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Lorenzo Cianni, Geraldo Sartori, Fabiana Rosini, Daniela De Vita, Gabriel Pires, Bianca Rebelo Lopes, Andrei Leitão, Antonio C B Burtoloso, Carlos A Montanari
Cruzain is the major cysteine protease of Trypanosoma cruzi, the etiological agent of Chagas disease. Reversible covalent cruzain inhibitors can block the steps of cell differentiation in the parasite and kill the organism. To this end, the description of how inhibitors modified at the P2/P3 positions lead to analogs with greater cruzain affinity to the S2/S3 subsites is of fundamental importance. Albeit many efforts are being employed in the characterization of the interaction processes with S2 subsite, little is known about the cruzain S3 subsite...
April 26, 2018: Bioorganic Chemistry
Alexey Surov, Gordian Hamerla, Hans Jonas Meyer, Karsten Winter, Stefan Schob, Eckhard Fiedler
PURPOSE: To analyze several histopathological features and their possible correlations with whole lesion histogram analysis derived from ADC maps in meningioma. MATERIALS AND METHODS: The retrospective study involved 36 patients with primary meningiomas. For every tumor, the following histogram analysis parameters of apparent diffusion coefficient (ADC) were calculated: ADCmean , ADCmax , ADCmin , ADCmedian , ADCmode , ADC percentiles: P10, P25, P75, P90, as well kurtosis, skewness, and entropy...
May 18, 2018: Magnetic Resonance Imaging
Xi Hu, Fangyuan Li, Shuying Wang, Fan Xia, Daishun Ling
Nanoassembly technology has emerged as a powerful tool for targeted drug delivery and provides a basis for fabricating medical theranostic nanosystems. However, it is extremely difficult to concentrate nanoparticles at tumor sites, and the poor target-to-background ratio undoubtedly obstructs the accurate diagnosis and effective therapy of cancerous tissues. Importantly, the addition of biological stimulus-responsive groups to nanoassembly systems can enable a biological stimulus-driven assembly-disassembly mutual switch or structural composition/conformation change, thereby amplifying the imaging signal and/or enhancing the therapeutic effect...
May 21, 2018: Advanced Healthcare Materials
Tomomi Shimazaki, Motomichi Tashiro, Takahito Nakajima
A bulk-heterojunction structure is often employed to develop high-performance organic photocells, in which the donor and acceptor regions are complexly intertwined. In such situations, mesoscopic-scale islands and peninsulas that compose the donor materials may be formed in the acceptor region. Alternatively, the donor region may extend deeply into the acceptor region. This yields mesoscopic-size impurities that can create obstacles in the charge separation (exciton dissociation) process of organic photocells and prevents the dissociation of excitons (electron-hole pairs)...
May 21, 2018: Physical Chemistry Chemical Physics: PCCP
Jayangika N Dahanayake, Katie R Mitchell-Koch
The enzyme Candida Antarctica lipase B (CALB) serves here as a model for understanding connections among hydration layer dynamics, solvation shell structure, and protein surface structure. The structure and dynamics of water molecules in the hydration layer were characterized for regions of the CALB surface, divided around each α-helix, β-sheet, and loop structure. Heterogeneous hydration dynamics were observed around the surface of the enzyme, in line with spectroscopic observations of other proteins. Regional differences in the structure of the biomolecular hydration layer were found to be concomitant with variations in dynamics...
May 21, 2018: Physical Chemistry Chemical Physics: PCCP
Sergei Khrapunov
The thermodynamic analyses of proteins, protein-ligands and protein-nucleic acid complexes involves the entropy-enthalpy (S-H) compensation phenomenon. We have examined the question whether the observed compensation is artificial or reflects anything more than the well-known laws of statistical thermodynamics (so-called extra-thermodynamic compensation). We have shown that enthalpy-entropy compensation (EEC) is mainly the trivial consequence of the basic thermodynamic laws and there are no experimental evidences for existence of the extra-thermodynamic compensation...
