Caution: Chemical Instability of Natural Biomolecules During Routine Analysis

Natural products (NPs) constitute a significant source of active biomolecules widely used in medicine, pharmacology and cosmetics. However, NPs structural characterization has the drawback of their chemical instability during the extraction steps and their likely transformation during the analytical protocol. In particular, tamariscol and conocephalenol are two compounds largely used in the cosmetic industry for their odorant properties. Thus, in the present study, we focused on the evolution of these two metabolites (extracted from Frullania tamarisci and Conocephalum conicum, respectively), as followed by NMR. Interestingly, we found that, once dissolved in deuterated chloroform, these two tertiary alcohols are both subjected to transformation processes, leading to degradation compounds with altered structures. Accordingly, these detected degradation compounds have been fully characterized by NMR and the experimental findings were supported by computational chemistry data.

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STRUCTURE DETERMINATION OF TpRu(PPh3){κ2-N, O-NH=C(Ph)N=C(Ph)O}: A STORY OF HOW COMPUTATIONAL STUDIES CONTRIBUTE TO THE STRUCTURAL CHARACTERIZATION PROCESS

Journal of Theoretical and Computational Chemistry ◽

10.1142/s021963360900471x ◽

2009 ◽

Vol 08 (03) ◽

pp. 417-422 ◽

Cited By ~ 1

Author(s):

WENXU ZHENG ◽

CHUNG WING LEUNG ◽

ZHONGYUAN ZHOU ◽

CHAK PO LAU ◽

ZHENYANG LIN

Keyword(s):

Molecular Structure ◽

Computational Chemistry ◽

Structural Characterization ◽

Structure Determination ◽

Structure Elucidation ◽

Computational Studies

In this paper, we described the process involved in the structure determination of TpRu ( PPh 3){κ2-N, O- NH = C ( Ph ) N = C ( Ph ) O } and demonstrated the tremendous help of computational chemistry in the molecular structure elucidation.

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Fate of selected volatile organic substances in aqueous environment

Water Quality Research Journal ◽

10.2166/wqrj.1989.007 ◽

1989 ◽

Vol 24 (1) ◽

pp. 119-142 ◽

Cited By ~ 2

Author(s):

Glen R. Chodola ◽

Nihar Biswas ◽

Jatinder K. Bewtra ◽

Carl C. St. Pierre ◽

Richard G. Zytner

Keyword(s):

Mass Flux ◽

Methylene Chloride ◽

Volume Ratio ◽

Aqueous Environment ◽

Direct Photolysis ◽

Air Interface ◽

Volatile Organic ◽

Mathematical Equations ◽

Experimental Findings ◽

Transformation Processes

Abstract Laboratory studies were conducted to evaluate the influence of several processes on the behaviour and fate of synthetic volatile organic chemicals in an aqueous environment. Five organic priority pollutants, benzene, methylene chloride, tetrachloroethylene, toluene and trichloroethylene, were investigated to determine their susceptibility to the transformation processes of direct photolysis and hydrolysis under various pH, temperatures and concentrations. In addition, benzene, methylene chloride, tetrachloroethylene, toluene and trichloroethylene were examined for volatilization from the water surface as well as mass flux by diffusion into water. The experimental findings for direct photolysis indicated that the susceptibility was negligible for all the selected organic compounds. However, methylene chloride, tetrachloroethylene and trichloroethylene were found to be susceptible to hydrolysis when the aquatic environment is basic and has an elevated temperature. Benzene, methylene chloride, tetrachloroethylene, toluene and trichloroethylene exhibited relatively rapid rates of volatilization and these rates were significantly influenced by the area to volume ratio. The overall Liquid film coefficients at the water-air interface for benzene, methylene chloride, tetrachloroethylene, toluene and trichloroethylene were observed to be 0.21, 0.69, 0.64 and 0.07 m/d, respectively, under the specified conditions. The mass flux experiments indicated that, under quiescent conditions, the mass transfer occurring at the water-chemical interfaces of submerged pools of tetrachloroethylene and methylene chloride was low, thus providing an opportunity for clean up. Benzene and toluene floated to the surface and rapidly volatilized into the atmosphere. Mathematical equations have been developed to predict mass flux of such substances under given conditions.

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Phase behavior of cationic and anionic surfactants at low concentrations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100123878 ◽

1992 ◽

Vol 50 (1) ◽

pp. 694-695

Author(s):

E. Naranjo

Keyword(s):

Phase Behavior ◽

Structural Characterization ◽

Dynamic Systems ◽

Anionic Surfactants ◽

Intermolecular Forces ◽

Stable Form ◽

Surfactant Mixtures ◽

Low Concentrations ◽

Cationic And Anionic Surfactants ◽

General Method

Equilibrium vesicles, those which are the stable form of aggregation and form spontaneously on mixing surfactant with water, have never been demonstrated in single component bilayers and only rarely in lipid or surfactant mixtures. Designing a simple and general method for producing spontaneous and stable vesicles depends on a better understanding of the thermodynamics of aggregation, the interplay of intermolecular forces in surfactants, and an efficient way of doing structural characterization in dynamic systems.

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New ultrastructural findings about Borrelia burgdorferi by cryofixation, negative staining, thin sectioning and scanning techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100160467 ◽

1990 ◽

Vol 48 (3) ◽

pp. 582-583

Author(s):

S. F. Hayes ◽

M. D. Corwin ◽

T. G. Schwan ◽

D. W. Dorward ◽

W. Burgdorfer

Keyword(s):

Lyme Disease ◽

Borrelia Burgdorferi ◽

Structural Characterization ◽

Negative Staining ◽

Low Speed ◽

Thin Sectioning ◽

Ultrastructural Findings

Characterization of Borrelia burgdorferi strains by means of negative staining EM has become an integral part of many studies related to the biology of the Lyme disease organism. However, relying solely upon negative staining to compare new isolates with prototype B31 or other borreliae is often unsatisfactory. To obtain more satisfactory results, we have relied upon a correlative approach encompassing a variety EM techniques, i.e., scanning for topographical features and cryotomy, negative staining and thin sectioning to provide a more complete structural characterization of B. burgdorferi.For characterization, isolates of B. burgdorferi were cultured in BSK II media from which they were removed by low speed centrifugation. The sedimented borrelia were carefully resuspended in stabilizing buffer so as to preserve their features for scanning and negative staining. Alternatively, others were prepared for conventional thin sectioning and for cryotomy using modified procedures. For thin sectioning, the fixative described by Ito, et al.

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