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Single molecule biophysics

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https://www.readbyqxmd.com/read/28646215/single-molecule-and-multiple-bond-characterization-of-catch-bond-associated-cytoadhesion-in-malaria
#1
Ying Bena Lim, Juzar Thingna, Jianshu Cao, Chwee Teck Lim
The adhesion of malaria infected red blood cells (iRBCs) to host endothelial receptors in the microvasculature, or cytoadhesion, is associated with severe disease pathology such as multiple organ failure and cerebral malaria. Malaria iRBCs have been shown to bind to several receptors, of which intercellular adhesion molecule 1 (ICAM-1) upregulation in brain microvasculature is the only one correlated to cerebral malaria. We utilize a biophysical approach to study the interactions between iRBCs and ICAM-1. At the single molecule level, force spectroscopy experiments reveal that ICAM-1 forms catch bond interactions with Plasmodium falciparum parasite iRBCs...
June 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28636917/kinesin-processivity-is-determined-by-a-kinetic-race-from-a-vulnerable-one-head-bound-state
#2
Keith J Mickolajczyk, William O Hancock
Kinesin processivity, defined as the average number of steps that occur per interaction with a microtubule, is an important biophysical determinant of the motor's intracellular capabilities. Despite its fundamental importance to the diversity of tasks that kinesins carry out in cells, no existing quantitative model fully explains how structural differences between kinesins alter kinetic rates in the ATPase cycle to produce functional changes in processivity. Here we use high-resolution single-molecule microscopy to directly observe the stepping behavior of kinesin-1 and -2 family motors with different length neck-linker domains...
June 20, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28630155/haemolytic-actinoporins-interact-with-carbohydrates-using-their-lipid-binding-module
#3
Koji Tanaka, Jose M M Caaveiro, Koldo Morante, Kouhei Tsumoto
Pore-forming toxins (PFTs) are proteins endowed with metamorphic properties that enable them to stably fold in water solutions as well as in cellular membranes. PFTs produce lytic pores on the plasma membranes of target cells conducive to lesions, playing key roles in the defensive and offensive molecular systems of living organisms. Actinoporins are a family of potent haemolytic toxins produced by sea anemones vigorously studied as a paradigm of α-helical PFTs, in the context of lipid-protein interactions, and in connection with nanopore technologies...
August 5, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28626560/selective-single-molecule-nanopore-sensing-of-proteins-using-dna-aptamer-functionalised-gold-nanoparticles
#4
Xiaoyan Lin, Aleksandar P Ivanov, Joshua B Edel
Single molecule detection methods, such as nanopore sensors have found increasing importance in applications ranging from gaining a better understanding of biophysical processes to technology driven solutions such as DNA sequencing. However, challenges remain especially in relation to improving selectivity to probe specific targets or to alternatively enable detection of smaller molecules such as small-sized proteins with a sufficiently high signal-to-noise ratio. In this article, we propose a solution to these technological challenges by using DNA aptamer-modified gold nanoparticles (AuNPs) that act as a molecular carrier through the nanopore sensor...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28625737/insights-into-the-conformations-and-dynamics-of-intrinsically-disordered-proteins-using-single-molecule-fluorescence
#5
REVIEW
Gregory-Neal Gomes, Claudiu C Gradinaru
Most proteins are not static structures, but many of them are found in a dynamic state, exchanging conformations on various time scales as a key aspect of their biological function. An entire spectrum of structural disorder exists in proteins and obtaining a satisfactory quantitative description of these states remains a challenge. Single-molecule fluorescence spectroscopy techniques are uniquely suited for this task, by measuring conformations without ensemble averaging and kinetics without interference from asynchronous processes...
June 15, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28615444/the-human-mitochondrial-single-strand-dna-binding-protein-displays-distinct-kinetics-and-thermodynamics-of-dna-binding-and-exchange
#6
Yufeng Qian, Kenneth A Johnson
The human mitochondrial SSB (mtSSB) is a homo-tetrameric protein, involved in mtDNA replication and maintenance. Although mtSSB is structurally similar to SSB from Escherichia coli (EcoSSB), it lacks the C-terminal disordered domain but little is known about the biophysics of mtSSB-ssDNA interactions. Here, we characterized the kinetics and thermodynamics of mtSSB binding to ssDNA by equilibrium titrations and stopped-flow kinetic measurements. We show that the mtSSB tetramer can bind to ssDNA in two distinct binding modes: (SSB)30 and (SSB)60, defined by DNA binding site sizes of 30 and 60 nt, respectively...
June 14, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28591514/elastin-like-polypeptide-linkers-for-single-molecule-force-spectroscopy
#7
Wolfgang Ott, Markus A Jobst, Magnus S Bauer, Ellis Durner, Lukas F Milles, Michael A Nash, Hermann E Gaub
Single-molecule force spectroscopy (SMFS) is by now well established as a standard technique in biophysics and mechanobiology. In recent years, the technique has benefitted greatly from new approaches to bioconjugation of proteins to surfaces. Indeed, optimized immobilization strategies for biomolecules and refined purification schemes are being steadily adapted and improved, which in turn has enhanced data quality. In many previously reported SMFS studies, poly(ethylene glycol) (PEG) was used to anchor molecules of interest to surfaces and/or cantilever tips...