May 20, 2018: Current Protein & Peptide Science
Tooba Siddiqui, Mohammad Khalid Zia, Syed Saqib Ali, Haseeb Ahsan, Fahim Halim Khan
Hypochlorous acid, an active bleaching agent is one of the major oxidants produced by neutrophils under physiological conditions. It is a potent reactive oxygen species (ROS) which causes oxidation of biomolecules. Treatment of proteins with hypochlorite results in direct oxidative damage to proteins. Alpha-2-macroglobulin is a major proteinase inhibitor and it can inhibit proteinase of any kind regardless of specificity and catalytic mechanism. The proteinase-antiproteinase balance plays an important role in mediating inflammation associated tissue destruction...
May 17, 2018: International Journal of Biological Macromolecules
Yimei Zhang, Liqun Wang, Jie Chen, Yalong Zhao, Yuxian Lai, Panpan Wu
The conventional risk assessment methods may be defective for more effective health risk assessment due to ignoring heavy metal species and the accuracy and integrity of sampling and analysis results. Using the accurate and integral data to quantify the human health effects of metal species can provide great support for more effective health risk assessment. This study presents a new methodology to optimize sampling and analysis results for implementing the spatial human health risk of heavy metal species in contaminated sites...
May 17, 2018: Science of the Total Environment
Matthew W Wittstein, Joseph M Starobin, Randy J Schmitz, Sandra J Shulz, Francis Jay Haran, Christopher K Rhea
BACKGROUND: Aging and pathology result in changes in the dynamics of several physiological subsystems. Often, these changes are concurrent, altering the dynamics between subsystems. Cardiac and gait rhythms are one example in which patterns change during physical activity. AIMS: The purpose of this research is to simultaneously monitor changes in cardiac and gait rhythms when participants complete various treadmill walking tasks-normal speed, fast speed, and while synchronizing steps with a blinking metronome...
May 17, 2018: Aging Clinical and Experimental Research
Rossana Scutari, Monica Faieta, Roberta D'Arrigo, Lavinia Fabeni, Cristina Mussini, Andrea Cossarizza, Claudio Casoli, Carlo Federico Perno, Valentina Svicher, Claudia Alteri, Stefano Aquaro
The aim of this study is to evaluate the amino acid variability of HIV-1 Gp41, C2-V3, and Nef in a group of patients characterized by different disease progression rates. HIV-1 sequences were collected from 19 Long term non progressor patients (LTNPs), 9 slow progressors (SPs), and 11 rapid progressors (RPs). Phylogenetic trees were estimated by MEGA 6. Differences in amino acid variability among sequences belonging to the 3 groups have been evaluated by amino acid divergence, Shannon entropy analysis, and the number of amino acid mutations (defined as amino acid variations compared with HxB2)...
May 17, 2018: Virus Genes
Tongfeng Weng, Jie Zhang, Michael Small, Bahareh Harandizadeh, Pan Hui
We propose a unified framework to evaluate and quantify the search time of multiple random searchers traversing independently and concurrently on complex networks. We find that the intriguing behaviors of multiple random searchers are governed by two basic principles-the logarithmic growth pattern and the harmonic law. Specifically, the logarithmic growth pattern characterizes how the search time increases with the number of targets, while the harmonic law explores how the search time of multiple random searchers varies relative to that needed by individual searchers...
March 2018: Physical Review. E
Dipanjan Mandal, Trisha Nath, R Rajesh
We study the different phases and the phase transitions in a system of Y-shaped particles, examples of which include immunoglobulin-G and trinaphthylene molecules, on a triangular lattice interacting exclusively through excluded volume interactions. Each particle consists of a central site and three of its six nearest neighbors chosen alternately, such that there are two types of particles which are mirror images of each other. We study the equilibrium properties of the system using grand canonical Monte Carlo simulations that implement an algorithm with cluster moves that is able to equilibrate the system at densities close to full packing...
March 2018: Physical Review. E
Luca Ornigotti, Artem Ryabov, Viktor Holubec, Radim Filip
The trajectories of an overdamped particle in a highly unstable potential diverge so rapidly, that the variance of position grows much faster than its mean. A description of the dynamics by moments is therefore not informative. Instead, we propose and analyze local directly measurable characteristics, which overcome this limitation. We discuss the most probable particle position (position of the maximum of the probability density) and the local uncertainty in an unstable cubic potential, V(x)∼x^{3}, both in the transient regime and in the long-time limit...
