To be launched on Aug 2015
 
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An efficient two-step subcellular fractionation method for the enrichment of insulin granules from INS-1 cells
Yan Chen, Zhiping Xia, Lifen Wang, Yong Yu, Pingsheng Liu, Eli Song, Tao Xu
Biophysics Reports    2015, 1 (1): 34-40.   DOI: 10.1007/s41048-015-0008-x
Abstract   PDF (1234KB)
Insulin is one of the key regulators for blood glucose homeostasis. More than 99% of insulin is secreted from the pancreatic β-cells. Within each β-cell, insulin is packaged and processed in insulin secretary granules (ISGs) before its exocytosis. Insulin secretion is a complicated but well-organized dynamic process that includes the budding of immature ISGs (iISGs) from the trans-Golgi network, iISG maturation, and mature ISG (mISG) fusion with plasma membrane. However, the molecular mechanisms involved in this process are largely unknown. It is therefore crucial to separate and enrich iISGs and mISGs before determining their distinct characteristics and protein contents. Here, we developed an efficient two-step subcellular fractionation method for the enrichment of iISGs and mISGs from INS-1 cells: OptiPrep gradient purification followed by Percoll solution purification. We demonstrated that by using this method, iISGs and mISGs can be successfully distinguished and enriched. This method can be easily adapted to investigate SGs in other cells or tissues, thereby providing a useful tool for elucidating the mechanisms of granule maturation and secretion.
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Phosphorylation and function of DGAT1 in skeletal muscle cells
Jinhai Yu, Yiran Li, Fei Zou, Shimeng Xu, Pingsheng Liu
Biophysics Reports    2015, 1 (1): 41-50.   DOI: 10.1007/s41048-015-0004-1
Abstract   PDF (5854KB)
Aberrant intramuscular triacylglycerol (TAG) storage in human skeletal muscle is closely related to insulin insensitivity. Excessive lipid storage can induce insulin resistance of skeletal muscle, and under severe conditions, lead to type 2 diabetes. The balance of interconversion between diacylglycerol and TAG greatly influences lipid storage and utilization. Diacylglycerol O-acyltransferase 1 (DGAT1) plays a key role in this process, but its activation and phosphorylation requires further dissection. In this study, 12 putative conserved phosphorylation sites of DGAT1 were identified by examining amino acid conservation of DGAT1 in different species. Another 12 putative phosphorylation sites were also found based on bioinformatics predictions and previous reports. Meanwhile, several phosphorylation sites of DGAT1 were verified by phosphorylation mass spectrometry analysis of purified DGAT1 from mouse myoblast C2C12 cells. Using single point mutations, a regulatory role of 3 putative phosphorylation sites was dissected. Finally, using truncation mutations, a potential domain of DGAT1 that was involved in the regulation of enzymatic activity was revealed. This study provides useful information for further understanding DGAT1 activity regulation.
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CONTENTS
Biophysics Reports    2016, 2 (5-6): 0-0.   DOI:
Abstract   PDF (4843KB)
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CONTENTS
Biophysics Reports    2018, 4 (2): 0-0.   DOI:
Abstract   PDF (1221KB)
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Analysis of chromatin bersin Hela cells with electron tomography
Xiaomin Li, Hongli Feng, Jianguo Zhang, Lei Sun, Ping Zhu
Biophysics Reports    2015, 1 (1): 51-60.   DOI: 10.1007/x41048-015-0009-9
Abstract   PDF (2590KB)
The presence and folding pattern of chromatin in eukaryotic cells remain elusive and controversial. In this study, we prepared ultra-thin sections of Hela cells with three different fixation and sectioning methods, i.e., chemical fixation, high pressure freezing with freeze substitution, and cryo-ultramicro- tomy with SEM-FIB (focused ion beam), and analyzed in vivo architecture of chromatin fibers in Hela nuclei with electron tomography technology. The results suggest that the chromatin fibers in eukaryotic Hela cells are likely organized in an architecture with a diameter of about 30 nm.
