Covalent Structures (covalent + structure)

Distribution by Scientific Domains

Selected Abstracts

Fluoromethyl Cations and Group XIV Congeners AHnF3-n+ (A: Si, Ge, Sn, Pb; n = 0,2): From Covalent Structures to Ion-Molecule Complexes

CHEMINFORM, Issue 43 2006
Paola Antoniotti
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

A simple and highly successful C-terminal sequence analysis of proteins by mass spectrometry

Hiroki Kuyama Dr.
Abstract A simple and efficient method for C-terminal sequencing of proteins has long been pursued because it would provide substantial information for identifying the covalent structure, including post-translational modifications. However, there are still significant impediments to both direct sequencing from C termini of proteins and specific isolation of C-terminal peptides from proteins. We describe here a highly successful, de novo C-terminal sequencing method of proteins by employing succinimidyloxycarbonylmethyl tris (2,4,6-trimethoxyphenyl) phosphonium bromide and mass spectrometry. [source]

Synthesis and structural characterization of a mimetic membrane-anchored prion protein

FEBS JOURNAL, Issue 6 2006
Matthew R. Hicks
During pathogenesis of transmissible spongiform encephalopathies (TSEs) an abnormal form (PrPSc) of the host encoded prion protein (PrPC) accumulates in insoluble fibrils and plaques. The two forms of PrP appear to have identical covalent structures, but differ in secondary and tertiary structure. Both PrPC and PrPSc have glycosylphospatidylinositol (GPI) anchors through which the protein is tethered to cell membranes. Membrane attachment has been suggested to play a role in the conversion of PrPC to PrPSc, but the majority of in vitro studies of the function, structure, folding and stability of PrP use recombinant protein lacking the GPI anchor. In order to study the effects of membranes on the structure of PrP, we synthesized a GPI anchor mimetic (GPIm), which we have covalently coupled to a genetically engineered cysteine residue at the C-terminus of recombinant PrP. The lipid anchor places the protein at the same distance from the membrane as does the naturally occurring GPI anchor. We demonstrate that PrP coupled to GPIm (PrP,GPIm) inserts into model lipid membranes and that structural information can be obtained from this membrane-anchored PrP. We show that the structure of PrP,GPIm reconstituted in phosphatidylcholine and raft membranes resembles that of PrP, without a GPI anchor, in solution. The results provide experimental evidence in support of previous suggestions that NMR structures of soluble, anchor-free forms of PrP represent the structure of cellular, membrane-anchored PrP. The availability of a lipid-anchored construct of PrP provides a unique model to investigate the effects of different lipid environments on the structure and conversion mechanisms of PrP. [source]

Detection and characterization of variant and modified structures of proteins in blood and tissues by mass spectrometry

Akira Shimizu
Abstract Some variant proteins cause diseases, and some diseases result in increases of proteins with abnormally modified structures. The detection, characterization, and estimation of the relative amounts of protein variants and abnormally modified proteins are important for clinical diagnosis and for elucidation of the mechanisms of the pathogenesis of diseases. Analysis of the covalent structures of proteins using matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF-MS) and liquid chromatography-electrospray ionization MS (LC-ESI-MS), which had been developed by the early 1990s, have largely replaced analyses by conventional protein chemistry. Here, we review the detection and characterization of hemoglobin variants, HbA1c measurement, detection of carbohydrate-deficient transferrin, and identification of variants of transthyretin (TTR) and Cu/Zn-superoxide dismutase (SOD-1) using soft ionization MS. We also propose the diagnostic application of the signals of modified forms of TTR, that is, S-sulfonated TTR and S-homocysteinyl TTR. The relative peak height ratio of the abnormal/normal components gives valuable information about the instability of variants and enables the detection of unstable Hb subunits or thalassemia heterozygotes. We found unique modified structures of TTR that suggested changes in amyloid fibrils. 2006 Wiley Periodicals, Inc. [source]

Engineering hydrogen-bonded duplexes

Bing Gong
Abstract Based on several simple, readily available building blocks, oligoamide strands carrying various arrays of hydrogen-bond donors and acceptors, i.e. hydrogen-bonding sequences, have been designed and synthesized. Detailed characterization indicates that these oligoamide strands associate via their hydrogen-bonding edges into doubled stranded pairs (duplexes), which are characterized by programmable sequence specificity and adjustable stability. Using these hydrogen-bonded duplexes as association units, supramolecular structures, such as ,-sheets and non-covalent block copolymers, are obtained by simply mixing the corresponding components. Recently, by incorporating reversible covalent interactions into these hydrogen-bonded duplexes, sequence-specific formation of covalently linked structures has been realized under thermodynamic conditions, which has opened an entirely new avenue to the development of previously unknown dynamic covalent structures such as various block copolymers. Copyright 2007 Society of Chemical Industry [source]