March 2018: Physical Review. E
Julian Lee
Time-reversal symmetry of the microscopic laws dictates that the equilibrium distribution of a stochastic process must obey the condition of detailed balance. However, cyclic Markov processes that do not admit equilibrium distributions with detailed balance are often used to model systems driven out of equilibrium by external agents. I show that for a Markov model without detailed balance, an extended Markov model can be constructed, which explicitly includes the degrees of freedom for the driving agent and satisfies the detailed balance condition...
March 2018: Physical Review. E
Manish Sharma, Deepanshu Goyal, P V Achuth, U Rajendra Acharya
Sleep related disorder causes diminished quality of lives in human beings. Sleep scoring or sleep staging is the process of classifying various sleep stages which helps to detect the quality of sleep. The identification of sleep-stages using electroencephalogram (EEG) signals is an arduous task. Just by looking at an EEG signal, one cannot determine the sleep stages precisely. Sleep specialists may make errors in identifying sleep stages by visual inspection. To mitigate the erroneous identification and to reduce the burden on doctors, a computer-aided EEG based system can be deployed in the hospitals, which can help identify the sleep stages, correctly...
May 10, 2018: Computers in Biology and Medicine
Yuchao Wu, Darshil U Shah, Baoyuan Wang, Ji Liu, Xiaohe Ren, Michael H Ramage, Oren A Scherman
Spider silk is a fascinating material, combining high strength and elasticity that outperforms most synthetic fibers. Another intriguing feature of spider silk is its ability to "supercontract," shrinking up to 50% when exposed to water. This is likely on account of the entropy-driven recoiling of secondary structured proteins when water penetrates the spider silk. In contrast, humidity-driven contraction in synthetic fibers is difficult to achieve. Here, inspired by the spider silk model, a supercontractile fiber (SCF), which contracts up to 50% of its original length at high humidity, comparable to spider silk, is reported...
May 18, 2018: Advanced Materials
Masahiro Hotta, Yasusada Nambu, Koji Yamaguchi
We propose a model with multiple qubits that reproduces the thermal properties of four-dimensional Schwarzschild black holes (BHs) by simultaneously taking account of the emission of Hawking particles and the zero-energy soft-hair evaporation at the horizon. The results verify that the entanglement entropy between a qubit and other subsystems, including emitted radiation, is much larger than the BH entropy analogue of the qubit, as opposed to the Page curve prediction. Our result suggests that early Hawking radiation is entangled with soft hair and that late Hawking radiation can be highly entangled with the degrees of freedom of a BH, avoiding the emergence of a firewall at the horizon...
May 4, 2018: Physical Review Letters
Kai Qi, Michael Bachmann
By means of the principle of minimal sensitivity we generalize the microcanonical inflection-point analysis method by probing derivatives of the microcanonical entropy for signals of transitions in complex systems. A strategy of systematically identifying and locating independent and dependent phase transitions of any order is proposed. The power of the generalized method is demonstrated in applications to the ferromagnetic Ising model and a coarse-grained model for polymer adsorption onto a substrate. The results shed new light on the intrinsic phase structure of systems with cooperative behavior...
May 4, 2018: Physical Review Letters
Nicholas J Porter, Florence F Wagner, David W Christianson
Among the metal-dependent histone deacetylases, the class IIb isozyme HDAC6 is remarkable because of its role in the regulation of microtubule dynamics in the cytosol. Selective inhibition of HDAC6 results in microtubule hyperacetylation, leading to cell cycle arrest and apoptosis, which is a validated strategy for cancer chemotherapy and the treatment of other disorders. HDAC6 inhibitors generally consist of a Zn2+ -binding group such as a hydroxamate, a linker, and a capping group; the capping group is a critical determinant of isozyme selectivity...
May 18, 2018: Biochemistry
Rachel Walker, Jonathan D Schoenfeld, Shari Pilon-Thomas, Jan Poleszczuk, Heiko Enderling
The potential for local radiation therapy to elicit systemic (abscopal) anti-tumor immune responses has been receiving a significant amount of attention over the last decade. We recently developed a mathematical framework designed to simulate the systemic dissemination of activated T cells among multiple metastatic sites. This framework allowed the identification of non-intuitive patterns of T cell redistribution after localized therapy, and offered suggestions as to the optimal site to irradiate in order to increase the magnitude of an immune-mediated abscopal response...
September 2017: Convergent Science Physical Oncology
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