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Biophysics Reports: focus on theoretical and technical advances
Tao Xu
Biophysics Reports    2015, 1 (1): 1-1.   DOI: 10.1007/s41048-015-0010-3
Abstract   PDF (301KB)
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Biophysics Reports    DOI:
Visualizing the Ensemble Structures of Protein Complexes Using Chemical Cross-Linking Coupled with Mass Spectrometry
Zhou Gong, Yue-He Ding, Xu Dong, Na Liu, E. Erquan Zhang, Meng-Qiu Dong, Chun Tang
Biophysics Reports    2015, 1 (3): 127-138.   DOI: 10.1007/s41048-015-0015-y
Abstract   PDF (1992KB)
Chemical cross-linking coupled with mass spectrometry (CXMS) identifies protein residues that are close in space, and has been increasingly used for modeling the structures of protein complexes. Here we show that a single structure is usually sufficient to account for the intermolecular cross-links identified for a stable complex with sub-μmol/L binding affinity. In contrast,we show that the distance between two cross-linked residues in the different subunits of a transient or fleeting complex may exceed the maximum length of the cross-linker used, and the cross-links cannot be fully accounted for with a unique complex structure. We further show that the seemingly incompatible cross-links identified with high confidence arise from alternative modes of protein-protein interactions. By converting the intermolecular crosslinks to ambiguous distance restraints, we established a rigid-body simulated annealing refinement protocol to seek the minimum set of conformers collectively satisfying the CXMS data. Hence we demonstrate that CXMS allows the depiction of the ensemble structures of protein complexes and elucidates the interaction dynamics for transient and fleeting complexes.
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Using integrated correlative cryo-light and electron microscopy to directly observe syntaphilin-immobilized neuronal mitochondria in situ
Shengliu Wang, Shuoguo Li, Gang Ji, Xiaojun Huang, Fei Sun
Biophysics Reports    2017, 3 (1-3): 8-16.   DOI: 10.1007/s41048-017-0035-x
Abstract   PDF (3069KB)
Correlative cryo-fluorescence and cryo-electron microscopy (cryo-CLEM) system has been fast becoming a powerful technique with the advantage to allow the fluorescent labeling and direct visualization of the close-to-physiologic ultrastructure in cells at the same time, offering unique insights into the ultrastructure with specific cellular function. There have been various engineered ways to achieve cryo-CLEM including the commercial FEI iCorr system that integrates fluorescence microscope into the column of transmission electron microscope. In this study, we applied the approach of the cryo-CLEMbased iCorr to image the syntaphilin-immobilized neuronal mitochondria in situ to test the performance of the FEI iCorr system and determine its correlation accuracy. Our study revealed the various morphologies of syntaphilin-immobilized neuronal mitochondria that interact with microtubules and suggested that the cryo-CLEM procedure by the FEI iCorr system is suitable with a half micron-meter correlation accuracy to study the cellular organelles that have a discrete distribution and large size, e.g. mitochondrion, Golgi complex, lysosome, etc.
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Choosing proper fluorescent dyes, proteins, and imaging techniques to study mitochondrial dynamics in mammalian cells
Xingguo Liu, Liang Yang, Qi Long, David Weaver, György Hajnóczky
Biophysics Reports    2017, 3 (4-6): 64-72.   DOI: 10.1007/s41048-017-0037-8
Abstract   PDF (459KB)
Mitochondrial dynamics refers to the processes maintaining mitochondrial homeostasis, including mitochondrial fission, fusion, transport, biogenesis, and mitophagy. Mitochondrial dynamics is essential for maintaining the metabolic function of mitochondria as well as their regulatory roles in cell signaling. In this review, we summarize the recently developed imaging techniques for studying mitochondrial dynamics including:mitochondrial-targeted fluorescent proteins and dyes, live-cell imaging using photoactivation, photoswitching and cell fusion, mitochondrial transcription and replication imaging by in situ hybridization, and imaging mitochondrial dynamics by super-resolution microscopy. Moreover, we discuss examples of how to choose and combine proper fluorescent dyes and/or proteins.
