Influence of water–protein hydrogen bonding on the stability of Trp-cage miniprotein. A comparison between the TIP3P and TIP4P-Ew water models

2011 ◽  
Vol 13 (44) ◽  
pp. 19840 ◽  
Author(s):  
Dietmar Paschek ◽  
Ryan Day ◽  
Angel E. García
Keyword(s):  
Hydrogen Bonding ◽  
Influence Of Water ◽  
Water Models ◽  
The Stability

scholarly journals One-Dimensional Organic–Inorganic Material (C6H9N2)2BiCl5: From Synthesis to Structural, Spectroscopic, and Electronic Characterizations

2021 ◽  
Vol 22 (4) ◽  
pp. 2030
Author(s):  
Hela Ferjani ◽  
Hammouda Chebbi ◽  
Mohammed Fettouhi
Keyword(s):  
Hydrogen Bonding ◽  
Density Functional ◽  
Crystal Packing ◽  
Diffuse Reflectance Spectrum ◽  
Enrichment Ratio ◽  
One Dimensional ◽  
Organic Part ◽  
Fukui Indices ◽  
The Stability ◽  
The One

The new organic–inorganic compound (C6H9N2)2BiCl5 (I) has been grown by the solvent evaporation method. The one-dimensional (1D) structure of the allylimidazolium chlorobismuthate (I) has been determined by single crystal X-ray diffraction. It crystallizes in the centrosymmetric space group C2/c and consists of 1-allylimidazolium cations and (1D) chains of the anion BiCl52−, built up of corner-sharing [BiCl63−] octahedra which are interconnected by means of hydrogen bonding contacts N/C–H⋯Cl. The intermolecular interactions were quantified using Hirshfeld surface analysis and the enrichment ratio established that the most important role in the stability of the crystal structure was provided by hydrogen bonding and H···H interactions. The highest value of E was calculated for the contact N⋯C (6.87) followed by C⋯C (2.85) and Bi⋯Cl (2.43). These contacts were favored and made the main contribution to the crystal packing. The vibrational modes were identified and assigned by infrared and Raman spectroscopy. The optical band gap (Eg = 3.26 eV) was calculated from the diffuse reflectance spectrum and showed that we can consider the material as a semiconductor. The density functional theory (DFT) has been used to determine the calculated gap, which was about 3.73 eV, and to explain the electronic structure of the title compound, its optical properties, and the stability of the organic part by the calculation of HOMO and LUMO energy and the Fukui indices.

Seventh International Conference on the Stability of Ships and Ocean Vehicles (STAB’ 2000)—A Review

2001 ◽  
Vol 38 (01) ◽  
pp. 1-8
Author(s):  
Vadim L. Belenky
Keyword(s):  
High Speed ◽  
Test Procedures ◽  
International Conference ◽  
Water On Deck ◽  
Beam Seas ◽  
Damage Stability ◽  
Influence Of Water ◽  
Roll Stabilization ◽  
The Stability ◽  
Operational Aspects

A brief review is given of the papers presented at the 7th International Conference on the Stability of Ships and Ocean Vehicles, held 7–12 February 2000 in Launceston, Australia. The review covers the following stability-related subjects: human factors, stability standards, operational aspects, influence of water on deck, damage stability, stability in following and quartering seas, stability of high-speed craft and sailing yachts, nonlinear dynamics of ships, test procedures, roll stabilization and cargo shift, waves and the environment, rolling in beam seas and stability of particular types of ships.

scholarly journals Development of spray-dried co-precipitate of amorphous celecoxib containing storage and compression stabilizers

2007 ◽  
Vol 57 (3) ◽  
pp. 287-300 ◽  
Author(s):  
Ravindra Dhumal ◽  
Shamkant Shimpi ◽  
Anant Paradkar
Keyword(s):  
Hydrogen Bonding ◽  
Solid Dispersion ◽  
Dissolution Profile ◽  
Scanning Calorimetry ◽  
Unit Operations ◽  
Bonding Interaction ◽  
Amorphous Drugs ◽  
The Stability ◽  
Amorphous Drug ◽  
Spray Dried

