On-line Separation and Detection of Peptides by Capillary Electrophoresis / Electrospray FT-ICR-MS

Recently, capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI- MS) has been rapidly developed as a powerful analytical tool for charged species ranged from small molecules such as carboxylic acids1, phenolic compounds2, metal species3, tetramines4, herbicides5, drugs and drug metabolites6 to peptides and proteins7, 8. The ESI mode has proven to be sensitive, versatile and relatively easy to use in combination with CE. CE confers rapid analysis and efficient separ…     

Construction and Analysis of N-phosphoryl Peptide Libraries

N-Phosphoryl peptide libraries were constructed by transformation from homo-oligopeptide libraries, which was synthesized by self-assembly of amino acids with the assistance of phosphorus oxychloride. Electrospray ionization mass spectrometry (ESI-MS) was used to monitor the reaction.     

Enthalpies of solvation for N-alkylamides in water and in carbon tetrachloride at 25°C

Molar enthalpies of solution at infinite dilution have been determined at 25°C for several N-alkyl and N,N-dialkylamides in water and in carbon tetrachloride, using a Calvet-type rotating calorimeter, and solution concentrations below 5×10^–2 molal. Relevant enthalpies of transfer between the two solvents also have been derived. Molar enthalpies of solvation have been obtained by adding enthalpies of vaporization to solution values. Results are compared with those of other laboratories on other substituted amides, and their dependence on the number of carbon atoms in the chain is discussed. A possible computation of solvation enthalpies of functional groups is suggested and results for hydration of peptide or similar groups present in the compounds examined are discussed in terms of current models of their hydration and hydrogen bond formation.Presented at the sixth Italian meeting on Calorimetry and Thermal Analysis (AICAT) held in Naples, December 4–7, 1984.     

A Novel Anti-Inflammatory d-Peptide Inhibits Disease Phenotype Progression in an ALS Mouse Model

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by selective neuronal death in the brain stem and spinal cord. The cause is unknown, but an increasing amount of evidence has firmly certified that neuroinflammation plays a key role in ALS pathogenesis. Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and has been implicated as driver of disease progression. Here, we describe a treatment study demonstrating the therapeutic potential of a tandem version of the well-known all-d-peptide RD2 (RD2RD2) in a transgenic mouse model of ALS (SOD1*G93A). Mice were treated intraperitoneally for four weeks with RD2RD2 vs. placebo. SOD1*G93A mice were tested longitudinally during treatment in various behavioural and motor coordination tests. Brain and spinal cord samples were investigated immunohistochemically for gliosis and neurodegeneration. RD2RD2 treatment in SOD1*G93A mice resulted not only in a reduction of activated astrocytes and microglia in both the brain stem and lumbar spinal cord, but also in a rescue of neurons in the motor cortex. RD2RD2 treatment was able to slow progression of the disease phenotype, especially the motor deficits, to an extent that during the four weeks treatment duration, no significant progression was observed in any of the motor experiments. Based on the presented results, we conclude that RD2RD2 is a potential therapeutic candidate against ALS.     

Studies on synthesis and molecular dynamics simulation of dendrimers containing amino acids and peptides

A series of poly(ether-amide) dendrimers with amino acids and peptides as the peripheral functional groups was synthesized, and their structures were confirmed by nuclear magnetic resonance (NMR) and electrospray ionization-mass spectrometry (ESI-MS) spectrometry. Molecular dynamics simulation of the peptide dendrimers in solution was performed, indicating that, the prior conformations of the dendrimers were atom number dependent, i.e., with the increases of the atom number, the prior conformations were more spherical. Also, the amino acid α-C atom radial distribution indicated that, with larger peripheral groups, more back-folding of the dendrimers occurred. __________ Translated from Acta Chimica Sinica, 2007, 65(1): 21–26 [译自: 化学 通报]     

Solvation of amino acid residues in water and urea-water mixtures: Volumes and heat capacities of 20 amino acids in water and in 8 molar urea at 25°C

