Analytical procedures for quantification of peptides in pharmaceutical research by liquid chromatography–mass spectrometry

Peptide quantification by liquid chromatography–mass spectrometry (LC–MS) combines the high resolving power of reversed-phase (RP) chromatography with the excellent selectivity and sensitivity of mass spectrometric detection. On the basis of comprehensive practical experience in the analysis of small molecules, pharmaceutical research is developing technologies for analysis of a growing number of peptidic drug candidates. This article is a detailed review of procedures based on LC–MS techniques for quantitative determination of peptides. With the focus on pharmaceutical applications several technologies for sample preparation, various aspects of peptide chromatography, important characteristics of ESI–MS, selectivity of MS-detection modes, the large variability of internal standards, and modern instrumentation are discussed. The demand for reliable, robust, sensitive, and accurate methods is discussed using numerous examples from the literature, complemented by experiments and results from our laboratory.     

Unconjugated methoxylated catecholamine metabolites in human saliva. Quantitation methodology and comparison with plasma levels

A newly developed method for the simultaneous extraction and quantitation of the unconjugated levels of the catecholamine metabolites vanilmandelic acid (VMA), 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) and homovanillic acid (HVA) in plasma by high performance liquid chromatography with electrochemical detection was modified and applied to studies of human saliva. The assay had a mean coefficient of variation under 3% for each of the metabolites. Levels of plasma VMA, MHPG and HVA were measured in 28 normal subjects and compared to their saliva levels, obtained before and after stimulation by mastication. Significant correlations were found between plasma and saliva MHPG and HVA, but there was no correlation between plasma and saliva VMA. Salivary MHPG and HVA can be reproducibly assayed and may be useful tools for indications of changes in central and peripheral catecholamine metabolism.     

4-Manifold topology I: Subexponential groups

The technical lemma underlying the 5-dimensional topologicals-cobordism conjecture and the 4-dimensional topological surgery conjecture is a purely smooth category statement about locating ₁-null immersions of disks. These conjectures are theorems precisely for those fundamental groups (good groups) where the ₁-null disk lemma (NDL) holds. We expand the class of known good groups to all groups of subexponential growth and those that can be formed from these by a finite number of application of two operations: (1) extension and (2) direct limit. The finitely generated groups in this class are amenable and no amenable group is known to lie outside this class.Oblatum 20-II-1995 & 26-V-1995The first author is supported by the IHES, the Guggenheim foundation and the NSF.The second author is supported by the IHES and the Humboldt foundation.