Vibrational Raman optical activity characterization of poly(l-proline) II helix in alanine oligopeptides

A vibrational Raman optical activity (ROA) study of a series of alanine peptides in aqueous solution is presented. The seven-alanine peptide Acetyl-OOAAAAAAAOO-Amide (OAO), recently shown by NMR and UVCD to adopt a predominantly poly(l-proline II) (PPII) helical conformation in aqueous solution, gave an ROA spectrum very similar to that of disordered poly(l-glutamic acid) which has long been considered to adopt the PPII conformation, both being dominated by a strong positive extended amide III ROA band at approximately 1319 cm-1 together with weak positive amide I ROA intensity at approximately 1675 cm-1. A series of alanine peptides Ala2-Ala6 studied in their cationic states in aqueous solution at low pH displayed ROA spectra which steadily evolved toward that of OAO with increasing chain length. As well as confirming that alanine peptides can support the PPII conformation in aqueous solution, our results also confirm the previous ROA band assignments for PPII structure, thereby reinforcing the foundation for ongoing ROA studies of unfolded and partially folded proteins.     

Multi-nuclear platinum complexes encapsulated in cucurbit[n]uril as an approach to reduce toxicity in cancer treatment

The dinuclear platinum complex trans-[[Pt(NH(3))(2)Cl](2)micro-dpzm](2+)(di-Pt) binds inside cucurbit[7]uril with slow exchange kinetics which does not significantly affect the cytotoxicity of the dinuclear complex but reactivity at the platinum centre is reduced.     

Effect of single-point sequence alterations on the aggregation propensity of a model protein

Sequences of contemporary proteins are believed to have evolved through a process that optimized their overall fitness, including their resistance to deleterious aggregation. Biotechnological processing may expose therapeutic proteins to conditions that are much more conducive to aggregation than those encountered in a cellular environment. An important task of protein engineering is to identify alternative sequences that would protect proteins when processed at high concentrations without altering their native structure associated with specific biological function. Our computational studies exploit parallel tempering simulations of coarse-grained model proteins to demonstrate that isolated amino acid residue substitutions can result in significant changes in the aggregation resistance of the protein in a crowded environment while retaining protein structure in isolation. A thermodynamic analysis of protein clusters subject to competing processes of folding and association shows that moderate mutations can produce effects similar to those caused by changes in system conditions, including temperature, concentration, and solvent composition, that affect the aggregation propensity. The range of conditions where a protein can resist aggregation can therefore be tuned by sequence alterations, although the protein generally may retain its generic ability for aggregation.     

A comparative study of the ability of different techniques to extract menthol from Mentha piperita

Supercritical fluid extraction, direct thermal desorption, hydroalcoholic extraction, and atomization are used to extract menthol from leaf plants of Mentha piperita. The investigated methods are comparatively evaluated on the basis of their reliability to determine the enantiomeric distribution of menthol. The enantioselectivity required for the gas chromatographic analysis is achieved using Octakis (2,6-di-O-n-pentyl-3-O-butyryl)-gamma-cyclodextrin as the stationary phase. From the obtained results, it is established that there is a significant effect of the combination of pressure and temperature to achieve the effective isolation and fractionation of the less and most volatile compounds using supercritical fluids.     

The Effects of Alkali Metal Cations on Product Distributions in Cucurbit[n]uril Synthesis

The synthesis of new cryptands containing 1-methyl or 1-hexadecyl-pyrazole is described in high yield using metal templated [3+2] tripodal condensation.     

A new approach based on off‐line coupling of high‐performance liquid chromatography with gas chromatography‐mass spectrometry to determine acrylamide in coffee brew

A new method based on off‐line coupling of LC with GC in replacement of conventional sample preparation techniques is proposed to analyze acrylamide in coffee brews. The method involves the preseparation of the sample by LC, the collection of the selected fraction, its concentration under nitrogen, and subsequent analysis by GC coupled with MS. The composition of the LC mobile phase and the flow rate were studied to select those conditions that allowed separation of acrylamide without coeluting compounds. Under the conditions selected recoveries close to 100% were achieved while LODs and LOQs equal to 5 and 10 μg/L for acrylamide in brewed coffee were obtained. The method developed enabled the reliable detection of acrylamide in spiked coffee beverage samples without further clean‐up steps or sample manipulation.