June 12, 2017: ACS Nano
https://www.readbyqxmd.com/read/28538142/an-introduction-to-infinite-hmms-for-single-molecule-data-analysis
#8
REVIEW
Ioannis Sgouralis, Steve Pressé
The hidden Markov model (HMM) has been a workhorse of single-molecule data analysis and is now commonly used as a stand-alone tool in time series analysis or in conjunction with other analysis methods such as tracking. Here, we provide a conceptual introduction to an important generalization of the HMM, which is poised to have a deep impact across the field of biophysics: the infinite HMM (iHMM). As a modeling tool, iHMMs can analyze sequential data without a priori setting a specific number of states as required for the traditional (finite) HMM...
May 23, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28529337/dynamic-chromatin-technologies-from-individual-molecules-to-epigenomic-regulation-in-cells
#9
REVIEW
Olivier Cuvier, Beat Fierz
The establishment and maintenance of chromatin states involves multiscale dynamic processes integrating transcription factor and multiprotein effector dynamics, cycles of chemical chromatin modifications, and chromatin structural organization. Recent developments in genomic technologies are emerging that are enabling a view beyond ensemble- and time-averaged properties and are revealing the importance of dynamic chromatin states for cell fate decisions, differentiation and reprogramming at the single-cell level...
May 22, 2017: Nature Reviews. Genetics
https://www.readbyqxmd.com/read/28505809/dissociation-rates-from-single-molecule-pulling-experiments-under-large-thermal-fluctuations-or-large-applied-force
#10
Masoud Abkenar, Thomas H Gray, Alessio Zaccone
Theories that are used to extract energy-landscape information from single-molecule pulling experiments in biophysics are all invariably based on Kramers' theory of the thermally activated escape rate from a potential well. As is well known, this theory recovers the Arrhenius dependence of the rate on the barrier energy and crucially relies on the assumption that the barrier energy is much larger than k_{B}T (limit of comparatively low thermal fluctuations). As was shown already in Dudko et al. [Phys. Rev...
April 2017: Physical Review. E
https://www.readbyqxmd.com/read/28489428/a-single-molecule-view-of-genome-editing-proteins-biophysical-mechanisms-for-tales-and-crispr-cas9
#11
Luke Cuculis, Charles M Schroeder
Exciting new advances in genome engineering have unlocked the potential to radically alter the treatment of human disease. In this review, we discuss the application of single-molecule techniques to uncover the mechanisms behind two premier classes of genome editing proteins: transcription activator-like effector nucleases (TALENs) and the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system (Cas). These technologies have facilitated a striking number of gene editing applications in a variety of organisms; however, we are only beginning to understand the molecular mechanisms governing the DNA editing properties of these systems...
May 10, 2017: Annual Review of Chemical and Biomolecular Engineering
https://www.readbyqxmd.com/read/28482279/improving-certainty-in-single-molecule-imaging
#12
REVIEW
John Sh Danial, Ana J García-Sáez
The spatiotemporal organization of biological entities and the complex network of interactions they sponsor has proven challenging to visualize. Modern biophysics has brought a wealth of techniques for probing cellular structure and dynamics of which fluorescence-based single molecule detection has emerged as a powerful tool. In this review, we summarize notable breakthroughs in biological research based on single molecule imaging, identify prevailing shortcomings in single molecule detection and present current opinion on ameliorating some of its limitations for wider applicability...
May 5, 2017: Current Opinion in Structural Biology
https://www.readbyqxmd.com/read/28448574/fusion-expression-of-occludin-extracellular-loops-and-an-%C3%AE-helical-bundle-a-new-research-model-for-tight-junction
#13
Xiaojing Chi, Xia Zhao, Wei Wang, Yuqiang Niu, Min Cheng, Xiuying Liu, Sheng Cui, Wei Yang
Tight junctions (TJs) are the outermost structures of intercellular junctions and are highly specialized membrane domains involved in many important cellular processes. However, most TJ proteins are four-time transmembrane proteins and are difficult to express in their correct soluble form, which limits their functional study and therapeutic application. Human occludin (OCLN) is a major component of TJs and an essential co-receptor for hepatitis C virus (HCV) cell entry. To explore expression strategy for recombinant TJ proteins possessing integrated and functional extracellular loops, OCLN was here used as a model molecule, and several prokaryotic fusion constructs were designed by docking OCLN extracellular loops (ECLs) to HIV-1 gp41 NHR and CHR six-helical bundle (6HV1); then their biophysical features and anti-HCV activity were evaluated...
