Evidence that atypical protein kinase C-lambda and atypical protein kinase C-zeta participate in Ras-mediated reorganization of the F-actin cytoskeleton

Liver fatty acid binding protein (L-FABP) appears to contain several different forms that may result from post-translational modification or bound ligand. To further assess this possibility, L-FABP was purified from rat liver homogenate and two putative isoforms separated using a sulfonyl column, a strong cation exchange resin. Fraction I eluted at 0.2 M NaCl, had a pI of 7.59, and following a final size exclusion step contained > 98% L-FABP. Fraction II eluted at 1.0 M NaCl, had a pI of 7.59, and following a final size exclusion step contained > 99% L-FABP. Both fractions contained approx. 0.15 moles of endogenous bound fatty acid per mole of protein, while L-FABP not subjected to the cation exchange step contained 0.75 moles of fatty acid per mole of protein. Fractions I and II had a greater proportion of saturated and monounsaturated fatty acids with a large reduction in polyunsaturated fatty acids compared to L-FABP not fractionated by cation exchange. Mass spectral analysis indicated the molecular mass of Fraction I was 14,315.02 +/- 0.35 Da and Fraction II was 14,315.86 +/- 0.34 Da. The peptide map for each fraction was determined by limited digestion of each fraction with either trypsin, Asp-N, or chymotrypsin to yield overlapping peptide fragments. Mass spectral analysis of these digests indicated the two proteins had identical amino acid fragments and that Cys69 was reduced and there were no Asn to Asp exchanges. Hence, these two forms of L-FABP were not isoforms and were not the result of differences in bound fatty acid. It is proposed that these two distinct forms of rat L-FABP were structural conformers based on two alternative folding pathways.     

The effect of binary cosolvent systems (glycerol–sucrose mixtures) on the heat-induced gelation mechanism of bovine serum albumin

The influence of cosolvent composition on the thermal denaturation and gelation of bovine serum albumin (BSA) has been studied. Cosolvent composition was varied by changing the ratio of glycerol to sucrose in 40 wt% cosolvent solutions containing BSA. Differential scanning calorimetry measurements on 0.5 wt% BSA solutions showed that the thermal denaturation temperature of the protein increased with increasing sucrose content. Temperature scanning dynamic shear rheology and turbidity measurements on 4 wt% BSA solutions showed that the gelation temperature and final gel strength increased with increasing sucrose concentration. These observations were attributed to the fact that sucrose was more effective than glycerol at increasing the thermal stability and attraction between globular BSA molecules through a steric exclusion effect. The molecular origin of these effects is the tendency for the system to minimize the contact area of the protein molecules with the surrounding cosolvent solution.     

A hardware demonstrator for TD-CDMA

TD-CDMA is an air interface concept for third-generation mobile radio systems. It utilizes a combination of the three elementary multiple-access schemes: frequency-division multiple access (FDMA), time-division multiple access (TDMA) and code-division multiple access (CDMA). Multiple-access interference (MAI) and intersymbol interference (ISI) are combated by joint detection of all simultaneous signals of the same cell, achieving a high spectrum efficiency. The authors have been involved in the implementation of a first experimental hardware setup of a TD-CDMA mobile radio system. Important objectives of this project are the demonstration of the economic feasibility of CDMA receivers utilizing joint detection and the performance verification of TD-CDMA by measurement campaigns. The authors present a new way of modeling the TD-CDMA receiver in the form of a data-flow model. This model serves as a starting point for the systematic design of an efficient software architecture for TD-CDMA based on a multiprocessor system. The complete digital signal processing (DSP) of a mobile terminal or of a base station can be implemented on a single Texas Instruments digital signal processor TMS320C80. Measurement results obtained by first field trials are presented. The system parameters of the TD-CDMA demonstrator described are similar but not equal to those chosen for the time-division duplex (TDD) mode of the UMTS terrestrial air interface according to the ETSI decision taken in January 1998.