Read by QxMD icon Read


Zhengrong Yang, Qingxian Zhou, Leo Mok, Anukriti Singh, Douglas J Swartz, Ina L Urbatsch, Christie G Brouillette
Structural changes in mouse P-glycoprotein (Pgp) induced by thermal unfolding were studied by differential scanning calorimetry (DSC), circular dichroism and fluorescence spectroscopy to gain insight into the solution conformation(s) of this ABC transporter that may not be apparent from current crystal structures. DSC of reconstituted Pgp showed two thermal unfolding transitions in the absence of MgATP, suggesting that each transition involved the cooperative unfolding of two or more interacting structural domains...
October 23, 2016: Biochimica et Biophysica Acta
Eileen K Jaffe
Porphobilinogen synthase (PBGS), also known as 5-aminolevulinate dehydratase, is an essential enzyme in the biosynthesis of all tetrapyrroles, which function in respiration, photosynthesis, and methanogenesis. Throughout evolution, PBGS adapted to a diversity of cellular niches and evolved to use an unusual variety of metal ions both for catalytic function and to control protein multimerization. With regard to the active site, some PBGSs require Zn(2+); a subset of those, including human PBGS, contain a constellation of cysteine residues that acts as a sink for the environmental toxin Pb(2+)...
October 26, 2016: Accounts of Chemical Research
Johnny J Perez, David A Watson, Robert J Levis
Nonresonant laser vaporization combined with high resolution time-of-flight mass spectrometry enables analysis of a casing after discharge of a firearm revealing organic signature molecules including methyl centralite (MC), diphenylamine (DPA), N-nitrosodiphenylamine (N-NO-DPA), 4-nitrodiphenylamine (4-NDPA), a DPA adduct and multiple unidentified features not observed in previous mass spectral measurements. Collision-induced dissociation measurements of unknown GSR signature ions reveals inorganic barium and derivatives BaOH, BaOHCH3, BaCH3COO remaining from the primer...
October 26, 2016: Analytical Chemistry
Philip R Nicovich, Miro Janco, Tom Sobey, Mehul Gajwani, Peyman Obeidy, Renee Whan, Katharina Gaus, Peter Gunning, Adelle Cf Coster, Till Böcking
Reconstitution of actin filaments on surfaces for observation of filament-associated protein dynamics by fluorescence microscopy is currently an exciting field in biophysics. Here we examine the effects of attaching actin filaments to surfaces on the binding and dissociation kinetics of a fluorescence-labelled tropomyosin, a rod-shaped protein that forms continuous strands wrapping around the actin filament. Two attachment modalities of the actin to the surface are explored: where the actin filament is attached to the surface at multiple points along its length; and where the actin filament is attached at one end and aligned parallel to the surface by buffer flow...
October 26, 2016: Cytoskeleton
Zhale Rajavi, Ali Lashgari, Hamideh Sabbaghi, Narges Behradfar, Mehdi Yaseri
PURPOSE: To determine the incidence and related risk factors of reoperation among patients with infantile exotropia who were operated on at Imam Hossein Medical Center, Tehran, Iran, from 2001 to 2015. METHODS: In this study, 82 children (55 girls and 27 boys) with infantile exotropia were divided into two groups 3 months after their first operation: children with horizontal deviation of 10 prism diopters (PD) or less (n = 64; success group) and those with horizontal deviation greater than 10 PD (n = 18; failure group)...
October 25, 2016: Journal of Pediatric Ophthalmology and Strabismus
Allan M Oliveira, Julia H Lehman, Anne B McCoy, W Carl Lineberger
We report the negative ion photoelectron spectroscopy of the hydroxymethoxide anion, H2C(OH)O(-). The photoelectron spectra show that 3.49 eV photodetachment produces two distinct electronic states of the neutral hydroxymethoxy radical (H2C(OH)O(⋅)). The H2C(OH)O(⋅) ground state (X̃ (2)A) photoelectron spectrum exhibits a vibrational progression consisting primarily of the OCO symmetric and asymmetric stretches, the OCO bend, as well as combination bands involving these modes with other, lower frequency modes...