Development of spray-dried co-precipitate of amorphous celecoxib containing storage and compression stabilizersThe purpose of this study was to obtain an amorphous system with minimum unit operations that will prevent recrystallization of amorphous drugs since preparation, during processing (compression) and further storage. Amorphous celecoxib, solid dispersion (SD) of celecoxib with polyvinyl pyrrollidone (PVP) and co-precipitate with PVP and carrageenan (CAR) in different ratios were prepared by the spray drying technique and compressed into tablets. Saturation solubility and dissolution studies were performed to differentiate performance after processing. Differential scanning calorimetry and X-ray powder difraction revealed the amorphous form of celecoxib, whereas infrared spectroscopy revealed hydrogen bonding between celecoxib and PVP. The dissolution profile of the solid dispersion and co-precipitate improved compared to celecoxib and amorphous celecoxib. Amorphous celecoxib was not stable on storage whereas the solid dispersion and co-precipitate powders were stable for 3 months. Tablets of the solid dispersion of celecoxib with PVP and physical mixture with PVP and carrageenan showed better resistance to recrystallization than amorphous celecoxib during compression but recrystallized on storage. However, tablets of co-precipitate with PVP and carageenan showed no evidence of crystallinity during stability studies with comparable dissolution profiles. This extraordinary stability of spray-dried co-precipitate tablets may be attributed to the cushioning action provided by the viscoelastic polymer CAR and hydrogen bonding interaction between celecoxib and PVP. The present study demonstrates the synergistic effect of combining two types of stabilizers, PVP and CAR, on the stability of amorphous drug during compression and storage as compared to their effect when used alone.

Influence of Water Flow on the Stability of Geosynthetic-Soil Layered Systems on Slopes

1995 ◽  
Vol 2 (6) ◽  
pp. 1149-1180 ◽  
Author(s):  
J.P. Giroud ◽  
R.C. Bachus ◽  
R. Bonaparte
Keyword(s):  
Water Flow ◽  
Layered Systems ◽  
Influence Of Water ◽  
The Stability

An assessment of oxime-oximato hydrogen bonding: A structural and thermodynamic study of copper(II) complexes

1978 ◽  
Vol 31 (4) ◽  
pp. 723 ◽  
Author(s):  
EA Daniel ◽  
FC March ◽  
HKJ Powell ◽  
WT Robinson ◽  
JM Russell
Keyword(s):  
Hydrogen Bonding ◽  
Methyl Ether ◽  
Complex Cation ◽  
Steric Effects ◽  
Apical Position ◽  
X Ray ◽  
Methyl Substitution ◽  
Perchlorate Ion ◽  
Nitrogen Donor ◽  
The Stability

Copper(II) complexes formed by the diamine dioxime ligand 4,4,9,9- tetramethyl-5,8-diazadodecane-2,11-dione dioxime (H2dddo) and its O-methyl ether (Hddmo) and bis-O-methyl ether (dddm) have been studied. The log K (potentiometric) and ΔH (calorimetric) values are reported for formation of the four-coordinate complexes [Cu(Hddmo)]2+ and [Cu(dddm)]2+ and for the deprotonation of [Cu(Hddmo)]2+ to give [Cu(ddmo)]+ at 25°C, I = 0.1 M NaCl. (log K = 12.11 � 0.04, 9.10�0.02 and -6.76�0.09; ΔH= -43�2, -17.9�0.4 and +21.9�0.9 kJ mol-1 respectively.) Comparison with data for [Cu(H2dddo)]2+ and [Cu(Hdddo)]+ affords information about the relative contributions of (i) oxime deprotonation (c. 105.6), and (ii) oxime oximato hydrogen bonding (c. 103.5), to the stability of these (non-conjugated) dioxime complexes. The formation of intramolecular (oxime-oximato) hydrogen bonds is favoured by a positive ΔS; intermolecular bonds (oximato-solvent) give rise to a negative ΔS. ��� A single-crystal X-ray molecular structure determination is reported for the complex Cu(dddm)-(ClO4)2. In the solid state the complex cation is square pyramidal with one perchlorate ion weakly coordinated in the apical position and the four nitrogen donor atoms forming a distorted square plane about the copper atom. Steric effects associated with O-methyl substitution are assessed. Steric hindrance between adjacent =NOR groups does not increase measurably when =NOH is replaced by =NOMe.

Physical Stability and Lyophilization of Poly(ε-caprolactone)-b-Poly(ethyleneglycol)-b-Poly(ε-caprolactone) Micelles

2006 ◽  
Vol 6 (9) ◽  
pp. 3032-3039 ◽  
Author(s):  
Yong Hu ◽  
Yin Ding ◽  
Yuan Li ◽  
Xiqun Jiang ◽  
Changzheng Yang ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Carbonyl Group ◽  
Fluorescence Spectra ◽  
Physical Stability ◽  
Storage Period ◽  
Aqueous Dispersion ◽  
Hydroxyl Group ◽  
Core Shell ◽  
Ft Ir ◽  
The Stability

