiao, Qi-Cheng; Hu, Zhi-An; Zhang, Jun

    2015-02-01

    The neuropeptides orexin-A and orexin-B are produced by one group of neurons located in the lateral hypothalamic/perifornical area. However, the orexins are widely released in entire brain including various central motor control structures. Especially, the loss of orexins has been demonstrated to associate with several motor deficits. Here, we first summarize the present knowledge that describes the anatomical and morphological connections between the orexin system and various central motor control structures. In the next section, the direct influence of orexins on related central motor control structures is reviewed at molecular, cellular, circuitry, and motor activity levels. After the summarization, the characteristic and functional relevance of the orexin system's direct influence on central motor control function are demonstrated and discussed. We also propose a hypothesis as to how the orexin system orchestrates central motor control in a homeostatic regulation manner. Besides, the importance of the orexin system's phasic modulation on related central motor control structures is highlighted in this regulation manner. Finally, a scheme combining the homeostatic regulation of orexin system on central motor control and its effects on other brain functions is presented to discuss the role of orexin system beyond the pure motor activity level, but at the complex behavioral level.

  11. Stepping motor controller

    DOEpatents

    Bourret, S.C.; Swansen, J.E.

    1982-07-02

    A stepping motor is microprocessor controlled by digital circuitry which monitors the output of a shaft encoder adjustably secured to the stepping motor and generates a subsequent stepping pulse only after the preceding step has occurred and a fixed delay has expired. The fixed delay is variable on a real-time basis to provide for smooth and controlled deceleration.

  12. Stepping motor controller

    DOEpatents

    Bourret, Steven C.; Swansen, James E.

    1984-01-01

    A stepping motor is microprocessingly controlled by digital circuitry which monitors the output of a shaft encoder adjustably secured to the stepping motor and generates a subsequent stepping pulse only after the preceding step has occurred and a fixed delay has expired. The fixed delay is variable on a real-time basis to provide for smooth and controlled deceleration.

  13. Induction motor control

    NASA Technical Reports Server (NTRS)

    Hansen, Irving G.

    1990-01-01

    Electromechanical actuators developed to date have commonly utilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilizes induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high frequency power distribution and management techniques developed by NASA for Space Station Freedom.

  14. Induction motor control

    NASA Technical Reports Server (NTRS)

    Hansen, Irving G.

    1990-01-01

    Electromechanical actuators developed to date have commonly ultilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilized induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high-frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high-frequency power distribution and management techniques developed by NASA for Space Station Freedom.

  15. ISRO's solid rocket motors

    NASA Astrophysics Data System (ADS)

    Nagappa, R.; Kurup, M. R.; Muthunayagam, A. E.

    1989-08-01

    Solid rocket motors have been the mainstay of ISRO's sounding rockets and the first generation satellite launch vehicles. For the new launch vehicle under development also, the solid rocket motors contribute significantly to the vehicle's total propulsive power. The rocket motors in use and under development have been developed for a variety of applications and range in size from 30 mm dia employing 450 g of solid propellant—employed for providing a spin to the apogee motors—to the giant 2.8 m dia motor employing nearly 130 tonnes of solid propellant. The initial development, undertaken in 1967 was of small calibre motor of 75 mm dia using a double base charge. The development was essentially to understand the technological elements. Extruded aluminium tubes were used as a rocket motor casing. The fore and aft closures were machined from aluminium rods. The grain was a seven-pointed star with an enlargement of the port at the aft end and was charged into the chamber using a polyester resin system. The nozzle was a metallic heat sink type with graphite throat insert. The motor was ignited with a black powder charge and fired for 2.0 s. Subsequent to this, further developmental activities were undertaken using PVC plastisol based propellants. A class of sounding rockets ranging from 125 to 560 mm calibre were realized. These rocket motors employed improved designs and had delivered lsp ranging from 2060 to 2256 Ns/kg. Case bonding could not be adopted due to the higher cure temperatures of the plastisol propellants but improvements were made in the grain charging techniques and in the design of the igniters and the nozzle. Ablative nozzles based on asbestos phenolic and silica phenolic with graphite inserts were used. For the larger calibre rocket motors, the lsp could be improved by metallic additives. In the early 1970s designs were evolved for larger and more efficient motors. A series of 4 motors for the country's first satellite launch vehicle SLV-3 were

  16. Motor Priming in Neurorehabilitation

    PubMed Central

    Stoykov, Mary Ellen; Madhavan, Sangeetha

    2014-01-01

    Priming is a type of implicit learning wherein a stimulus prompts a change in behavior. Priming has been long studied in the field of psychology. More recently, rehabilitation researchers have studied motor priming as a possible way to facilitate motor learning. For example, priming of the motor cortex is associated with changes in neuroplasticity that are associated with improvements in motor performance. Of the numerous motor priming paradigms under investigation, only a few are practical for the current clinical environment, and the optimal priming modalities for specific clinical presentations are not known. Accordingly, developing an understanding of the various types of motor priming paradigms and their underlying neural mechanisms is an important step for therapists in neurorehabilitation. Most importantly, an understanding of the methods and their underlying mechanisms is essential for optimizing rehabilitation outcomes. The future of neurorehabilitation is likely to include these priming methods, which are delivered prior to or in conjunction with primary neurorehabilitation therapies. In this Special Interest article we discuss those priming paradigms that are supported by the greatest amount of evidence including: (i) stimulation-based priming, (ii) motor imagery and action observation, (iii) sensory priming, (iv) movement-based priming, and (v) pharmacological priming. PMID:25415551

  17. The induction motor

    NASA Astrophysics Data System (ADS)

    Redinz, José Arnaldo

    2015-09-01

    We obtain analytical expressions for the torques and angular speed of an induction motor with a simple geometry, resembling the geometry of the first induction motor investigated by Arago in 1824. The rotor is a conducting disc rotating between the magnetic poles of two off-axis solenoids, displaced in space by 90^\\circ from each other. We apply our results to discuss a theory for the ubiquitous electromechanical watt-hour meter. For comparison of the theoretical result for the angular speed with measurements, we propose a simple experiment in which an induction motor with an aluminum disc rotor is constructed.

  18. Self-organization of microtubules and motors

    NASA Astrophysics Data System (ADS)

    Ndlec, F. J.; Surrey, T.; Maggs, A. C.; Leibler, S.

    1997-09-01

    Cellular structures are established and maintained through a dynamic interplay between assembly and regulatory processes. Self-organization of molecular components provides a variety of possible spatial structures: the regulatory machinery chooses the most appropriate to express a given cellular function. Here we study the extent and the characteristics of self-organization using microtubules and molecular motors as a model system. These components are known to participate in the formation of many cellular structures, such as the dynamic asters found in mitotic and meiotic spindles. Purified motors and microtubules have previously been observed to form asters in vitro. We have reproduced this result with a simple system consisting solely of multi-headed constructs of the motor protein kinesin and stabilized microtubules. We show that dynamic asters can also be obtained from a homogeneous solution of tubulin and motors. By varying the relative concentrations of the components, we obtain a variety of self-organized structures. Further, by studying this process in a constrained geometry of micro-fabricated glass chambers, we demonstrate that the same final structure can be reached through different assembly `pathways'.

  19. Physics of protein motility and motor proteins

    NASA Astrophysics Data System (ADS)

    Kolomeisky, Anatoly B.

    2013-09-01

    Motor proteins are enzymatic molecules that transform chemical energy into mechanical motion and work. They are critically important for supporting various cellular activities and functions. In the last 15 years significant progress in understanding the functioning of motor proteins has been achieved due to revolutionary breakthroughs in single-molecule experimental techniques and strong advances in theoretical modelling. However, microscopic mechanisms of protein motility are still not well explained, and the collective efforts of many scientists are needed in order to solve these complex problems. In this special section the reader will find the latest advances on the difficult road to mapping motor proteins dynamics in various systems. Recent experimental developments have allowed researchers to monitor and to influence the activity of single motor proteins with a high spatial and temporal resolution. It has stimulated significant theoretical efforts to understand the non-equilibrium nature of protein motility phenomena. The latest results from all these advances are presented and discussed in this special section. We would like to thank the scientists from all over the world who have reported their latest research results for this special section. We are also grateful to the staff and editors of Journal of Physics: Condensed Matter for their invaluable help in handling all the administrative and refereeing activities. The field of motor proteins and protein motility is fast moving, and we hope that this collection of articles will be a useful source of information in this highly interdisciplinary area. Physics of protein motility and motor proteins contents Physics of protein motility and motor proteinsAnatoly B Kolomeisky Identification of unique interactions between the flexible linker and the RecA-like domains of DEAD-box helicase Mss116 Yuan Zhang, Mirkó Palla, Andrew Sun and Jung-Chi Liao The load dependence of the physical properties of a molecular motor

  20. Advanced motor and motor control development

    NASA Astrophysics Data System (ADS)

    Wuertz, Kenneth L.; Beauchamp, Edward D.

    1988-08-01

    The capability of operating a high speed permanent magnet brushless dc motor with electronic controller over a wide load and speed range was demonstrated. A centrifugal pump was used as the loading mechanism and hydraulic fluid was pumped in simulation of an aircraft engine fuel pump requirement. A motor speed of 45,000 rpm was reached and a maximum output of 68.5 hp was demonstrated. The response of the system to step commands for speed change was established. Reduction of size and weight of electronic control was established as a primary future goal. The program system concept with minor rotating machine improvements is viable for high speed drive applications up to 100-hp level.

  1. System and method for motor parameter estimation

    SciTech Connect

    Luhrs, Bin; Yan, Ting

    2014-03-18

    A system and method for determining unknown values of certain motor parameters includes a motor input device connectable to an electric motor having associated therewith values for known motor parameters and an unknown value of at least one motor parameter. The motor input device includes a processing unit that receives a first input from the electric motor comprising values for the known motor parameters for the electric motor and receive a second input comprising motor data on a plurality of reference motors, including values for motor parameters corresponding to the known motor parameters of the electric motor and values for motor parameters corresponding to the at least one unknown motor parameter value of the electric motor. The processor determines the unknown value of the at least one motor parameter from the first input and the second input and determines a motor management strategy for the electric motor based thereon.

  2. MotorWeek

    ScienceCinema

    None

    2016-07-12

    In 2008, PBS's MotorWeek, television's original automotive magazine, visited Argonne's Transportation Technology R&D Center "to learn what it really takes to make clean power sources a viable reality."

  3. MotorWeek

    SciTech Connect

    2009-01-01

    In 2008, PBS's MotorWeek, television's original automotive magazine, visited Argonne's Transportation Technology R&D Center "to learn what it really takes to make clean power sources a viable reality."

  4. Piezoelectric Rotary Tube Motor

    NASA Technical Reports Server (NTRS)

    Fisher, Charles D.; Badescu, Mircea; Braun, David F.; Culhane, Robert

    2011-01-01

    A custom rotary SQUIGGLE(Registered TradeMark) motor has been developed that sets new benchmarks for small motor size, high position resolution, and high torque without gear reduction. Its capabilities cannot be achieved with conventional electromagnetic motors. It consists of piezoelectric plates mounted on a square flexible tube. The plates are actuated via voltage waveforms 90 out of phase at the resonant frequency of the device to create rotary motion. The motors were incorporated into a two-axis postioner that was designed for fiber-fed spectroscopy for ground-based and space-based projects. The positioner enables large-scale celestial object surveys to take place in a practical amount of time.

  5. High Power Density Motors

    NASA Technical Reports Server (NTRS)

    Kascak, Daniel J.

    2004-01-01

    With the growing concerns of global warming, the need for pollution-free vehicles is ever increasing. Pollution-free flight is one of NASA's goals for the 21" Century. , One method of approaching that goal is hydrogen-fueled aircraft that use fuel cells or turbo- generators to develop electric power that can drive electric motors that turn the aircraft's propulsive fans or propellers. Hydrogen fuel would likely be carried as a liquid, stored in tanks at its boiling point of 20.5 K (-422.5 F). Conventional electric motors, however, are far too heavy (for a given horsepower) to use on aircraft. Fortunately the liquid hydrogen fuel can provide essentially free refrigeration that can be used to cool the windings of motors before the hydrogen is used for fuel. Either High Temperature Superconductors (HTS) or high purity metals such as copper or aluminum may be used in the motor windings. Superconductors have essentially zero electrical resistance to steady current. The electrical resistance of high purity aluminum or copper near liquid hydrogen temperature can be l/lOO* or less of the room temperature resistance. These conductors could provide higher motor efficiency than normal room-temperature motors achieve. But much more importantly, these conductors can carry ten to a hundred times more current than copper conductors do in normal motors operating at room temperature. This is a consequence of the low electrical resistance and of good heat transfer coefficients in boiling LH2. Thus the conductors can produce higher magnetic field strengths and consequently higher motor torque and power. Designs, analysis and actual cryogenic motor tests show that such cryogenic motors could produce three or more times as much power per unit weight as turbine engines can, whereas conventional motors produce only 1/5 as much power per weight as turbine engines. This summer work has been done with Litz wire to maximize the current density. The current is limited by the amount of heat it

  6. Rocket Motor Microphone Investigation

    NASA Technical Reports Server (NTRS)

    Pilkey, Debbie; Herrera, Eric; Gee, Kent L.; Giraud, Jerom H.; Young, Devin J.

    2010-01-01

    At ATK's facility in Utah, large full-scale solid rocket motors are tested. The largest is a five-segment version of the reusable solid rocket motor, which is for use on the Ares I launch vehicle. As a continuous improvement project, ATK and BYU investigated the use of microphones on these static tests, the vibration and temperature to which the instruments are subjected, and in particular the use of vent tubes and the effects these vents have at low frequencies.

  7. Motor Energy Conservation Measures

    SciTech Connect

    Ian Metzger, Jesse Dean

    2010-12-31

    This software requires inputs of simple motor inventory information and calculates the energy and cost benefits of various retrofit opportunities. This tool includes energy conservation measures for: High Efficiency Motor retrofit and Cogged V-belts retrofit. This tool calculates energy savings, demand reduction, cost savings, and building life cycle costs including: simple payback, discounted payback, net-present value, and savings to investment ratio. In addition this tool also displays the environmental benefits of a project.

  8. Myosin V motor proteins

    PubMed Central

    Vale, Ronald D.

    2003-01-01

    Mammalian myosin V motors transport cargo processively along actin filaments. Recent biophysical and structural studies have led to a detailed understanding of the mechanism of myosin V, making it perhaps the best understood cytoskeletal motor. In addition to describing the mechanism, this review will illustrate how “dynamic” single molecule measurements can synergize with “static” protein structural studies to produce amazingly clear information on the workings of a nanometer-scale machine. PMID:14610051

  9. Gigahertz resonance characteristics of nanotube linear motor

    NASA Astrophysics Data System (ADS)

    Kang, Jeong-Won; Choi, Young Gyu; Ryu, Gi Han; Won, Chung Sang

    2008-08-01

    We investigated a linear carbon nanotube motor serving as the key building block for nanoscale motion control by using molecular dynamics simulations. This linear nanomotor, is based on the electrostatically telescoping multi-walled carbon-nanotube with ultralow intershell sliding friction, is controlled by the gate potential with the capacitance feedback sensing. The resonant harmonic peaks are induced by the interference between the driving frequencies and its self-frequency. The temperature is very important factor to operate this nanomotor.

  10. Cooperative protofilament switching emerges from inter-motor interference in multiple-motor transport.

    PubMed

    Ando, David; Mattson, Michelle K; Xu, Jing; Gopinathan, Ajay

    2014-01-01

    Within living cells, the transport of cargo is accomplished by groups of molecular motors. Such collective transport could utilize mechanisms which emerge from inter-motor interactions in ways that are yet to be fully understood. Here we combined experimental measurements of two-kinesin transport with a theoretical framework to investigate the functional ramifications of inter-motor interactions on individual motor function and collective cargo transport. In contrast to kinesin's low sidestepping frequency when present as a single motor, with exactly two kinesins per cargo, we observed substantial motion perpendicular to the microtubule. Our model captures a surface-associated mode of kinesin, which is only accessible via inter-motor interference in groups, in which kinesin diffuses along the microtubule surface and rapidly "hops" between protofilaments without dissociating from the microtubule. Critically, each kinesin transitions dynamically between the active stepping mode and this weak surface-associated mode enhancing local exploration of the microtubule surface, possibly enabling cellular cargos to overcome macromolecular crowding and to navigate obstacles along microtubule tracks without sacrificing overall travel distance. PMID:25434968

  11. Changes in motor unit populations in motor neurone disease.

    PubMed Central

    Carleton, S A; Brown, W F

    1979-01-01

    In motor neurone disease changes in the functional properties of motor units, including the surface voltage, latency, conduction velocity, and response to repetitive stimulation, were investigated. Progression was marked by motor unit loss, increase in the proportion of larger motor unit potentials, and inclusion of motor unit potentials larger than normal in the remaining motor unit population. Even late in the disease, motor unit potentials with a low surface voltage persisted. The relationship between motor unit potentials, surface voltage, and latency, present in control subjects, broke down in motor neurone disease, large motor unit potentials having abnormally long latencies and small motor unit potentials unexpectedly short latencies. Amplitude decrements were more frequent and severe in motor unit potentials at later stages in the disease, particularly in those units with lower surface voltages. In one surviving motor unit potential there was evidence suggestive of functional recovery. The observations point to complex changes in the functional properties of motor units in motor neurone disease. PMID:216781

  12. Electric vehicle motors and controllers

    NASA Astrophysics Data System (ADS)

    Secunde, R. R.

    Improved and advanced components being developed include electronically commutated permanent magnet motors of both drum and disk configuration, an unconventional brush commutated motor, and ac induction motors and various controllers. Test results on developmental motors, controllers, and combinations thereof indicate that efficiencies of 90% and higher for individual components, and 80% to 90% for motor/controller combinations can be obtained at rated power. The simplicity of the developmental motors and the potential for ultimately low cost electronics indicate that one or more of these approaches to electric vehicle propulsion may eventually displace presently used controllers and brush commutated dc motors.

  13. Electric vehicle motors and controllers

    NASA Technical Reports Server (NTRS)

    Secunde, R. R.

    1981-01-01

    Improved and advanced components being developed include electronically commutated permanent magnet motors of both drum and disk configuration, an unconventional brush commutated motor, and ac induction motors and various controllers. Test results on developmental motors, controllers, and combinations thereof indicate that efficiencies of 90% and higher for individual components, and 80% to 90% for motor/controller combinations can be obtained at rated power. The simplicity of the developmental motors and the potential for ultimately low cost electronics indicate that one or more of these approaches to electric vehicle propulsion may eventually displace presently used controllers and brush commutated dc motors.

  14. Cryogenic testing of stepper motors

    NASA Astrophysics Data System (ADS)

    Pompea, S. M.; Bartko, F.; Houck, J. R.

    1982-10-01

    Stepper motors may be used in several subsystems of the planned Shuttle Infrared Telescope Facility. Very high reliability is required in all considered applications. An investigation was, therefore, conducted to study the operational reliability of stepper motors, taking into account tests with a type of stepper motor which had previously performed well in uncooled spectrographic instruments. Two stepper motors were tested, in vacuum, at liquid nitrogen temperature. One motor was lubricated with a vacuum stable grease, while the other used unlubricated bearings. Both motors failed after less than 18,000 revolutions. The failure of the unlubricated motor indicated that motor modifications would have to be made to achieve operation at liquid helium temperature. The motor was modified to compensate for the magnitude of different thermal contractions. It was then found that modified stepper motors can perform reliably at LHe temperature for extended periods.

  15. Patterns and intrinsic fluctuations in semi-dilute motor-filament systems.

    SciTech Connect

    Swaminathan, S.; Ziebert, F.; Aranson, I. S.; Karpeev, D.; Northwestern Univ.; UMR CNRS Gulliver

    2010-04-01

    We perform Brownian dynamics simulations of molecular motor-induced ordering and structure formations in semi-dilute cytoskeletal filament solutions. In contrast to the previously studied dilute case where binary filament interactions prevail, the semi-dilute regime is characterized by multiple motor-mediated interactions. Moreover, the forces and torques exerted by motors on filaments are intrinsically fluctuating quantities. We incorporate the influences of thermal and motor fluctuations into our model as additive and multiplicative noises, respectively. Numerical simulations reveal that filament bundles and vortices emerge from a disordered initial state. Subsequent analysis of motor noise effects reveals: (i) Pattern formation is very robust against fluctuations in motor force; (ii) bundle formation is associated with a significant reduction of the motor fluctuation contributions; (iii) the time scale of vortex formation and coalescence decreases with increases in motor noise amplitude.

  16. Kinetic mechanism of the fastest motor protein, Chara myosin.

    PubMed

    Ito, Kohji; Ikebe, Mitsuo; Kashiyama, Taku; Mogami, Toshifumi; Kon, Takahide; Yamamoto, Keiichi

    2007-07-01

    Chara corallina class XI myosin is by far the fastest molecular motor. To investigate the molecular mechanism of this fast movement, we performed a kinetic analysis of a recombinant motor domain of Chara myosin. We estimated the time spent in the strongly bound state with actin by measuring rate constants of ADP dissociation from actin.motor domain complex and ATP-induced dissociation of the motor domain from actin. The rate constant of ADP dissociation from acto-motor domain was >2800 s(-1), and the rate constant of ATP-induced dissociation of the motor domain from actin at physiological ATP concentration was 2200 s(-1). From these data, the time spent in the strongly bound state with actin was estimated to be <0.82 ms. This value is the shortest among known values for various myosins and yields the duty ratio of <0.3 with a V(max) value of the actin-activated ATPase activity of 390 s(-1). The addition of the long neck domain of myosin Va to the Chara motor domain largely increased the velocity of the motility without increasing the ATP hydrolysis cycle rate, consistent with the swinging lever model. In addition, this study reveals some striking kinetic features of Chara myosin that are suited for the fast movement: a dramatic acceleration of ADP release by actin (1000-fold) and extremely fast ATP binding rate.

  17. Nanoconfined catalytic Ångström-size motors

    SciTech Connect

    Colberg, Peter H. Kapral, Raymond

    2015-11-14

    Self-propelled chemically powered synthetic micron and nano-scale motors are being intensively studied because of the wide range of potential applications that exploit their directed motion. This paper considers even smaller Ångström-size synthetic motors. Such very small motors in bulk solution display effects arising from their self-propulsion. Recent experiments have shown that small-molecule catalysts and single enzyme molecules exhibit properties that have been attributed to their chemical activity. Molecular dynamics is used to investigate the properties of very small Ångström-size synthetic chemically powered sphere-dimer motors in a simple atomic-like solvent confined between walls separated by distances of tens of nanometers. Evidence for strong structural ordering of the motors between the walls, which reflects the finite size of solvent molecules and depends on solvent depletion forces, is provided. Dynamical properties, such as average motor velocity, orientational relaxation, and mean square displacement, are anisotropic and depend on the distance from the walls. This research provides information needed for potential applications that use molecular-scale motors in the complex confined geometries encountered in biology and the laboratory.

  18. Dimerization of mammalian kinesin-3 motors results in superprocessive motion.

    PubMed

    Soppina, Virupakshi; Norris, Stephen R; Dizaji, Aslan S; Kortus, Matt; Veatch, Sarah; Peckham, Michelle; Verhey, Kristen J

    2014-04-15

    The kinesin-3 family is one of the largest among the kinesin superfamily and its members play important roles in a wide range of cellular transport activities, yet the molecular mechanisms of kinesin-3 regulation and cargo transport are largely unknown. We performed a comprehensive analysis of mammalian kinesin-3 motors from three different subfamilies (KIF1, KIF13, and KIF16). Using Forster resonance energy transfer microscopy in live cells, we show for the first time to our knowledge that KIF16B motors undergo cargo-mediated dimerization. The molecular mechanisms that regulate the monomer-to-dimer transition center around the neck coil (NC) segment and its ability to undergo intramolecular interactions in the monomer state versus intermolecular interactions in the dimer state. Regulation of NC dimerization is unique to the kinesin-3 family and in the case of KIF13A and KIF13B requires the release of a proline-induced kink between the NC and subsequent coiled-coil 1 segments. We show that dimerization of kinesin-3 motors results in superprocessive motion, with average run lengths of ∼10 μm, and that this property is intrinsic to the dimeric kinesin-3 motor domain. This finding opens up studies on the mechanistic basis of motor processivity. Such high processivity has not been observed for any other motor protein and suggests that kinesin-3 motors are evolutionarily adapted to serve as the marathon runners of the cellular world.

