Analysis of human blood plasma and hen egg white by chiroptical spectroscopic methods (ECD, VCD, ROA)

Chiroptical methods are widely used in structural and conformational analyses of biopolymers. The application of these methods to investigations of biofluids would provide new avenues for the molecular diagnosis of protein-misfolding diseases. In this work, samples of human blood plasma and hen egg white were analyzed using a combination of conventional and chiroptical methods: ultraviolet absorption/electronic circular dichroism (UV/ECD), Fourier transform infrared absorption/vibrational circular dichroism (FTIR/VCD), and Raman scattering/Raman optical activity (Raman/ROA). For comparison, the main components of these substances—human serum albumin (HSA) and ovalbumin (Ova)—were also analyzed by these methods. The ultraviolet region of the ECD spectrum was analyzed using the CDNN CD software package to evaluate the secondary structures of the proteins. The UV/ECD, FTIR/VCD, and Raman/ROA spectra of the substances were quite similar to those of the corresponding major proteins, while some differences were also detected and explained. The conclusions drawn from the FTIR/VCD and Raman/ROA data were in good agreement with the secondary structures calculated from ECD. The results obtained in this work demonstrate that the chiroptical methods used here can be applied to analyze not only pure protein solutions but also more complex systems, such as biological fluids.

Dielectric response of imidazolium-based room-temperature ionic liquids

We have used microwave dielectric relaxation spectroscopy to study the picosecond dynamics of five low-viscosity, highly conductive room temperature ionic liquids based on 1-alkyl-3-methylimidazolium cations paired with the bis((trifluoromethyl)sulfonyl)imide anion. Up to 20 GHz the dielectric response is bimodal. The longest relaxation component at the time scale of several 100 ps reveals strongly nonexponential dynamics and correlates with the viscosity in a manner consistent with hydrodynamic predictions for the diffusive reorientation of dipolar ions. Methyl substitution at the C2 position destroys this correlation. The time constants of the weak second process at the 20 ps time scale are practically the same for each salt. This intermediate process seems to correlate with similar modes in optical Kerr effect spectra, but its physical origin is unclear. The missing high-frequency portion of the spectra indicates relaxation beyond the upper cutoff frequency of 20 GHz, presumably due to subpicosecond translational and librational displacements of ions in the cage of their counterions. There is no evidence for orientational relaxation of long-lived ion pairs.     

High resolution broad line 13C NMR and relaxation in solid norbornadiene

High resolution NMR of rare spins in solids has been used for selective measurement through transverse relaxation of the shapes of lines corresponding to nonequivalent ¹³C nuclei in solid norbornadiende between 195 and 225 K. The broad lines have different shapes and widths, whose temperature dependence indicates slow translational diffusion of molecules.     

QSAR modeling of endpoints for peptides which is based on representation of the molecular structure by a sequence of amino acids

The representation of the molecular structure by a system (sequence) of amino acids has been used to establish quantitative structure–property/activity relationships (QSPR/QSAR) which can be used for (i) bioactivities of epitope-peptides, (ii) antibacterial potencies of polypeptides, and (iii) the binding affinity of peptides that bind to the class I major histocompatibility complex molecule HLA-A*0201. The representation of the peptide structure has been done via 1-letter abbreviations of amino acids, i.e., A (alanine), C (cysteine), D (aspartic), etc. This approach allows classifying amino acids according to their function in a biochemical process (promoters of increase or decrease of an endpoint).     

Carbohydrate‐based copolyesters made from bicyclic acetalized galactaric acid

Mixtures of the dimethyl esters of adipic acid and 2,3:4,5‐di‐O‐methylene‐galactaric acid (Galx) were made to react in the melt with either 1,6‐hexanediol or 1,12‐dodecanediol to produce linear polycyclic copolyesters with aldarate unit contents varying from 10 up to 90 mole %. The copolyesters had weight–average molecular weights in the ～35,000–45,000 g mol^?1 range and a random microstructure, and were thermally stable up to nearly 300 °C. They displayed T_g in the ‐50 to ‐7 °C range with values largely increasing with the content in galactarate units. All the copolyesters were semicrystalline with T_m between 20 and 90 °C but only those made from 1,12‐dodecanediol were able to crystallize from the melt at a crystallization rate that decreased as the contents in the two comonomers approached each other. Copolyesters containing minor amounts of galactarate units adopted the crystal structure characteristic of aliphatic polyesters but a new crystal polymorph was formed when the cyclic sugar units became the majority. Stress–strain parameters were sensitively affected by composition of the copolyesters with the mechanical behavior changing from flexible/ductile to stiff/brittle with the replacement of adipate units by the galactarate units. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Silyl modification of biologically active compounds. 13. Synthesis,cytotoxicity and antibacterial action of N‐methyl‐N‐(2‐triorganylsiloxyethyl)‐1,2,3,4‐tetrahydro(iso)quinolinium iodides

A series of N‐methyl‐N‐(2‐triorganylsiloxyethyl)‐1,2,3,4‐tetrahydro(iso)quinolinium iodides has been synthesized via dehydrocondensation reaction of N‐(2‐hydroxyethyl)‐1,2,3,4‐tetrahydroisoquinoline, N‐(2‐hydroxyethyl)‐1,2,3,4‐tetrahydroquinoline and 4,4‐dimethyl‐N‐(2‐hydroxyethyl)‐4‐sila‐1,2,3,4‐tetrahydroisoquinoline with trialkyl(aryl)hydrosilanes and subsequent alkylation, and characterized by ¹H, ¹³C and ²⁹Si NMR and mass spectroscopy. The biological activity data exhibited a marked enhancement of inhibitory activity against tumour cell lines and almost all the test bacterial/fungal strains in comparison with their 2‐hydroxyethyl precursors. Cytotoxicity in the microgram range against HT‐1080 (human fibrosarcoma) and MG‐22A (mouse hepatoma) cancer cell lines was observed for most of compounds. Copyright © 2012 John Wiley & Sons, Ltd.