A quantitative approach to optical resolution

Significant statistical relationships have been found between the parameters characterizing the results and circumstances of the resolutions of seventeen phenylglycine derivatives. The successful predictions given for the results of six independent resolutions prove the utility of these relationships.     

New approach to recycling of thermosets

The decrosslinking of thermosetting reaction injection molded (RIM) polyurethane-urea products with the smallest amounts of glycols was studied. The effects of the reaction conditions on the properties of liquid oligomers were determined. Successful scale-up studies and utilization of the resulting liquid oligomers for preparation of RIM products, coatings and adhesives are described.     

A simple and practical phase-separation approach to the recycling of a homogeneous metathesis catalyst

The air stable asarone-derived Ru carbene 16, a robust olefin metathesis catalyst, can be easily separated after reaction by deposition on silica gel and reused up to nine times. This procedure provides products of excellent purity with low Ru content.     

An approach to quantitative proteome analysis by labeling tryptophan residues

This report describes a method for quantification and sequence identification of individual proteins in complex mixtures. The method is based on labeling with the chemical reagent 2-nitrobenzenesulfenyl chloride (NBSCl) in conjunction with tandem mass spectrometry. In this method, selective introduction of the 2-nitrobenzenesulfenyl (NBS) moiety onto tryptophan residues is achieved, and a 6 Da mass differential is generated using (13)C(6)-labeled NBSCl (NBSCl-(13)C(6)) and (12)C(6)-labeled NBSCl (NBSCl-(12)C(6)). The 6 Da mass differential between the NBS-(12)C(6)-labeled and the NBS-(13)C(6)-labeled peptides assigns a mass signature to all tryptophan-containing peptides in any pool of proteolytic digests for protein identification through peptide mass mapping. Using this strategy, we compared the protein expression in rat sera using a normal (control) rat (Crj:Wistar) and a hyperglycemic rat (GK/Crj). The stable isotope dilution techniques used in this method provide highly accurate relative quantification. The NBS approach offers a widely applicable means of analyzing protein mixtures derived from biological samples, and the method described here presents an effective and simplified approach to proteome analysis.     

A stoichiometric approach to quantitative structure-property relationships (QSPR)

An unusual analogy between the quantitative structure-property relationships (QSPR), stoichiometry, chemical thermodynamics, and kinetics is presented. Namely, the conventional ordinary least-squares (OLS) QSPR analysis is modified so as to explicitly minimize the residuals of the species subject to a set of linear relations among the residuals. The ways the linear relations among the residuals are visualized and defined totally resemble the formalism of chemical stoichiometry and, therefore, were called isostructural reactions. It is further proved that the residuals may be uniquely partitioned into a sum of contributions associated with a set of isostructural reactions that have the same properties as the response reactions (RERs) previously deduced by us from chemical thermodynamics and kinetics. This finding is shown to be a useful tool for a deeper understanding of the QSPR. In particular, the isostructural RERs approach may be effectively used to detect the outliers.     

A multivariate approach to saccharide quantitative structure-activity relationships exemplified by two series of 9-hydroxyellipticine glycosides

Multivariate saccharide quantitative structure-activity relationships (QSARs) have been developed for two series of 9-hydroxyellipticine glycosides. In order to describe the structural variation of the glycoside moieties, thirteen chromatographic variables were used. Eleven D-glycosides and seven L-glycosides were used in separate QSARs to model 9-hydroxyellipticine glycoside antitumour activity against L 1210 leukemia. The multivariate partial least squares (PLS) method was used to establish the QSARs.     

A graph-theoretic approach to quantitative structure—activity/reactivity studies

Characterization of molecular species based on the use of suitable graph invariants (graph paths, in particular) can provide a quantitative means of encoding structure; the technique is complementary to commoner approaches to studies of quantitative structure— activity relationships. Graph path encoding is here applied to quantitative studies of relationships between molecular structures and biological activity; the examples are the rates of various substrate reactions with hexoldnase, and the potential opiate-like activity of enkephalin analogs.     

Possible approach to the quantitative evaluation of the asymmetry of molecules

A. V. Bogatskii Physicochemical Institute, Academy of Sciences of the Ukrainian SSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 28, No. 4, pp. 45–49, September–October, 1987.     

A quantitative approach to the analysis of supermicron dispersions by field-flow fractionation with UV-vis detectors. The application of an absolute method

Summary Quantitative analysis in field-flow fractionation is becoming a necessary requirement for routine applications, instrumental optimization and scale-up to preparative separations. The use of detection systems which show complex dependence on sample characteristics (i.e. UV spectrometry) has hindered the application of quantitative methods of analysis in field-flow fractionation. A standardless model, shown valid in flow-through, homogeneous systems, is applied here to a heterogeneous system (dispersed supermicron particles) in field-flow fractionation by single peak area measurements. Absolute analysis in the fractionation of spherical silica particles for high-performance liquid chromatography column packing by gravitational field-flow fractionation with UV-Vis detectors is presented. It has been shown that for such samples extinction coefficients are independent of sample concentration and are determined by the size and density of the particles. The accuracy of such an approach to absolute analysis is discussed. In memory of J. C. Giddings Presented at FFF'95-Fifth International Symposium on Field-Flow Fractionation, Park City, UT, USA, July 10–12 1995.     

Hydrogen analysis by elastic recoil spectrometry: A new approach for absolute quantitative measurement

We have developed an absolute, quantitative procedure to determine the hydrogen content and to describe its concentration profile in the near-surface region of solids. The experimental technique used is the Elastic Recoil Detection Analysis of protons induced by helium-4 beam bombardment in the energy range 1.8 MeV. The deconvolution of the recoil spectra is obtained by means of a computer program which simulates all the physical processes of⁴He/¹H interaction. The hydrogen content is calculated using a new recoil cross section expression. The analyses are performed in silicon crystals implanted with hydrogen at 10 keV. The implantation dose is evaluated with an accuracy of 10% and the hydrogen depth profile is given with an accuracy of ±10 nm around 200 nm.     

A quantitative approach to studying structures and orientation at self-assembled monolayer/fluid interfaces

Self-assembled monolayers (SAMs) have become a standard tool for exploring surface interactions. Although well characterized, SAMs are known to undergo structural and conformational changes in the presence of solution, yet the ability to quantify these changes remains an obstacle due to limited analytical techniques. In this study, we determine changes in structure and conformation of CH3, OH, and COOH terminated hexadecanethiols on gold in water by means of a new technique known as evanescence reflection spectroscopy. This FTIR application, in conjunction with a semiempirical formalism, is capable of providing both qualitative and quantitative understanding of the molecular structure and orientation at the solid/liquid interface.