The stability and lyophilization of core–shell PCL-PEG-PCL micelles were investigated by fluorescence spectra, DLS, DSC, WAXD, and FT-IR. The prepared micelles were not stable when they were stored in aqueous dispersion under different condition. Their size increased in the first 20 days and decreased gradually when the storage period was extended. Lyophilization experiment showed that the cryoprotective agent (glucose) was an essential additive to protect the micelles from aggregating during the lyophilization process. After lyophilizing and re-dispersion, the PCL-PEG-PCL micelles became larger in size compared to as-prepared ones. DSC, WAXD, and IR measurements indicated the hydrogen bonding was formed between the hydroxyl group in glucose and the carbonyl group in PCL-PEG-PCL micelles. The effect of added glucose on protection of micelles from aggregation can be explained by the formation of hydrogen bonding with PCL-PEG-PCL micelles and the formation of solid glucose matrix.

scholarly journals Influence of water evaporation/absorption on the stability of glycerol–water marbles

RSC Advances ◽  
2019 ◽  
Vol 9 (59) ◽  
pp. 34465-34471 ◽  
Author(s):  
Xinxing Lin ◽  
Wei Ma ◽  
Lihui Chen ◽  
Liulian Huang ◽  
Hui Wu ◽  
...  
Keyword(s):  
Water Evaporation ◽  
Glycerol Water ◽  
Influence Of Water ◽  
The Stability

The influence of water evaporation and absorption on the stability of aqueous glycerol marbles was investigated.

Effects of methoxy-substituted metalloporphyrins in catalytic alkene epoxidation by n-Bu4NHSO5

2010 ◽  
Vol 14 (04) ◽  
pp. 335-342 ◽  
Author(s):  
Amineh Aghabali ◽  
Nasser Safari
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
High Activity ◽  
Solvent Mixture ◽  
Steric Effects ◽  
Reaction Condition ◽  
Reaction Solution ◽  
Phenyl Rings ◽  
Active Intermediate ◽  
The Stability

TPPMnOAc and four different kinds of manganese tetraphenylporphyrin acetates were synthesized using different numbers of methoxy substituents in various positions of the phenyl rings. These porphyrins were used as catalysts in the epoxidation of various alkenes with tetra-n-butylammonium hydrogen monopersulfate (n- Bu 4 NHSO 5) as the oxidant and imidazole as the axial base. The following order of catalytic activity was obtained: TPPMnOAc ≥ T (2,3- OMeP ) PMnOAc > T (4- OMeP ) PMnOAc > T (3,4- OMeP ) PMnOAc > T (2,4,6- OMeP ) PMnOAc . By studying the UV-vis spectra in the reaction solution, the stability of the applied methoxy porphyrins and the effect of this factor on obtained yields were investigated. Lower catalytic activity in some of the methoxy porphyrins emphasized steric effects and special hydrogen bonding among the reaction elements. However, the stability of T (2,3- OMeP ) PMnOAc under our reaction condition was considerable and high activity was observed. By adding small amounts of alcohol to the reaction solution, the effect of the solvent mixture was previewed and steps were taken to identify the active intermediate of the catalyst in these conditions.

Study on Influence of Polyethylene Glycol on Dispersion of Pyrite Powder in Aqueous Solution

2012 ◽  
Vol 554-556 ◽  
pp. 349-352
Author(s):  
Dan Li ◽  
Zhou Lan Yin ◽  
Qi Yuan Chen
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Bonding ◽  
Polyethylene Glycol ◽  
Spectroscopic Analysis ◽  
Ph Value ◽  
Aqueous Suspension ◽  
Dispersion Stability ◽  
The Stability ◽  
High Degree ◽  
Effective Additive

The influences of three kinds of polyethylene glycol (PEG), namely PEG-200, PEG-1000 and PEG-20000, on the dispersion stability of pyrite powder in aqueous solution were investigated by spectrophotometry. The results indicated that the stability of pyrite powder dispersed in aqueous solution was remarkably dependent upon the molecular weight and content of PEG, pH value of suspension, and ultrasonication power. Among three kinds of polyethylene glycol, PEG-20000 was the most effective additive to improve the dispersion stability and wettability of pyrite powder in water. When 8% PEG-20000 was employed as the dispersant, the best dispersion stability of pyrite powder in aqueous solution could be obtained under the conditions of pH at 5-6 and 100-W ultrasonication power. The FTIR spectroscopic analysis showed that the adsorption between the polyethylene glycol and pyrite ore powder was formed by hydrogen bonding. The adsorption of polyethylene glycol onto the surface of pyrite powder via hydrogen bonding provided a high degree of steric stabilization, which effectively prohibited the aggregation of pyrite powder, and thus the dispersion stability of as-formed aqueous suspension was promoted.

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