  19. Nanoconfined catalytic Ångström-size motors.

    PubMed

    Colberg, Peter H; Kapral, Raymond

    2015-11-14

    Self-propelled chemically powered synthetic micron and nano-scale motors are being intensively studied because of the wide range of potential applications that exploit their directed motion. This paper considers even smaller Ångström-size synthetic motors. Such very small motors in bulk solution display effects arising from their self-propulsion. Recent experiments have shown that small-molecule catalysts and single enzyme molecules exhibit properties that have been attributed to their chemical activity. Molecular dynamics is used to investigate the properties of very small Ångström-size synthetic chemically powered sphere-dimer motors in a simple atomic-like solvent confined between walls separated by distances of tens of nanometers. Evidence for strong structural ordering of the motors between the walls, which reflects the finite size of solvent molecules and depends on solvent depletion forces, is provided. Dynamical properties, such as average motor velocity, orientational relaxation, and mean square displacement, are anisotropic and depend on the distance from the walls. This research provides information needed for potential applications that use molecular-scale motors in the complex confined geometries encountered in biology and the laboratory. PMID:26567683

  20. Regulation of mitotic spindle formation by the RhoA guanine nucleotide exchange factor ARHGEF10

    PubMed Central

    Aoki, Takuji; Ueda, Shuji; Kataoka, Tohru; Satoh, Takaya

    2009-01-01

    Background The Dbl family guanine nucleotide exchange factor ARHGEF10 was originally identified as the product of the gene associated with slowed nerve-conduction velocities of peripheral nerves. However, the function of ARHGEF10 in mammalian cells is totally unknown at a molecular level. ARHGEF10 contains no distinctive functional domains except for tandem Dbl homology-pleckstrin homology and putative transmembrane domains. Results Here we show that RhoA is a substrate for ARHGEF10. In both G1/S and M phases, ARHGEF10 was localized in the centrosome in adenocarcinoma HeLa cells. Furthermore, RNA interference-based knockdown of ARHGEF10 resulted in multipolar spindle formation in M phase. Each spindle pole seems to contain a centrosome consisting of two centrioles and the pericentriolar material. Downregulation of RhoA elicited similar phenotypes, and aberrant mitotic spindle formation following ARHGEF10 knockdown was rescued by ectopic expression of constitutively activated RhoA. Multinucleated cells were not increased upon ARHGEF10 knockdown in contrast to treatment with Y-27632, a specific pharmacological inhibitor for the RhoA effector kinase ROCK, which induced not only multipolar spindle formation, but also multinucleation. Therefore, unregulated centrosome duplication rather than aberration in cytokinesis may be responsible for ARHGEF10 knockdown-dependent multipolar spindle formation. We further isolated the kinesin-like motor protein KIF3B as a binding partner of ARHGEF10. Knockdown of KIF3B again caused multipolar spindle phenotypes. The supernumerary centrosome phenotype was also observed in S phase-arrested osteosarcoma U2OS cells when the expression of ARHGEF10, RhoA or KIF3B was abrogated by RNA interference. Conclusion Collectively, our results suggest that a novel RhoA-dependent signaling pathway under the control of ARHGEF10 has a pivotal role in the regulation of the cell division cycle. This pathway is not involved in the regulation of

  1. A New Type of Motor: Pneumatic Step Motor

    PubMed Central

    Stoianovici, Dan; Patriciu, Alexandru; Petrisor, Doru; Mazilu, Dumitru; Kavoussi, Louis

    2011-01-01

    This paper presents a new type of pneumatic motor, a pneumatic step motor (PneuStep). Directional rotary motion of discrete displacement is achieved by sequentially pressurizing the three ports of the motor. Pulsed pressure waves are generated by a remote pneumatic distributor. The motor assembly includes a motor, gearhead, and incremental position encoder in a compact, central bore construction. A special electronic driver is used to control the new motor with electric stepper indexers and standard motion control cards. The motor accepts open-loop step operation as well as closed-loop control with position feedback from the enclosed sensor. A special control feature is implemented to adapt classic control algorithms to the new motor, and is experimentally validated. The speed performance of the motor degrades with the length of the pneumatic hoses between the distributor and motor. Experimental results are presented to reveal this behavior and set the expectation level. Nevertheless, the stepper achieves easily controllable precise motion unlike other pneumatic motors. The motor was designed to be compatible with magnetic resonance medical imaging equipment, for actuating an image-guided intervention robot, for medical applications. For this reason, the motors were entirely made of nonmagnetic and dielectric materials such as plastics, ceramics, and rubbers. Encoding was performed with fiber optics, so that the motors are electricity free, exclusively using pressure and light. PneuStep is readily applicable to other pneumatic or hydraulic precision-motion applications. PMID:21528106

  2. A New Type of Motor: Pneumatic Step Motor.

    PubMed

    Stoianovici, Dan; Patriciu, Alexandru; Petrisor, Doru; Mazilu, Dumitru; Kavoussi, Louis

    2007-02-01

    This paper presents a new type of pneumatic motor, a pneumatic step motor (PneuStep). Directional rotary motion of discrete displacement is achieved by sequentially pressurizing the three ports of the motor. Pulsed pressure waves are generated by a remote pneumatic distributor. The motor assembly includes a motor, gearhead, and incremental position encoder in a compact, central bore construction. A special electronic driver is used to control the new motor with electric stepper indexers and standard motion control cards. The motor accepts open-loop step operation as well as closed-loop control with position feedback from the enclosed sensor. A special control feature is implemented to adapt classic control algorithms to the new motor, and is experimentally validated. The speed performance of the motor degrades with the length of the pneumatic hoses between the distributor and motor. Experimental results are presented to reveal this behavior and set the expectation level. Nevertheless, the stepper achieves easily controllable precise motion unlike other pneumatic motors. The motor was designed to be compatible with magnetic resonance medical imaging equipment, for actuating an image-guided intervention robot, for medical applications. For this reason, the motors were entirely made of nonmagnetic and dielectric materials such as plastics, ceramics, and rubbers. Encoding was performed with fiber optics, so that the motors are electricity free, exclusively using pressure and light. PneuStep is readily applicable to other pneumatic or hydraulic precision-motion applications. PMID:21528106

  3. A versatile stepping motor controller for systems with many motors

    SciTech Connect

    Feng, S.K.; Siddons, D.P.

    1989-01-01

    A versatile system for controlling beamlines or complex experimental setups is described. The system as currently configured can control up to 32 motors, with all motors capable of full speed operation concurrently. There are 2 limit switch inputs for each motor, and a further input to accept a reference position marker. The motors can be controlled via a front panel keyboard with display, or by a host computer over an IEEE-488 interface. Both methods can be used together if required. There is an emergency stop'' key on the front panel keyboard to stop the motion of all motors without losing track of the motors' position. 3 refs., 4 figs., 1 tab.

  4. Magnetostrictive direct drive motor

    NASA Technical Reports Server (NTRS)

    Naik, Dipak; Dehoff, P. H.

    1991-01-01

    Highly magnetostrictive materials such as Tb.3Dy.7Fe2, commercially known as TERFENOL-D, have been used to date in a variety of devices such as high power actuators and linear motors. The larger magnetostriction available in twinned single crystal TERFENOL-D, approx. 2000 ppm at moderate magnetic field strengths, makes possible a new generation of magnetomechanical devices. NASA researchers are studying the potential of this material as the basis for a direct microstepping rotary motor with torque densities on the order of industrial hydraulics and five times greater than that of the most efficient, high power electric motors. Such a motor would be a micro-radian stepper, capable of precision movements and self-braking in the power-off state. Innovative mechanical engineering techniques are juxtaposed on proper magnetic circuit design to reduce losses in structural flexures, inertias, thermal expansions, eddy currents, and magneto-mechanical coupling, thus optimizing motor performance and efficiency. Mathematical models are presented, including magnetic, structural, and both linear and nonlinear dynamic calculations and simulations. In addition, test results on prototypes are presented.

  5. Robust transport by multiple motors with nonlinear force-velocity relations and stochastic load sharing

    NASA Astrophysics Data System (ADS)

    Kunwar, Ambarish; Mogilner, Alexander

    2010-03-01

    Transport by processive molecular motors plays an important role in many cell biological phenomena. In many cases, motors work together to transport cargos in the cell, so it is important to understand the mechanics of the multiple motors. Based on earlier modeling efforts, here we study effects of nonlinear force-velocity relations and stochastic load sharing on multiple motor transport. We find that when two or three motors transport the cargo, then the nonlinear and stochastic effects compensate so that the mechanical properties of the transport are robust. Similarly, the transport is insensitive to compliance of the cargo-motor links. Furthermore, the rate of movement against moderate loads is not improved by increasing the small number of motors. When the motor number is greater than 4, correlations between the motors become negligible, and the earlier analytical mean-field theory of the multiple motor transport holds. We predict that the effective diffusion of the cargo driven by the multiple motors under load increases by an order of magnitude compared to that for the single motor. Finally, our simulations predict that the stochastic effects are responsible for a significant dispersion of velocities generated by the 'tug-of-war' of the multiple opposing motors.

  6. Robust transport by multiple motors with nonlinear force–velocity relations and stochastic load sharing

    PubMed Central

    Kunwar, Ambarish; Mogilner, Alexander

    2010-01-01

    Transport by processive molecular motors plays an important role in many cell biological phenomena. In many cases, motors work together to transport cargos in the cell, so it is important to understand the mechanics of the multiple motors. Based on earlier modeling efforts, here we study effects of nonlinear force–velocity relations and stochastic load sharing on multiple motor transport. We find that when two or three motors transport the cargo, then the nonlinear and stochastic effects compensate so that the mechanical properties of the transport are robust. Similarly, the transport is insensitive to compliance of the cargo-motor links. Furthermore, the rate of movement against moderate loads is not improved by increasing the small number of motors. When the motor number is greater than 4, correlations between the motors become negligible, and the earlier analytical mean-field theory of the multiple motor transport holds. We predict that the effective diffusion of the cargo driven by the multiple motors under load increases by an order of magnitude compared to that for the single motor. Finally, our simulations predict that the stochastic effects are responsible for a significant dispersion of velocities generated by the ‘tug-of-war’ of the multiple opposing motors. PMID:20147778

  7. A catalytic oligomeric motor that walks along a filament track

    NASA Astrophysics Data System (ADS)

    Huang, Mu-Jie; Kapral, Raymond

    2015-06-01

    Most biological motors in the cell execute chemically powered conformational changes as they walk on biopolymer filaments in order to carry out directed transport functions. Synthetic motors that operate in a similar manner are being studied since they have the potential to perform similar tasks in a variety of applications. In this paper, a synthetic nanomotor that moves along a filament track, without invoking motor conformational changes, is constructed and its properties are studied in detail. The motor is an oligomer comprising three linked beads with specific binding properties. The filament track is a stiff polymer chain, also described by a linear chain of linked coarse-grained molecular groups modeled as beads. Reactions on the filament that are catalyzed by a motor bead and use fuel in the environment, in conjunction within the binding affinities of the motor beads to the filament beads, lead to directed motion. The system operates out of equilibrium due to the state of the filament and supply of fuel. The motor, filament, and surrounding medium are all described at microscopic level that permits a full analysis of the motor motion. A stochastic model that captures the main trends seen in the simulations is also presented. The results of this study point to some of the key features that could be used to construct nanomotors that undergo biased walks powered by chemical reactions on filaments.

  8. A catalytic oligomeric motor that walks along a filament track.

    PubMed

    Huang, Mu-Jie; Kapral, Raymond

    2015-06-28

    Most biological motors in the cell execute chemically powered conformational changes as they walk on biopolymer filaments in order to carry out directed transport functions. Synthetic motors that operate in a similar manner are being studied since they have the potential to perform similar tasks in a variety of applications. In this paper, a synthetic nanomotor that moves along a filament track, without invoking motor conformational changes, is constructed and its properties are studied in detail. The motor is an oligomer comprising three linked beads with specific binding properties. The filament track is a stiff polymer chain, also described by a linear chain of linked coarse-grained molecular groups modeled as beads. Reactions on the filament that are catalyzed by a motor bead and use fuel in the environment, in conjunction within the binding affinities of the motor beads to the filament beads, lead to directed motion. The system operates out of equilibrium due to the state of the filament and supply of fuel. The motor, filament, and surrounding medium are all described at microscopic level that permits a full analysis of the motor motion. A stochastic model that captures the main trends seen in the simulations is also presented. The results of this study point to some of the key features that could be used to construct nanomotors that undergo biased walks powered by chemical reactions on filaments. PMID:26133457

  9. Dualities in the analysis of phage DNA packaging motors

    PubMed Central

    Serwer, Philip; Jiang, Wen

    2012-01-01

    The DNA packaging motors of double-stranded DNA phages are models for analysis of all multi-molecular motors and for analysis of several fundamental aspects of biology, including early evolution, relationship of in vivo to in vitro biochemistry and targets for anti-virals. Work on phage DNA packaging motors both has produced and is producing dualities in the interpretation of data obtained by use of both traditional techniques and the more recently developed procedures of single-molecule analysis. The dualities include (1) reductive vs. accretive evolution, (2) rotation vs. stasis of sub-assemblies of the motor, (3) thermal ratcheting vs. power stroking in generating force, (4) complete motor vs. spark plug role for the packaging ATPase, (5) use of previously isolated vs. new intermediates for analysis of the intermediate states of the motor and (6) a motor with one cycle vs. a motor with two cycles. We provide background for these dualities, some of which are under-emphasized in the literature. We suggest directions for future research. PMID:23532204

  10. A catalytic oligomeric motor that walks along a filament track

    SciTech Connect

    Huang, Mu-Jie Kapral, Raymond

    2015-06-28

    Most biological motors in the cell execute chemically powered conformational changes as they walk on biopolymer filaments in order to carry out directed transport functions. Synthetic motors that operate in a similar manner are being studied since they have the potential to perform similar tasks in a variety of applications. In this paper, a synthetic nanomotor that moves along a filament track, without invoking motor conformational changes, is constructed and its properties are studied in detail. The motor is an oligomer comprising three linked beads with specific binding properties. The filament track is a stiff polymer chain, also described by a linear chain of linked coarse-grained molecular groups modeled as beads. Reactions on the filament that are catalyzed by a motor bead and use fuel in the environment, in conjunction within the binding affinities of the motor beads to the filament beads, lead to directed motion. The system operates out of equilibrium due to the state of the filament and supply of fuel. The motor, filament, and surrounding medium are all described at microscopic level that permits a full analysis of the motor motion. A stochastic model that captures the main trends seen in the simulations is also presented. The results of this study point to some of the key features that could be used to construct nanomotors that undergo biased walks powered by chemical reactions on filaments.

  11. Role of motor unit structure in defining function

    NASA Technical Reports Server (NTRS)

    Monti, R. J.; Roy, R. R.; Edgerton, V. R.

    2001-01-01

    Motor units, defined as a motoneuron and all of its associated muscle fibers, are the basic functional units of skeletal muscle. Their activity represents the final output of the central nervous system, and their role in motor control has been widely studied. However, there has been relatively little work focused on the mechanical significance of recruiting variable numbers of motor units during different motor tasks. This review focuses on factors ranging from molecular to macroanatomical components that influence the mechanical output of a motor unit in the context of the whole muscle. These factors range from the mechanical properties of different muscle fiber types to the unique morphology of the muscle fibers constituting a motor unit of a given type and to the arrangement of those motor unit fibers in three dimensions within the muscle. We suggest that as a result of the integration of multiple levels of structural and physiological levels of organization, unique mechanical properties of motor units are likely to emerge. Copyright 2001 John Wiley & Sons, Inc.

  12. A structural pathway for activation of the kinesin motor ATPase

    PubMed Central

    Yun, Mikyung; Zhang, Xiaohua; Park, Cheon-Gil; Park, Hee-Won; Endow, Sharyn A.

    2001-01-01

    Molecular motors move along actin or microtubules by rapidly hydrolyzing ATP and undergoing changes in filament-binding affinity with steps of the nucleotide hydrolysis cycle. It is generally accepted that motor binding to its filament greatly increases the rate of ATP hydrolysis, but the structural changes in the motor associated with ATPase activation are not known. To identify the conformational changes underlying motor movement on its filament, we solved the crystal structures of three kinesin mutants that decouple nucleotide and microtubule binding by the motor, and block microtubule-activated, but not basal, ATPase activity. Conformational changes in the structures include a disordered loop and helices in the switch I region and a visible switch II loop, which is disordered in wild-type structures. Switch I moved closer to the bound nucleotide in two mutant structures, perturbing water-mediated interactions with the Mg2+. This could weaken Mg2+ binding and accelerate ADP release to activate the motor ATPase. The structural changes we observe define a signaling pathway within the motor for ATPase activation that is likely to be essential for motor movement on microtubules. PMID:11387196

  13. Motor-mediated alignment of microtubules in semidilute mixtures

    NASA Astrophysics Data System (ADS)

    Swaminathan, Sumanth; Ziebert, Falko; Karpeev, Dmitry; Aranson, Igor S.

    2009-03-01

    We propose and study a model of molecular motor-induced ordering in a cytoskeletal filament solution for the semidilute case. Motors attach to a pair of filaments and walk along the pair bringing them into closer alignment. In the semidilute regime multiple motors can bind a filament to several others and, for a critical motor density, induce a transition to an ordered phase with a nonzero mean orientation. The motors, on the one hand, cause closer filament alignment, and, on the other hand, induce fluctuations that are dependent on the relative orientation of the filaments to which the motors are attached. We develop a spatially homogenous, mean-field theory that explicitly accounts for a force-dependent detachment rate of motors, which in turn affects the mean and the fluctuations of the net force acting on a filament. This model considers each filament to be in motor contact with all other filaments in the solution. We show that the transition to the oriented state changes from second order to first order when the force-dependent detachment becomes important.

  14. B13+: Photodriven Molecular Wankel Engine

    SciTech Connect

    Zhang, Jin; Sergeeva, Alina P.; Sparta, Manuel; Alexandrova, Anastassia N.

    2012-07-09

    Synthetic molecular motors that are capable of delivering controlled movement upon energy input are one of the key building blocks in nanomachinery. The major energy sources of molecular motors are from chemical reactions, photon beams, or electric current, which are converted into mechanical forces through the excitation of the electronic states of the molecule. The energy scale of the electronic excitation is normally two orders of magnitude larger than the molecular vibrational frequencies. To reduce the heat dissipation and increase the energy utilization efficiency, a motor running purely on the electronic ground-state (GS) potential energy surfaces is highly desirable.

  15. An autonomous chemically fuelled small-molecule motor

    NASA Astrophysics Data System (ADS)

    Wilson, Miriam R.; Solà, Jordi; Carlone, Armando; Goldup, Stephen M.; Lebrasseur, Nathalie; Leigh, David A.

    2016-06-01

    Molecular machines are among the most complex of all functional molecules and lie at the heart of nearly every biological process. A number of synthetic small-molecule machines have been developed, including molecular muscles, synthesizers, pumps, walkers, transporters and light-driven and electrically driven rotary motors. However, although biological molecular motors are powered by chemical gradients or the hydrolysis of adenosine triphosphate (ATP), so far there are no synthetic small-molecule motors that can operate autonomously using chemical energy (that is, the components move with net directionality as long as a chemical fuel is present). Here we describe a system in which a small molecular ring (macrocycle) is continuously transported directionally around a cyclic molecular track when powered by irreversible reactions of a chemical fuel, 9-fluorenylmethoxycarbonyl chloride. Key to the design is that the rate of reaction of this fuel with reactive sites on the cyclic track is faster when the macrocycle is far from the reactive site than when it is near to it. We find that a bulky pyridine-based catalyst promotes carbonate-forming reactions that ratchet the displacement of the macrocycle away from the reactive sites on the track. Under reaction conditions where both attachment and cleavage of the 9-fluorenylmethoxycarbonyl groups occur through different processes, and the cleavage reaction occurs at a rate independent of macrocycle location, net directional rotation of the molecular motor continues for as long as unreacted fuel remains. We anticipate that autonomous chemically fuelled molecular motors will find application as engines in molecular nanotechnology.

  16. Micromachine Wedge Stepping Motor

    SciTech Connect

    Allen, J.J.; Schriner, H.K.

    1998-11-04

    A wedge stepping motor, which will index a mechanism, has been designed and fabricated in the surface rnicromachine SUMMiT process. This device has demonstrated the ability to index one gear tooth at a time with speeds up to 205 teeth/see. The wedge stepper motor has the following features, whi:h will be useful in a number of applications. o The ability to precisely position mechanical components. . Simple pulse signals can be used for operation. o Only 2 drive signals are requixed for operation. o Torque and precision capabilities increase with device size . The device to be indexed is restrained at all times by the wedge shaped tooth that is used for actuation. This paper will discuss the theory of operation and desi=m of the wedge stepping motor. The fabrication and testing of I he device will also be presented.

  17. Bent shaft motor

    DOEpatents

    Benavides, Gilbert L.

    1998-01-01

    A nonelectromagnetic motor comprising a base, a bent shaft which is rotable relative to the base wherein the bent shaft comprises a straight portion aligned with a main axis and an offset portion that is offset with respect to the main axis; and a drive means for driving the offset portion of the bent shaft along a generally circular path in a plane perpendicular to the main axis to rotate the bent shaft. The bent shaft and drive means for driving the bent shaft can be selected from piezoelectric, magnetostrictive, rheological and shape memory alloys. The drive means of the nonelectromagnetic motor can additionally comprise a shell which shell surrounds and houses the bent shaft and precesses or gyrates which in turn causes the bent drive shaft to rotate. The nonelectromagnetic motor does not rely on friction for the application of torque upon a rotor.

  18. Bent shaft motor

    DOEpatents

    Benavides, G.L.

    1998-05-05

    A nonelectromagnetic motor comprising a base, a bent shaft which is rotatable relative to the base wherein the bent shaft comprises a straight portion aligned with a main axis and an offset portion that is offset with respect to the main axis; and a drive means for driving the offset portion of the bent shaft along a generally circular path in a plane perpendicular to the main axis to rotate the bent shaft. The bent shaft and drive means for driving the bent shaft can be selected from piezoelectric, magnetostrictive, rheological and shape memory alloys. The drive means of the nonelectromagnetic motor can additionally comprise a shell which shell surrounds and houses the bent shaft and precesses or gyrates which in turn causes the bent drive shaft to rotate. The nonelectromagnetic motor does not rely on friction for the application of torque upon a rotor. 11 figs.

  19. ac bidirectional motor controller

    NASA Technical Reports Server (NTRS)

    Schreiner, K.

    1988-01-01

    Test data are presented and the design of a high-efficiency motor/generator controller at NASA-Lewis for use with the Space Station power system testbed is described. The bidirectional motor driver is a 20 kHz to variable frequency three-phase ac converter that operates from the high-frequency ac bus being designed for the Space Station. A zero-voltage-switching pulse-density-modulation technique is used in the converter to shape the low-frequency output waveform.

  20. The functional alterations associated with motor imagery training: a comparison between motor execution and motor imagery of sequential finger tapping

    NASA Astrophysics Data System (ADS)

    Zhang, Hang; Yao, Li; Long, Zhiying

    2011-03-01

    Motor imagery training, as an effective strategy, has been more and more applied to mental disorders rehabilitation and motor skill learning. Studies on the neural mechanism underlying motor imagery have suggested that such effectiveness may be related to the functional congruence between motor execution and motor imagery. However, as compared to the studies on motor imagery, the studies on motor imagery training are much fewer. The functional alterations associated with motor imagery training and the effectiveness of motor imagery training on motor performance improvement still needs further investigation. Using fMRI, we employed a sequential finger tapping paradigm to explore the functional alterations associated with motor imagery training in both motor execution and motor imagery task. We hypothesized through 14 consecutive days motor imagery training, the motor performance could be improved and the functional congruence between motor execution and motor imagery would be sustained form pre-training phase to post-training phase. Our results confirmed the effectiveness of motor imagery training in improving motor performance and demonstrated in both pre and post-training phases, motor imagery and motor execution consistently sustained the congruence in functional neuroanatomy, including SMA (supplementary motor cortex), PMA (premotor area); M1( primary motor cortex) and cerebellum. Moreover, for both execution and imagery tasks, a similar functional alteration was observed in fusiform through motor imagery training. These findings provided an insight into the effectiveness of motor imagery training and suggested its potential therapeutic value in motor rehabilitation.

