Free energy drives a wide range of molecular processes such as solvation, binding, chemical reactions and conformational change. Given the central importance of binding, a wide range of methods exist to calculate it, whether based on scoring functions, machine-learning, classical or electronic structure methods, alchemy, or explicit evaluation of energy and entropy. Here we present a new energy–entropy (EE) method to calculate the host–guest binding free energy directly from molecular dynamics (MD) simulation. Entropy is evaluated using Multiscale Cell Correlation (MCC) which uses force and torque covariance and contacts at two different length scales. The method is tested on a series of seven host–guest complexes in the SAMPL8 (Statistical Assessment of the Modeling of Proteins and Ligands) “Drugs of Abuse” Blind Challenge. The EE-MCC binding free energies are found to agree with experiment with an average error of 0.9 kcal mol?1. MCC makes clear the origin of the entropy changes, showing that the large loss of positional, orientational, and to a lesser extent conformational entropy of each binding guest is compensated for by a gain in orientational entropy of water released to bulk, combined with smaller decreases in vibrational entropy of the host, guest and contacting water.
Fungi are considered good producers of industrially valuable enzymes with higher enzymatic activities. Among these cellulases are group of extracellular enzymes commonly employed in many industries for the hydrolysis of cellulolytic material. Aspergillus fumigatus produced exoglucanase having high enzymatic activity (83 U/gds) during the solid-state fermentation of wheat straw under optimum physical and nutritional conditions. Maximum production was obtained after 72 h of fermentation, at 55 °C temperature, pH 5.5, 80 % moisture level, and 2 mL fungal inoculum. Production was further increased by the addition of fructose (0.3 %) as additional carbon source, peptone (0.4 %) as nitrogen source, Tween-80 (0.3 %) as surfactant, and ammonium sulfate (0.2 %) in media. Exoglucanase was 2.30-folds purified by adding 40 % ammonium sulfate with volumetric activity 95.4 U/gds and specific activity 14.74 U/mg. Further, it was 5.18-folds purified by gel filtration chromatography with volumetric activity 115.2 U/gds and specific activity 33.10 U/mg. Purified exoglucanase has maximum activity at 55 °C and pH 4.8 using 1 % Avicel aqueous solution as substrate. The Km and Vmax were 4.34 mM and 7.29 μM/min, respectively. Calcium, magnesium, and zinc ions have positive effect on exoglucanase activity. 相似文献
Tumor‐promoting characteristics of seven esters, 1 – 7 , obtained from the latex of Euphorbia cauducifolia L. was appraised by carrying out NMRI mice back skin. The structures of 1 – 7 were elucidated by spectroscopic techniques like 1H‐ and 13C‐NMR, 2D‐NMR (HMQC, HMBC, HOHAHA (homonuclear Hartmann–Hahn), NOESY, and NOE), FT‐IR, UV, and MS as esters of 17‐hydroxyingenol, namely 17‐[(2Z,4E,6Z)‐deca‐2,4,6‐trienoyloxy]ingenol ( 1 ), 3‐O‐angeloyl‐17‐[(2Z,4E,6Z)‐deca‐2,4,6‐trienoyloxy]ingenol ( 2 ), 3‐O‐acetyl‐20‐O‐angeloyl‐17‐hydroxyingenol ( 3 ), 17‐(acetyloxy)‐3‐O‐angelyl‐ingenol ( 4 ), 20‐O‐acetyl‐3‐O‐angeloyl‐17‐hydroxyingenol ( 5 ), 3‐O‐angelyl‐17‐(benzoyloxy)ingenol ( 6 ) and 20‐O‐acetyl‐3‐O‐angelyl‐17‐(benzoyloxy)ingenol ( 7 ). Compounds 1 – 4 were isolated for the first time, whereas 5 – 7 are known metabolites but detected for the first time in this plant. Biological investigations revealed that these compounds are tumor promoters. 相似文献
Using Ruscheweyh derivative and convolution operator, we introduce a new subclass of analytic functions defined in the unit disc. Some inclusion results, a radius problem and some other interesting properties of this class are investigated. 相似文献
In this paper, making use of a linear operator we introduce and study certain new classes of meromorphic functions. We derive some inclusion results. These classes contain many known classes as a special case. 相似文献