Updating knowledge on new medically important scorpion species in Mexico.

The increment in the number of scorpion envenoming cases in Mexico is mainly associated to the rapid growth of the urban areas, and consequently, to the invasion of natural habitats of these arachnids. On the other hand, there is a great diversity of scorpion species, so it is indispensable to identify those of medical importance, which we now know are many more than the 7-8 previously reported as dangerous to humans. Because different LD50 values have been reported for the venom of the same species, probably due to variations in the experimental conditions used, in this work we determined the LD50 values for the venoms of 13 different species of scorpions using simple but systematic procedures. This information constitutes a referent on the level of toxicity of medically important scorpion species from Mexico and establishes the bases for a more comprehensive assessment of the neutralizing capacity of current and developing antivenoms.

Repetitive use of polyacrylamide gels for the analysis and purification of oligonucleotides.

The repetitive use of polyacrylamide slab gels for the analysis of oligonucleotides by ultraviolet (UV) shadowing across the complete electrophoresis cassette is addressed. Visualization of the samples is possible by preparing the gel between a quartz plate and a highly sensitive glass fluorescent plate whose preparation is described here. Within a working day, gels can be reloaded up to five times with no detriment to the resolution of the oligonucleotide bands. Taking advantage of this detection approach, we also devised a strategy to reuse gels in the purification of oligonucleotides, combining electroelution and subsequent concentration of the samples using centrifugal filter units.

Influence of the germline sequence on the thermodynamic stability and fibrillogenicity of human lambda 6 light chains.

Light chain-associated amyloidosis is a fatal disease characterized by the aggregation and pathologic deposition of monoclonal light chain-related fragments as amyloid fibrils in organs or tissues throughout the body. Notably, it has been observed that proteins encoded by the lambda variable light chain (V(L)) gene segment 6a are invariably associated with amyloid deposition; however, the contribution of the gene to this phenomenon has not been established. In this regard, we have determined the thermodynamic stability and kinetics of in vitro fibrillogenesis of a recombinant (r) V(L) protein, designated 6aJL2, which contains the predicted sequences encoded by the 6a and JL2 germline genes. Additionally, we studied a 6a mutant (6aJL2-Arg25Gly), that is present in approximately 25% of all amyloid-associated lambda6 light chains. Remarkably, the wild-type 6aJL2 protein was more stable than were all known amyloidogenic kappa and lambda light chains for which stability parameters are available; more importantly, it was even more so (and less fibrillogenic) than the only clinically proven nonamyloidogenic lambda6 protein, Jto. Conversely, the mutated 6aJL2-R25G molecule was considerably less stable and more fibrillogenic than was the native 6aJL2. Our data indicate that the propensity of lambda6 light chains to form amyloid can not be attributed to thermodynamic instability of the germline-encoded Vlambda6 domain, but rather, is dependent on sequence alterations that render such proteins amyloidogenic.

(1)H, (13)C and (15)N resonance assignment of 6aJL2(R25G), a highly fibrillogenic lambdaVI light chain variable domain.

An allotypic variation at position 25 influences the fibrillogenicity of lambdaVI light chains, which are related to humoral immune response and have been associated with AL amyloidosis. The full resonance assignment and a preliminary structural characterization of 6aJL2(R25G) are reported.