The modification of the triple helical structure of gelatin in aqueous solution I. The influence of anionic surfactants,pH-value,and temperature

The modification of the triple helical structure in aqueous gelatin solutions by changing pH and adding alkyl sulphates at 298 K and after rechilling the solution to 283 K was investigated by CD-measurement. At 298 K the triple helical content at the IEP of the gelatin has its maximum value. It is only weakly affected by adding sodium dodecyl sulphate (SDDS) at concentrations <10^–4 M/dm³. The unfolding of the triple helix affected by pH and SDDS is reversible by rechilling the solution. The triple helical content of gelatin solutions decreases at SDDS concentrations higher than 10^–4 M/dm³. In all cases the decrease of the amount of triple helical structure is connected with an increase of the cis-configuration in single chains and leads to chain reversals. At sufficiently high SDDS concentrations-sheets are formed. These changes are thermally irreversible. Sodium decyl sulphate (SDS) has a more minor influence than SDDS except in the range of the c.m.c. of SDS. At sufficiently high SDS concentrations,-turns appear.     

New antiferromagnetic properties of manganese gallium sulfides MnGa2S4-α and MnGa2S4-β

The α and β phases of MnGa₂S₄-α and β have been prepared and characterized. Single crystals of the α-phase have been grown by the vapor phase transport method ; their structure found monoclinic, space group C 2/c, has been refined by the X-ray technique and the positional and thermal parameters are reported. Both compounds are antiferromagnetic with Néel temperatures of 23.5 K and 11 K, for α and β respectively. EPR spectra show a single line, exchange-narrowed at 300 K, with a strong critical broadening above T_N. These results are discussed in relation with the crystal structure and the possible superexchange interactions between the Mn²⁺.     

Substrate specificity analysis of protein kinase complex Dbf2-Mob1 by peptide library and proteome array screening

Background  

The mitotic exit network (MEN) is a group of proteins that form a signaling cascade that is essential for cells to exit mitosis in Saccharomyces cerevisiae. The MEN has also been implicated in playing a role in cytokinesis. Two components of this signaling pathway are the protein kinase Dbf2 and its binding partner essential for its kinase activity, Mob1. The components of MEN that act upstream of Dbf2-Mob1 have been characterized, but physiological substrates for Dbf2-Mob1 have yet to be identified.     

Proton conductive membranes of sulfonated poly(ether ketone ketone)

Poly(ether ketone ketone) was sulfonated using fumic sulfuric acid and used for preparation of proton conductive membranes. The sulfonation degree was evaluated by elemental and thermal analysis and the IEC values were determined by titration. The proton conductivity of membranes with sulfonation degrees up to 70% was determined as a function of temperature by impedance spectroscopy. Membranes with sulfonation degree 38–70% were tested in DMFC experiments. Their performance was comparable to Nafion^® with the same pretreatment and clearly better than sulfonated poly(ether ether ketone) membranes with similar functionalization. The methanol crossover was lower than that of Nafion^® in the same conditions.     

Electrochemical Behavior of Indoles with Methyl,Benzyl, and Dibenzyl-4-yl Groups

2,3-Dimethylindole, N-benzyl-2-methylindole, and 2-(dibenzyl-4-yl)-7-benzylindole (DBBI) under conditions for potentiodynamic electrochemical polymerization (0.3–0.9 V vs. Ag/Ag⁺ in acetonitrile) underwent dimerization reactions as was shown by simulation of the potentiodynamic cycles. But DBBI alone polymerized (and only on Au), obviously because of its free N and C(3) positions. This conducting polymer could be technically interesting, because it does not show redox activities in the potential range 0.0–1.1 V vs. the Ag/AgCl electrode. __________ Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1320–1322, September, 2005.