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Dye-based mito-thermometry and its application in thermogenesis of brown adipocytes
Tao-Rong Xie, Chun-Feng Liu, Jian-Sheng Kang
Biophysics Reports    2017, 3 (4-6): 85-91.   DOI: 10.1007/s41048-017-0039-6
Abstract   PDF (5803KB)
Mitochondrion is the main intracellular site for thermogenesis and attractive energy expenditure targeting for obesity therapy. Here, we develop a method of mitochondrial thermometry based on Rhodamine B methyl ester, which equilibrates as a thermosensitive mixture of nonfluorescent and fluorescent resonance forms. Using this approach, we are able to demonstrate that the efficacy of norepinephrine-induced thermogenesis is low, and measure the maximum transient rate of temperature increase in brown adipocytes.
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Energy coupling mechanisms of AcrB-like RND transporters
Xuejun C. Zhang, Min Liu, Lei Han
Biophysics Reports    2017, 3 (4-6): 73-84.   DOI: 10.1007/s41048-017-0042-y
Abstract   PDF (1543KB)
Prokaryotic AcrB-like proteins belong to a family of transporters of the RND superfamily, and as main contributing factor to multidrug resistance pose a tremendous threat to future human health. A unique feature of AcrB transporters is the presence of two separate domains responsible for carrying substrate and generating energy. Significant progress has been made in elucidating the three-dimensional structures of the homo-trimer complexes of AcrB-like transporters, and a three-step functional rotation was identified for this class of transporters. However, the detailed mechanisms for the transduction of the substrate binding signal, as well as the energy coupling processes between the functionally distinct domains remain to be established. Here, we propose a model for the interdomain communication in AcrB that explains how the substrate binding signal from the substrate-carrier domain triggers protonation in the transmembrane domain. Our model further provides a plausible mechanism that explains how protonation induces conformational changes in the substrate-carrier domain. We summarize the thermodynamic principles that govern the functional cycle of the AcrB trimer complex.
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Protocol for analyzing protein ensemble structures from chemical cross-links using DynaXL
Zhou Gong, Zhu Liu, Xu Dong, Yue-He Ding, Meng-Qiu Dong, Chun Tang
Biophysics Reports    2017, 3 (4-6): 100-108.   DOI: 10.1007/s41048-017-0044-9
Abstract   PDF (788KB)
Chemical cross-linking coupled with mass spectroscopy (CXMS) is a powerful technique for investigating protein structures. CXMS has been mostly used to characterize the predominant structure for a protein, whereas cross-links incompatible with a unique structure of a protein or a protein complex are often discarded. We have recently shown that the so-called over-length cross-links actually contain protein dynamics information. We have thus established a method called DynaXL, which allow us to extract the information from the over-length cross-links and to visualize protein ensemble structures. In this protocol, we present the detailed procedure for using DynaXL, which comprises five steps. They are identification of highly confident cross-links, delineation of protein domains/subunits, ensemble rigidbody refinement, and final validation/assessment. The DynaXL method is generally applicable for analyzing the ensemble structures of multi-domain proteins and protein-protein complexes, and is freely available at www.tanglab.org/resources.
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CONTENTS
Biophysics Reports    2017, 3 (1-3): 0-0.   DOI:
Abstract   PDF (5527KB)
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Docking-based inverse virtual screening: methods, applications, and challenges
Xianjin Xu, Marshal Huang, Xiaoqin Zou
Biophysics Reports    2018, 4 (1): 1-16.   DOI: 10.1007/s41048-017-0045-8
Abstract   PDF (610KB)
Identifying potential protein targets for a small-compound ligand query is crucial to the process of drug development. However, there are tens of thousands of proteins in human alone, and it is almost impossible to scan all the existing proteins for a query ligand using current experimental methods. Recently, a computational technology called docking-based inverse virtual screening (IVS) has attracted much attention. In docking-based IVS, a panel of proteins is screened by a molecular docking program to identify potential targets for a query ligand. Ever since the first paper describing a docking-based IVS program was published about a decade ago, the approach has been gradually improved and utilized for a variety of purposes in the field of drug discovery. In this article, the methods employed in dockingbased IVS are reviewed in detail, including target databases, docking engines, and scoring function methodologies. Several web servers developed for non-expert users are also reviewed. Then, a number of applications are presented according to different research purposes, such as target identification, side effects/toxicity, drug repositioning, drug-target network development, and receptor design. The review concludes by discussing the challenges that docking-based IVS needs to overcome to become a robust tool for pharmaceutical engineering.