The limiting partial molar volumes V ^o and heat capacities C _p ^o of 20 amino acids have been determined in water and in 8 molar urea at 25.0°C using flow calorimetry and flow densimetry. The side chain contributions to V ^o and C _p ^o were obtained as the difference between the properties of the various amino acids and those of glycine, both in water and in 8M urea. The solvent accessible surface area of the amino acid residues were obtained using a method developed by Hermann, and the total surface areas were separated into their hydrophobic A _Hb and hydrophilic components. In water, C _p ^o values for the various residues C _p ^o (R) were found well correlated with A _Hb , though much less so in the urea solution. Hence, C _p ^o (R) values, in water yield a good estimate of side chain hydrophobicity, but the (waterurea) transfer heat capacities appear strongly affected by specific solvation effects in the urea solution.Presented at the sixth Italian meeting on Calorimetry and Thermal Analysis (AICAT) held in Naples, December 4–7, 1984.     

Microwave-assisted reaction of peptide formation by amino acid with phosphate:Exploration of the most possible channels for the origin of life

The formation of peptides and then protein by small abiological molecules clusters such as amino acid is a key stage in the origin of life[1]. More and more ex- perimental results showed that phosphate plays an important role in the formation of biomolecules in prebiotic chemical evolution. The principal reservoirs of biochemical energy are phosphates (such as ATP). The peculiar role of phosphates in contemporary life might suggest its essential role in prebiotic energy conversion, syntheses …     

Structure of YM-254890, a Novel Gq/11 Inhibitor from Chromobacterium sp. QS3666

The isolation and structure elucidation of YM-254890, a novel G_q/11 inhibitor from Chromobacterium sp. QS3666, is described. The gross structure was determined by one- and two-dimensional NMR studies and mass spectrometry. YM-254890 is a cyclic depsipeptide containing uncommon amino acids; β-hydroxyleucine (two residues), N,O-dimethylthreonine and N-methyldehydroalanine. YM-254890 exists as a mixture of two conformers in a variety of NMR solvents, and the distinction between major and minor conformers appears to lie in the geometry of the amide bond between 3-phenyllactic acid and N-methyldehydroalanine. The absolute stereochemistery was elucidated by Marfey's analysis and chiral HPLC analysis of the acid hydrolysate of YM-254890.     

Identification of low molecular weight proteins isolated by 2-D liquid separations

Proteins with molecular mass (M(r)) <20 kDa are often poorly separated in 2-D sodium dodecyl sulfate polyacrylamide gel electrophoresis. In addition, low-M(r) proteins may not be readily identified using peptide mass fingerprinting (PMF) owing to the small number of peptides generated in tryptic digestion. In this work, we used a 2-D liquid separation method based on chromatofocusing and non-porous silica reversed-phase high-performance liquid chromatography to purify proteins for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric (MALDI-TOFMS) analysis and protein identification. Several proteins were identified using the PMF method where the result was supported using an accurate M(r) value obtained from electrospray ionization TOFMS. However, many proteins were not identified owing to an insufficient number of peptides observed in the MALDI-TOF experiments. The small number of peptides detected in MALDI-TOFMS can result from internal fragmentation, the few arginines in its sequence and incomplete tryptic digestion. MALDI-QTOFMS/MS can be used to identify many of these proteins. The accurate experimental M(r) and pI confirm identification and aid in identifying post-translational modifications such as truncations and acetylations. In some cases, high-quality MS/MS data obtained from the MALDI-QTOF spectrometer overcome preferential cleavages and result in protein identification.     

Final elucidation of the absolute configuration of the signal metabolite hormaomycin

The complete absolute configuration of hormaomycin 1 a has been established by HPLC and HPLC/MS experiments with appropriately derivatized 4-propylprolines, (2S,4S)-6 and (2R,4R)-6, as well as 4-(Z)-propenylprolines, cis-5 and trans-5, and also feeding experiments with enantiomerically pure samples of the deuterium-labeled 3-(2'-nitrocyclopropyl)alanine, (2S)-3,3-[D2]15 and (2S)-2,2'-[D2]15, and 4-(Z)-propenylproline 2',4-[D2]-(2S,4R)-5. The latter five amino acids were prepared for the first time and allowed one to unequivocally assign the hitherto unknown absolute configurations of the last four stereocenters in hormaomycin 1 a. As a bonus, some new information about the biosynthesis of this molecule has also been gathered.