No description available.

No description available.

The importance of tryptophan in the combining sites of anti-DNP antibodies is evaluated from a series of model studies. The thermodynamic parameters characterizing the formation of a DNP/tryptophan complex are determined. The contribution of this interaction to the affinity and specificity of anti-DNP antibodies is discussed. The accuracy of antibody combining site structures generated by model-building is examined, using available crystallographic data. The average error of alpha-carbon atom positions is estimated to be 1-2 Å. The binding of nitrophenyl compounds to the V_L dimer of the DNP-binding mouse myeloma protein 315 is investigated by ¹H n.m.r. It is concluded that any corformational changes are small, and that the physical basis for the DNP-binding specificity of the V_L dimer is the conservation of structural features which are important in determining the specificity of the intact protein 315. A model of the combining site of the V_L dimer is described. The proposed site is a large cavity bounded by the aromatic side-chains of the Trp-93_L and Tyr-34_L residues. The structure is able to explain the large upfield chemical shift changes of the ligand resonances observed on binding. The kinetic parameters and structural extent of the pH-dependent conformational change of the V_L dimer are investigated by fluorescence and ¹H n.m.r. The transition does not obey a reversible one-step mechanism, and is limited in extent. The involvement of two tyrosine residues in the hypervariable regions of protein 315 is investigated by specific nitration. Nitration of Tyr-34_L has no effect on the affinity of protein 315 or of the V_L dimer for several ligands. It is concluded that no hydrogen bond is formed between the phenolic group of Tyr-34_L and the 2-nitro group of the ligand. From measurements of the perturbation of the visible absorption spectrum of protein 315 nitrated at Tyr-33_H, it is concluded that this residue is in proximity to the side-chains, but not the nitrophenyl rings, of bound ligands. Several aspects of the interaction of a homogeneous mouse anti-DNP antibody, protein A3, with nitrophenyl and similar ligands are described. The findings are discussed in relation to the heterogeneity and cross-reactivity of antisera.

No description available.

The tryptophan productivity of the genetically-manipulated strain JP4153 was increased 2.5-fold by introducing pMU78, a medium copy-number plasmid carrying a feedback-resistant trp operon. JP4153(pMU78) produced 23.5 g/l of tryptophan at a rate of 0.7 g/l/h when grown at 37 degrees C in a defined glucose and ammonium salts medium in a bench-scale fermentor. / During prolonged cultivation in the presence of antibiotic, the recombinant strain generated faster-growing, production-defective variants, which harboure mutated derivatives of pMU78. Insertion sequences were responsible for the two predominant types of mutation. The plasmid element ISI02 mediated deletions extending into the promoter-proximal region of the plasmid-borne trp operon. ISI0-Right, a chromosomal element, inserted into the promoter/trpE region of the plasmid. Three methods were employed to increase the structural stability of JP4153(pMU78) during the course of the production process. First, the growth of seed cultures was carried out at 30 degrees C, the permissive temperature for the trpS378 mutation carried by the host strain. Second, the seed culture medium was modified by the addition of yeast extract, which appeared to reduce the selective disadvantage conferred by the plasmid. Third, ISI02was deleted from pMU78 to create pMU88. (For complete abstract open document)

Thesis (Ph. D.)--University of Melbourne, 1993. / Typescript (photocopy). Includes bibliographical references (leaves 229-252).

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xxvi, 324 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 186-198).

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xv, 327 p.; also includes graphics (some col.) Includes bibliographical references (p. 315-327). Available online via OhioLINK's ETD Center

Thesis (M. S.)--Wake Forest University Graduate School of Arts and Sciences, Molecular Genetics Program, May 2003. / Kent E. Vrana, advisor. Includes curriculum vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Abstracted in Dissertation abstracts, v. 20 (1959) no. 3, p. 1009. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 138-146).