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AIM interneurons mediate feeding suppression through the TYRA-2 receptor in C. elegans
Jiajun Fu, Haining Zhang, Wenming Huang, Xinyu Zhu, Yi Sheng, Eli Song, Tao Xu
Biophysics Reports    2018, 4 (1): 17-24.   DOI: 10.1007/s41048-018-0046-2
Abstract   PDF (1528KB)
Feeding behavior is the most fundamental behavior in C. elegans. Our previous results have dissected the central integration circuit for the regulation of feeding, which integrates opposing sensory inputs and regulates feeding behavior in a nonlinear manner. However, the peripheral integration that acts downstream of the central integration circuit to modulate feeding remains largely unknown. Here, we find that a Gai/o-coupled tyramine receptor, TYRA-2, is involved in peripheral feeding suppression. TYRA-2 suppresses feeding behavior via the AIM interneurons, which receive tyramine/octopamine signals from RIM/RIC neurons in the central integration circuit. Our results reveal previously unidentified roles for the receptor TYRA-2 and the AIM interneurons in feeding regulation, providing a further understanding of how biogenic amines tyramine and octopamine regulate feeding behavior.
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Determining the target protein localization in 3D using the combination of FIB-SEM and APEX2
Yang Shi, Li Wang, Jianguo Zhang, Yujia Zhai, Fei Sun
Biophysics Reports    2017, 3 (4-6): 92-99.   DOI: 10.1007/s41048-017-0043-x
Abstract   PDF (1163KB)
Determining the cellular localization of proteins of interest at nanometer resolution is necessary for elucidating their functions. Besides super-resolution fluorescence microscopy, conventional electron microscopy (EM) combined with immunolabeling or clonable EM tags provides a unique approach to correlate protein localization information and cellular ultrastructural information. However, there are still rare cases of such correlation in three-dimensional (3D) spaces. Here, we developed an approach by combining the focus ion beam scanning electron microscopy (FIB-SEM) and a promising clonable EM tag APEX2 (an enhanced ascorbate peroxidase 2) to determine the target protein localization within 3D cellular ultrastructural context. We further utilized this approach to study the 3D localization of mitochondrial dynamics-related proteins (MiD49/51, Mff, Fis1, and Mfn2) in the cells where the target proteins were overexpressed. We found that all the target proteins were located at the surface of the mitochondrial outer membrane accompanying with mitochondrial clusters. Mid49/51, Mff, and hFis1 spread widely around the mitochondrial surface while Mfn2 only exists at the contact sites.
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Physics-based RNA structure prediction
Xiaojun Xu, Shi-Jie Chen
Biophysics Reports    2015, 1 (1): 2-13.   DOI: 10.1007/s41048-015-0001-4
Abstract   PDF (1685KB)
Despite the success of RNA secondary structure prediction for simple, short RNAs, the problem of predicting RNAs with long-range tertiary folds remains. Furthermore, RNA 3D structure prediction is hampered by the lack of the knowledge about the tertiary contacts and their thermodynamic parameters. Low-resolution structural modeling enables us to estimate the conformational entropies for a number of tertiary folds through rigorous statistical mechanical calculations. The models lead to 3D tertiary folds at coarse-grained level. The coarse-grained structures serve as the initial structures for all-atom molecular dynamics refinement to build the final all-atom 3D structures. In this paper, we present an overview of RNA computational models for secondary and tertiary structures' predictions and then focus on a recently developed RNA statistical mechanical model—the Vfold model. The main emphasis is placed on the physics behind the models, including the treatment of the non-canonical interactions in secondary and tertiary structure modelings, and the correlations to RNA functions.
