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Nanomaterials with different characteristics are offering many ingenious sensing approaches with interest for simple and disposable paper-based (bio)sensing applications. In this study, the colorimetric discrimination of alanine enantiomers is examined and, more importantly, AuNPs-embedded paper-based lab-in-a-syringe (LIS) device is developed as a sensing strategy. The LIS consists of two cellulose acetate membranes: the conjugate pad capturing the analyte and the detection pad signaling the presence of the captured analyte, both are sandwiched between reusable plastic filter holders connected to a disposable syringe. The principle of LIS assay is based on the enantioselective interaction occurring between the inherently chiral AuNPs and enantiomers in the first filter holder, which results in aggregation of AuNPs to give a distinct colour change from red to purple in solution and finally the aggregated AuNPs is kept on the detection pad through vertical-flow operation. AuNPs show an enantioselective recognition response toward L-Alanine and limit of detection (LOD) value is determined as 0.77mM. In addition, we demonstrate the efficiency of the LIS device for detecting L-Alanine in human serum. The proposed LIS assay has some advantages such as useful for naked-eye observation, disposable, not time-consuming, inexpensive, no need of advanced instruments, easy to prepare and easy to handle. In the field, the approach which is the first demonstration of applicability of LIS device to show simple colorimetric enantioselective sensing of chiral species with a fast readout in less than 5min is truly new and may have broad interest in enantiosensing of various chiral molecules., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The atomistic description of the folding process of a structureless chain of amino acids to a functioning protein is still considered to be a challenge for computational biophysics. An in-depth understanding of protein-folding can be achieved through atomistic dynamics accounting for the solvent effects, combined with the theoretical description of conformational changes in shorter polypeptide chains. The present paper studies the folding transitions in short polypeptide chains consisting of 11 alanine residues in explicit solvent employing all-atom molecular dynamics. The multiple observed folding ↔ unfolding events of the peptide are interpreted as a dynamic process and rationalised through the analysis of the potential energy surface of the system. It is demonstrated that alanine polypeptide folding dynamics is governed by the backbone dihedral angles and involves the formation of spontaneously folded α -helices which emerge and live for ca. 1–20 picoseconds. The helical content within the polypeptide at different temperatures was quantified through a statistical mechanics approach, which showed a reasonable agreement with the results of molecular dynamics simulations and experiments performed for alanine-rich peptides. [ABSTRACT FROM AUTHOR]

Lanthionine has been detected incidentally in the urine of a patient with an abdominal pseudo-tumor, possibly caused by a Yersinia infection. The L- and/or D-form together with the meso-form were present. The identity of the amino acid was confirmed by GC-MS of the N-trifluoroacetyl methyl ester derivative. The abnormal amino acid was thought to be not of endogenous origin. The possibility that it was produced by gut bacteria is considered.

A detailed investigation is reported about the biodegradation of poly[Lys(DL-Alam)], m approximately 3, (AK) the common inside area of a branched polypeptide model system developed by our group over the last decade. Enzymatic hydrolysis was carried out by the exopeptidase aminopeptidase M, or the endopeptidase trypsin, or their mixture. Ion-exchange column chromatography, paper electrophoresis and thin-layer chromatography were utilised to achieve separation of metabolites. Breakdown products were identified by the aid of synthetic oligopeptides representing the potential fragments (DL-Ala2, DL-Ala3, Lys(DL-Alam), m = 1-3). The kinetics and the degree of enzymatic degradation were determined. The ratio of peptide/amino acid amounts in the hydrolysate was found to be 1.07 after 24 h treatment with aminopeptidase M, 3.0 with trypsin and 1.3 with aminopeptidase - trypsin mixture. The overall results indicated that the proteolysis of AK by an aminopeptidase M and trypsin mixture proceeds stepwise at multiple sites on the polypeptide chain. The degradation is significantly retarded as compared to that of alpha- or epsilon-polylysine. A mechanism of degradation is suggested based on the experimental results.

The response of umbilical cord blood lymphocytes (UCBL) to PHA and Con A is strongly dependent upon the presence of dialyzable plasma components. The impaired response of human cells in the presence of dialyzed human plasma was restored by calf thymus extract. In the present experiments we have further purified calf thymus extract by means of paper electrophoresis and chromatography on thin-layer cellulose plates. We reached the conclusion that the active material in this model is a single amino acid, alanine. When the different isomeric forms of alanine were tested, we found that L-alanine is the only biologically active material. In addition, we have observed here that the allogeneic response of UCBL is also dependent upon the presence of dialyzable plasma components. This impaired allogeneic response of UCBL in the presence of DHP was restored by addition of L-alanine. The present findings suggest that, under in vitro conditions, for human cells to respond to mitogenic or allogeneic stimulation L-alanine is essential.

The accumulation of d-alanine, l-alanine, glycine, and d-cycloserine in Escherichia coli was found to be mediated by at least two transport systems. The systems for d-alanine and glycine are related, and are separate from that involved in the accumulation of l-alanine. d-Cycloserine appears to be primarily transported by the d-alanine-glycine system. The accumulation of d-alanine, glycine, and d-cycloserine was characterized by two line segments in the Lineweaver-Burk analysis, whereas the accumulation of l-alanine was characterized by a single line segment. d-Cycloserine was an effective inhibitor of glycine and d-alanine accumulation, and l-cycloserine was an effective inhibitor of l-alanine transport. The systems were further differentiated by effects of azide, enhancement under various growth conditions, and additional inhibitor studies. Since the primary access of d-cycloserine in E. coli is via the d-alanine-glycine system, glycine might be expected to be a better antagonist of d-cycloserine inhibition than l-alanine. Glycine and d-alanine at 10(-5)m antagonized the effect of d-cycloserine in E. coli, whereas this concentration of l-alanine had no effect.

Membrane transport of beta-alanine, l-alanine, and l-proline was studied in a beta-alanine transaminaseless mutant (strain 67) of Pseudomonas fluorescens. In this mutant beta-alanine is metabolically inert, and it was therefore possible to demonstrate active transport of this substrate in the absence of intracellular catabolism. The permease which catalyzes the uptake of beta-alanine also transports l-proline and l-alanine. This common transport system was distinguished from permeases which transport only l-alanine and only l-proline by competition studies in strain 67 and by studies of transport specificity in a permeaseless mutant (strain 67/4MTR).

A strain identified as Corynebacterium fascians was found to accumulate extracellular D-alanine from glycerol. Cultural conditions for the accumulation of D-alanine were investigated and, as a result, a yield of 7 g of D-alanine per liter was obtained after a 96-h incubation in a medium containing 5% glycerol, 4% (NH(4))(2)HPO(4), and 0.3% corn steep liquor. Optical purity of D-alanine was dependent upon the concentration of corn steep liquor. At the optimal condition, almost optically pure D-alanine was formed and readily isolated (5 g/liter) from the fermentation broth. The product was not contaminated with any detectable amount of other amino acids, except for glycine which was present at a concentration of less than 1 percent.