  1. Motor current signature analysis method for diagnosing motor operated devices

    DOEpatents

    Haynes, Howard D.; Eissenberg, David M.

    1990-01-01

    A motor current noise signature analysis method and apparatus for remotely monitoring the operating characteristics of an electric motor-operated device such as a motor-operated valve. Frequency domain signal analysis techniques are applied to a conditioned motor current signal to distinctly identify various operating parameters of the motor driven device from the motor current signature. The signature may be recorded and compared with subsequent signatures to detect operating abnormalities and degradation of the device. This diagnostic method does not require special equipment to be installed on the motor-operated device, and the current sensing may be performed at remote control locations, e.g., where the motor-operated devices are used in accessible or hostile environments.

  2. Molecular-beam gas-sampling system

    NASA Technical Reports Server (NTRS)

    Young, W. S.; Knuth, E. L.

    1972-01-01

    A molecular beam mass spectrometer system for rocket motor combustion chamber sampling is described. The history of the sampling system is reviewed. The problems associated with rocket motor combustion chamber sampling are reported. Several design equations are presented. The results of the experiments include the effects of cooling water flow rates, the optimum separation gap between the end plate and sampling nozzle, and preliminary data on compositions in a rocket motor combustion chamber.

  3. 46 CFR 169.684 - Overcurrent protection for motors and motor branch circuits.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Overcurrent protection for motors and motor branch... motors and motor branch circuits. (a) Except as provided in paragraph (d) of this section, each motor... motor that is responsive to motor current or to both motor current and temperature may be used. (b)...

  4. 46 CFR 169.684 - Overcurrent protection for motors and motor branch circuits.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Overcurrent protection for motors and motor branch... motors and motor branch circuits. (a) Except as provided in paragraph (d) of this section, each motor... motor that is responsive to motor current or to both motor current and temperature may be used. (b)...

  5. Magnetically Coupled Adjustable Speed Motor Drives - Motor Tip Sheet #13

    SciTech Connect

    2008-07-01

    Alternating current electric motors rotate at a nearly constant speed that is determined by motor design and line frequency. Energy savings of 50% or more may be available when fixed speed systems are modified to allow the motor speed to match variable load requirements of a centrifugal fan or pump.

  6. Method for assessing motor insulation on operating motors

    DOEpatents

    Kueck, John D.; Otaduy, Pedro J.

    1997-01-01

    A method for monitoring the condition of electrical-motor-driven devices. The method is achieved by monitoring electrical variables associated with the functioning of an operating motor, applying these electrical variables to a three phase equivalent circuit and determining non-symmetrical faults in the operating motor based upon symmetrical components analysis techniques.

  7. Method for assessing motor insulation on operating motors

    DOEpatents

    Kueck, J.D.; Otaduy, P.J.

    1997-03-18

    A method for monitoring the condition of electrical-motor-driven devices is disclosed. The method is achieved by monitoring electrical variables associated with the functioning of an operating motor, applying these electrical variables to a three phase equivalent circuit and determining non-symmetrical faults in the operating motor based upon symmetrical components analysis techniques. 15 figs.

  8. Reciprocating Linear Electric Motor

    NASA Technical Reports Server (NTRS)

    Goldowsky, M. P.

    1984-01-01

    Features include structural simplicity and good force/displacement characteristics. Reciprocating motor has simple, rugged construction, relatively low reciprocating weight, improved power delivery, and improved force control. Wear reduced by use of magnetic bearings. Intended to provide drivers for long-lived Stirling-cycle cryogenic refrigerators, concept has less exotic applications, such as fuel pumps.

  9. Perceptual-Motor Dysfunction.

    ERIC Educational Resources Information Center

    Pyfer, Jean L.

    Discussed are theoretical and treatment aspects of perceptual motor dysfunction and rehabilitation in 4- to 12-year-old academically failing children involved in a 3-year investigation at the University of Kansas. The program is said to stress increasing the amount of stimulation received by sensory receptors of the vestibular, reflex, and haptic…

  10. Solid rocket motors

    NASA Technical Reports Server (NTRS)

    Carpenter, Ronn L.

    1993-01-01

    Structural requirements, materials and, especially, processing are critical issues that will pace the introduction of new types of solid rocket motors. Designers must recognize and understand the drivers associated with each of the following considerations: (1) cost; (2) energy density; (3) long term storage with use on demand; (4) reliability; (5) safety of processing and handling; (6) operability; and (7) environmental acceptance.

  11. Thiokol Solid Rocket Motors

    NASA Technical Reports Server (NTRS)

    Graves, S. R.

    2000-01-01

    This paper presents viewgraphs on thiokol solid rocket motors. The topics include: 1) Communications; 2) Military and government intelligence; 3) Positioning satellites; 4) Remote sensing; 5) Space burial; 6) Science; 7) Space manufacturing; 8) Advertising; 9) Space rescue space debris management; 10) Space tourism; 11) Space settlements; 12) Hazardous waste disposal; 13) Extraterrestrial resources; 14) Fast package delivery; and 15) Space utilities.

  12. Solid rocket motors

    NASA Astrophysics Data System (ADS)

    Carpenter, Ronn L.

    1993-02-01

    Structural requirements, materials and, especially, processing are critical issues that will pace the introduction of new types of solid rocket motors. Designers must recognize and understand the drivers associated with each of the following considerations: (1) cost; (2) energy density; (3) long term storage with use on demand; (4) reliability; (5) safety of processing and handling; (6) operability; and (7) environmental acceptance.

  13. The St. Louis Motor

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    2011-01-01

    The St. Louis Motor, invented in 1909, is unique among physics apparatus for being named for a geographical place rather than a physicist. The sturdy little device (Fig. 1) has never been out of production. Any older school or physics department that has not done a catastrophic housecleaning in the last 20 years will certainly have a small flock…

  14. Mechanical solar motor: A concept

    NASA Technical Reports Server (NTRS)

    Hein, L. A.; Myers, W. N.

    1975-01-01

    Motor is proposed to convert radiation from sun directly into mechanical energy. Motor utilizes thermal expansion of liquid, heated by sun, as driving force. Unlike most thermally powered systems, it does not require that liquid be converted into vapor.

  15. Thermal motor positions magnetometer sensors

    NASA Technical Reports Server (NTRS)

    Kerwin, W. J.; Scott, S. G.

    1966-01-01

    Reversing, thermal, motor-driven device positions magnetometer sensors for checking zero offset. The device alternately positions two sensors at fixed positions 90 degrees apart. The thermal motor is fabricated completely of nonmagnetic materials.

  16. Electric motor model repair specifications

    SciTech Connect

    1995-08-01

    These model repair specifications list the minimum requirements for repair and overhaul of polyphase AC squireel cage induction motors. All power ranges, voltages, and speeds of squirrel cage motors are covered.

  17. Velocity Fluctuations in Kinesin-1 Gliding Motility Assays Originate in Motor Attachment Geometry Variations.

    PubMed

    Palacci, Henri; Idan, Ofer; Armstrong, Megan J; Agarwal, Ashutosh; Nitta, Takahiro; Hess, Henry

    2016-08-01

    Motor proteins such as myosin and kinesin play a major role in cellular cargo transport, muscle contraction, cell division, and engineered nanodevices. Quantifying the collective behavior of coupled motors is critical to our understanding of these systems. An excellent model system is the gliding motility assay, where hundreds of surface-adhered motors propel one cytoskeletal filament such as an actin filament or a microtubule. The filament motion can be observed using fluorescence microscopy, revealing fluctuations in gliding velocity. These velocity fluctuations have been previously quantified by a motional diffusion coefficient, which Sekimoto and Tawada explained as arising from the addition and removal of motors from the linear array of motors propelling the filament as it advances, assuming that different motors are not equally efficient in their force generation. A computational model of kinesin head diffusion and binding to the microtubule allowed us to quantify the heterogeneity of motor efficiency arising from the combination of anharmonic tail stiffness and varying attachment geometries assuming random motor locations on the surface and an absence of coordination between motors. Knowledge of the heterogeneity allows the calculation of the proportionality constant between the motional diffusion coefficient and the motor density. The calculated value (0.3) is within a standard error of our measurements of the motional diffusion coefficient on surfaces with varying motor densities calibrated by landing rate experiments. This allowed us to quantify the loss in efficiency of coupled molecular motors arising from heterogeneity in the attachment geometry. PMID:27414063

  18. Self-organized pattern formation in motor-microtubule mixtures

    NASA Astrophysics Data System (ADS)

    Sankararaman, Sumithra; Menon, Gautam I.; Sunil Kumar, P. B.

    2004-09-01

    We model the stable self-organized patterns obtained in the nonequilibrium steady states of mixtures of molecular motors and microtubules. In experiments [Nédélec , Nature (London) 389, 305 (1997); Surrey , Science 292, 1167 (2001)] performed in a quasi-two-dimensional geometry, microtubules are oriented by complexes of motor proteins. This interaction yields a variety of patterns, including arrangements of asters, vortices, and disordered configurations. We model this system via a two-dimensional vector field describing the local coarse-grained microtubule orientation and two scalar density fields associated to molecular motors. These scalar fields describe motors which either attach to and move along microtubules or diffuse freely within the solvent. Transitions between single aster, spiral, and vortex states are obtained as a consequence of confinement, as parameters in our model are varied. For systems in which the effects of confinement can be neglected, we present a map of nonequilibrium steady states, which includes arrangements of asters and vortices separately as well as aster-vortex mixtures and fully disordered states. We calculate the steady state distribution of bound and free motors in aster and vortex configurations of microtubules and compare these to our simulation results, providing qualitative arguments for the stability of different patterns in various regimes of parameter space. We study the role of crowding or “saturation” effects on the density profiles of motors in asters, discussing the role of such effects in stabilizing single asters. We also comment on the implications of our results for experiments.

  19. Multiple stage miniature stepping motor

    DOEpatents

    Niven, William A.; Shikany, S. David; Shira, Michael L.

    1981-01-01

    A stepping motor comprising a plurality of stages which may be selectively activated to effect stepping movement of the motor, and which are mounted along a common rotor shaft to achieve considerable reduction in motor size and minimum diameter, whereby sequential activation of the stages results in successive rotor steps with direction being determined by the particular activating sequence followed.

  20. Experiments with a DC Motor

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2010-01-01

    Experiments with an electric motor provide good opportunity to demonstrate some basic laws of electricity and magnetism. The aim of the experiments with a low-power dc motor is to show how the motor approaches its steady rotation and how its torque, mechanical power and efficiency depend on the rotation velocity. The tight relationship between the…

  1. Motor Education: Educational Development Programs.

    ERIC Educational Resources Information Center

    Tansley, A. E.

    This booklet presents educational programs and activities focusing on motor skills for 5- to 9-year-old children and older children with learning problems. The premise of the activities is that the acquisition of motor skills is essential to basic learning. The role of language as a mediator and controller of motor development is emphasized. The…

  2. Motor Vehicle Theft. Special Report.

    ERIC Educational Resources Information Center

    Harlow, Caroline Wolf

    Thirteen years of data from the National Crime Survey were analyzed to examine the characteristics of motor vehicle theft, to identify trends during the past 13 years, and to determine who are most likely to be victims of motor vehicle theft. All motor vehicle thefts reported to the National Crime Survey from 1973 through 1985 were examined.…

  3. Speed control for synchronous motors

    NASA Technical Reports Server (NTRS)

    Packard, H.; Schott, J.

    1981-01-01

    Feedback circuit controls fluctuations in speed of synchronous ac motor. Voltage proportional to phase angle is developed by phase detector, rectified, amplified, compared to threshold, and reapplied positively or negatively to motor excitation circuit. Speed control reduces wow and flutter of audio turntables and tape recorders, and enhances hunting in gyroscope motors.

  4. Motor sequence learning and motor adaptation in primary cervical dystonia.

    PubMed

    Katschnig-Winter, Petra; Schwingenschuh, Petra; Davare, Marco; Sadnicka, Anna; Schmidt, Reinhold; Rothwell, John C; Bhatia, Kailash P; Edwards, Mark J

    2014-06-01

    Motor sequence learning and motor adaptation rely on overlapping circuits predominantly involving the basal ganglia and cerebellum. Given the importance of these brain regions to the pathophysiology of primary dystonia, and the previous finding of abnormal motor sequence learning in DYT1 gene carriers, we explored motor sequence learning and motor adaptation in patients with primary cervical dystonia. We recruited 12 patients with cervical dystonia and 11 healthy controls matched for age. Subjects used a joystick to move a cursor from a central starting point to radial targets as fast and accurately as possible. Using this device, we recorded baseline motor performance, motor sequence learning and a visuomotor adaptation task. Patients with cervical dystonia had a significantly higher peak velocity than controls. Baseline performance with random target presentation was otherwise normal. Patients and controls had similar levels of motor sequence learning and motor adaptation. Our patients had significantly higher peak velocity compared to controls, with similar movement times, implying a different performance strategy. The preservation of motor sequence learning in cervical dystonia patients contrasts with the previously observed deficit seen in patients with DYT1 gene mutations, supporting the hypothesis of differing pathophysiology in different forms of primary dystonia. Normal motor adaptation is an interesting finding. With our paradigm we did not find evidence that the previously documented cerebellar abnormalities in cervical dystonia have a behavioral correlate, and thus could be compensatory or reflect "contamination" rather than being directly pathological.

  5. MotorMaster database of three-phase electric motors

    SciTech Connect

    Stickney, B.L.

    1993-12-31

    Selecting the right motor for a new or replacement application used to be a daunting task. Making an intelligent choice involved a search through a stack of motor catalogs for information on efficiency, voltage, speed, horsepower, torque, service factor, power factor, frame type, and cost. The MotorMaster software package, available from the Washington State Energy Office, takes the drudgery out of motor selection by enabling rapid analysis of the most efficient and cost-effective single-speed three-phase induction motors. It has a built-in motor database, easy to use comparison and analysis features, and can calculate utility rebates and simple paybacks. By speeding the selection process and providing comprehensive economic justification for the final equipment choice, software tools like MotorMaster can become an important component of utility DSM programs. And as a bonus, wide use of such software may lead to more systematic and consistent use of energy efficient equipment.

  6. A Cytoplasmic Dynein Tail Mutation Impairs Motor Processivity

    PubMed Central

    Ori-McKenney, Kassandra M.; Xu, Jing; Gross, Steven P.; Vallee, Richard B.

    2012-01-01

    Mutations in the tail of the cytoplasmic dynein molecule have been reported to cause neurodegenerative disease in mice. The mutant mouse strain Legs at Odd Angles (Loa) exhibits impaired retrograde axonal transport, but the molecular deficiencies in the mutant dynein molecule, and how they contribute to neurodegeneration, are unknown. To address these questions, we purified wild-type and mutant mouse dynein. Using biochemical, single molecule, and live cell imaging techniques, we find a strong inhibition of motor run-length in vitro and in vivo, and significantly altered motor domain coordination in the mutant dynein. These results suggest a potential role for the dynein tail in motor function, and provide the first direct evidence for a link between single-motor processivity and disease. PMID:21102439

  7. A synthetic DNA motor that transports nanoparticles along carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cha, Tae-Gon; Pan, Jing; Chen, Haorong; Salgado, Janette; Li, Xiang; Mao, Chengde; Choi, Jong Hyun

    2014-01-01

    Intracellular protein motors have evolved to perform specific tasks critical to the function of cells such as intracellular trafficking and cell division. Kinesin and dynein motors, for example, transport cargoes in living cells by walking along microtubules powered by adenosine triphosphate hydrolysis. These motors can make discrete 8 nm centre-of-mass steps and can travel over 1 µm by changing their conformations during the course of adenosine triphosphate binding, hydrolysis and product release. Inspired by such biological machines, synthetic analogues have been developed including self-assembled DNA walkers that can make stepwise movements on RNA/DNA substrates or can function as programmable assembly lines. Here, we show that motors based on RNA-cleaving DNA enzymes can transport nanoparticle cargoes--CdS nanocrystals in this case--along single-walled carbon nanotubes. Our motors extract chemical energy from RNA molecules decorated on the nanotubes and use that energy to fuel autonomous, processive walking through a series of conformational changes along the one-dimensional track. The walking is controllable and adapts to changes in the local environment, which allows us to remotely direct `go' and `stop' actions. The translocation of individual motors can be visualized in real time using the visible fluorescence of the cargo nanoparticle and the near-infared emission of the carbon-nanotube track. We observed unidirectional movements of the molecular motors over 3 µm with a translocation velocity on the order of 1 nm min-1 under our experimental conditions.

  8. Motor technology for mining applications advances

    SciTech Connect

    Fiscor, S.

    2009-08-15

    AC motors are steadily replacing DC motors in mining and mineral processing equipment, requiring less maintenance. The permanent magnet rotor, or the synchronous motor, has enabled Blador to introduce a line of cooling tower motors. Synchronous motors are soon likely to take over from the induction motor. 1 photo.

  9. Big Savings from Smart Motors

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Chesebrough-Pond's operates 32 plants across the nation and in those plants are more than 10,000 electric motors. In an effort to cut down on waste of electrical power used by these motors, Chesebrough organized a Corporate Advanced Technology Group to devise ways of improving productivity and cut manufacturing costs. Chesebrough used NASA's Marshall Space Flight Center's Power Factor Controller technology as a departure point for development of their own computerized motor controller that enables motors to operate at maximum efficiency regardless of the motor's applications or operating condition.

  10. Ironless armature torque motor

    NASA Technical Reports Server (NTRS)

    Fisher, R. L.

    1972-01-01

    Four iron-less armature torque motors, four Hall device position sensor assemblies, and two test fixtures were fabricated. The design approach utilized samarium cobalt permanent magnets, a large airgap, and a three-phase winding in a stationary ironless armature. Hall devices were employed to sense rotor position. An ironless armature torque motor having an outer diameter of 4.25 inches was developed to produce a torque constant of 65 ounce-inches per ampere with a resistance of 20.5 ohms. The total weight, including structural elements, was 1.58 pounds. Test results indicated that all specifications were met except for generated voltage waveform. It is recommended that investigations be made concerning the generated voltage waveform to determine if it may be improved.

  11. Advanced Motor Drives Studies

    NASA Technical Reports Server (NTRS)

    Ehsani, M.; Tchamdjou, A.

    1997-01-01

    This report presents an evaluation of advanced motor drive systems as a replacement for the hydrazine fueled APU units. The replacement technology must meet several requirements which are particular to the space applications and the Orbiter in general. Some of these requirements are high efficiency, small size, high power density. In the first part of the study several motors are compared, based on their characteristics and in light of the Orbiter requirements. The best candidate, the brushless DC is chosen because of its particularly good performance with regards to efficiency. Several power electronics drive technologies including the conventional three-phase hard switched and several soft-switched inverters are then presented. In the last part of the study, a soft-switched inverter is analyzed and compared to its conventional hard-switched counterpart. Optimal efficiency is a basic requirement for space applications and the soft-switched technology represents an unavoidable trend for the future.

  12. Magnetostrictive direct drive motors

    NASA Technical Reports Server (NTRS)

    Naik, Dipak; Dehoff, P. H.

    1992-01-01

    A new rare earth alloy, Terfenol-D, combines low frequency operation and extremely high energy density with high magnetostriction. Its material properties make it suitable as a drive element for actuators requiring high output torque. The high strains, the high forces and the high controllability of Terfenol alloys provide a powerful and challenging basis for new ways to generate motion in actuators. Two prototypes of motors using Terfenol-D rods were developed at NASA Goddard. The basic principles of operation are provided of the motor along with other relevant details. A conceptual design of a torque limiting safety clutch/brake under development is illustrated. Also, preliminary design drawings of a linear actuator using Terfenol-D is shown.

  13. Understanding social motor coordination.

    PubMed

    Schmidt, R C; Fitzpatrick, Paula; Caron, Robert; Mergeche, Joanna

    2011-10-01

    Recently there has been much interest in social coordination of motor movements, or as it is referred to by some researchers, joint action. This paper reviews the cognitive perspective's common coding/mirror neuron theory of joint action, describes some of its limitations and then presents the behavioral dynamics perspective as an alternative way of understanding social motor coordination. In particular, behavioral dynamics' ability to explain the temporal coordination of interacting individuals is detailed. Two experiments are then described that demonstrate how dynamical processes of synchronization are apparent in the coordination underlying everyday joint actions such as martial art exercises, hand-clapping games, and conversations. The import of this evidence is that emergent dynamic patterns such as synchronization are the behavioral order that any neural substrate supporting joint action (e.g., mirror systems) would have to sustain.

  14. Motor learning by observing.

    PubMed

    Mattar, Andrew A G; Gribble, Paul L

    2005-04-01

    Learning complex motor behaviors like riding a bicycle or swinging a golf club is based on acquiring neural representations of the mechanical requirements of movement (e.g., coordinating muscle forces to control the club). Here we provide evidence that mechanisms matching observation and action facilitate motor learning. Subjects who observed a video depicting another person learning to reach in a novel mechanical environment (imposed by a robot arm) performed better when later tested in the same environment than subjects who observed similar movements but no learning; moreover, subjects who observed learning of a different environment performed worse. We show that this effect is not based on conscious strategies but instead depends on the implicit engagement of neural systems for movement planning and control. PMID:15820701

  15. Prospective errors determine motor learning

    PubMed Central

    Takiyama, Ken; Hirashima, Masaya; Nozaki, Daichi

    2015-01-01

    Diverse features of motor learning have been reported by numerous studies, but no single theoretical framework concurrently accounts for these features. Here, we propose a model for motor learning to explain these features in a unified way by extending a motor primitive framework. The model assumes that the recruitment pattern of motor primitives is determined by the predicted movement error of an upcoming movement (prospective error). To validate this idea, we perform a behavioural experiment to examine the model’s novel prediction: after experiencing an environment in which the movement error is more easily predictable, subsequent motor learning should become faster. The experimental results support our prediction, suggesting that the prospective error might be encoded in the motor primitives. Furthermore, we demonstrate that this model has a strong explanatory power to reproduce a wide variety of motor-learning-related phenomena that have been separately explained by different computational models. PMID:25635628

  16. An Electrostatic Stepper Motor

    NASA Astrophysics Data System (ADS)

    Partington, E. C.; Wong, Edward Chun Kay; Bullough, W. A.

    This paper describes a new concept in pulse controlled motor and precision linear actuator techniques. Piezo translators [PZT] employed to provide reciprocating primary motion are connected to a load via a controllable electrorheological fluid [ERF] clutch to form a programmable speed and step-width drive. Ideal considerations are used to quantify the limiting potential of the drive and details are given of its development and progress.

  17. EPDM rocket motor insulation

    NASA Technical Reports Server (NTRS)

    Guillot, David G. (Inventor); Harvey, Albert R. (Inventor)

    2003-01-01

    A novel and improved EPDM formulation for a solid propellant rocket motor is described wherein hexadiene EPDM monomer components are replaced by alkylidene norbornene components and with appropriate adjustment of curing and other additives functionally-required rheological and physical characteristics are achieved with the desired compatibility with any one of a plurality of solid filler materials, e.g. powder silica, carbon fibers or aramid fibers, and with appropriate adhesion and extended storage or shelf life characteristics.

  18. EPDM rocket motor insulation

    NASA Technical Reports Server (NTRS)

    Guillot, David G. (Inventor); Harvey, Albert R. (Inventor)

    2004-01-01

    A novel and improved EPDM formulation for a solid propellant rocket motor is described wherein hexadiene EPDM monomer components are replaced by alkylidene norbornene components, and, with appropriate adjustment of curing and other additives, functionally required rheological and physical characteristics are achieved with the desired compatibility with any one of a plurality of solid filler materials, e.g., powder silica, carbon fibers or aramid fibers, and with appropriate adhesion and extended storage or shelf-life characteristics.

  19. EPDM rocket motor insulation

    NASA Technical Reports Server (NTRS)

    Guillot, David G. (Inventor); Harvey, Albert R. (Inventor)

    2008-01-01

    A novel and improved EPDM formulation for a solid propellant rocket motor is described wherein hexadiene EPDM monomer components are replaced by alkylidene norbornene components, and, with appropriate adjustment of curing and other additives, functionally required rheological and physical characteristics are achieved with the desired compatibility with any one of a plurality of solid filler materials, e.g., powder silica, carbon fibers or aramid fibers, and with appropriate adhesion and extended storage or shelf-life characteristics.

  20. Hydraulic motor for cars

    SciTech Connect

    Gagnon, D.C.