September 28, 2016: Journal of Chemical Physics
Zhaodong Liu, Zhen Yao, Mingguang Yao, Jiayin Lv, Shuanglong Chen, Quanjun Li, Hang Lv, Tianyi Wang, Shuangchen Lu, Ran Liu, Bo Liu, Jing Liu, Zhiqiang Chen, Bo Zou, Tian Cui, Bingbing Liu
We present a joint experimental and theoretical study on the high-pressure behavior of bromine confined in the one-dimensional (1D) nanochannels of zeolite AlPO4-5 (AFI) single crystals. Raman scattering experiments indicate that loading bromine into AFI single crystals can lead to the formation of bromine molecular chains inside the nanochannels of the crystals. High-pressure Raman and X-ray diffraction studies demonstrate that high pressure can increase the length of the confined bromine molecular chains and modify the inter- and intramolecular interactions of the molecules...
September 28, 2016: Journal of Chemical Physics
Ryuichi Okamoto, Akira Onuki
We investigate ionization at a solid-water interface in an applied electric field. We attach an electrode to a dielectric film bearing silanol or carboxyl groups with an areal density Γ0, where the degree of dissociation α is determined by the proton density in water close to the film. We show how α depends on the density n0 of NaOH in water and the surface charge density σm on the electrode. For σm > 0, the protons are expelled away from the film, leading to an increase in α. In particular, in the range 0 < σm < eΓ0, self-regulation occurs to realize α ≅ σm/eΓ0 for n0 ≪ nc, where nc is 0...
September 28, 2016: Journal of Chemical Physics
V Beutner, S G Zhang, H Meyer, J Kłos
We present the first measurement of a bound-state spectrum of the NO-He complex. The recorded spectrum is associated with the first overtone transition of the NO moiety. The IR absorption is detected by exciting the vibrationally excited complex to the Ã-state dissociation continuum. The resulting NO(A) fragment is subsequently ionized in the same laser pulse. We recorded two bands centered around the NO monomer rotational lines, Q11(0.5) and R11(0.5), consistent with an almost free rotation of the NO fragment within the complex...
September 28, 2016: Journal of Chemical Physics
Jonathan Tennyson
In what has been described as the fourth age of quantum chemistry, variational nuclear motion programs are now routinely being used to obtain the vibration-rotation levels and corresponding wavefunctions of small molecules to the sort of high accuracy demanded by comparison with spectroscopy. In this perspective, I will discuss the current state-of-the-art which, for example, shows that these calculations are increasingly competitive with measurements or, indeed, replacing them and thus becoming the primary source of data on key processes...
September 28, 2016: Journal of Chemical Physics
Tahereh Nemati Aram, Petrutza Anghel-Vasilescu, Asghar Asgari, Matthias Ernzerhof, Didier Mayou
We present a novel simple model to describe molecular photocells where the energy conversion process takes place by a single molecular donor-acceptor complex attached to electrodes. By applying quantum scattering theory, an open quantum system method, the coherent molecular photocell is described by a wave function. We analyze photon absorption, energy conversion, and quantum yield of a molecular photocell by considering the effects of electron-hole interaction and non-radiative recombination. We model the exciton creation, dissociation, and subsequent effects on quantum yield in the energy domain...
September 28, 2016: Journal of Chemical Physics
Anirban Ghosh, Rajat K Chaudhuri, Sudip Chattopadhyay
A four-component (4c) relativistic state specific multireference coupled cluster (4c-SSMRCC) method has been developed and applied to compute the ground state spectroscopic constants of Ag2, Cu2, Au2, and I2. The reference functions used in these calculations are obtained using computationally inexpensive improved virtual orbital-complete active space configuration interaction scheme. Rigorous size-extensivity and insensitivity towards the intruder state problem make our method an interesting choice for the calculation of the dissociation energy surface...
September 28, 2016: Journal of Chemical Physics
Mohammad M Rafiee Fanood, Maurice H M Janssen, Ivan Powis
Enantiomers of the monoterpene limonene have been investigated by (2 + 1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway...