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Phenylboronic acid-functionalized magnetic nanoparticles for one-step saccharides enrichment and mass spectrometry analysis
Xiangdong Xue, Yuanyuan Zhao, Xu Zhang, Chunqiu Zhang, Anil Kumar, Xiaoning Zhang, Guozhang Zou, Paul C. Wang, Jinchao Zhang, Xing-Jie Liang
Biophysics Reports    DOI: 10.1007/s41048-015-0002-3
Abstract   PDF (1530KB)
In this work, 2-(2-aminoethoxy) ethanolblocked phenylboronic acid-functionalized magnetic nanoparticles (blocked PMNPs) were fabricated for selective enrichment of different types of saccharides. The phenylboronic acid was designed for capturing the cis-diols moieties on saccharides molecules, and the 2-(2-aminoethoxy) ethanol can deplete the nonspecific absorption of peptides and proteins which always coexisted with saccharides. For mass spectrometry analysis, the PMNPs bound saccharides can be directly applied onto the MALDI plate with matrix without removing the PMNPs. By PMNPs, the simple saccharide (glucose) could be detected in pmol level. The complex saccharides can also be reliably purified and analyzed; 16 different Nglycans were successfully identified fromovalbumin, and the high-abundance N-glycans can be detected even when the ovalbumin was in very low concentration (2 μg). In human milk, ten different oligosaccharides were identified, and the lactose can still be detected when the human milk concentration was low to 0.01 μL.
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Solubilization and purification of recombinant modified C-reactive protein from inclusion bodies using reversible anhydride modification
Lawrence A. Potempa, Zhen-Yu Yao, Shang-Rong Ji, János G. Filep, Yi Wu
Biophysics Reports    2015, 1 (1): 18-33.   DOI: 10.1007/s41048-015-0003-2
Abstract   PDF (2149KB)
The precise function of C-reactive protein (CRP) as a regulator of inflammation in health and disease continues to evolve. The true understanding of its role in host defense responses has been hampered by numerous reports of comparable systems with contradictory interpretations of CRP as a stimulator, suppressor, or benign contributor to such processes. These discrepancies may be explained in part by the existence of a naturally occurring CRP isoform, termed modified CRP (i.e., mCRP), that is expressed when CRP subunits are dissociated into monomeric structures. The free mCRP subunit undergoes a non-proteolytic conformational change that has unique solubility, antigenicity, and bioactivity compared to the subunits that remain associated in the native, pentameric CRP molecule (i.e., pCRP). As specific reagents have been developed to identify and quantify mCRP, it has become apparent that this isoform can be formed spontaneously in calcium-free solutions. Furthermore, mCRP can be expressed on perturbed cell membranes with as little as 24-48 h incubation in tissue culture. Because mCRP has the same size as pCRP subunits as evaluated by SDS-PAGE, its presence in a pCRP reagent would not be apparent using this technique to evaluate purity. Finally, because many antibody reagents purported to be specific for "CRP" contains some, or substantial specificity tomCRP, antigen-detection techniques using such reagents may fail to distinguish the specific CRP isoform detected. All these caveats concerning CRP structures and measurements suggest that the aforementioned contradictory studies may reflect to some extent on distinctive bioactivities of mCRP rather than on pCRP. To provide a reliable, abundant supply of mCRP for separate and comparable studies, a recombinant proteinwas engineered and expressed in E. coli (i.e., recombinant mCRP or rmCRP). Synthesized protein was produced as inclusion bodies which proved difficult to solubilize for purification and characterization. Herein, we describe a method using anhydride reagents to effectively solubilize rmCRP and allow for chromatographic purification in high yield and free of contaminating endotoxin. Furthermore, the purified rmCRP reagent represents an excellent comparable protein to the biologically produced mCRP and as a distinctive reagent from pCRP. Deciphering the true function of CRP in both health and disease requires a knowledge, understanding, and reliable supply of each of its structures so to define the distinctive effects of each on the body's response to tissue damaging events.
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Fabrication and modification of implantable optrode arrays for in vivo optogenetic applications
Lulu Wang, Kang Huang, Cheng Zhong, Liping Wang, Yi Lu
Biophysics Reports    2018, 4 (2): 82-93.   DOI: 10.1007/s41048-018-0052-4
Abstract   PDF (11462KB)
Recent advances in optogenetics have established a precisely timed and cell-specific methodology for understanding the functions of brain circuits and the mechanisms underlying neuropsychiatric disorders. However, the fabrication of optrodes, a key functional element in optogenetics, remains a great challenge. Here, we report reliable and efficient fabrication strategies for chronically implantable optrode arrays. To improve the performance of the fabricated optrode arrays, surfaces of the recording sites were modified using optimized electrochemical processes. We have also demonstrated the feasibility of using the fabricated optrode arrays to detect seizures in multiple brain regions and inhibit ictal propagation in vivo. Furthermore, the results of the histology study imply that the electrodeposition of composite conducting polymers notably alleviated the inflammatory response and improved neuronal survival at the implant/neural-tissue interface. In summary, we provide reliable and efficient strategies for the fabrication and modification of customized optrode arrays that can fulfill the requirements of in vivo optogenetic applications.