    1986-09-02

    A hydraulic motor for a car is described comprising, in combination, an automotive vehicle engine for travel self-propulsion, including a block, a plurality of cylinders in the block, a piston slidable in each cylinder, a crankshaft in the block, a piston rod connected between the crankshaft and each of the pistons, a power take-off gear on the crankshaft for the travel self-propulsion, and the engine including a hydraulic means for driving the pistons in the cylinders.

  1. The St. Louis Motor

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2011-10-01

    The St. Louis Motor, invented in 1909, is unique among physics apparatus for being named for a geographical place rather than a physicist. The sturdy little device (Fig. 1) has never been out of production. Any older school or physics department that has not done a catastrophic housecleaning in the last 20 years will certainly have a small flock of them in the back room.

  2. Libert-E Motor

    ERIC Educational Resources Information Center

    Sieloff, Susan F.; Kinnunen, Raymond; Chevarley, Joseph

    2011-01-01

    Kei Yun Wong has big dreams. She has been entrusted with the United States launch of Libert-E Motor, a new line of Chinese-manufactured electric scooters. With only $750,000 of her original budget of $3 million left, she needs to make sure that the launch succeeds, as it represents the initial step in her desire to create the first Chinese global…

  3. Motor Fuel Excise Taxes

    SciTech Connect

    2015-09-01

    A new report from the National Renewable Energy Laboratory (NREL) explores the role of alternative fuels and energy efficient vehicles in motor fuel taxes. Throughout the United States, it is common practice for federal, state, and local governments to tax motor fuels on a per gallon basis to fund construction and maintenance of our transportation infrastructure. In recent years, however, expenses have outpaced revenues creating substantial funding shortfalls that have required supplemental funding sources. While rising infrastructure costs and the decreasing purchasing power of the gas tax are significant factors contributing to the shortfall, the increased use of alternative fuels and more stringent fuel economy standards are also exacerbating revenue shortfalls. The current dynamic places vehicle efficiency and petroleum use reduction polices at direct odds with policies promoting robust transportation infrastructure. Understanding the energy, transportation, and environmental tradeoffs of motor fuel tax policies can be complicated, but recent experiences at the state level are helping policymakers align their energy and environmental priorities with highway funding requirements.

  4. Dyspraxia, Motor Function and Visual-Motor Integration in Autism

    PubMed Central

    Miller, M.; Chukoskie, L.; Zinni, M.; Townsend, J.; Trauner, D.

    2014-01-01

    This project assessed dyspraxia in high-functioning school aged children with autism with a focus on Ideational Praxis. We examined the association of specific underlying motor function including eye movement with ideational dyspraxia (sequences of skilled movements) as well as the possible role of visual-motor integration in dyspraxia. We found that compared to IQ-, sex- and age-matched typically developing children, the children with autism performed significantly worse on: Ideational and Buccofacial praxis; a broad range of motor tests, including measures of simple motor skill, timing and accuracy of saccadic eye movements and motor coordination; and tests of visual-motor integration. Impairments in individual children with autism were heterogeneous in nature, although when we examined the praxis data as a function of a qualitative measure representing motor timing, we found that children with poor motor timing performed worse on all praxis categories and had slower and less accurate eye movements while those with regular timing performed as well as typical children on those same tasks. Our data provide evidence that both motor function and visual-motor integration contribute to dyspraxia. We suggest that dyspraxia in autism involves cerebellar mechanisms of movement control and the integration of these mechanisms with cortical networks implicated in praxis. PMID:24742861

  5. Wholly Synthetic Molecular Machines.

    PubMed

    Cheng, Chuyang; Stoddart, J Fraser

    2016-06-17

    The past quarter of a century has witnessed an increasing engagement on the part of physicists and chemists in the design and synthesis of molecular machines de novo. This minireview traces the development of artificial molecular machines from their prototypes in the form of shuttles and switches to their emergence as motors and pumps where supplies of energy in the form of chemical fuel, electrochemical potential and light activation become a minimum requirement for them to function away from equilibrium. The challenge facing this rapidly growing community of scientists and engineers today is one of putting wholly synthetic molecules to work, both individually and as collections. Here, we highlight some of the recent conceptual and practical advances relating to the operation of wholly synthetic rotary and linear motors.

  6. Wind motor applications for transportation

    SciTech Connect

    Lysenko, G.P.; Grigoriev, B.V.; Karpin, K.B.

    1996-12-31

    Motion equation for a vehicle equipped with a wind motor allows, taking into account the drag coefficients, to determine the optimal wind drag velocity in the wind motor`s plane, and hence, obtain all the necessary data for the wind wheel blades geometrical parameters definition. This optimal drag velocity significantly differs from the flow drag velocity which determines the maximum wind motor power. Solution of the motion equation with low drag coefficients indicates that the vehicle speed against the wind may be twice as the wind speed. One of possible transportation wind motor applications is its use on various ships. A ship with such a wind motor may be substantially easier to steer, and if certain devices are available, may proceed in autonomous control mode. Besides, it is capable of moving within narrow fairways. The cruise speed of a sailing boat and wind-motored ship were compared provided that the wind velocity direction changes along a harmonic law with regard to the motion direction. Mean dimensionless speed of the wind-motored ship appears to be by 20--25% higher than that of a sailing boat. There was analyzed a possibility of using the wind motors on planet rovers in Mars or Venus atmospheric conditions. A Mars rover power and motor system has been assessed for the power level of 3 kW.

  7. How Biophysics May Help Us Understand the Flagellar Motor of Bacteria Which Cause Infections.

    PubMed

    Baker, Matthew A B

    2016-01-01

    Motor proteins are molecules which convert chemical energy to mechanical work and are responsible for motility across all levels: for transport within a cell, for the motion of an individual cell in its surroundings, and for movement in multicellular aggregates, such as muscles. The bacterial flagellar motor is one of the canonical examples of a molecular complex made from several motor proteins, which self-assembles on demand and provides the locomotive force for bacteria. This locomotion provides a key aspect of bacteria's prevalence. Here, we outline the biophysics behind the assembly, the energetics, the switching and the rotation of this remarkable nanoscale electric motor that is Nature's first wheel.

  8. How Biophysics May Help Us Understand the Flagellar Motor of Bacteria Which Cause Infections.

    PubMed

    Baker, Matthew A B

    2016-01-01

    Motor proteins are molecules which convert chemical energy to mechanical work and are responsible for motility across all levels: for transport within a cell, for the motion of an individual cell in its surroundings, and for movement in multicellular aggregates, such as muscles. The bacterial flagellar motor is one of the canonical examples of a molecular complex made from several motor proteins, which self-assembles on demand and provides the locomotive force for bacteria. This locomotion provides a key aspect of bacteria's prevalence. Here, we outline the biophysics behind the assembly, the energetics, the switching and the rotation of this remarkable nanoscale electric motor that is Nature's first wheel. PMID:27193546

  9. Spinal motor neuron migration and the significance of topographic organization in the nervous system.

    PubMed

    Kania, Artur

    2014-01-01

    The nervous system displays a high degree of topographic organisation such that neuronal soma position is closely correlated to axonal trajectory. One example of such order is the myotopic organisation of the motor system where spinal motor neuron position parallels that of target muscles. This chapter will discuss the molecular mechanisms underlying motor neuron soma positioning, which include transcriptional control of Reelin signaling and cadherin expression. As the same transcription factors have been shown to control motor axon innervation of target muscles, a simple mechanism of topographic organisation specification is becoming evident raising the question of how coordinating soma position with axon trajectory might be important for nervous system wiring and its function.

  10. Bacterial Flagellar Motor Switch in Response to CheY-P Regulation and Motor Structural Alterations.

    PubMed

    Ma, Qi; Sowa, Yoshiyuki; Baker, Matthew A B; Bai, Fan

    2016-03-29

    The bacterial flagellar motor (BFM) is a molecular machine that rotates the helical filaments and propels the bacteria swimming toward favorable conditions. In our previous works, we built a stochastic conformational spread model to explain the dynamic and cooperative behavior of BFM switching. Here, we extended this model to test whether it can explain the latest experimental observations regarding CheY-P regulation and motor structural adaptivity. We show that our model predicts a strong correlation between rotational direction and the number of CheY-Ps bound to the switch complex, in agreement with the latest finding from Fukuoka et al. It also predicts that the switching sensitivity of the BFM can be fine-tuned by incorporating additional units into the switch complex, as recently demonstrated by Yuan et al., who showed that stoichiometry of FliM undergoes dynamic change to maintain ultrasensitivity in the motor switching response. In addition, by locking some rotor switching units on the switch complex into the stable clockwise-only conformation, our model has accurately simulated recent experiments expressing clockwise-locked FliG(ΔPAA) into the switch complex and reproduced the increased switching rate of the motor.

  11. Stepwise translocation of nucleic acid motors

    PubMed Central

    Myong, Sua; Ha, Taekjip

    2010-01-01

    Summary Recent single molecule studies have made a significant contribution to the understanding of the molecular mechanism involved in the movement of motor proteins which process DNA and RNA. Measurement of stepsize in two disparate motors, NS3 helicase and ribosome both revealed three basepair steps which consist of three hidden substeps. Combined with previous structural studies, NS3 is likely taking a single nucleotide step of translocation coupled to one ATP binding event and this mode may be conserved in multitude of helicases. Such a stepwise translocation movement appears to occur through main contacts with the phosphate backbone. Double stranded RNA and DNA motor, RIG-I and Φ29 respectively showed translocation on a duplex while tracking exclusively a single stranded RNA/DNA in a directional manner, 5′ to 3′ in both cases. Spontaneous dynamics displayed by ribosome ratcheting and SSB (single stranded DNA binding protein) diffusing on DNA were rectified by interacting cofactors and proteins, EF-G and RecA respectively. PMID:20061135

  12. Steps in the Bacterial Flagellar Motor

    PubMed Central

    Mora, Thierry; Yu, Howard; Sowa, Yoshiyuki; Wingreen, Ned S.

    2009-01-01

    The bacterial flagellar motor is a highly efficient rotary machine used by many bacteria to propel themselves. It has recently been shown that at low speeds its rotation proceeds in steps. Here we propose a simple physical model, based on the storage of energy in protein springs, that accounts for this stepping behavior as a random walk in a tilted corrugated potential that combines torque and contact forces. We argue that the absolute angular position of the rotor is crucial for understanding step properties and show this hypothesis to be consistent with the available data, in particular the observation that backward steps are smaller on average than forward steps. We also predict a sublinear speed versus torque relationship for fixed load at low torque, and a peak in rotor diffusion as a function of torque. Our model provides a comprehensive framework for understanding and analyzing stepping behavior in the bacterial flagellar motor and proposes novel, testable predictions. More broadly, the storage of energy in protein springs by the flagellar motor may provide useful general insights into the design of highly efficient molecular machines. PMID:19851449

  13. Multimotor Driven Cargos: From Single Motor under Load to the Role of Motor-Motor Coupling.

    PubMed

    Peker, Itay; Granek, Rony

    2016-07-01

    Motor proteins constitute an essential part of the cellular machinery. They have been the subject of intensive studies in the past two decades. Yet, when several motors simultaneously carry a single cargo, the effect of motor-motor coupling, such as mutual stalling and jamming, remains unclear. We commence by constructing a general model for single motor motion, which is a product of a derived load-dependent expression and a phenomenological motor specific function. Forming the latter according to recent single molecule measurements for a given load, the model correctly predicts the motor full step-size distribution for all other measured loads. We then use our proposed model to predict transport properties of multimotor complexes, with particular attention to 1-dimensional constructs with variable flexibility, motor density, and number of motors: (i) a chain of motors connected by springs, a recently studied construction of a pair, and (ii) an array of motors all connected by identical springs to a stiff rod, which is essentially a mirror image of standard gliding motility assays. In both systems, and for any number of carrying motors, we find that, while low flexibility results in a strongly damped velocity, increased flexibility renders an almost single motor velocity. Comparing our model based simulations to recent gliding assays we find remarkable qualitative agreement. We also demonstrate consistency with other multimotor motility assays. In all cases, the characteristic spring constant, that controls the crossover behavior between high and low velocity regimes, is found to be the stalling force divided by the mean step size. We conjecture that this characteristic spring constant can serve as a tool for engineering multimotor complexes. PMID:27044876

  14. Wind motor machine

    SciTech Connect

    Goedecke, A.

    1984-12-25

    An improved wind motor machine having a wind rotor rotatable about a vertical axis. The rotor core body of the machine is provided with convexly curved wind application surfaces and coacting outer wing bodies having load supporting airplane wing-shaped cross-sections. The efficiency of the machine is improved by means of stream guiding bodies disposed in the intermediate space between the rotor core body and the wing bodies. These stream guiding bodies extend in a desired streaming direction, that is normal to the rotational axis of the wind body, which insures substantially laminar air streaming within the intermediate space.

  15. Electric motor analysis at Dofasco

    SciTech Connect

    Brooks, D.; Morgan, V.A.; Nicholas, J.R. Jr.

    1997-03-01

    Initiatives adopted by Dofasco to enhance electric motor reliability and availability include: Enhancement of the electrical repair shop testing and repair capabilities; More stringent standards for motor repair service vendors; Application of predictive technologies to motors in service within manufacturing units; Training of personnel in electrical predictive condition monitoring and analysis methods; and Periodic audit and comparison of central support and operating unit predictive technology application and integration. The basis for the initiative is discussed together with illustrative case histories.

  16. Apogee motor rocketry reliability improvements

    NASA Technical Reports Server (NTRS)

    Behm, J.; Dowler, W.; Gin, W.

    1974-01-01

    Since 1963, solid propellant apogee motors have been placing satellites into geosynchronous orbits. Major technological breakthroughs are not required to satisfy future mission requirements; however, there is a need to improve reliability to enhance cost effectiveness. Several management test options are discussed. A summary of results and conclusions derived from review of missions, where failure of a solid motor was inferred, and correlation of system factors with failures are reported. Highlights of a solid motor diagnostic instrumentation study are presented. Finally, recommendations are provided for areas of future apogee motor upgrade, which will increase project cost effectiveness by reducing the potential for future flight failures.

  17. Force per cross-sectional area from molecules to muscles: a general property of biological motors

    PubMed Central

    Meyer-Vernet, Nicole

    2016-01-01

    We propose to formally extend the notion of specific tension, i.e. force per cross-sectional area—classically used for muscles, to quantify forces in molecular motors exerting various biological functions. In doing so, we review and compare the maximum tensions exerted by about 265 biological motors operated by about 150 species of different taxonomic groups. The motors considered range from single molecules and motile appendages of microorganisms to whole muscles of large animals. We show that specific tensions exerted by molecular and non-molecular motors follow similar statistical distributions, with in particular, similar medians and (logarithmic) means. Over the 1019 mass (M) range of the cell or body from which the motors are extracted, their specific tensions vary as Mα with α not significantly different from zero. The typical specific tension found in most motors is about 200 kPa, which generalizes to individual molecular motors and microorganisms a classical property of macroscopic muscles. We propose a basic order-of-magnitude interpretation of this result. PMID:27493785

  18. Model Studies of the Dynamics of Bacterial Flagellar Motors

    SciTech Connect

    Bai, F; Lo, C; Berry, R; Xing, J

    2009-03-19

    The Bacterial Flagellar Motor is a rotary molecular machine that rotates the helical filaments which propel swimming bacteria. Extensive experimental and theoretical studies exist on the structure, assembly, energy input, power generation and switching mechanism of the motor. In our previous paper, we explained the general physics underneath the observed torque-speed curves with a simple two-state Fokker-Planck model. Here we further analyze this model. In this paper we show (1) the model predicts that the two components of the ion motive force can affect the motor dynamics differently, in agreement with the latest experiment by Lo et al.; (2) with explicit consideration of the stator spring, the model also explains the lack of dependence of the zero-load speed on stator number in the proton motor, recently observed by Yuan and Berg; (3) the model reproduces the stepping behavior of the motor even with the existence of the stator springs and predicts the dwelling time distribution. Predicted stepping behavior of motors with two stators is discussed, and we suggest future experimental verification.

  19. Toll-Like Receptor 4 Deficiency Impairs Motor Coordination

    PubMed Central

    Zhu, Jian-Wei; Li, Yi-Fei; Wang, Zhao-Tao; Jia, Wei-Qiang; Xu, Ru-Xiang

    2016-01-01

    The cerebellum plays an essential role in balance and motor coordination. Purkinje cells (PCs) are the sole output neurons of the cerebellar cortex and are critical for the execution of its functions, including motor coordination. Toll-like receptor (TLR) 4 is involved in the innate immune response and is abundantly expressed in the central nervous system; however, little is known about its role in cerebellum-related motor functions. To address this question, we evaluated motor behavior in TLR4 deficient mice. We found that TLR4−∕− mice showed impaired motor coordination. Morphological analyses revealed that TLR4 deficiency was associated with a reduction in the thickness of the molecular layer of the cerebellum. TLR4 was highly expressed in PCs but not in Bergmann glia or cerebellar granule cells; however, loss of TLR4 decreased the number of PCs. These findings suggest a novel role for TLR4 in cerebellum-related motor coordination through maintenance of the PC population. PMID:26909014

  20. Evaluation of synthetic linear motor-molecule actuation energetics

    NASA Astrophysics Data System (ADS)

    Brough, Branden; Northrop, Brian H.; Schmidt, Jacob J.; Tseng, Hsian-Rong; Houk, Kendall N.; Fraser Stoddart, J.; Ho, Chih-Ming

    2006-06-01

    By applying atomic force microscope (AFM)-based force spectroscopy together with computational modeling in the form of molecular force-field simulations, we have determined quantitatively the actuation energetics of a synthetic motor-molecule. This multidisciplinary approach was performed on specifically designed, bistable, redox-controllable [2]rotaxanes to probe the steric and electrostatic interactions that dictate their mechanical switching at the single-molecule level. The fusion of experimental force spectroscopy and theoretical computational modeling has revealed that the repulsive electrostatic interaction, which is responsible for the molecular actuation, is as high as 65 kcal·mol-1, a result that is supported by ab initio calculations. computational modeling | force spectroscopy | molecular motors | switchable rotaxanes

  1. How actin initiates the motor activity of Myosin.

    PubMed

    Llinas, Paola; Isabet, Tatiana; Song, Lin; Ropars, Virginie; Zong, Bin; Benisty, Hannah; Sirigu, Serena; Morris, Carl; Kikuti, Carlos; Safer, Dan; Sweeney, H Lee; Houdusse, Anne

    2015-05-26

    Fundamental to cellular processes are directional movements driven by molecular motors. A common theme for these and other molecular machines driven by ATP is that controlled release of hydrolysis products is essential for using the chemical energy efficiently. Mechanochemical transduction by myosin motors on actin is coupled to unknown structural changes that result in the sequential release of inorganic phosphate (Pi) and MgADP. We present here a myosin structure possessing an actin-binding interface and a tunnel (back door) that creates an escape route for Pi with a minimal rotation of the myosin lever arm that drives movements. We propose that this state represents the beginning of the powerstroke on actin and that Pi translocation from the nucleotide pocket triggered by actin binding initiates myosin force generation. This elucidates how actin initiates force generation and movement and may represent a strategy common to many molecular machines.

  2. Catch-slip bonds can be dispensable for motor force regulation during skeletal muscle contraction

    NASA Astrophysics Data System (ADS)

    Dong, Chenling; Chen, Bin

    2015-07-01

    It is intriguing how multiple molecular motors can perform coordinated and synchronous functions, which is essential in various cellular processes. Recent studies on skeletal muscle might have shed light on this issue, where rather precise motor force regulation was partly attributed to the specific stochastic features of a single attached myosin motor. Though attached motors can randomly detach from actin filaments either through an adenosine triphosphate (ATP) hydrolysis cycle or through "catch-slip bond" breaking, their respective contribution in motor force regulation has not been clarified. Here, through simulating a mechanical model of sarcomere with a coupled Monte Carlo method and finite element method, we find that the stochastic features of an ATP hydrolysis cycle can be sufficient while those of catch-slip bonds can be dispensable for motor force regulation.

  3. 27. View, looking north, of motor house; the electric motor ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. View, looking north, of motor house; the electric motor and electric-powered winch are housed in section of building to the left. Photo by Jet Lowe, HAER, 1989. - Puget Sound Power & Light Company, White River Hydroelectric Project, 600 North River Avenue, Dieringer, Pierce County, WA

  4. Motor power control circuit for ac induction motors

    NASA Technical Reports Server (NTRS)

    Nola, F. J. (Inventor)

    1983-01-01

    A motor power control of the type which functions by controlling the power factor wherein one of the parameters of power factor current on time is determined by the on time of a triac through which current is supplied to the motor. By means of a positive feedback circuit, a wider range of control is effected.

  5. Experimental demonstration of a single-molecule electric motor.

    PubMed

    Tierney, Heather L; Murphy, Colin J; Jewell, April D; Baber, Ashleigh E; Iski, Erin V; Khodaverdian, Harout Y; McGuire, Allister F; Klebanov, Nikolai; Sykes, E Charles H

    2011-10-01

    For molecules to be used as components in molecular machines, methods that couple individual molecules to external energy sources and that selectively excite motion in a given direction are required. Significant progress has been made in the construction of molecular motors powered by light and by chemical reactions, but electrically driven motors have not yet been built, despite several theoretical proposals for such motors. Here we report that a butyl methyl sulphide molecule adsorbed on a copper surface can be operated as a single-molecule electric motor. Electrons from a scanning tunnelling microscope are used to drive the directional motion of the molecule in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. The direction and rate of the rotation are related to the chiralities of both the molecule and the tip of the microscope (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices. PMID:21892165

  6. Chopped molecular beam multiplexing system

    NASA Technical Reports Server (NTRS)

    Adams, Billy R. (Inventor)

    1986-01-01

    The integration of a chopped molecular beam mass spectrometer with a time multiplexing system is described. The chopping of the molecular beam is synchronized with the time intervals by a phase detector and a synchronous motor. Arithmetic means are generated for phase shifting the chopper with respect to the multiplexer. A four channel amplifier provides the capacity to independently vary the baseline and amplitude in each channel of the multiplexing system.

  7. 76 FR 12792 - Petition for Exemption From the Federal Motor Vehicle Motor Theft Prevention Standard; General...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-08

    ... TRANSPORTATION National Highway Traffic Safety Administration Petition for Exemption From the Federal Motor Vehicle Motor Theft Prevention Standard; General Motors Corporation AGENCY: National Highway Traffic.... SUMMARY: This document grants in full the petition of General Motors Corporation's (GM) petition for...

  8. Motor field sensitivity for preoperative localization of motor cortex

    PubMed Central

    Lin, Peter T.; Berger, Mitchel S.; Nagarajan, Srikantan S.

    2014-01-01

    Object In this study the role of magnetic source imaging for preoperative motor mapping was evaluated by using a single-dipole localization method to analyze motor field data in 41 patients. Methods Data from affected and unaffected hemispheres were collected in patients performing voluntary finger flexion movements. Somatosensory evoked field (SSEF) data were also obtained using tactile stimulation. Dipole localization using motor field (MF) data was successful in only 49% of patients, whereas localization with movement evoked field (MEF) data was successful in 66% of patients. When the spatial distribution of MF and MEF dipoles in relation to SSEF dipoles was analyzed, the motor dipoles were not spatially distinct from somatosensory dipoles. Conclusions The findings in this study suggest that single-dipole localization for the analysis of motor data is not sufficiently sensitive and is nonspecific, and thus not clinically useful. PMID:17044563

  9. Cytoskeletal motor-driven active self-assembly in in vitro systems.

    PubMed

    Lam, A T; VanDelinder, V; Kabir, A M R; Hess, H; Bachand, G D; Kakugo, A

    2016-01-28

    Molecular motor-driven self-assembly has been an active area of soft matter research for the past decade. Because molecular motors transform chemical energy into mechanical work, systems which employ molecular motors to drive self-assembly processes are able to overcome kinetic and thermodynamic limits on assembly time, size, complexity, and structure. Here, we review the progress in elucidating and demonstrating the rules and capabilities of motor-driven active self-assembly. We focus on the types of structures created and the degree of control realized over these structures, and discuss the next steps necessary to achieve the full potential of this assembly mode which complements robotic manipulation and passive self-assembly.