September 28, 2016: Journal of Chemical Physics
Mark Wijzenbroek, Darcey Helstone, Jörg Meyer, Geert-Jan Kroes
We have performed calculations on the dissociative chemisorption of H2 on un-reconstructed and reconstructed Au(111) with density functional theory, and dynamics calculations on this process on un-reconstructed Au(111). Due to a very late barrier for dissociation, H2 + Au(111) is a candidate H2-metal system for which the dissociative chemisorption could be considerably affected by the energy transfer to electron-hole pairs. Minimum barrier geometries and potential energy surfaces were computed for six density functionals...
October 14, 2016: Journal of Chemical Physics
Andrei Kryjevski, Brendan Gifford, Svetlana Kilina, Dmitri Kilin
Efficient multiple exciton generation (MEG) in chiral single-wall carbon nanotubes (SWCNTs) is present within the solar spectrum range as shown by the many-body perturbation theory calculations combined with the density functional theory simulations. To describe the impact ionization process, we calculate exciton-to-biexciton decay rates R1→2 and biexciton-to-exciton rates R2→1 in the (6,2) and (10,5) SWCNTs. Within the solar energy range, we predict R1→2 ∼ 10(14) s(-1), while biexciton-to-exciton recombination is weak with R2→1/R1→2 ≤ 10(-2)...
October 21, 2016: Journal of Chemical Physics
S M A Cruz, J M C Marques, F B Pereira
We propose improvements to our evolutionary algorithm (EA) [J. M. C. Marques and F. B. Pereira, J. Mol. Liq. 210, 51 (2015)] in order to avoid dissociative solutions in the global optimization of clusters with competing attractive and repulsive interactions. The improved EA outperforms the original version of the method for charged colloidal clusters in the size range 3 ≤ N ≤ 25, which is a very stringent test for global optimization algorithms. While the Bernal spiral is the global minimum for clusters in the interval 13 ≤ N ≤ 18, the lowest-energy structure is a peculiar, so-called beaded-necklace, motif for 19 ≤ N ≤ 25...
October 21, 2016: Journal of Chemical Physics
Saman Alavi, Ryo Ohmura
When compressed with water or ice under high pressure and low temperature conditions, some gases form solid gas hydrate inclusion compounds which have higher melting points than ice under those pressures. In this work, we study the balance of the guest-water and water-water interaction energies that lead to the formation of the clathrate hydrate phases. In particular, molecular dynamics simulations with accurate water potentials are used to study the energetics of the formation of structure I (sI) and II (sII) clathrate hydrates of methane, ethane, and propane...
October 21, 2016: Journal of Chemical Physics
Roger F Loring
Optically detected single-turnover measurements of biological and inorganic catalysts provide a detailed picture of structural and dynamical influences on catalytic activity. Measurement at the single-molecule level of catalysis of a fluorogenic reaction (or its reverse) yields a stochastic fluorescence trajectory reflecting the statistics of individual reaction and product dissociation events. Analysis of time correlations displayed by this trajectory reveals reaction details inaccessible in a bulk measurement of averaged dynamics...
October 7, 2016: Journal of Chemical Physics
S Buathong, M Kelley, F B Dunning
Electron transfer in collisions between low-n, n = 12, Rydberg atoms and targets that attach low-energy electrons can lead to the formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair that orbit each other at large separations. Measurements of the velocity and angular distribution of ion-pair states produced in collisions with 1,1,1-C2Cl3F3, CBrCl3, BrCN, and Fe(CO)5 are used to show that electron transfer reactions furnish a new technique with which to examine the lifetime and decay energetics of the excited intermediates formed during dissociative electron capture...
October 7, 2016: Journal of Chemical Physics
Michael A Lee, Naveed Bakh, Gili Bisker, Emery N Brown, Michael S Strano
Cortisol is an important glucocorticoid hormone whose biochemistry influences numerous physiological and pathological processes. Moreover, it is a biomarker of interest for a number of conditions, including posttraumatic stress disorder, Cushing's syndrome, Addison's disease, and others. An implantable biosensor capable of real time monitoring of cortisol concentrations in adipose tissue may revolutionize the diagnosis and treatment of these disorders, as well as provide an invaluable research tool. Toward this end, a mathematical model, informed by the physiological literature, is developed to predict dynamic cortisol concentrations in adipose, muscle, and brain tissues, where a significant number of important processes with cortisol occur...
October 26, 2016: Advanced Healthcare Materials
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"