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MetaDP: a comprehensive web server for disease prediction of 16S rRNA metagenomic datasets
Xilin Xu, Aiping Wu, Xinlei Zhang, Mingming Su, Taijiao Jiang, Zhe-Ming Yuan
Biophysics Reports    2016, 2 (5-6): 106-115.   DOI: 10.1007/s41048-016-0033-4
Abstract   PDF (986KB)
High-throughput sequencing-based metagenomics has garnered considerable interest in recent years. Numerous methods and tools have been developed for the analysis of metagenomic data. However, it is still a daunting task to install a large number of tools and complete a complicated analysis, especially for researchers with minimal bioinformatics backgrounds. To address this problem, we constructed an automated software named MetaDP for 16S rRNA sequencing data analysis, including data quality control, operational taxonomic unit clustering, diversity analysis, and disease risk prediction modeling. Furthermore, a support vector machine-based prediction model for intestinal bowel syndrome (IBS) was built by applying MetaDP to microbial 16S sequencing data from 108 children. The success of the IBS prediction model suggests that the platform may also be applied to other diseases related to gut microbes, such as obesity, metabolic syndrome, or intestinal cancer, among others (http://metadp.cn:7001/).
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CONTENTS
Biophysics Reports    2018, 4 (1): 0-0.   DOI:
Abstract   PDF (7596KB)
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Particle segmentation algorithm for flexible single particle reconstruction
Qiang Zhou, Niyun Zhou, Hong-Wei Wang
Biophysics Reports    DOI: 10.1007/s41048-017-0038-7
Abstract   PDF (2908KB)
As single particle cryo-electron microscopy has evolved to a new era of atomic resolution, sample heterogeneity still imposes a major limit to the resolution of many macromolecular complexes, especially those with continuous conformational flexibility. Here, we describe a particle segmentation algorithm towards solving structures of molecules composed of several parts that are relatively flexible with each other. In this algorithm, the different parts of a target molecule are segmented from raw images according to their alignment information obtained from a preliminary 3D reconstruction and are subjected to single particle processing in an iterative manner. This algorithm was tested on both simulated and experimental data and showed improvement of 3D reconstruction resolution of each segmented part of the molecule than that of the entire molecule.
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The advent of structural biology in situ by single particle cryoelectron tomography
Jesús G. Galaz-Montoya, Steven J. Ludtke
Biophysics Reports    DOI: 10.1007/s41048-017-0040-0
Abstract   PDF (4263KB)
Single particle tomography (SPT), also known as subtomogram averaging, is a powerful technique uniquely poised to address questions in structural biology that are not amenable to more traditional approaches like X-ray crystallography, nuclear magnetic resonance, and conventional cryoEM single particle analysis. Owing to its potential for in situ structural biology at subnanometer resolution, SPT has been gaining enormous momentum in the last five years and is becoming a prominent, widely used technique. This method can be applied to unambiguously determine the structures of macromolecular complexes that exhibit compositional and conformational heterogeneity, both in vitro and in situ. Here we review the development of SPT, highlighting its applications and identifying areas of ongoing development.
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Implications for directionality of nanoscale forces in bacterial attachment
Jan J. T. M. Swartjes, Deepak H. Veeregowda
Biophysics Reports    2015, 1 (3): 120-126.   DOI: 10.1007/s41048-016-0019-2
Abstract   PDF (1432KB)
Adhesion and friction are closely related and play a predominant role in many natural processes. From the wall-clinging feet of the gecko to bacteria forming a biofilm, in many cases adhesion is a necessity to survive. The direction in which forces are applied has shown to influence the bond strength of certain systems tremendously and can mean the difference between adhesion and detachment. The spatula present on the extension of the feet of the gecko can either attach or detach, based on the angle at which they are loaded. Certain proteins are known to unfold at different loads, depending on the direction at which the load is applied and some bacteria have specific receptors which increase their bond strength in the presence of shear. Bacteria adhere to any man-made surface despite the presence of shear forces due to running fluids, air flow, and other causes. In bacterial adhesion research, however, adhesion forces are predominantly measured perpendicularly to surfaces, whereas other directions are often neglected. The angle of shear forces acting on bacteria or biofilms will not be at a 90 angle, as shear induced by flow is often along the surface. Measuring at different angles or even lateral to the surface will give a more complete overview of the adhesion forces and mechanism, perhaps even resulting in alternative means to discourage bacterial adhesion or promote removal.