  10. Aberrant supplementary motor complex and limbic activity during motor preparation in motor conversion disorder.

    PubMed

    Voon, Valerie; Brezing, Christina; Gallea, Cecile; Hallett, Mark

    2011-11-01

    Conversion disorder (CD) is characterized by unexplained neurological symptoms presumed related to psychological issues. The main hypotheses to explain conversion paralysis, characterized by a lack of movement, include impairments in either motor intention or disruption of motor execution, and further, that hyperactive self-monitoring, limbic processing or top-down regulation from higher order frontal regions may interfere with motor execution. We have recently shown that CD with positive abnormal or excessive motor symptoms was associated with greater amygdala activity to arousing stimuli along with greater functional connectivity between the amygdala and supplementary motor area. Here we studied patients with such symptoms focusing on motor initiation. Subjects performed either an internally or externally generated 2-button action selection task in a functional MRI study. Eleven CD patients without major depression and 11 age- and gender-matched normal volunteers were assessed. During both internally and externally generated movement, conversion disorder patients relative to normal volunteers had lower left supplementary motor area (SMA) (implicated in motor initiation) and higher right amygdala, left anterior insula, and bilateral posterior cingulate activity (implicated in assigning emotional salience). These findings were confirmed in a subgroup analysis of patients with tremor symptoms. During internally versus externally generated action in CD patients, the left SMA had lower functional connectivity with bilateral dorsolateral prefrontal cortices. We propose a theory in which previously mapped conversion motor representations may in an arousing context hijack the voluntary action selection system, which is both hypoactive and functionally disconnected from prefrontal top-down regulation.

  11. Motor neurons and the generation of spinal motor neuron diversity

    PubMed Central

    Stifani, Nicolas

    2014-01-01

    Motor neurons (MNs) are neuronal cells located in the central nervous system (CNS) controlling a variety of downstream targets. This function infers the existence of MN subtypes matching the identity of the targets they innervate. To illustrate the mechanism involved in the generation of cellular diversity and the acquisition of specific identity, this review will focus on spinal MNs (SpMNs) that have been the core of significant work and discoveries during the last decades. SpMNs are responsible for the contraction of effector muscles in the periphery. Humans possess more than 500 different skeletal muscles capable to work in a precise time and space coordination to generate complex movements such as walking or grasping. To ensure such refined coordination, SpMNs must retain the identity of the muscle they innervate. Within the last two decades, scientists around the world have produced considerable efforts to elucidate several critical steps of SpMNs differentiation. During development, SpMNs emerge from dividing progenitor cells located in the medial portion of the ventral neural tube. MN identities are established by patterning cues working in cooperation with intrinsic sets of transcription factors. As the embryo develop, MNs further differentiate in a stepwise manner to form compact anatomical groups termed pools connecting to a unique muscle target. MN pools are not homogeneous and comprise subtypes according to the muscle fibers they innervate. This article aims to provide a global view of MN classification as well as an up-to-date review of the molecular mechanisms involved in the generation of SpMN diversity. Remaining conundrums will be discussed since a complete understanding of those mechanisms constitutes the foundation required for the elaboration of prospective MN regeneration therapies. PMID:25346659

  12. Torque control for electric motors

    NASA Technical Reports Server (NTRS)

    Bernard, C. A.

    1980-01-01

    Method for adjusting electric-motor torque output to accomodate various loads utilizes phase-lock loop to control relay connected to starting circuit. As load is imposed, motor slows down, and phase lock is lost. Phase-lock signal triggers relay to power starting coil and generate additional torque. Once phase lock is recoverd, relay restores starting circuit to its normal operating mode.

  13. Motor Coordination and Executive Functions

    ERIC Educational Resources Information Center

    Michel, Eva

    2012-01-01

    Since Piaget, the view that motor and cognitive development are interrelated has gained wide acceptance. However, empirical research on this issue is still rare. Few studies show a correlation of performance in cognitive and motor tasks in typically developing children. More specifically, Diamond A. (2000) hypothesizes an involvement of executive…

  14. Motors and Bulbs in Series

    ERIC Educational Resources Information Center

    Whitaker, Robert J.

    2009-01-01

    One of Paul Hewitt's "Figuring Physics" that appeared in this journal dealt with the heating of a motor. This phenomenon can be demonstrated with a miniature motor and a bulb as part of a series of activities with "batteries and bulbs." Students examine the effect on the brightness of a single bulb when a second, identical bulb is placed in series…

  15. Conical Bearingless Motor/Generators

    NASA Technical Reports Server (NTRS)

    Kascak, P.; Jansen, R.; Dever, T.

    2008-01-01

    Motor/generators based on conical magnetic bearings have been invented as an improved alternative to prior such machines based, variously, on radial and/or axial magnetic bearings. Both the present and prior machines are members of the class of so-called bearingless or self bearing (in the sense of not containing mechanical bearings) rotary machines. Each motor/generator provides both a torque and force allowing it to either function as a motor and magnetic bearing or a generator and magnetic bearing concurrently. Because they are not subject to mechanical bearing wear, these machines have potentially long operational lives and can function without lubrication and over wide ranges of speed and temperature that include conditions under which lubricants would become depleted, degraded, or ineffective and mechanical bearings would fail. The figure shows three typical configurations of conical bearingless motor/generators. The main elements of each motor/generator are concentric rotor and stator portions having conically tapered surfaces facing each other across a gap. Because a conical motor/generator imposes both radial and axial magnetic forces, it acts, in effect, as a combination of an axial and a radial magnetic bearing. Therefore, only two conical motor/generators - one at each end of a rotor - are needed to effect complete magnetic leviation of the rotor, whereas previously, it was necessary to use a combination of an axial and a radial magnetic bearing at each end of the rotor to achieve complete magnetic levitation and a separate motor to provide torque.

  16. Alternative Motor Fuel Use Model

    1992-11-16

    AMFU is a tool for the analysis and prediction of motor fuel use by highway vehicles. The model advances the art of vehicle stock modeling by including a representation of the choice of motor fuel for flexible and dual fuel vehicles.

  17. Advanced solid propellant motor insulation

    NASA Technical Reports Server (NTRS)

    Smith, P. L.; Russ, R. F.

    1972-01-01

    An advanced lightweight insulation system suitable for use in long duration, low pressure planetary orbiter-type motor applications was developed. Experiments included the screening of various filler and binder materials with optimization studies combining the best of each. Small scale test motor data were used to judge the degree of success.

  18. Retention of Motor Skills: Review.

    ERIC Educational Resources Information Center

    Schendel, J. D.; And Others

    A summary of an extensive literature survey deals with the variables known or suspected to affect the retention of learned motor behaviors over lengthy no-practice intervals. Emphasis was given to research conducted by or for the military. The variables that may affect the retention of motor skills were dichotomized into task variables and…

  19. Power control for ac motor

    NASA Technical Reports Server (NTRS)

    Dabney, R. W. (Inventor)

    1984-01-01

    A motor controller employing a triac through which power is supplied to a motor is described. The open circuit voltage appearing across the triac controls the operation of a timing circuit. This timing circuit triggers on the triac at a time following turn off which varies inversely as a function of the amplitude of the open circuit voltage of the triac.

  20. Motor-operated gearbox efficiency

    SciTech Connect

    DeWall, K.G.; Watkins, J.C.; Bramwell, D.; Weidenhamer, G.H.

    1996-12-01

    Researchers at the Idaho National Engineering Laboratory recently conducted tests investigating the operating efficiency of the power train (gearbox) in motor-operators typically used in nuclear power plants to power motor-operated valves. Actual efficiency ratios were determined from in-line measurements of electric motor torque (input to the operator gearbox) and valve stem torque (output from the gearbox) while the operators were subjected to gradually increasing loads until the electric motor stalled. The testing included parametric studies under reduced voltage and elevated temperature conditions. As part of the analysis of the results, the authors compared efficiency values determined from testing to the values published by the operator manufacturer and typically used by the industry in calculations for estimating motor-operator capabilities. The operators they tested under load ran at efficiencies lower than the running efficiency (typically 50%) published by the operator manufacturer.

  1. Piezoelectric wave motor

    DOEpatents

    Yerganian, Simon Scott

    2001-07-17

    A piezoelectric motor having a stator in which piezoelectric elements are contained in slots formed in the stator transverse to the desired wave motion. When an electric field is imposed on the elements, deformation of the elements imposes a force perpendicular to the sides of the slot, deforming the stator. Appropriate frequency and phase shifting of the electric field will produce a wave in the stator and motion in a rotor. In a preferred aspect, the piezoelectric elements are configured so that deformation of the elements in direction of an imposed electric field, generally referred to as the d.sub.33 direction, is utilized to produce wave motion in the stator. In a further aspect, the elements are compressed into the slots so as to minimize tensile stresses on the elements in use.

  2. Piezoelectric wave motor

    DOEpatents

    Yerganian, Simon Scott

    2003-02-11

    A piezoelectric motor having a stator in which piezoelectric elements are contained in slots formed in the stator transverse to the desired wave motion. When an electric field is imposed on the elements, deformation of the elements imposes a force perpendicular to the sides of the slot, deforming the stator. Appropriate frequency and phase-shifting of the electric field will produce a wave in the stator and motion in a rotor. In a preferred aspect, the piezoelectric elements are configured so that deformation of the elements in the direction of an imposed electric field, generally referred to as the d.sub.33 direction, is utilized to produce wave motion in the stator. In a further aspect, the elements are compressed into the slots so as to minimize tensile stresses on the elements in use.

  3. Magnetic bearing and motor

    NASA Technical Reports Server (NTRS)

    Studer, Philip A. (Inventor)

    1983-01-01

    A magnetic bearing assembly (10) has an intermediate rotatable section (33) having an outer cylindrical member (30) coaxially suspended by a torsion wire (72) around an axially polarized cylindrical magnet (32). Axial alignment between the pole faces (40-43) of the intermediate section (33) and end surfaces (50-53) of opposed end bells (20, 22) provides a path of least reluctance across intervening air gaps (60-63) for the magnetic flux emanating from magnet (32). Radial dislocation increases the reluctance and creates a radial restoring force. Substitution of radially polarized magnets 107 fixed to a magnetically permeable cylinder (32') and insertion of pairs of armature coil windings (109-112) between the cylinder pair (33') provides an integral magnetic bearing and torsion motor (100) able to provide arcuately limited rotational drive.

  4. Reciprocating linear motor

    NASA Technical Reports Server (NTRS)

    Goldowsky, Michael P. (Inventor)

    1987-01-01

    A reciprocating linear motor is formed with a pair of ring-shaped permanent magnets having opposite radial polarizations, held axially apart by a nonmagnetic yoke, which serves as an axially displaceable armature assembly. A pair of annularly wound coils having axial lengths which differ from the axial lengths of the permanent magnets are serially coupled together in mutual opposition and positioned with an outer cylindrical core in axial symmetry about the armature assembly. One embodiment includes a second pair of annularly wound coils serially coupled together in mutual opposition and an inner cylindrical core positioned in axial symmetry inside the armature radially opposite to the first pair of coils. Application of a potential difference across a serial connection of the two pairs of coils creates a current flow perpendicular to the magnetic field created by the armature magnets, thereby causing limited linear displacement of the magnets relative to the coils.

  5. Industrial motor repair in the United States

    SciTech Connect

    Schueler, V.; Leistner, P.; Douglass, J.

    1994-09-01

    This report characterizes the motor repair industry in the United States; summarizes current motor repair and testing practice; and identifies barriers to energy motor repair practice and recommends strategies for overcoming those barriers.

  6. Activities for a Perceptual Motor Program.

    ERIC Educational Resources Information Center

    Brinning, Dorothy; And Others

    Perceptual motor activities for physically handicapped children are presented in the areas of fine and gross motor skills. Also detailed are activities to develop body image, visual motor skills, and tactile and auditory perception. (JD)

  7. Synthetic molecular walkers.

    PubMed

    Leigh, David A; Lewandowska, Urszula; Lewandowski, Bartosz; Wilson, Miriam R

    2014-01-01

    In biological systems, molecular motors have been developed to harness Brownian motion and perform specific tasks. Among the cytoskeletal motor proteins, kinesins ensure directional transport of cargoes to the periphery of the cell by taking discrete steps along microtubular tracks. In the past decade there has been an increasing interest in the development of molecules that mimic aspects of the dynamics of biological systems and can became a starting point for the creation of artificial transport systems.To date, both DNA-based and small-molecule walkers have been developed, each taking advantage of the different chemistries available to them. DNA strollers exploit orthogonal base pairing and utilize strand-displacement reactions to control the relative association of the component parts. Small-molecule walkers take advantage of the reversibility of weak noncovalent interactions as well as the robustness of dynamic covalent bonds in order to transport molecular fragments along surfaces and molecular tracks using both diffusional processes and ratchet mechanisms. Here we review both types of synthetic systems, including their designs, dynamics, and how they are being used to perform functions by controlled mechanical motion at the molecular level.

  8. Closed-Loop Motor-Speed Control

    NASA Technical Reports Server (NTRS)

    Smith, Matthew A.; Delcher, Ray C.; Huston, Steven W.

    1989-01-01

    Electronic motor-speed control circuit designed to operate in electrically noisy environment. Includes optoelectronic pick-up device, placed inside motor housing to provide speed feedback signal. Automatically maintains speed motor at commanded value. Measures speed of motor in terms of frequency of pulses of infrared light chopped by fan blades of motor. Difference between measured and commanded speeds serves as control signal for external amplifier driving motor. Major advantage of circuit is low cost.

  9. Morphological characteristics of motor neurons do not determine their relative susceptibility to degeneration in a mouse model of severe spinal muscular atrophy.

    PubMed

    Thomson, Sophie R; Nahon, Joya E; Mutsaers, Chantal A; Thomson, Derek; Hamilton, Gillian; Parson, Simon H; Gillingwater, Thomas H

    2012-01-01

    Spinal muscular atrophy (SMA) is a leading genetic cause of infant mortality, resulting primarily from the degeneration and loss of lower motor neurons. Studies using mouse models of SMA have revealed widespread heterogeneity in the susceptibility of individual motor neurons to neurodegeneration, but the underlying reasons remain unclear. Data from related motor neuron diseases, such as amyotrophic lateral sclerosis (ALS), suggest that morphological properties of motor neurons may regulate susceptibility: in ALS larger motor units innervating fast-twitch muscles degenerate first. We therefore set out to determine whether intrinsic morphological characteristics of motor neurons influenced their relative vulnerability to SMA. Motor neuron vulnerability was mapped across 10 muscle groups in SMA mice. Neither the position of the muscle in the body, nor the fibre type of the muscle innervated, influenced susceptibility. Morphological properties of vulnerable and disease-resistant motor neurons were then determined from single motor units reconstructed in Thy.1-YFP-H mice. None of the parameters we investigated in healthy young adult mice - including motor unit size, motor unit arbor length, branching patterns, motor endplate size, developmental pruning and numbers of terminal Schwann cells at neuromuscular junctions - correlated with vulnerability. We conclude that morphological characteristics of motor neurons are not a major determinant of disease-susceptibility in SMA, in stark contrast to related forms of motor neuron disease such as ALS. This suggests that subtle molecular differences between motor neurons, or extrinsic factors arising from other cell types, are more likely to determine relative susceptibility in SMA.

  10. ACR-12 ionotropic acetylcholine receptor complexes regulate inhibitory motor neuron activity in Caenorhabditis elegans.

    PubMed

    Petrash, Hilary A; Philbrook, Alison; Haburcak, Marian; Barbagallo, Belinda; Francis, Michael M

    2013-03-27

    Heterogeneity in the composition of neurotransmitter receptors is thought to provide functional diversity that may be important in patterning neural activity and shaping behavior (Dani and Bertrand, 2007; Sassoè-Pognetto, 2011). However, this idea has remained difficult to evaluate directly because of the complexity of neuronal connectivity patterns and uncertainty about the molecular composition of specific receptor types in vivo. Here we dissect how molecular diversity across receptor types contributes to the coordinated activity of excitatory and inhibitory motor neurons in the nematode Caenorhabditis elegans. We show that excitatory and inhibitory motor neurons express distinct populations of ionotropic acetylcholine receptors (iAChRs) requiring the ACR-12 subunit. The activity level of excitatory motor neurons is influenced through activation of nonsynaptic iAChRs (Jospin et al., 2009; Barbagallo et al., 2010). In contrast, synaptic coupling of excitatory and inhibitory motor neurons is achieved through a second population of iAChRs specifically localized at postsynaptic sites on inhibitory motor neurons. Loss of ACR-12 iAChRs from inhibitory motor neurons leads to reduced synaptic drive, decreased inhibitory neuromuscular signaling, and variability in the sinusoidal motor pattern. Our results provide new insights into mechanisms that establish appropriately balanced excitation and inhibition in the generation of a rhythmic motor behavior and reveal functionally diverse roles for iAChR-mediated signaling in this process. PMID:23536067

  11. Molecular Programming with DNA

    NASA Astrophysics Data System (ADS)

    Winfree, Erik

    2009-05-01

    Information can be stored in molecules and processed by molecular reactions. Molecular information processing is at the heart of all biological systems; might it soon also be at the heart of non-biological synthetic chemical systems? Perhaps yes. One technological approach comes from DNA nanotechnology and DNA computing, where DNA is used as a non-biological informational polymer that can be rationally designed to create a rich class of molecular systems -- for example, DNA molecules that self-assemble precisely, that fold into complex nanoscale objects, that act as mechanical actuators and molecular motors, and that make decisions based on digital and analog logic. I will argue that to fully exploit their design potential, we will need to invent programming languages for specifying the behavior of information-based molecular systems, to create theoretical tools for understanding and analyzing the behavior of molecular programs, to develop compilers that automate the design of molecules with the desired behaviors, and to expand experimental techniques so that the implementation and debugging of complex molecular systems becomes as commonplace and practical as computer programming.

  12. Translational studies exploring neuroplasticity associated with motor skill learning and the regulatory role of the dopamine system.

    PubMed

    Diaz Heijtz, Rochellys; Forssberg, Hans

    2015-04-01

    Cerebral palsy (CP) is a heterogeneous group of neurodevelopmental disorders associated with lifelong motor impairment and disability. Current intervention programmes aim to capitalize on the neuroplasticity of the undamaged part of the brain to improve motor functions, by engaging individuals in active motor learning and training. In this review, we highlight recent animal studies (1) exploring cellular and molecular mechanisms contributing to neuroplasticity during motor training, (2) assessing the functional role of the mesocortical dopaminergic system in motor skill learning, and (3) exploring the impact of naturally occurring genetic variation in dopamine-related gene expression on the acquisition and performance of fine motor skills. Finally, the potential influence of the dopamine system on the outcome of motor learning interventions in cerebral palsy is discussed. PMID:25690110

  13. Submersible canned motor mixer pump

    SciTech Connect

    Guardiani, Richard F.; Pollick, Richard D.

    1997-01-01

    A mixer pump used in a waste tank for mobilizing high-level radioactive liquid waste having a column assembly containing power cables, a motor housing with electric motor means which includes a stator can of a stator assembly and a rotor can of a rotor assembly, and an impeller assembly with an impeller connected to a shaft of the rotor assembly. The column assembly locates the motor housing with the electric motor means adjacent to the impeller which creates an hydraulic head, and which forces the liquid waste into the motor housing to cool the electric motor means and to lubricate radial and thrust bearing assemblies. Hard-on-hard bearing surfaces of the bearing assemblies and a ring assembly between the impeller and electric motor means act to grind down large particles in the liquid waste flow. These larger particles are received in slots in the static bearing members of the radial bearing assemblies. Only solid waste particles smaller than the clearances in the system can pass therethrough, thereby resisting damage to and the interruption of the operation of the mixer pump.

  14. Submersible canned motor transfer pump

    DOEpatents

    Guardiani, Richard F.; Pollick, Richard D.; Nyilas, Charles P.; Denmeade, Timothy J.

    1997-01-01

    A transfer pump used in a waste tank for transferring high-level radioactive liquid waste from a waste tank and having a column assembly, a canned electric motor means, and an impeller assembly with an upper impeller and a lower impeller connected to a shaft of a rotor assembly. The column assembly locates a motor housing with the electric motor means adjacent to the impeller assembly which creates an hydraulic head, and which forces the liquid waste, into the motor housing to cool the electric motor means and to cool and/or lubricate the radial and thrust bearing assemblies. Hard-on-hard bearing surfaces of the bearing assemblies and a ring assembly between the upper impeller and electric motor means grind large particles in the liquid waste flow. Slots in the static bearing member of the radial bearing assemblies further grind down the solid waste particles so that only particles smaller than the clearances in the system can pass therethrough, thereby resisting damage to and the interruption of the operation of the transfer pump. The column assembly is modular so that sections can be easily assembled, disassembled and/or removed. A second embodiment employs a stator jacket which provides an alternate means for cooling the electric motor means and lubricating and/or cooling the bearing assemblies, and a third embodiment employs a variable level suction device which allows liquid waste to be drawn into the transfer pump from varying and discrete levels in the waste tank.

  15. Submersible canned motor mixer pump

    DOEpatents

    Guardiani, R.F.; Pollick, R.D.

    1997-10-07

    A mixer pump is described used in a waste tank for mobilizing high-level radioactive liquid waste having a column assembly containing power cables, a motor housing with electric motor means which includes a stator can of a stator assembly and a rotor can of a rotor assembly, and an impeller assembly with an impeller connected to a shaft of the rotor assembly. The column assembly locates the motor housing with the electric motor means adjacent to the impeller which creates an hydraulic head, and which forces the liquid waste into the motor housing to cool the electric motor means and to lubricate radial and thrust bearing assemblies. Hard-on-hard bearing surfaces of the bearing assemblies and a ring assembly between the impeller and electric motor means act to grind down large particles in the liquid waste flow. These larger particles are received in slots in the static bearing members of the radial bearing assemblies. Only solid waste particles smaller than the clearances in the system can pass there through, thereby resisting damage to and the interruption of the operation of the mixer pump. 10 figs.

  16. Solid rocket motor witness test

    NASA Technical Reports Server (NTRS)

    Welch, Christopher S.

    1991-01-01

    The Solid Rocket Motor Witness Test was undertaken to examine the potential for using thermal infrared imagery as a tool for monitoring static tests of solid rocket motors. The project consisted of several parts: data acquisition, data analysis, and interpretation. For data acquisition, thermal infrared data were obtained of the DM-9 test of the Space Shuttle Solid Rocket Motor on December 23, 1987, at Thiokol, Inc. test facility near Brigham City, Utah. The data analysis portion consisted of processing the video tapes of the test to produce values of temperature at representative test points on the rocket motor surface as the motor cooled down following the test. Interpretation included formulation of a numerical model and evaluation of some of the conditions of the motor which could be extracted from the data. These parameters included estimates of the insulation remaining following the tests and the thickness of the charred layer of insulation at the end of the test. Also visible was a temperature signature of the star grain pattern in the forward motor segment.

  17. The Neurospora organelle motor: a distant relative of conventional kinesin with unconventional properties.

    PubMed Central

    Steinberg, G; Schliwa, M

    1995-01-01

    The "conventional" kinesins comprise a conserved family of molecular motors for organelle transport that have been identified in various animal species. Organelle motors from other phyla have not yet been analyzed at the molecular level. Here we report the identification, biochemical and immunological characterization, and molecular cloning of a cytoplasmic motor in a "lower" eukaryote, the Ascomycete fungus Neurospora crassa. This motor, termed Nkin (for Neurospora kinesin), exhibits several unique structural and functional features, including a high rate of microtubule transport, a lack of copurifying light chains, a second P-loop motif, and an overall sequence organization reminiscent of a kinesin-like protein. However, a greater than average sequence homology in the motor domain and the presence of a highly conserved region in the C-terminus identify Nkin as a distant relative of the family of conventional kinesins. A molecular phylogenetic analysis suggests Nkin to have diverged early in the evolution of this family of motors. The discovery of Nkin may help identify domains important for specific biological functions in conventional kinesins. Images PMID:8589459

  18. Ultra-Compact Motor Controller

    NASA Technical Reports Server (NTRS)

    Townsend, William T.; Cromwell, Adam; Hauptman, Traveler; Pratt, Gill Andrews

    2012-01-01

    This invention is an electronically commutated brushless motor contro ller that incorporates Hall-array sensing in a small, 42-gram packag e that provides 4096 absolute counts per motor revolution position s ensing. The unit is the size of a miniature hockey puck, and is a 44 -pin male connector that provides many I/O channels, including CANbus , RS-232 communications, general-purpose analog and digital I/O (GPI O), analog and digital Hall inputs, DC power input (18-90 VDC, 0-l0 A), three-phase motor outputs, and a strain gauge amplifier.

