No description available.

The presence of the purine nucleotide inosine monophosphate (IMP) was studied in direct relationship to the development and expression of cell mediated immunity in guinea pigs using DNCB or Histoplasma capsulatum as sensitizing antigens. The IMP content of T-cell enriched lymphocytic lysates was measured by isocratic high pressure liquid chromatography (HPLC). Intracellular IMP levels of cells from homologously skin tested sensitized animals were significantly increased one day after skin testing when compared to the concentrations found in these cells during the period following sensitization. Concurrent with these observations were the findings that the absolute lymphocyte counts and histoplasmin stimulated in vitro blastogenic responses increased following sensitization while the PHA-induced proliferative response decreased slightly. One day after skin testing, when IMP levels had increased, there was a slight decrease in lymphocyte numbers and a marked decrease in the PHA response. Cells collected at this time and cultured in vitro with histoplasmin responded with increased levels of protein production and increased IMP levels. These data suggest (1) the proliferative response of cells from sensitized animals appears to be associated with lower levels of intracellular IMP, and (2) sensitized cells stimulated in vivo with antigen appear to have characteristically higher IMP concentrations.

No description available.

No description available.

The objective of this investigation was to examine the changes in the nucleotide pools of Azotobacter vinelandii during the growth cycle. Endogenous ribonucleotides were extracted from A. vinelandii using trichloroacetic acid (TCA; 12% w/v). The 5' mono-, di- and triphosphates of adenine, guanine, uracil and cytosine were separated and quantified by anion-exchange high performance liquid chromatography. Results indicated that the adenylate energy charge of A. vinelandii paralleled the growth rate during exponential phase and that it declined rapidly as the stationary phase was reached. In addition, the amount of each nucleotide in A. vinelandii tended to increase in the logarithmic phase and decrease in the stationary phase in a similar manner to the energy charge.

Thesis advisor: Larry W. McLaughlin / Nucleic acids are responsible for maintaining the biological information responsible for the activities of all known living organisms. Research of nucleic acids provides opportunities to help understand, prevent, and cure disease in addition to allowing us to gain a greater appreciation for the wonders of nature. This work presents the synthesis and properties of several modified nucleosides. Chapter 2 presents an improved synthesis of R and S 6,5'-cyclouridine, which are rigidified nucleosides locked in the anti conformation. This work helps to understand the properties of these interesting molecules and will allow scientists to synthesize large quantities of these monomers for future research. Chapter 3 presents the synthesis of novel 6,6'-(S)-cyclo-2'-deoxyuridine. This work is highlighted by a zinc mediated cyclization to form a seven-membered ring; the first published reaction of its kind. The compound itself is a mimic of thymidine that also has the base locked in the anti position. Lastly, Chapter 4 presents work on 6' extended backbone nucleosides. These molecules have the potential to form a new type of helical structure and will help us to gain a greater understanding of the properties and dynamics that contribute to duplex stability in DNA. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

A Thesis Submitted to the Faculty of Medicine University of the Witwatersrand, Johannesburg for the Degree of Doctor of Philosophy, / The cell type exclusively dealt with in this thesis is the human blood neutrophil, which is also referred to in the text as polymorphonuclear leukocyte (PMN). The experimental work in this thesis has been accomplished using one immunological and a number of biochemical investigative techniques. The former is the Boyden technique (Boyden, 1962) for the quantitative assessment of leucocyte motility. / IT2018

Errata pasted onto front end-paper. Includes bibliographical references (leaves 82-86). Describes the preparation and characterisation of a novel series of organoplatinum(II) complexes with hydrogen-bonding functionality.

GTPases are found in all domains of life and are highly conserved. In eukaryotes, they serve as signalling molecules for many cellular processes. However, the prokaryotic GTPases play a very different role and are found to be associated with ribosome function. Among the 11 conserved GTPases, Der is the most interesting in prokaryotes. It possesses a unique structure with two GTPase domains (G-Domains) tethered by a variable length acidic linker and a carboxyl terminal KH-like domain. The exact function of Der is still under investigation and most of the data suggest that it is important for 50S ribosomal assembly or stability. In order to investigate the function of Escherichia coli Der (Ec-Der), expression plasmids for wild-type and mutated proteins were created and the proteins were successfully expressed. The expression of the mutant protein that lacked G-Domain 1 was toxic to the cells and it was found that some large ribosomal proteins were missing from the ribosomes of these cells. In addition, other macromolecular complexes such as the GroEL/GroES chaperonin appeared not to be assembled under these conditions. The activities of both wild-type and mutated proteins were also tested and found to be dependent on potassium ions (K+), which enhanced nucleotide binding. Additionally, intra-molecular control over nucleotide binding and release was also observed for Ec-Der. The in vitro selection of RNA aptamers with nanomolar affinity for Ec-Der produced aptamers that contained short variable sequences. These aptamers affected the growth of the E. coli cells and caused a change in cellular morphology that had been noted previously during Ec-Der over-expression. Ec-Der showed high affinity (nM) to both selected RNA and the unselected RNA library. The activity of Ec-Der and Era was inhibited in the presence of any sequence of RNA that has the length of greater than 16 nucleotides. RNA was also cross-linked to Ec-Der in the presence of GTP, but not GDP, suggesting that RNA was a regulator of the Ec-Der GTPase cycle. Based on these results, it is speculated that Ec-Der might be involved in more than one function. It may be acting at the level of the membrane (based on cellular morphology reported here and by Hwang and Inouye 2001) and may also take part in processes related to ribosome function. Regulation of protein activity by RNA length has not been predicted or described and this may represent a novel mean of regulation of the Era subfamily of GTPases.

The design and optimization of chemotherapeutic molecules through molecular modeling is a rapidly growing aspect of drug design. The recent increase in computer power and accompanying decrease in the cost of hardware has led to the wide use of computational chemistry in the development of new drugs. In addition, virtual screening of compound libraries also aids in the rapid development of new drugs. In that regard, there are three computational projects in addition to a project involving the synthesis of potential inhibitors that compile the research presented herein. The first project involves molecular mechanics simulations of isoadenosine analogues as potential inhibitors of S-adenosylhomocysteine hydrolase (SAHase). These analogues possess a carbocyclic moiety at the N-3 position instead of the normal N-9. The second project involves molecular mechanics simulations on flexible nucleosides as bioprobes of biologically significant enzymes. These purine analogues have nucleobases that are separated into their imidazole and pyrimidine rings connected by a single carbon-carbon bond.. This feature imparts flexibility to the base. The third project involves molecular dynamics simulations on expanded purine nucleotides in modified DNA. These compounds possess a heteroaromatic spacer ring inserted between the imidazole and pyrimidine portions of adenosine and guanosine purine rings. These analogues were and are incorporated into 10- and 20-mer DNA strands to investigate the effects on DNA. The final project focuses on the synthesis of a series of chlorinated 3-deazaadenosine analogues as potential anticancer agents. These 3-deazaadenine analogues have chlorine systematically placed in the 2-, 6- and 8-positions of adenine.