2017: PloS One
https://www.readbyqxmd.com/read/28435614/time-resolved-biophysical-approaches-to-nucleocytoplasmic-transport
#14
REVIEW
Francesco Cardarelli
Molecules are continuously shuttling across the nuclear envelope barrier that separates the nucleus from the cytoplasm. Instead of being just a barrier to diffusion, the nuclear envelope is rather a complex filter that provides eukaryotes with an elaborate spatiotemporal regulation of fundamental molecular processes, such as gene expression and protein translation. Given the highly dynamic nature of nucleocytoplasmic transport, during the past few decades large efforts were devoted to the development and application of time resolved, fluorescence-based, biophysical methods to capture the details of molecular motion across the nuclear envelope...
2017: Computational and Structural Biotechnology Journal
https://www.readbyqxmd.com/read/28434999/smfret-experiments-of-the-rna-polymerase-ii-transcription-initiation-complex
#15
REVIEW
Nicole Malkusch, Thilo Dörfler, Julia Nagy, Tobias Eilert, Jens Michaelis
Single-molecule fluorescence and in particular single-molecule Förster Resonance Energy Transfer (smFRET) is a powerful tool to provide real-time information on the dynamic architecture of large macromolecular structures such as eukaryotic transcription initiation complexes. In contrast to other structural biology methods, not only structural details, but dynamics transitions are revealed thus closing in on the underlying molecular mechanisms. Here, we describe a comprehensive quantitative biophysical toolbox which can be used for rigorous analysis of dynamic protein-nucleic acid complexes and is applied to the study of eukaryotic transcription initiation...
April 19, 2017: Methods: a Companion to Methods in Enzymology
https://www.readbyqxmd.com/read/28424742/fret-from-single-to-multiplexed-signaling-events
#16
REVIEW
Gertrude Bunt, Fred S Wouters
Förster resonance energy transfer (FRET) is a powerful tool for the visualization of molecular signaling events such as protein activities and interactions in cells. In its different implementations, FRET microscopy has been mainly used for monitoring single events. Recently, there has been a trend of extending FRET imaging towards the simultaneous detection of multiple events and interactions. The concomitant increase in experimental complexity requires a deeper understanding of the biophysical background of FRET...
April 2017: Biophysical Reviews
https://www.readbyqxmd.com/read/28424741/catalytic-robustness-and-torque-generation-of-the-f1-atpase
#17
REVIEW
Hiroyuki Noji, Hiroshi Ueno, Duncan G G McMillan
The F1-ATPase is the catalytic portion of the FoF1 ATP synthase and acts as a rotary molecular motor when it hydrolyzes ATP. Two decades have passed since the single-molecule rotation assay of F1-ATPase was established. Although several fundamental issues remain elusive, basic properties of F-type ATPases as motor proteins have been well characterized, and a large part of the reaction scheme has been revealed by the combination of extensive structural, biochemical, biophysical, and theoretical studies. This review is intended to provide a concise summary of the fundamental features of F1-ATPases, by use of the well-described model F1 from the thermophilic Bacillus PS3 (TF1)...
April 2017: Biophysical Reviews
https://www.readbyqxmd.com/read/28414321/an-orthogonal-single-molecule-experiment-reveals-multiple-attempt-dynamics-of-type-ia-topoisomerases
#18
Kathryn H Gunn, John F Marko, Alfonso Mondragón
Topoisomerases are enzymes that are involved in maintaining the topological state of cellular DNA. Their dynamic characteristics remain poorly understood despite numerous structural, biophysical and biochemical studies. Recent single-molecule experiments revealed that an important feature of the type IA topoisomerase mechanism is the presence of pauses between relaxation events. However, these experiments could not determine whether the protein remains DNA bound during the pauses or what relationship may exist between protein domain movements and topological changes in the DNA...
May 2017: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/28406920/experimental-and-mathematical-analysis-of-camp-nanodomains
#19
Christian Lohse, Andreas Bock, Isabella Maiellaro, Annette Hannawacker, Lothar R Schad, Martin J Lohse, Wolfgang R Bauer
In their role as second messengers, cyclic nucleotides such as cAMP have a variety of intracellular effects. These complex tasks demand a highly organized orchestration of spatially and temporally confined cAMP action which should be best achieved by compartmentalization of the latter. A great body of evidence suggests that cAMP compartments may be established and maintained by cAMP degrading enzymes, e.g. phosphodiesterases (PDEs). However, the molecular and biophysical details of how PDEs can orchestrate cAMP gradients are entirely unclear...
2017: PloS One
https://www.readbyqxmd.com/read/28375735/single-molecule-studies-of-telomeres-and-telomerase
#20
Joseph W Parks, Michael D Stone
Telomeres are specialized chromatin structures that protect chromosome ends from dangerous processing events. In most tissues, telomeres shorten with each round of cell division, placing a finite limit on cell growth. In rapidly dividing cells, including the majority of human cancers, cells bypass this growth limit through telomerase-catalyzed maintenance of telomere length. The dynamic properties of telomeres and telomerase render them difficult to study using ensemble biochemical and structural techniques...
March 22, 2017: Annual Review of Biophysics
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