  19. State observer for synchronous motors

    DOEpatents

    Lang, Jeffrey H.

    1994-03-22

    A state observer driven by measurements of phase voltages and currents for estimating the angular orientation of a rotor of a synchronous motor such as a variable reluctance motor (VRM). Phase voltages and currents are detected and serve as inputs to a state observer. The state observer includes a mathematical model of the electromechanical operation of the synchronous motor. The characteristics of the state observer are selected so that the observer estimates converge to the actual rotor angular orientation and velocity, winding phase flux linkages or currents.

  20. The Advanced Solid Rocket Motor

    NASA Technical Reports Server (NTRS)

    Mitchell, Royce E.

    1992-01-01

    The paper describes the Advanced Solid Rocket Motor (ASRM) that is being developed to replace, in 1997, the Redesigned Solid Rocket Motor which currently boosts the Space Shuttle. The ASRM will contain features to improve motor safety (fewer potential leak paths, improved seal materials, stronger case material, and fewer nozzle and case joints), an improved ignition system using through-bulkhead initiators, and highly reproducible manufacturing and inspection techniques with a large number of automated procedures. The ASRM will be able to deliver 12,000 lbs greater payloads to any given orbit of the Shuttle. There are also environmental improvements, realized by waste propellant recovery.

  1. 26. View, looking east, of motor house; the electric motor ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    26. View, looking east, of motor house; the electric motor and electric-powered winch are housed in section of building to the left. The U-bolt and concrete deadman which anchors the cable of the tramway is to the right. Photo by Jet Lowe, HAER, 1989. - Puget Sound Power & Light Company, White River Hydroelectric Project, 600 North River Avenue, Dieringer, Pierce County, WA

  2. Conformational Transitions in Molecular Systems

    NASA Astrophysics Data System (ADS)

    Bachmann, M.; Janke, W.

    2008-11-01

    Proteins are the "work horses" in biological systems. In almost all functions specific proteins are involved. They control molecular transport processes, stabilize the cell structure, enzymatically catalyze chemical reactions; others act as molecular motors in the complex machinery of molecular synthetization processes. Due to their significance, misfolds and malfunctions of proteins typically entail disastrous diseases, such as Alzheimer's disease and bovine spongiform encephalopathy (BSE). Therefore, the understanding of the trinity of amino acid composition, geometric structure, and biological function is one of the most essential challenges for the natural sciences. Here, we glance at conformational transitions accompanying the structure formation in protein folding processes.

  3. A synthetic DNA motor that transports nanoparticles along carbon nanotubes.

    PubMed

    Cha, Tae-Gon; Pan, Jing; Chen, Haorong; Salgado, Janette; Li, Xiang; Mao, Chengde; Choi, Jong Hyun

    2014-01-01

    Intracellular protein motors have evolved to perform specific tasks critical to the function of cells such as intracellular trafficking and cell division. Kinesin and dynein motors, for example, transport cargoes in living cells by walking along microtubules powered by adenosine triphosphate hydrolysis. These motors can make discrete 8 nm centre-of-mass steps and can travel over 1 µm by changing their conformations during the course of adenosine triphosphate binding, hydrolysis and product release. Inspired by such biological machines, synthetic analogues have been developed including self-assembled DNA walkers that can make stepwise movements on RNA/DNA substrates or can function as programmable assembly lines. Here, we show that motors based on RNA-cleaving DNA enzymes can transport nanoparticle cargoes-CdS nanocrystals in this case-along single-walled carbon nanotubes. Our motors extract chemical energy from RNA molecules decorated on the nanotubes and use that energy to fuel autonomous, processive walking through a series of conformational changes along the one-dimensional track. The walking is controllable and adapts to changes in the local environment, which allows us to remotely direct 'go' and 'stop' actions. The translocation of individual motors can be visualized in real time using the visible fluorescence of the cargo nanoparticle and the near-infared emission of the carbon-nanotube track. We observed unidirectional movements of the molecular motors over 3 µm with a translocation velocity on the order of 1 nm min(-1) under our experimental conditions.

  4. Understanding motor acts and motor intentions in Williams syndrome.

    PubMed

    Sparaci, Laura; Stefanini, Silvia; Marotta, Luigi; Vicari, Stefano; Rizzolatti, Giacomo

    2012-06-01

    Williams syndrome (WS) is a rare genetic disorder associated with unusually hyper-social demeanor and ease with strangers. These personality traits are accompanied by difficulties in social interactions, possibly related, at least in part, to a difficulty in understanding others' mental states. Studies on mentalizing capacities in individuals with WS have often led to contrasting results, some studies revealing specific impairments, others highlighting spared mentalizing capacities. So far, however, no study investigated the performance of individuals with WS in non-inferential understanding of others' motor intentions. In the present study we investigated this capacity by using a computer-based behavioral task using pictures of hand-object interactions. We asked individuals with WS first to describe what the other was doing (i.e. a task implying no kind of intention reading), and secondly, if successful in answering the first question, to describe the motor intention underlying the observed motor acts (i.e. why an act was being done, a task requiring non-inferential motor intention understanding). Results showed that individuals with WS made more errors in understanding what the other was doing (i.e. understanding a motor act) compared to both mental-age matched controls and chronological-age matched peers with typical development, while showing mental-age appropriate performance in understanding why an individual was acting (i.e. understanding a motor intention). These findings suggest novel perspectives for understanding impairments in social behavior in WS.

  5. Turn Motors Off When Not in Use - Motor Tip Sheet #10

    SciTech Connect

    2008-07-01

    Motors use no energy when turned off. Reducing motor operating time by just 10% usually saves more energy than replacing a standard efficiency motor with a NEMA Premium® efficiency motor. In fact, given that 97% of the life cycle cost of purchasing and operating a motor is energy-related, turning a motor off 10% of the time could reduce energy costs enough to purchase three new motors.

  6. Magnetic bearing and motor

    NASA Technical Reports Server (NTRS)

    Studer, P. A. (Inventor)

    1983-01-01

    A magnetic bearing for passively suspending a rotatable element subjected to axial and radial thrust forces is disclosed. The magnetic bearing employs a taut wire stretched along the longitudinal axis of the bearing between opposed end pieces and an intermediate magnetic section. The intermediate section is segmented to provide oppositely directed magnetic flux paths between the end pieces and may include either an axially polarized magnets interposed between the segments. The end pieces, separated from the intermediate section by air gaps, control distribution of magnetic flux between the intermediate section segments. Coaxial alignment of the end pieces with the intermediate section minimizes magnetic reluctance in the flux paths endowing the bearing with self-centering characteristics when subjected to radial loads. In an alternative embodiment, pairs of oppositely wound armature coils are concentrically interposed between segments of the intermediate section in concentric arcs adjacent to radially polarized magnets to equip a magnetic bearing as a torsion drive motor. The magnetic suspension bearing disclosed provides long term reliability without maintenance with application to long term space missions such as the VISSR/VAS scanning mirror instrument in the GOES program.

  7. Mechanical thermal motor

    NASA Technical Reports Server (NTRS)

    Hein, L. A.; Myers, W. N. (Inventor)

    1976-01-01

    An apparatus is described for converting thermal energy such as solar energy into mechanical motion for driving fluid pumps and similar equipment. The thermal motor comprises an inner concentric cylinder carried by a stationary core member. The core member has a cylindrical disc plate fixed adjacent to a lower portion and extending radially from it. An outer concentric cylinder rotatably carried on the disc plate defining a space between the inner and outer concentric cylinders. A spiral tubular member encircles the inner concentric cylinder and is contained within the space between the inner and outer cylinders. One portion is connected to the inner concentric cylinder and a second portion connected to the outer concentric cylinder. A heated fluid is conveyed through the tubular member and is periodically cooled causing the tubular member to expand and contract. This causes the outer concentric cylinder to reciprocally rotate on the base plate accordingly. The reciprocating motion of the outer concentric cylinder is then utilized to drive a pump member in a pump chamber.

  8. Plasma motor generator system

    NASA Technical Reports Server (NTRS)

    Hite, Gerald E.

    1987-01-01

    The significant potential advantages of a plasma motor generator system over conventional systems for the generation of electrical power and propulsion for spacecraft in low Earth orbits warrants its further investigation. The two main components of such a system are a long insulated wire and the plasma generating hollow cathodes needed to maintain electrical contact with the ionosphere. Results of preliminary theoretical and experimental investigations of this system are presented. The theoretical work involved the equilibrium configurations of the wire and the nature of small oscillation about these equilibrium positions. A particularly interesting result was that two different configurations are allowed when the current is above a critical value. Experimental investigations were made of the optimal starting and running conditions for the proposed, low current hollow cathodes. Although optimal ranges of temperature, argon pressure and discharge voltage were identified, start up became progressively more difficult. This supposed depletion or contamination of the emissive surface could be countered by the addition of new emissive material.

  9. Bifurcation of Velocity Distributions in Cooperative Transport of Filaments by Fast and Slow Motors

    PubMed Central

    Li, Xin; Lipowsky, Reinhard; Kierfeld, Jan

    2013-01-01

    Several intracellular processes are governed by two different species of molecular motors, fast and slow ones, that both move in the same direction along the filaments but with different velocities. The transport of filaments arising from the cooperative action of these motors has been recently studied by three in vitro experiments, in which the filament velocity was measured for varying fraction of the fast motors adsorbed onto substrate surfaces in a gliding assay. As the fast motor fraction was increased, two experiments found a smooth change whereas the third one observed an abrupt increase of the filament velocity. Here, we show that all of these experimental results reflect the competition between fast and slow motors and can be understood in terms of an underlying saddle-node bifurcation. The comparison between theory and experiment leads to predictions for the detachment forces of the two motor species. Our theoretical study shows the existence of three different motility regimes: 1), fast transport with a single velocity; 2), slow transport with a single velocity; and 3), bistable transport, where the filament velocity stochastically switches between fast and slow transport. We determine the parameter regions for these regimes in terms of motility diagrams as a function of the surface fraction of fast motors and microscopic single-motor parameters. An abrupt increase of the filament velocity for an increasing fraction of fast motors is associated with the occurrence of bistable transport. PMID:23442917

  10. Asymmetric Brownian motor driven by bubble formation in a hydrophobic channel.

    PubMed

    Arai, Noriyoshi; Yasuoka, Kenji; Koishi, Takahiro; Ebisuzaki, Toshikazu

    2010-10-26

    The "asymmetric brownian ratchet model" is a variation of Feynman's ratchet and pawl system proposed. In this model, a system consisting of a motor and a rail has two binding states. One is the random brownian state, and the other is the asymmetric potential state. When the system is alternatively switched between these states, the motor can be driven in one direction. This model is believed to explain nanomotor behavior in biological systems. The feasibility of the model has been demonstrated using electrical and magnetic forces; however, switching of these forces is unlikely to be found in biological systems. In this paper, we propose an original mechanism of transition between states by bubble formation in a nanosized channel surrounded by hydrophobic atoms. This amounts to a nanoscale motor system using bubble propulsion. The motor system consists of a hydrophobic motor and a rail on which hydrophobic patterns are printed. Potential asymmetry can be produced by using a left-right asymmetric pattern shape. Hydrophobic interactions are believed to play an important role in the binding of biomolecules and molecular recognition. The bubble formation is controlled by changing the width of the channel by an atomic distance (∼0.1 nm). Therefore, the motor is potentially more efficient than systems controlled by other forces, in which a much larger change in the motor position is necessary. We have simulated the bubble-powered motor using dissipative particle dynamics and found behavior in good agreement with that of motor proteins. Energy efficiency is as high as 60%.

  11. 75 FR 50797 - Motor Carrier Safety Advisory Committee Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-17

    ... Federal Motor Carrier Safety Administration Motor Carrier Safety Advisory Committee Public Meeting AGENCY: Federal Motor Carrier Safety Administration (FMCSA), DOT. ACTION: Notice of Motor Carrier Safety Advisory Committee Meeting. SUMMARY: FMCSA announces that its Motor Carrier Safety Advisory Committee (MCSAC)...

  12. 75 FR 72863 - Motor Carrier Safety Advisory Committee Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-26

    ... Federal Motor Carrier Safety Administration Motor Carrier Safety Advisory Committee Public Meeting AGENCY: Federal Motor Carrier Safety Administration, DOT. ACTION: Notice of Motor Carrier Safety Advisory Committee Meeting. SUMMARY: FMCSA announces that the Agency's Motor Carrier Safety Advisory Committee...

  13. 76 FR 12214 - Motor Carrier Safety Advisory Committee Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-04

    ... Federal Motor Carrier Safety Administration Motor Carrier Safety Advisory Committee Public Meeting AGENCY: Federal Motor Carrier Safety Administration, DOT. ACTION: Notice: Announcement of Motor Carrier Safety Advisory Committee meeting; request for comment. SUMMARY: The Federal Motor Carrier Safety...

  14. Small Solid Rocket Motor Test

    NASA Video Gallery

    It was three-two-one to brilliant fire as NASA's Marshall Space Flight Center tested a small solid rocket motor designed to mimic NASA's Space Launch System booster. The Mar. 14 test provides a qui...

  15. Battery powererd electric motor vehicle

    SciTech Connect

    Muhlbacker, K.

    1984-02-28

    A battery powered vehicle is provided with a vehicle frame and an electric motor whose main shaft is connected to a differential gear by means of a gear train with a variable transmission ratio, the motor shaft and all gear shafts being parallel to the axle of the driving wheels. In order to achieve a compact design and to avoid power-consuming drive elements the electric motor and the variable transmission gear as well as a potential reducing gear mounted between the latter and the differential gear, are positioned on a subframe which is connected to the housing of the driving wheel axle on the one side whereas the other side carrying the electric motor is attached to the vehicle frame by means of a cardanic suspension.

  16. Drill-motor holding fixture

    NASA Technical Reports Server (NTRS)

    Chartier, E. N.; Culp, L. N.

    1980-01-01

    Guide improves accuracy and reduces likelihood of bit breakage in drilling large work pieces. Drill motor is mounted on pipe that slides on furniture clamp. Drill is driven into work piece by turning furniture-clamp handle.

  17. Perceptual decoupling or motor decoupling?

    PubMed

    Head, James; Helton, William S

    2013-09-01

    The current investigation was conducted to elucidate whether errors of commission in the Sustained Attention to Response Task (SART) are indicators of perceptual or motor decoupling. Twenty-eight participants completed SARTs with motor and perceptual aspects of the task manipulated. The participants completed four different SART blocks whereby stimuli location uncertainty and stimuli acquisition were manipulated. In previous studies of more traditional sustained attention tasks stimuli location uncertainty reduces sustained attention performance. In the case of the SART the motor manipulation (stimuli acquisition), but not the perceptual manipulation (stimuli location uncertainty) significantly reduced commission errors. The results suggest that the majority of SART commission errors are likely to be indicators of motor decoupling not necessarily perceptual decoupling.

  18. Motor activity improves temporal expectancy.

    PubMed

    Fautrelle, Lilian; Mareschal, Denis; French, Robert; Addyman, Caspar; Thomas, Elizabeth

    2015-01-01

    Certain brain areas involved in interval timing are also important in motor activity. This raises the possibility that motor activity might influence interval timing. To test this hypothesis, we assessed interval timing in healthy adults following different types of training. The pre- and post-training tasks consisted of a button press in response to the presentation of a rhythmic visual stimulus. Alterations in temporal expectancy were evaluated by measuring response times. Training consisted of responding to the visual presentation of regularly appearing stimuli by either: (1) pointing with a whole-body movement, (2) pointing only with the arm, (3) imagining pointing with a whole-body movement, (4) simply watching the stimulus presentation, (5) pointing with a whole-body movement in response to a target that appeared at irregular intervals (6) reading a newspaper. Participants performing a motor activity in response to the regular target showed significant improvements in judgment times compared to individuals with no associated motor activity. Individuals who only imagined pointing with a whole-body movement also showed significant improvements. No improvements were observed in the group that trained with a motor response to an irregular stimulus, hence eliminating the explanation that the improved temporal expectations of the other motor training groups was purely due to an improved motor capacity to press the response button. All groups performed a secondary task equally well, hence indicating that our results could not simply be attributed to differences in attention between the groups. Our results show that motor activity, even when it does not play a causal or corrective role, can lead to improved interval timing judgments. PMID:25806813

  19. Meissner-Effect Stepping Motor

    NASA Technical Reports Server (NTRS)

    Robertson, Glen A.

    1991-01-01

    Proposed stepping motor derives torque from diamagnetic repulsion produced by Meissner effect - exclusion of magnetic field from interior of superconductor. Design of motor takes advantage of silver-doped YB2Cu3O and other compounds superconductive at temperatures as high as that of liquid nitrogen. Skin of rotor cooled below its superconducting-transition temperature by liquid nitrogen. O-rings prevent leaks of liquid nitrogen from rotor. Weight, cost, and maintenance reduced.

  20. Solid rocket motor internal insulation

    NASA Technical Reports Server (NTRS)

    Twichell, S. E. (Editor); Keller, R. B., Jr.

    1976-01-01

    Internal insulation in a solid rocket motor is defined as a layer of heat barrier material placed between the internal surface of the case propellant. The primary purpose is to prevent the case from reaching temperatures that endanger its structural integrity. Secondary functions of the insulation are listed and guidelines for avoiding critical problems in the development of internal insulation for rocket motors are presented.

  1. A soft and dexterous motor

    NASA Astrophysics Data System (ADS)

    Anderson, Iain A.; Tse, Tony Chun Hin; Inamura, Tokushu; O'Brien, Benjamin M.; McKay, Thomas; Gisby, Todd

    2011-03-01

    We present a soft, bearing-free artificial muscle motor that cannot only turn a shaft but also grip and reposition it through a flexible gear. The bearing-free operation provides a foundation for low complexity soft machines, with multiple degree-of-freedom actuation, that can act simultaneously as motors and manipulators. The mechanism also enables an artificial muscle controlled gear change. Future work will include self-sensing feedback for precision, multidegree-of-freedom operation.

  2. Motor activity improves temporal expectancy.

    PubMed

    Fautrelle, Lilian; Mareschal, Denis; French, Robert; Addyman, Caspar; Thomas, Elizabeth

    2015-01-01

    Certain brain areas involved in interval timing are also important in motor activity. This raises the possibility that motor activity might influence interval timing. To test this hypothesis, we assessed interval timing in healthy adults following different types of training. The pre- and post-training tasks consisted of a button press in response to the presentation of a rhythmic visual stimulus. Alterations in temporal expectancy were evaluated by measuring response times. Training consisted of responding to the visual presentation of regularly appearing stimuli by either: (1) pointing with a whole-body movement, (2) pointing only with the arm, (3) imagining pointing with a whole-body movement, (4) simply watching the stimulus presentation, (5) pointing with a whole-body movement in response to a target that appeared at irregular intervals (6) reading a newspaper. Participants performing a motor activity in response to the regular target showed significant improvements in judgment times compared to individuals with no associated motor activity. Individuals who only imagined pointing with a whole-body movement also showed significant improvements. No improvements were observed in the group that trained with a motor response to an irregular stimulus, hence eliminating the explanation that the improved temporal expectations of the other motor training groups was purely due to an improved motor capacity to press the response button. All groups performed a secondary task equally well, hence indicating that our results could not simply be attributed to differences in attention between the groups. Our results show that motor activity, even when it does not play a causal or corrective role, can lead to improved interval timing judgments.

  3. Direct drive field actuator motors

    DOEpatents

    Grahn, A.R.

    1998-03-10

    A positive-drive field actuator motor is described which includes a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately. 62 figs.

  4. Segmented rail linear induction motor

    DOEpatents

    Cowan, Jr., Maynard; Marder, Barry M.

    1996-01-01

    A segmented rail linear induction motor has a segmented rail consisting of a plurality of nonferrous electrically conductive segments aligned along a guideway. The motor further includes a carriage including at least one pair of opposed coils fastened to the carriage for moving the carriage. A power source applies an electric current to the coils to induce currents in the conductive surfaces to repel the coils from adjacent edges of the conductive surfaces.

  5. Segmented rail linear induction motor

    DOEpatents

    Cowan, M. Jr.; Marder, B.M.

    1996-09-03

    A segmented rail linear induction motor has a segmented rail consisting of a plurality of nonferrous electrically conductive segments aligned along a guideway. The motor further includes a carriage including at least one pair of opposed coils fastened to the carriage for moving the carriage. A power source applies an electric current to the coils to induce currents in the conductive surfaces to repel the coils from adjacent edges of the conductive surfaces. 6 figs.

  6. Electrical stimulation and motor recovery.

    PubMed

    Young, Wise

    2015-01-01

    In recent years, several investigators have successfully regenerated axons in animal spinal cords without locomotor recovery. One explanation is that the animals were not trained to use the regenerated connections. Intensive locomotor training improves walking recovery after spinal cord injury (SCI) in people, and >90% of people with incomplete SCI recover walking with training. Although the optimal timing, duration, intensity, and type of locomotor training are still controversial, many investigators have reported beneficial effects of training on locomotor function. The mechanisms by which training improves recovery are not clear, but an attractive theory is available. In 1949, Donald Hebb proposed a famous rule that has been paraphrased as "neurons that fire together, wire together." This rule provided a theoretical basis for a widely accepted theory that homosynaptic and heterosynaptic activity facilitate synaptic formation and consolidation. In addition, the lumbar spinal cord has a locomotor center, called the central pattern generator (CPG), which can be activated nonspecifically with electrical stimulation or neurotransmitters to produce walking. The CPG is an obvious target to reconnect after SCI. Stimulating motor cortex, spinal cord, or peripheral nerves can modulate lumbar spinal cord excitability. Motor cortex stimulation causes long-term changes in spinal reflexes and synapses, increases sprouting of the corticospinal tract, and restores skilled forelimb function in rats. Long used to treat chronic pain, motor cortex stimuli modify lumbar spinal network excitability and improve lower extremity motor scores in humans. Similarly, epidural spinal cord stimulation has long been used to treat pain and spasticity. Subthreshold epidural stimulation reduces the threshold for locomotor activity. In 2011, Harkema et al. reported lumbosacral epidural stimulation restores motor control in chronic motor complete patients. Peripheral nerve or functional electrical

  7. Direct drive field actuator motors

    DOEpatents

    Grahn, Allen R.

    1998-01-01

    A positive-drive field actuator motor including a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately.

  8. Motor Activity Improves Temporal Expectancy

    PubMed Central

    Fautrelle, Lilian; Mareschal, Denis; French, Robert; Addyman, Caspar; Thomas, Elizabeth

    2015-01-01

    Certain brain areas involved in interval timing are also important in motor activity. This raises the possibility that motor activity might influence interval timing. To test this hypothesis, we assessed interval timing in healthy adults following different types of training. The pre- and post-training tasks consisted of a button press in response to the presentation of a rhythmic visual stimulus. Alterations in temporal expectancy were evaluated by measuring response times. Training consisted of responding to the visual presentation of regularly appearing stimuli by either: (1) pointing with a whole-body movement, (2) pointing only with the arm, (3) imagining pointing with a whole-body movement, (4) simply watching the stimulus presentation, (5) pointing with a whole-body movement in response to a target that appeared at irregular intervals (6) reading a newspaper. Participants performing a motor activity in response to the regular target showed significant improvements in judgment times compared to individuals with no associated motor activity. Individuals who only imagined pointing with a whole-body movement also showed significant improvements. No improvements were observed in the group that trained with a motor response to an irregular stimulus, hence eliminating the explanation that the improved temporal expectations of the other motor training groups was purely due to an improved motor capacity to press the response button. All groups performed a secondary task equally well, hence indicating that our results could not simply be attributed to differences in attention between the groups. Our results show that motor activity, even when it does not play a causal or corrective role, can lead to improved interval timing judgments. PMID:25806813

  9. Catalyst for converting synthesis gas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.

    1986-01-01

    The addition of an inert metal component, such as gold, silver or copper, to a Fischer-Tropsch catalyst comprising cobalt enables said catalyst to convert synthesis gas to liquid motor fuels at about 240.degree.-370.degree. C. with advantageously reduced selectivity of said cobalt for methane in said conversion. The catalyst composition can advantageously include a support component, such as a molecular sieve, co-catalyst/support component or a combination of such support components.

  10. Electric motor for laser-mechanical drilling

    DOEpatents

    Grubb, Daryl L.; Faircloth, Brian O.; Zediker, Mark S.