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Class C G protein-coupled receptors:reviving old couples with new partners
Thor C. Møller, David Moreno-Delgado, Jean-Philippe Pin, Julie Kniazeff
Biophysics Reports    2017, 3 (4-6): 57-63.   DOI: 10.1007/s41048-017-0036-9
Abstract   PDF (916KB)
G protein-coupled receptors (GPCRs) are key players in cell communication and are encoded by the largest family in our genome. As such, GPCRs represent the main targets in drug development programs. Sequence analysis revealed several classes of GPCRs:the class A rhodopsin-like receptors represent the majority, the class B includes the secretin-like and adhesion GPCRs, the class F includes the frizzled receptors, and the class C includes receptors for the main neurotransmitters, glutamate and GABA, and those for sweet and umami taste and calcium receptors. Class C receptors are far more complex than other GPCRs, being mandatory dimers, with each subunit being composed of several domains. In this review, we summarize our actual knowledge regarding the activation mechanism and subunit organization of class C GPCRs, and how this brings information for many other GPCRs.
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Radioligand saturation binding for quantitative analysis of ligand-receptor interactions
Chengyan Dong, Zhaofei Liu, Fan Wang
Biophysics Reports    2015, 1 (3): 148-155.   DOI: 10.1007/s41048-016-0016-5
Abstract   PDF (474KB)
The reversible combination of a ligand with specific sites on the surface of a receptor is one of the most important processes in biochemistry. A classic equation with a useful simple graphical method was introduced to obtain the equilibrium constant, Kd, and the maximum density of receptors, Bmax. The entire 125I-labeled ligand binding experiment includes three parts: the radiolabeling, cell saturation binding assays and the data analysis. The assay format described here is quick, simple, inexpensive, and effective, and provides a gold standard for the quantification of ligand-receptor interactions. Although the binding assays and quantitative analysis have not changed dramatically compared to the original methods, we integrate all the parts to calculate the parameters in one concise protocol and adjust many details according to our experience. In every step, several optional methods are provided to accommodate different experimental conditions. All these refinements make the whole protocol more understandable and user-friendly. In general, the experiment takes one person less than 8 h to complete, and the data analysis could be accomplished within 2 h.
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Thermodynamics of GPCR activation
Xuejun C. Zhang, Ye Zhou, Can Cao
Biophysics Reports    2015, 1 (3): 115-119.   DOI: 10.1007/s41048-016-0017-4
Abstract   PDF (594KB)
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Accelerating electron tomography reconstruction algorithm ICON with GPU
Yu Chen, Zihao Wang, Jingrong Zhang, Lun Li, Xiaohua Wan, Fei Sun, Fa Zhang
Biophysics Reports    DOI: 10.1007/s41048-017-0041-z
Abstract   PDF (1253KB)
Electron tomography (ET) plays an important role in studying in situ cell ultrastructure in threedimensional space. Due to limited tilt angles, ET reconstruction always suffers from the "missing wedge" problem. With a validation procedure, iterative compressed-sensing optimized NUFFT reconstruction (ICON) demonstrates its power in the restoration of validated missing information for low SNR biological ET dataset. However, the huge computational demand has become a major problem for the application of ICON. In this work, we analyzed the framework of ICON and classified the operations of major steps of ICON reconstruction into three types. Accordingly, we designed parallel strategies and implemented them on graphics processing units (GPU) to generate a parallel program ICON-GPU. With high accuracy, ICON-GPU has a great acceleration compared to its CPU version, up to 83.7×, greatly relieving ICON's dependence on computing resource.
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