Bifunctional cross-linking approaches for mass spectrometry-based investigation of nucleic acids and protein-nucleic acid assemblies.

With the goal of expanding the very limited toolkit of cross-linking agents available for nucleic acids and their protein complexes, we evaluated the merits of a wide range of bifunctional agents that may be capable of reacting with the functional groups characteristic of these types of biopolymers. The survey specifically focused on the ability of test reagents to produce desirable inter-molecular conjugates, which could reveal the identity of interacting components and the position of mutual contacts, while also considering a series of practical criteria for their utilization as viable nucleic acid probes. The survey employed models consisting of DNA, RNA, and corresponding protein complexes to mimic as close as possible typical applications. Denaturing polyacrylamide gel electrophoresis (PAGE) and mass spectrometric (MS) analyses were implemented in concert to monitor the formation of the desired conjugates. In particular, the former was used as a rapid and inexpensive tool for the efficient evaluation of cross-linker activity under a broad range of experimental conditions. The latter was applied after preliminary rounds of reaction optimization to enable full-fledged product characterization and, more significantly, differentiation between mono-functional and intra- versus inter-molecular conjugates. This information provided the feedback necessary to further optimize reaction conditions and explain possible outcomes. Among the reagents tested in the study, platinum complexes and nitrogen mustards manifested the most favorable characteristics for practical cross-linking applications, whereas other compounds provided inferior yields, or produced rather unstable conjugates that did not survive the selected analytical conditions. The observed outcomes will help guide the selection of the most appropriate cross-linking reagent for a specific task, whereas the experimental conditions described here will provide an excellent starting point for approaching these types of applications. As a whole, the results of the survey clearly emphasize that finding a universal reagent, which may afford excellent performance with all types of nucleic acid substrates, will require extending the exploration beyond the traditional chemistries employed to modify the constitutive functional groups of these vital biopolymers.

Primary splenic lymphoma in patient with hepatitis C virus infection: case report and review of the literature.

Primary splenic lymphoma is uncommon, constituting only 1-2% of all patients with malignant lymphoma. Despite the rarity of this malignancy, the number of primary splenic lymphoma being reported has increased due to its ambiguous definition used in the literature. We describe a case of a 41-year-old man with chronic hepatitis C virus infection presenting abdominal discomfort in the upper left quadrant, weakness, nausea and vomiting. Abdominal computed tomography revealed nodules in the congested splenic parenchyma. Splenectomy was performed and an analysis of the spleen diagnosed B-cell non-Hodgkin's lymphoma. Biopsy of the liver showed evidence of hepatitis C virus. Bone marrow biopsy revealed no tumor infiltration. The patient has been followed to date, has progressed quite well and remains essentially asymptomatic. Recently, an etiologically important role has been suggested for hepatitis C virus infection in the development of B-cell non Hodgkin's lymphoma. Lymphotropism of hepatitis C virus may play a pathological role in the development of non Hodgkin's lymphoma. It is important to add lymphoma to the list of differential diagnosis of extrahepatic disorders in patients with chronic hepatitis C virus infection.

Globin evolution in some species of the genus Bufo.

The globins of 10 species of toads of the genus Bufo have been analysed. From the values of the reciprocal rates between their amino acid residues a 'dissimilarity matrix' was made. In this have been included the values related to Discoglossus pictus and Xenopus laevis. The numerical data, derived from a computer program, gave a dendrogram representing the evolution of the analysed globins. This appears correlated to the geographical distribution and to the metabolic adaptation of the corresponding species of Bufo more than their chronological appearance.