    2015-07-07

    A high power laser drilling system utilizing an electric motor laser bottom hole assembly. A high power laser beam travels within the electric motor for advancing a borehole. High power laser drilling system includes a down hole electrical motor having a hollow rotor for conveying a high power laser beam through the electrical motor.

  11. Motor Development: From Classroom to Playground.

    ERIC Educational Resources Information Center

    Fain, Gerald S., Ed.; Burkhart, Ernie, Ed.

    Intended for the educator and recreator working with normal and exceptional children, the book provides an overview of perceptual motor terminology, development, and resources in addition to a state of the art paper. Presented are definitions of such terms as motor development, sensory motor development, and perceptual motor development.…

  12. 30 CFR 18.34 - Motors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Motors. 18.34 Section 18.34 Mineral Resources... PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Construction and Design Requirements § 18.34 Motors. Explosion-proof electric motor assemblies intended for use in approved equipment in...

  13. 30 CFR 18.34 - Motors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Motors. 18.34 Section 18.34 Mineral Resources... PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Construction and Design Requirements § 18.34 Motors. Explosion-proof electric motor assemblies intended for use in approved equipment in...

  14. Precision stop control for motors

    NASA Technical Reports Server (NTRS)

    Howard, David E. (Inventor); Montenegro, Justino (Inventor)

    2000-01-01

    An improved stop control system and method are provided for a motor having a drive mechanism in which the motor is coupled to a motor controller that controls the speed and position of the drive mechanism using a first signal indicative of a commanded position of the drive mechanism, a second signal indicative of the actual speed of the drive mechanism and a third signal indicative of the actual position of the drive mechanism. The improved system/method uses a first circuit that receives the first and third signal and generates an error signal indicative of a difference therebetween. A second circuit receives the error signal and compares same with a threshold position error. The result of this comparison is used to selectively supply the second signal (i.e., speed) to the motor controller at least whenever the error signal is less than the threshold position error so that the motor controller can use the second signal in conjunction with the third signal to stop the motor.

  15. The Bliss of Motor Abundance

    PubMed Central

    Latash, Mark L.

    2012-01-01

    Motor control is an area of natural science exploring how the nervous system interacts with other body parts and the environment to produce purposeful, coordinated actions. A central problem of motor control – the problem of motor redundancy – was formulated by Nikolai Bernstein as the problem of elimination of redundant degrees-of-freedom. Traditionally, this problem has been addressed using optimization methods based on a variety of cost functions. This review draws attention to a body of recent findings suggesting that the problem has been formulated incorrectly. An alternative view has been suggested as the principle of abundance, which considers the apparently redundant degrees-of-freedom as useful and even vital for many aspects of motor behavior. Over the past ten years, dozens of publications have provided support for this view based on the ideas of synergic control, computational apparatus of the uncontrolled manifold hypothesis, and the equilibrium-point (referent configuration) hypothesis. In particular, large amounts of “good variance” – variance in the space of elements that has no effect on the overall performance – have been documented across a variety of natural actions. “Good variance” helps an abundant system to deal with secondary tasks and unexpected perturbations; its amount shows adaptive modulation across a variety of conditions. These data support the view that there is no problem of motor redundancy; there is bliss of motor abundance. PMID:22246105

  16. Remote control of myosin and kinesin motors using light-activated gearshifting.

    PubMed

    Nakamura, Muneaki; Chen, Lu; Howes, Stuart C; Schindler, Tony D; Nogales, Eva; Bryant, Zev

    2014-09-01

    Cytoskeletal motors perform critical force generation and transport functions in eukaryotic cells. Engineered modifications of motor function provide direct tests of protein structure-function relationships and potential tools for controlling cellular processes or for harnessing molecular transport in artificial systems. Here, we report the design and characterization of a panel of cytoskeletal motors that reversibly change gears--speed up, slow down or switch directions--when exposed to blue light. Our genetically encoded structural designs incorporate a photoactive protein domain to enable light-dependent conformational changes in an engineered lever arm. Using in vitro motility assays, we demonstrate robust spatiotemporal control over motor function and characterize the kinetics of the optical gearshifting mechanism. We have used a modular approach to create optical gearshifting motors for both actin-based and microtubule-based transport.

  17. Remote control of myosin and kinesin motors using light-activated gearshifting.

    PubMed

    Nakamura, Muneaki; Chen, Lu; Howes, Stuart C; Schindler, Tony D; Nogales, Eva; Bryant, Zev

    2014-09-01

    Cytoskeletal motors perform critical force generation and transport functions in eukaryotic cells. Engineered modifications of motor function provide direct tests of protein structure-function relationships and potential tools for controlling cellular processes or for harnessing molecular transport in artificial systems. Here, we report the design and characterization of a panel of cytoskeletal motors that reversibly change gears--speed up, slow down or switch directions--when exposed to blue light. Our genetically encoded structural designs incorporate a photoactive protein domain to enable light-dependent conformational changes in an engineered lever arm. Using in vitro motility assays, we demonstrate robust spatiotemporal control over motor function and characterize the kinetics of the optical gearshifting mechanism. We have used a modular approach to create optical gearshifting motors for both actin-based and microtubule-based transport. PMID:25086603

  18. Force generation and step-size fluctuations in a dynein motor

    NASA Astrophysics Data System (ADS)

    Bameta, Tripti; Padinhateeri, Ranjith; Inamdar, Mandar M.

    2013-02-01

    Molecular motors such as dynein are known to move by taking steps of different sizes, depending on the load. Here, we develop a simple, discrete, minimal ratchet model for a motor that can take steps of sizes δ∘ and 2δ∘ in order to provide a bare-bones description of dynein. We obtain the force-velocity curves and diffusivity for this motor for different concentrations of ATP. We also study the mechano-chemical energy transduction and thermodynamic efficiency of the motor. Further, by investigating the statistics of step sizes for the motor, we show that the average step size and fluctuation in step sizes have a non-monotonic force dependence. We develop closed-form analytical expressions for all our results, which despite the simplicity of the model give a reasonable match with the known experiments and simulations on dynein.

  19. Remote control of myosin and kinesin motors using light-activated gearshifting

    PubMed Central

    Nakamura, Muneaki; Chen, Lu; Howes, Stuart C.; Schindler, Tony D.; Nogales, Eva

    2015-01-01

    Cytoskeletal motors perform critical force generation and transport functions in eukaryotic cells1,2. Engineered modifications of motor function provide direct tests of protein structure-function relationships and potential tools for controlling cellular processes or for harnessing molecular transport in artificial systems3,4. Here, we report the design and characterization of a panel of cytoskeletal motors that reversibly change gears—speed up, slow down or switch directions—when exposed to blue light. Our genetically encoded structural designs incorporate a photoactive protein domain to enable light-dependent conformational changes in an engineered lever arm. Using in vitro motility assays, we demonstrate robust spatiotemporal control over motor function and characterize the kinetics of the optical gearshifting mechanism. We have used a modular approach to create optical gearshifting motors for both actin-based and microtubule-based transport. PMID:25086603

  20. Motoric cognitive risk syndrome

    PubMed Central

    Annweiler, Cedric; Ayers, Emmeline; Barzilai, Nir; Beauchet, Olivier; Bennett, David A.; Bridenbaugh, Stephanie A.; Buchman, Aron S.; Callisaya, Michele L.; Camicioli, Richard; Capistrant, Benjamin; Chatterji, Somnath; De Cock, Anne-Marie; Ferrucci, Luigi; Giladi, Nir; Guralnik, Jack M.; Hausdorff, Jeffrey M.; Holtzer, Roee; Kim, Ki Woong; Kowal, Paul; Kressig, Reto W.; Lim, Jae-Young; Lord, Susan; Meguro, Kenichi; Montero-Odasso, Manuel; Muir-Hunter, Susan W.; Noone, Mohan L.; Rochester, Lynn; Srikanth, Velandai; Wang, Cuiling

    2014-01-01

    Objectives: Our objective is to report prevalence of motoric cognitive risk syndrome (MCR), a newly described predementia syndrome characterized by slow gait and cognitive complaints, in multiple countries, and its association with dementia risk. Methods: Pooled MCR prevalence analysis of individual data from 26,802 adults without dementia and disability aged 60 years and older from 22 cohorts from 17 countries. We also examined risk of incident cognitive impairment (Mini-Mental State Examination decline ≥4 points) and dementia associated with MCR in 4,812 individuals without dementia with baseline Mini-Mental State Examination scores ≥25 from 4 prospective cohort studies using Cox models adjusted for potential confounders. Results: At baseline, 2,808 of the 26,802 participants met MCR criteria. Pooled MCR prevalence was 9.7% (95% confidence interval [CI] 8.2%–11.2%). MCR prevalence was higher with older age but there were no sex differences. MCR predicted risk of developing incident cognitive impairment in the pooled sample (adjusted hazard ratio [aHR] 2.0, 95% CI 1.7–2.4); aHRs were 1.5 to 2.7 in the individual cohorts. MCR also predicted dementia in the pooled sample (aHR 1.9, 95% CI 1.5–2.3). The results persisted even after excluding participants with possible cognitive impairment, accounting for early dementia, and diagnostic overlap with other predementia syndromes. Conclusion: MCR is common in older adults, and is a strong and early risk factor for cognitive decline. This clinical approach can be easily applied to identify high-risk seniors in a wide variety of settings. PMID:25031288

  1. Coherent collective precession of molecular rotors with chiral propellers.

    PubMed

    Tabe, Yuka; Yokoyama, Hiroshi

    2003-12-01

    Successful attempts to manufacture synthetic molecular motors have recently been reported. However, compared with natural systems such as motor proteins, synthetic motors are smaller molecules and are therefore subject to thermal fluctuations that prevent them from performing any useful function. A mechanism is needed to amplify the single molecular motion to such a level that it becomes distinguishable from the thermal background. Condensation of molecular motors into soft ordered phases (such as liquid crystals) will be a feasible approach, because there is evidence that they support molecularly driven non-equilibrium motions. Here we show that a chiral liquid-crystalline monolayer spread on a glycerol surface acts as a condensed layer of molecular rotors, which undergo a coherent molecular precession driven by the transmembrane transfer of water molecules. Composed of simple rod-like molecules with chiral propellers, the monolayer exhibits a spatiotemporal pattern in molecular orientations that closely resembles 'target patterns' in Belousov-Zhabotinsky reactions. Inversion of either the molecular chirality or the transfer direction of water molecules reverses the rotation direction associated with switching from expanding to converging target patterns. Endowed only with the soft directional order, the liquid crystal is an optimal medium that helps molecular motors to manifest their individual motions collectively.

  2. Biomimetic Phases of Microtubule-Motor Mixtures

    NASA Astrophysics Data System (ADS)

    Ross, Jennifer

    2014-03-01

    We try to determine the universal principles of organization from the molecular scale that gives rise to architecture on the cellular scale. We are specifically interested in the organization of the microtubule cytoskeleton, a rigid, yet versatile network in most cell types. Microtubules in the cell are organized by motor proteins and crosslinkers. This work applies the ideas of statistical mechanics and condensed matter physics to the non-equilibrium pattern formation behind intracellular organization using the microtubule cytoskeleton as the building blocks. We examine these processes in a bottom-up manner by adding increasingly complex protein actors into the system. Our systematic experiments expose nature's laws for organization and has large impacts on biology as well as illuminating new frontiers of non-equilibrium physics.

  3. 41 CFR 102-34.85 - What motor vehicles require motor vehicle identification?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 41 Public Contracts and Property Management 3 2014-01-01 2014-01-01 false What motor vehicles require motor vehicle identification? 102-34.85 Section 102-34.85 Public Contracts and Property Management... 34-MOTOR VEHICLE MANAGEMENT Identifying and Registering Motor Vehicles Motor Vehicle...

  4. 41 CFR 102-34.85 - What motor vehicles require motor vehicle identification?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false What motor vehicles require motor vehicle identification? 102-34.85 Section 102-34.85 Public Contracts and Property Management... 34-MOTOR VEHICLE MANAGEMENT Identifying and Registering Motor Vehicles Motor Vehicle...

  5. The Infant Motor Profile: A Standardized and Qualitative Method to Assess Motor Behaviour in Infancy

    ERIC Educational Resources Information Center

    Heineman, Kirsten R.; Bos, Arend F.; Hadders-Algra, Mijna

    2008-01-01

    A reliable and valid instrument to assess neuromotor condition in infancy is a prerequisite for early detection of developmental motor disorders. We developed a video-based assessment of motor behaviour, the Infant Motor Profile (IMP), to evaluate motor abilities, movement variability, ability to select motor strategies, movement symmetry, and…

  6. 41 CFR 102-34.85 - What motor vehicles require motor vehicle identification?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false What motor vehicles require motor vehicle identification? 102-34.85 Section 102-34.85 Public Contracts and Property Management... 34-MOTOR VEHICLE MANAGEMENT Identifying and Registering Motor Vehicles Motor Vehicle...

  7. 41 CFR 102-34.85 - What motor vehicles require motor vehicle identification?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false What motor vehicles require motor vehicle identification? 102-34.85 Section 102-34.85 Public Contracts and Property Management... 34-MOTOR VEHICLE MANAGEMENT Identifying and Registering Motor Vehicles Motor Vehicle...

  8. Single molecule measurements and biological motors.

    PubMed

    Knight, Alex E; Mashanov, Gregory; Molloy, Justin E

    2005-12-01

    Recent technological advances in lasers and optical detectors have enabled a variety of new, single molecule technologies to be developed. Using intense and highly collimated laser light sources in addition to super-sensitive cameras, the fluorescence of single fluorophores can now be imaged in aqueous solution. Also, laser optical tweezers have enabled the piconewton forces produced by pair of interacting biomolecules to be measured directly. However, for a researcher new to the field to begin to use such techniques in their own research might seem a daunting prospect. Most of the equipment that is in use is custom-built. However, most of the equipment is essence fairly simple and the aim of this article is to provide an entry point to the field for a newcomer. It focuses mainly on those practical aspects which are not particularly well covered in the literature, and aims to provide an overview of the field as a whole with references and web links to more detailed sources elsewhere. Indeed, the opportunity to publish an article such as this on the Internet affords many new opportunities (and more space!) for presenting scientific ideas and information. For example, we have illustrated the nature of optical trap data with an interactive Java simulation; provided links to relevant web sites and technical documents, and included a large number of colour figures and plots. Our group's research focuses on molecular motors, and the bias of this article reflects this. It turns out that molecular motors have been a paradigm (or prototype) for single molecule research and the field has seen a rapid development in the techniques. It is hoped that the methods described here will be broadly applicable to other biological systems.

  9. Bio-Hybrid Micro/Nanodevices Powered by Flagellar Motor: Challenges and Strategies

    PubMed Central

    Kim, Jin-Woo; Tung, Steve

    2015-01-01

    Molecular motors, which are precision engineered by nature, offer exciting possibilities for bio-hybrid engineered systems. They could enable real applications ranging from micro/nano fluidics, to biosensing, to medical diagnoses. This review describes the fundamental biological insights and fascinating potentials of these remarkable sensing and actuation machines, in particular, bacterial flagellar motors, as well as their engineering perspectives with regard to applications in bio-engineered hybrid systems. PMID:26284237

  10. Molecular Communication: Simulation of Microtubule Topology

    NASA Astrophysics Data System (ADS)

    Moore, Michael J.; Enomoto, Akihiro; Nakano, Tadashi; Kayasuga, Atsushi; Kojima, Hiroaki; Sakakibara, Hitoshi; Oiwa, Kazuhiro; Suda, Tatsuya

    Molecular communication is one method for communication among biological nanomachines. Nanomachines are artificial or biological nano-scale devices that perform simple computation, sensing, or actuation. Future applications using nanomachines may require various communication mechanisms. For example, broadcast is one primitive communication for transmission from one sender to many receivers. In this paper, we discuss preliminary work on designing a molecular communication system that is adapted from the molecular motor transport mechanism existing in biological cells. In the proposed molecular motor mechanism, a sender releases information molecules, and molecular motors transport the information molecules along microtubule filaments to receiver nanomachines up to hundreds of micrometers away. This paper describes some possible arrangements for microtubule filaments and simulations to evaluate sending of one information molecule to many receivers. The simulation results indicate that the proposed molecular motor system transports simulated information molecules (100nm radius spheres) more quickly than a diffusion-only communication and that placement of receivers at the plus-end of microtubules results in lower propagation delay.

  11. Submersible canned motor transfer pump

    DOEpatents

    Guardiani, R.F.; Pollick, R.D.; Nyilas, C.P.; Denmeade, T.J.

    1997-08-19

    A transfer pump is described which is used in a waste tank for transferring high-level radioactive liquid waste from a waste tank and having a column assembly, a canned electric motor means, and an impeller assembly with an upper impeller and a lower impeller connected to a shaft of a rotor assembly. The column assembly locates a motor housing with the electric motor means adjacent to the impeller assembly which creates an hydraulic head, and which forces the liquid waste, into the motor housing to cool the electric motor means and to cool and/or lubricate the radial and thrust bearing assemblies. Hard-on-hard bearing surfaces of the bearing assemblies and a ring assembly between the upper impeller and electric motor means grind large particles in the liquid waste flow. Slots in the static bearing member of the radial bearing assemblies further grind down the solid waste particles so that only particles smaller than the clearances in the system can pass there through, thereby resisting damage to and the interruption of the operation of the transfer pump. The column assembly is modular so that sections can be easily assembled, disassembled and/or removed. A second embodiment employs a stator jacket which provides an alternate means for cooling the electric motor means and lubricating and/or cooling the bearing assemblies, and a third embodiment employs a variable level suction device which allows liquid waste to be drawn into the transfer pump from varying and discrete levels in the waste tank. 17 figs.

  12. ATP-dependent motor activity of the transcription termination factor Rho from Mycobacterium tuberculosis.

    PubMed

    D'Heygère, François; Schwartz, Annie; Coste, Franck; Castaing, Bertrand; Boudvillain, Marc

    2015-07-13

    The bacterial transcription termination factor Rho-a ring-shaped molecular motor displaying directional, ATP-dependent RNA helicase/translocase activity-is an interesting therapeutic target. Recently, Rho from Mycobacterium tuberculosis (MtbRho) has been proposed to operate by a mechanism uncoupled from molecular motor action, suggesting that the manner used by Rho to dissociate transcriptional complexes is not conserved throughout the bacterial kingdom. Here, however, we demonstrate that MtbRho is a bona fide molecular motor and directional helicase which requires a catalytic site competent for ATP hydrolysis to disrupt RNA duplexes or transcription elongation complexes. Moreover, we show that idiosyncratic features of the MtbRho enzyme are conferred by a large, hydrophilic insertion in its N-terminal 'RNA binding' domain and by a non-canonical R-loop residue in its C-terminal 'motor' domain. We also show that the 'motor' domain of MtbRho has a low apparent affinity for the Rho inhibitor bicyclomycin, thereby contributing to explain why M. tuberculosis is resistant to this drug. Overall, our findings support that, in spite of adjustments of the Rho motor to specific traits of its hosting bacterium, the basic principles of Rho action are conserved across species and could thus constitute pertinent screening criteria in high-throughput searches of new Rho inhibitors.

  13. Motor influences on judgment: Motor and cognitive integration.

    PubMed

    Mullet, Etienne; Cretenet, Joël; Dru, Vincent

    2014-02-01

    Performing motor behaviours (arm flexion vs. extension) that correspond also to lateralized peripheral activations (left vs. right side) of the motivational systems of approach versus avoidance have been previously shown to impact cognitive performance and judgment. Three experiments are reported that examined the combined effect of these variables, as a kind of motor integration, on the implementation of information integration rules in various judgment tasks: judging of a person's attractiveness from personality information, judging of the severity of health risk from alcohol and tobacco intake, and attributing blame to a perpetrator from information as to intent and severity of harm done. It was found that the congruence between these motivational activations consistently influenced the use of interactive information integration rules, compared to additive ones. This set of findings showed that cognitive rules might also be embodied. Motor integration affects cognitive integration in judgment.

  14. Improve Motor Operation at Off-Design Voltages - Motor Tip Sheet #9

    SciTech Connect

    2008-07-01

    Motors are designed to operate within +/- 10% of their nameplate rated voltages. When motors operate at conditions of over- or under-voltage, motor efficiency and other performance parameters are degraded.

  15. Three phase AC motor controller

    DOEpatents

    Vuckovich, Michael; Wright, Maynard K.; Burkett, John P.

    1984-03-20

    A motor controller for a three phase AC motor (10) which is adapted to operate bidirectionally from signals received either from a computer (30) or a manual control (32). The controller is comprised of digital logic circuit means which implement a forward and reverse command signal channel (27, 29) for the application of power through the forward and reverse power switching relays (16, 18, 20, 22). The digital logic elements are cross coupled to prevent activation of both channels simultaneously and each includes a plugging circuit (65, 67) for stopping the motor upon the removal of control signal applied to one of the two channels (27, 29) for a direction of rotation desired. Each plugging circuit (65, 67) includes a one-shot pulse signal generator (88, 102) which outputs a single pulse signal of predetermined pulsewidth which is adapted to inhibit further operation of the application of power in the channel which is being activated and to apply a reversal command signal to the other channel which provides a reversed phase application of power to the motor for a period defined by the pulse-width output of the one-shot signal generator to plug the motor (10) which will then be inoperative until another rotational command signal is applied to either of the two channels.

  16. Minimum Principles in Motor Control.

    PubMed

    Engelbrecht, Sascha E.

    2001-06-01

    Minimum (or minimal) principles are mathematical laws that were first used in physics: Hamilton's principle and Fermat's principle of least time are two famous example. In the past decade, a number of motor control theories have been proposed that are formally of the same kind as the minimum principles of physics, and some of these have been quite successful at predicting motor performance in a variety of tasks. The present paper provides a comprehensive review of this work. Particular attention is given to the relation between minimum theories in motor control and those used in other disciplines. Other issues around which the review is organized include: (1) the relation between minimum principles and structural models of motor planning and motor control, (2) the empirically-driven development of minimum principles and the danger of circular theorizing, and (3) the design of critical tests for minimum theories. Some perspectives for future research are discussed in the concluding section of the paper. Copyright 2001 Academic Press. PMID:11401453

  17. Filament overwrapped motor case technology

    NASA Astrophysics Data System (ADS)

    Compton, Joel P.

    1993-11-01

    Atlantic Research Corporation (ARC) joined with the French Societe Europeenne de Propulsion (SEP) to develop and deliver to the U.S. Navy a small quantity of composite filament wound rocket motors to demonstrate a manufacturing technique that was being applied at the two companies. It was perceived that the manufacturing technique could produce motors that would be light in weight, inexpensive to produce, and that had a good chance of meeting insensitive munitions (IM) requirements that were being formulated by the Navy in the early 1980s. Under subcontract to ARC, SEP designed, tested, and delivered 2.75-inch rocket motors to the U.S. Navy for IM tests that were conducted in 1989 at China Lake, California. The program was one of the first to be founded by Nunn Amendment money. The Government-to-Government program was sponsored by the Naval Air Systems Command and was monitored by the Naval Surface Warfare Center, Indian Head (NSWC-IH), Maryland. The motor propellant that was employed was a new, extruded composite formulation that was under development at the Naval Surface Warfare Center. The following paper describes the highlights of the program and gives the results of structural and ballistic static tests and insensitive munitions tests that were conducted on demonstration motors.

  18. Early identification of motor delay

    PubMed Central

    Harris, Susan R.

    2016-01-01

    Objective To describe the Harris Infant Neuromotor Test (HINT), an infant neuromotor test using Canadian norms published in 2010 that could be used to screen for motor delay during the first year of life. Quality of evidence Extensive research has been published on the intrarater, interrater, and test-retest reliability and the content, concurrent, predictive, and known-groups validity of the HINT, as well as on the sensitivity, specificity, and positive and negative predictive values of parental concerns, as assessed by the HINT. Most evidence is level II. Main message Diagnosing motor delays during the first year of life is important because these often indicate more generalized developmental delays or specific disabilities, such as cerebral palsy. Parental concerns about their children’s motor development are strongly predictive of subsequent diagnoses involving motor delay. Conclusion Only through early identification of developmental motor delays, initially with screening tools such as the HINT, is it possible to provide referrals for early intervention that could benefit both the infant and the family. PMID:27521388

  19. Reduced vibration motor winding arrangement

    SciTech Connect

    Slavik, C.J.; Rhudy, R.G.; Bushman, R.E.

    1995-12-31

    The present invention relates generally to an electric motor winding and, more particularly, to a three phase motor armature winding arrangement designed to reduce motor vibration and improve efficiency. An individual phase winding arrangement having a sixty electrical degree phase belt width for use with a three phase motor armature includes a delta connected phase winding portion and a wye connected phase winding portion. Both the delta and wye connected phase winding portions have a thirty electrical degree phase belt width. The delta and wye connected phase winding portions are each formed from a preselected number of individual coils each formed, in turn, from an unequal number of electrical conductor turns in the approximate ratio of {radical}3. The individual coils of the delta and wye connected phase winding portions may either be connected in series or parallel. This arrangement provides an armature winding for a three phase motor which retains the benefits of the widely known and utilized thirty degree phase belt concept, including improved mmf waveform and fundamental distribution factor.

  20. Disentangling motor execution from motor imagery with the phantom limb.

    PubMed

    Raffin, Estelle; Mattout, Jérémie; Reilly, Karen T; Giraux, Pascal

    2012-02-01

    Amputees can move their phantom limb at will. These 'movements without movements' have generally been considered as motor imagery rather than motor execution, but amputees can in fact perform both executed and imagined movements with their phantom and they report distinct perceptions during each task. Behavioural evidence for this dual ability comes from the fact that executed movements are associated with stump muscle contractions whereas imagined movements are not, and that phantom executed movements are slower than intact hand executed movements whereas the speed of imagined movements is identical for both hands. Since neither execution nor imagination produces any visible movement, we hypothesized that the perceptual difference between these two motor tasks relies on the activation of distinct cerebral networks. Using functional magnetic resonance imaging and changes in functional connectivity (dynamic causal modelling), we examined the activity associated with imagined and executed movements of the intact and phantom hands of 14 upper-limb amputees. Distinct but partially overlapping cerebral networks were active during both executed and imagined phantom limb movements (both performed at the same speed). A region of interest analysis revealed a 'switch' between execution and imagination; during execution there was more activity in the primary somatosensory cortex, the primary motor cortex and the anterior lobe of the cerebellum, while during imagination there was more activity in the parietal and occipital lobes, and the posterior lobe of the cerebellum. In overlapping areas, task-related differences were detected in the location of activation peaks. The dynamic causal modelling analysis further confirmed the presence of a clear neurophysiological distinction between imagination and execution, as motor imagery and motor execution had opposite effects on the supplementary motor area-primary motor cortex network. This is the first imaging evidence that the

  1. Dynein is the motor for retrograde axonal transport of organelles

    SciTech Connect

    Schnapp, B.J.; Reese, T.S.

    1989-03-01

    Vesicular organelles in axons of nerve cells are transported along microtubules either toward their plus ends (fast anterograde transport) or toward their minus ends (retrograde transport). Two microtubule-based motors were previously identified by examining plastic beads induced to move along microtubules by cytosol fractions from the squid giant axon: (i) an anterograde motor, kinesin, and (ii) a retrograde motor, which is characterized here. The retrograde motor, a cytosolic protein previously termed HMW1, was purified from optic lobes and extruded axoplasm by nucleotide-dependent microtubule affinity and release; microtubule gliding was used as the assay of motor activity. The following properties of the retrograde motor suggest that it is cytoplasmic dynein: (i) sedimentation at 20-22 S with a heavy chain of Mr greater than 200,000 that coelectrophoreses with the alpha and beta subunits of axonemal dynein, (ii) cleavage by UV irradiation in the presence of ATP and vanadate, and (iii) a molecular structure resembling two-headed dynein from axonemes. Furthermore, bead movement toward the minus end of microtubules was blocked when axoplasmic supernatants were treated with UV/vanadate. Treatment of axoplasmic supernatant with UV/vanadate also blocks the retrograde movement of purified organelles in vitro without changing the number of anterograde moving organelles, indicating that dynein interacts specifically with a subgroup of organelles programmed to move toward the cell body. However, purified optic lobe dynein, like purified kinesin, does not by itself promote the movement of purified organelles along microtubules, suggesting that additional axoplasmic factors are necessary for retrograde as well as anterograde transport.

  2. Dynamics of the bacterial flagellar motor with multiple stators

    PubMed Central

    Meacci, Giovanni; Tu, Yuhai

    2009-01-01

    The bacterial flagellar motor drives the rotation of flagellar filaments and enables many species of bacteria to swim. Torque is generated by interaction of stator units, anchored to the peptidoglycan cell wall, with the rotor. Recent experiments [Yuan J, Berg HC (2008) Proc Natl Acad Sci USA 105:1182–1185] show that at near-zero load the speed of the motor is independent of the number of stators. Here, we introduce a mathematical model of the motor dynamics that explains this behavior based on a general assumption that the stepping rate of a stator depends on the torque exerted by the stator on the rotor. We find that the motor dynamics can be characterized by two timescales: the moving-time interval for the mechanical rotation of the rotor and the waiting-time interval determined by the chemical transitions of the stators. We show that these two timescales depend differently on the load, and that their cross-over provides the microscopic explanation for the existence of two regimes in the torque-speed curves observed experimentally. We also analyze the speed fluctuation for a single motor by using our model. We show that the motion is smoothed by having more stator units. However, the mechanism for such fluctuation reduction is different depending on the load. We predict that the speed fluctuation is determined by the number of steps per revolution only at low load and is controlled by external noise for high load. Our model can be generalized to study other molecular motor systems with multiple power-generating units. PMID:19234112

  3. Visuomotor learning by passive motor experience.

    PubMed

    Sakamoto, Takashi; Kondo, Toshiyuki

    2015-01-01

    Humans can adapt to unfamiliar dynamic and/or kinematic transformations through the active motor experience. Recent studies of neurorehabilitation using robots or brain-computer interface (BCI) technology suggest that passive motor experience would play a measurable role in motor recovery, however our knowledge of passive motor learning is limited. To clarify the effects of passive motor experience on human motor learning, we performed arm reaching experiments guided by a robotic manipulandum. The results showed that the passive motor experience had an anterograde transfer effect on the subsequent motor execution, whereas no retrograde interference was confirmed in the ABA paradigm experiment. This suggests that the passive experience of the error between visual and proprioceptive sensations leads to the limited but actual compensation of behavior, although it is fragile and cannot be consolidated as a persistent motor memory.

  4. Multiple displacement motor driven power drive unit

    SciTech Connect

    Burandt, W. A.

    1985-12-03

    A multiple displacement motor driven power drive unit having two separate hydraulic systems each with a variable displacement hydraulic motor having its output connected to a torque summing gear train. A control provides for operation of one or the other of the motors at full displacement while the other motor is at zero displacement and free-wheels. There is a manual mechanical control operation with both motors simultaneously set at one-half of full displacement and driving the torque summing gear train. The change in motor displacements to one-half full displacement accomplishes velocity summing within the hydraulics. The multiple displacement motor driven power drive unit accomplishes the power efficiency of a multiple motor driven power drive unit utilizing a speed summing gear train with fixed displacement motors, but without the complexities associated with the use of a speed summing gear train and brakes.

  5. Control Circuit For Two Stepping Motors

    NASA Technical Reports Server (NTRS)

    Ratliff, Roger; Rehmann, Kenneth; Backus, Charles

    1990-01-01

    Control circuit operates two independent stepping motors, one at a time. Provides following operating features: After selected motor stepped to chosen position, power turned off to reduce dissipation; Includes two up/down counters that remember at which one of eight steps each motor set. For selected motor, step indicated by illumination of one of eight light-emitting diodes (LED's) in ring; Selected motor advanced one step at time or repeatedly at rate controlled; Motor current - 30 mA at 90 degree positions, 60 mA at 45 degree positions - indicated by high or low intensity of LED that serves as motor-current monitor; Power-on reset feature provides trouble-free starts; To maintain synchronism between control circuit and motors, stepping of counters inhibited when motor power turned off.

  6. Visuomotor learning by passive motor experience

    PubMed Central

    Sakamoto, Takashi; Kondo, Toshiyuki

    2015-01-01

    Humans can adapt to unfamiliar dynamic and/or kinematic transformations through the active motor experience. Recent studies of neurorehabilitation using robots or brain-computer interface (BCI) technology suggest that passive motor experience would play a measurable role in motor recovery, however our knowledge of passive motor learning is limited. To clarify the effects of passive motor experience on human motor learning, we performed arm reaching experiments guided by a robotic manipulandum. The results showed that the passive motor experience had an anterograde transfer effect on the subsequent motor execution, whereas no retrograde interference was confirmed in the ABA paradigm experiment. This suggests that the passive experience of the error between visual and proprioceptive sensations leads to the limited but actual compensation of behavior, although it is fragile and cannot be consolidated as a persistent motor memory. PMID:26029091

  7. Strain Mediated Adaptation Is Key for Myosin Mechanochemistry: Discovering General Rules for Motor Activity.

    PubMed

    Jana, Biman; Onuchic, José N

    2016-08-01

    A structure-based model of myosin motor is built in the same spirit of our early work for kinesin-1 and Ncd towards physical understanding of its mechanochemical cycle. We find a structural adaptation of the motor head domain in post-powerstroke state that signals faster ADP release from it compared to the same from the motor head in the pre-powerstroke state. For dimeric myosin, an additional forward strain on the trailing head, originating from the postponed powerstroke state of the leading head in the waiting state of myosin, further increases the rate of ADP release. This coordination between the two heads is the essence of the processivity of the cycle. Our model provides a structural description of the powerstroke step of the cycle as an allosteric transition of the converter domain in response to the Pi release. Additionally, the variation in structural elements peripheral to catalytic motor domain is the deciding factor behind diverse directionalities of myosin motors (myosin V & VI). Finally, we observe that there are general rules for functional molecular motors across the different families. Allosteric structural adaptation of the catalytic motor head in different nucleotide states is crucial for mechanochemistry. Strain-mediated coordination between motor heads is essential for processivity and the variation of peripheral structural elements is essential for their diverse functionalities. PMID:27494025

  8. Cooperativity of self-organized Brownian motors pulling on soft cargoes.

    PubMed

    Orlandi, Javier G; Blanch-Mercader, Carles; Brugués, Jan; Casademunt, Jaume

    2010-12-01

    We study the cooperative dynamics of Brownian motors moving along a one-dimensional track when an external load is applied to the leading motor, mimicking molecular motors pulling on membrane-bound cargoes in intracellular traffic. Due to the asymmetric loading, self-organized motor clusters form spontaneously. We model the motors with a two-state noise-driven ratchet formulation and study analytically and numerically the collective velocity-force and efficiency-force curves resulting from mutual interactions, mostly hard-core repulsion and weak (nonbinding) attraction. We analyze different parameter regimes including the limits of weak noise, mean-field behavior, rigid coupling, and large numbers of motors, for the different interactions. We present a general framework to classify and quantify cooperativity. We show that asymmetric loading leads generically to enhanced cooperativity beyond the simple superposition of the effects of individual motors. For weakly attracting interactions, the cooperativity is mostly enhanced, including highly coordinated motion of motors and complex nonmonotonic velocity-force curves, leading to self-regulated clusters. The dynamical scenario is enriched by resonances associated to commensurability of different length scales. Large clusters exhibit synchronized dynamics and bidirectional motion. Biological implications are discussed.

  9. Strain Mediated Adaptation Is Key for Myosin Mechanochemistry: Discovering General Rules for Motor Activity

    PubMed Central

    Jana, Biman; Onuchic, José N.

    2016-01-01

    A structure-based model of myosin motor is built in the same spirit of our early work for kinesin-1 and Ncd towards physical understanding of its mechanochemical cycle. We find a structural adaptation of the motor head domain in post-powerstroke state that signals faster ADP release from it compared to the same from the motor head in the pre-powerstroke state. For dimeric myosin, an additional forward strain on the trailing head, originating from the postponed powerstroke state of the leading head in the waiting state of myosin, further increases the rate of ADP release. This coordination between the two heads is the essence of the processivity of the cycle. Our model provides a structural description of the powerstroke step of the cycle as an allosteric transition of the converter domain in response to the Pi release. Additionally, the variation in structural elements peripheral to catalytic motor domain is the deciding factor behind diverse directionalities of myosin motors (myosin V & VI). Finally, we observe that there are general rules for functional molecular motors across the different families. Allosteric structural adaptation of the catalytic motor head in different nucleotide states is crucial for mechanochemistry. Strain-mediated coordination between motor heads is essential for processivity and the variation of peripheral structural elements is essential for their diverse functionalities. PMID:27494025

  10. Remote control for motor vehicle

    NASA Technical Reports Server (NTRS)

    Johnson, Dale R. (Inventor); Ciciora, John A. (Inventor)

    1984-01-01

    A remote controller is disclosed for controlling the throttle, brake and steering mechanism of a conventional motor vehicle, with the remote controller being particularly advantageous for use by severely handicapped individuals. The controller includes a remote manipulator which controls a plurality of actuators through interfacing electronics. The remote manipulator is a two-axis joystick which controls a pair of linear actuators and a rotary actuator, with the actuators being powered by electric motors to effect throttle, brake and steering control of a motor vehicle adapted to include the controller. The controller enables the driver to control the adapted vehicle from anywhere in the vehicle with one hand with minimal control force and range of motion. In addition, even though a conventional vehicle is adapted for use with the remote controller, the vehicle may still be operated in the normal manner.

  11. Techniques for studying protein trafficking and molecular motors in neurons

    PubMed Central

    Feng, Shanxi; Arnold, Don B.

    2016-01-01

    This review focuses on techniques that facilitate the visualization of protein trafficking. In the mid-1990’s the cloning of GFP allowed fluorescently tagged proteins to be expressed in cells and then visualized in real time. This advance allowed a glimpse, for the first time, of the complex system within cells for distributing proteins. It quickly became apparent, however, that time-lapse sequences of exogenously expressed GFP-labeled proteins can be difficult to interpret. Reasons for this include the relatively low signal that comes from moving proteins and high background rates from stationary proteins and other sources, as well as the difficulty of identifying the origins and destinations of specific vesicular carriers. In this review we will examine a range of techniques that have overcome these issues to varying degrees and discuss the insights into protein trafficking that they have enabled. We will concentrate on neurons, as they are highly polarized and, thus, their trafficking systems tend to be accessible for study. PMID:26800506

  12. Fish Chromatophores--From Molecular Motors to Animal Behavior.

    PubMed

    Sköld, Helen Nilsson; Aspengren, Sara; Cheney, Karen L; Wallin, Margareta

    2016-01-01

    Chromatophores are pigment-bearing cells of lower vertebrates, including fish that cater for the ability of individual animals to shift body coloration and pattern. Color change provides dynamic camouflage and various kinds of communication. It is also a spectacular example of phenotypic plasticity, and of significant importance for adaptation and survival in novel environments. Through different cellular mechanisms, color change can occur within minutes or more slowly over weeks. Chromatophores have different pigment types and are located not only in the skin, but also in the eyes and internally. While morphological color change, including seasonal color change, has received a lot of interest from evolutionary biologists and behavioral ecologists, the more rapid physiological color change has been largely a research subject for cell physiologists. In this cross-disciplinary review, we have highlighted emerging trends in pigment cell research and identified unsolved problems for future research. PMID:26811288

  13. ATP synthases from archaea: the beauty of a molecular motor.

    PubMed

    Grüber, Gerhard; Manimekalai, Malathy Sony Subramanian; Mayer, Florian; Müller, Volker

    2014-06-01

    Archaea live under different environmental conditions, such as high salinity, extreme pHs and cold or hot temperatures. How energy is conserved under such harsh environmental conditions is a major question in cellular bioenergetics of archaea. The key enzymes in energy conservation are the archaeal A1AO ATP synthases, a class of ATP synthases distinct from the F1FO ATP synthase ATP synthase found in bacteria, mitochondria and chloroplasts and the V1VO ATPases of eukaryotes. A1AO ATP synthases have distinct structural features such as a collar-like structure, an extended central stalk, and two peripheral stalks possibly stabilizing the A1AO ATP synthase during rotation in ATP synthesis/hydrolysis at high temperatures as well as to provide the storage of transient elastic energy during ion-pumping and ATP synthesis/-hydrolysis. High resolution structures of individual subunits and subcomplexes have been obtained in recent years that shed new light on the function and mechanism of this unique class of ATP synthases. An outstanding feature of archaeal A1AO ATP synthases is their diversity in size of rotor subunits and the coupling ion used for ATP synthesis with H(+), Na(+) or even H(+) and Na(+) using enzymes. The evolution of the H(+) binding site to a Na(+) binding site and its implications for the energy metabolism and physiology of the cell are discussed.

  14. Progress toward a rationally designed, chemically powered rotary molecular motor.

    PubMed

    Kelly, T Ross; Cai, Xiaolu; Damkaci, Fehmi; Panicker, Sreeletha B; Tu, Bin; Bushell, Simon M; Cornella, Ivan; Piggott, Matthew J; Salives, Richard; Cavero, Marta; Zhao, Yajun; Jasmin, Serge

    2007-01-17

    Building on prototype 1, which achieves 120 degrees of phosgene-powered unidirectional rotation to rotamer 6 (see Figure 5 in the full article), 7 was designed to accomplish repeated unidirectional rotation (see Scheme 7). Compound 7 contains an amino group on each blade of the triptycene and a 4-(dimethylamino)pyridine (DMAP) unit to selectively deliver phosgene (or its equivalent) to the amine in the "firing position". The synthesis of 7 is described: the key constructive steps are a benzyne addition to an anthracene to generate the triptycene, a stilbene photocyclization to construct the helicene, and a Stille coupling to incorporate the DMAP unit. The DMAP unit was shown to regioselectively relay 1,1'-carbonyldiimidazole (but not phosgene) to the proximal amino group, as designed, but rotation of the triptycene does not occur. Extensive attempts to troubleshoot the problem led to the conclusion that the requisite intramolecular urethane formation, as demonstrated in the prototype (1 --> 4), does not occur with 7 (to give 85) or 97 (to give 100). We speculate that either (i) hydrogen bonding between the hydroxypropyl group and functionality present in 7 but absent from 1 or (ii) a Bürgi-Dunitz (or similar) interaction involving the DMAP (see 106) prevents achievement of a conformation conducive to intramolecular urethane formation. PMID:17212418

  15. Fish Chromatophores--From Molecular Motors to Animal Behavior.

    PubMed

    Sköld, Helen Nilsson; Aspengren, Sara; Cheney, Karen L; Wallin, Margareta

    2016-01-01

    Chromatophores are pigment-bearing cells of lower vertebrates, including fish that cater for the ability of individual animals to shift body coloration and pattern. Color change provides dynamic camouflage and various kinds of communication. It is also a spectacular example of phenotypic plasticity, and of significant importance for adaptation and survival in novel environments. Through different cellular mechanisms, color change can occur within minutes or more slowly over weeks. Chromatophores have different pigment types and are located not only in the skin, but also in the eyes and internally. While morphological color change, including seasonal color change, has received a lot of interest from evolutionary biologists and behavioral ecologists, the more rapid physiological color change has been largely a research subject for cell physiologists. In this cross-disciplinary review, we have highlighted emerging trends in pigment cell research and identified unsolved problems for future research.

  16. Molecular pathways in dystonia

    PubMed Central

    Bragg, D. Cristopher; Armata, Ioanna A.; Nery, Flavia C.; Breakefield, Xandra O.; Sharma, Nutan

    2011-01-01

    The hereditary dystonias comprise a set of diseases defined by a common constellation of motor deficits. These disorders are most likely associated with different molecular etiologies, many of which have yet to be elucidated. Here we discuss recent advances in three forms of hereditary dystonia, DYT1, DYT6 and DYT16, which share a similar clinical picture: onset in childhood or adolescence, progressive spread of symptoms with generalized involvement of body regions and a steady state affliction without treatment. Unlike DYT1, the genes responsible for DYT6 and DYT16 have only recently been identified, with relatively little information about the function of the encoded proteins. Nevertheless, recent data suggest that these proteins may fit together within interacting pathways involved in dopaminergic signaling, transcriptional regulation, and cellular stress responses. This review focuses on these molecular pathways, highlighting potential common themes among these dystonias which may serve as areas for future research. PMID:21134457

  17. Miniaturization of Planar Horn Motors

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Ostlund, Patrick N.; Chang, Zensheu; Bao, Xiaoqi; Bar-Cohen, Yoseph; Widholm, Scott E.; Badescu, Mircea

    2012-01-01

    There is a great need for compact, efficient motors for driving various mechanisms including robots or mobility platforms. A study is currently underway to develop a new type of piezoelectric actuators with significantly more strength, low mass, small footprint, and efficiency. The actuators/motors utilize piezoelectric actuated horns which have a very high power density and high electromechanical conversion efficiency. The horns are fabricated using our recently developed novel pre-stress flexures that make them thermally stable and increases their coupling efficiency. The monolithic design and integrated flexures that pre-stresses the piezoelectric stack eliminates the use of stress bolt. This design allows embedding solid-state motors and actuators in any structure so that the only macroscopically moving parts are the rotor or the linear translator. The developed actuator uses a stack/horn actuation and has a Barth motor configuration, which potentially generates very large torque and speeds that do not require gearing. Finite element modeling and design tools were investigated to determine the requirements and operation parameters and the results were used to design and fabricate a motor. This new design offers a highly promising actuation mechanism that can potentially be miniaturized and integrated into systems and structures. It can be configured in many shapes to operate as multi-degrees of freedom and multi-dimensional motors/actuators including unidirectional, bidirectional, 2D and 3D. In this manuscript, we are reporting the experimental measurements from a bench top design and the results from the efforts to miniaturize the design using 2x2x2 mm piezoelectric stacks integrated into thin plates that are of the order of3 x 3x 0.2 cm.

  18. Miniaturization of planar horn motors

    NASA Astrophysics Data System (ADS)

    Sherrit, Stewart; Ostlund, Patrick N.; Chang, Zensheu; Bao, Xiaoqi; Bar-Cohen, Yoseph; Widholm, Scott E.; Badescu, Mircea

    2012-04-01

    There is a great need for compact, efficient motors for driving various mechanisms including robots or mobility platforms. A study is currently underway to develop a new type of piezoelectric actuators with significantly more strength, low mass, small footprint, and efficiency. The actuators/motors utilize piezoelectric actuated horns which have a very high power density and high electromechanical conversion efficiency. The horns are fabricated using our recently developed novel pre-stress flexures that make them thermally stable and increases their coupling efficiency. The monolithic design and integrated flexures that pre-stresses the piezoelectric stack eliminates the use of a stress bolt. This design allows embedding solid-state motors and actuators in any structure so that the only macroscopically moving parts are the rotor or the linear translator. The developed actuator uses a stack/horn actuation and has a Barth motor configuration, which potentially generates very large torque and speeds that do not require gearing. Finite element modeling and design tools were investigated to determine the requirements and operation parameters and the results were used to design and fabricate a motor. This new design offers a highly promising actuation mechanism that can potentially be miniaturized and integrated into systems and structures. It can be configured in many shapes to operate as multi-degrees of freedom and multi-dimensional motors/actuators including unidirectional, bidirectional, 2D and 3D. In this manuscript, we are reporting the experimental measurements from a bench top design and the results from the efforts to miniaturize the design using 2×2×2 mm piezoelectric stacks integrated into thin plates that are of the order of 3 × 3 × 0.2 cm.

  19. Homopolar motor with dual rotors

    DOEpatents

    Hsu, John S.

    1998-01-01

    A homopolar motor (10) has a field rotor (15) mounted on a frame (11) for rotation in a first rotational direction and for producing an electromagnetic field, and an armature rotor (17) mounted for rotation on said frame (11) within said electromagnetic field and in a second rotational direction counter to said first rotational direction of said field rotor (15). The two rotors (15, 17) are coupled through a 1:1 gearing mechanism (19), so as to travel at the same speed but in opposite directions. This doubles the output voltage and output power, as compared to a motor in which only the armature is rotated. Several embodiments are disclosed.

  20. Homopolar motor with dual rotors

    DOEpatents

    Hsu, J.S.

    1998-12-01

    A homopolar motor has a field rotor mounted on a frame for rotation in a first rotational direction and for producing an electromagnetic field, and an armature rotor mounted for rotation on said frame within said electromagnetic field and in a second rotational direction counter to said first rotational direction of said field rotor. The two rotors are coupled through a 1:1 gearing mechanism, so as to travel at the same speed but in opposite directions. This doubles the output voltage and output power, as compared to a motor in which only the armature is rotated. Several embodiments are disclosed. 7 figs.