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T J Thamann

Publications and source records attributed to T J Thamann.

10 recordsLinked to original sources
PubMed1999

A vibrational spectroscopic assignment of the disulfide bridges in recombinant bovine growth hormone and growth hormone analogs.

Disulfide stretching vibrations for bovine growth hormone (bGH) occur in a vibrational envelope centered at 540 cm-1 which spans 480-580 cm-1. A multitude of vibrational bands present in this envelope, that are not related to disulfide stretching, emphasize the need for model compounds when assigning S-S stretching modes. Raman spectroscopic data for bGH analogs, in which one or both of the two disulfide bridges have been selectively cleaved, have been used to characterize the S-S stretching envelope for the two cystine links in bGH. The Raman data for the r-bGH analogs indicate that the number of disulfide bonds present in r-bGH is determined, not by the observance of the presence or absence of a single spectral peak, but by the relative intensity of vibrational envelope from 520-560 cm-1. Cleavage of disulfide bridges in bGH results in a general decrease in vibrational spectral intensity in the 520-560 cm-1 range. This decrease in intensity is proportional to the number of cystine links severed.

Animals↗
PubMed1999

Vibrational spectroscopic studies of solid recombinant bovine growth hormone and related growth hormone analogs.

Infrared and Raman spectra have been obtained for lyophilized recombinant bovine growth hormone (r-bGH), partially reduced, and completely reduced r-bGH, plus a tryptic digest fragment of r-bGH. Amide I and II data indicate r-bGH to have substantial helical character. Partially reduced r-bGH, in which the carboxyl terminal disulfide bridge (residues 181, 189) has been cleaved, has slightly less helical content than r-bGH. The spectral data indicate that breaking the carboxyl terminal cystine link produces only localized structural alterations. The additional cleavage of the second disulfide bridge (residues 53,164) leads to a further decrease in helix content, accompanied by increases in beta-sheet and disordered structures. A tryptic digest r-bGH fragment (residues 96-133), which contains a small amount of biological activity (approximately 10%), has predominantly helical structure.

Amino Acid Sequence↗
PubMed1999

Tablet dissolution affected by a moisture mediated solid-state interaction between drug and disintegrant.

PURPOSE: To investigate the cause for decrease in delavirdine mesylate 200 mg tablet dissolution upon exposure to high humidity. METHODS: Dissolution testing was performed using the USP 2 (paddle) apparatus. Water in tablets was measured by Karl Fischer titration. 13C CP/MAS NMR was used to identify and quantify delavirdine form changes in tablets. FT-IR spectroscopy was used to monitor delavirdine form change in tablets and component mixes, and to investigate a solid state reaction with the disintegrant. RESULTS: Dissolution extent of delavirdine mesylate 200 mg tablets was substantially decreased after exposure to high humidity. This effect is related to the amount of water present in the tablet matrix. 13C CP/ MAS NMR detected about 30% conversion from the mesylate salt of delavirdine to its free base form in the tablet matrix. FT-IR spectroscopy demonstrated that a solid state reaction occurs between the freed methanesulfonic acid and the carboxyl sites on the croscarmellose sodium disintegrant. CONCLUSIONS: Water is thought to act as both a reaction medium and a plasticizer for croscarmellose sodium, facilitating protonation of the carboxyl sites on the disintegrant. This reaction has the potential to occur for any acid salt of a free base. The limiting solubility of delavirdine free base formed in the tablets accounts for much of the decrease in the extent of dissolution. A change in inter-particle bonding can explain the reduction in tablet deaggregation during dissolution.

Carboxymethylcellulose Sodium↗
PubMed1998

Raman spectroscopic studies of a dimeric form of recombinant bovine growth hormone.

Lyophilized dimeric recombinant bovine growth hormone (r-bGH) produced through incubation of r-bGH at 37 degrees C and 96% relative humidity for 8 days was examined by Raman spectroscopy. The secondary structure of the dimeric material is comparable to that of nonincubated r-bGH, due to the high similarity of the amide I, III, and V vibrational envelopes of the two samples. The dimeric material exhibits disulfide stretching that is indicative of the presence of only one disulfide bond (Cys53-Cys164). No sulfhydryl S-H stretching vibrations are observed, suggesting that cysteines from the cleaved disulfide bridge (Cys181-Cys189) are bound to nonsulfur atoms. Either high humidity (96%) or mild heat (37 degrees C) alone will cleave only one disulfide bond, but the final products are different. Incubation at ambient temperature and high humidity leads to a significant secondary structural change, while mild heat at very low humidity does not alter r-bGH secondary structure. Spectral data for incubations solely in mild heat are consistent with r-bGH structures that have lost the small loop (Cys181-Cys189) disulfide bridge, while incubations under only high humidity conditions are compatible with what would be expected if the large loop (Cys53-Cys164) cystine link was broken. Mild heat and high humidity are both present in dimer formation, yet only the small loop bridge is severed. The data suggest that heat may be the primary factor in determining which cystine link is broken. More severe heating (75 degrees C) cleaves both cystines and alters both secondary and tertiary structure.

Animals↗
PubMed1997

Spectroscopic studies on the conformational transitions of a bovine growth hormone releasing factor analog.

The secondary structure of the bovine growth hormone releasing factor analog, [Ile2, Ser8.28, Ala15, Leu27, Hse30] bGRF(1-30)-NH-Ethyl, acetate salt (U-90699F) was studied in solution by Fourier transform infrared and Raman spectroscopies. Spectroscopic studies revealed that concentrated aqueous solutions of U-90699F (100 mg ml-1) undergo a secondary structure transition from disordered coil/alpha-helix to intermolecular beta-sheet. Disordered coil and alpha-helical structure were grouped together in the infrared and Raman studies since the amide I vibrations are close in frequency and overlap in assignments was possible. Before the conformational transition, the facile exchange of the peptide's amide hydrogens for deuterium indicated that the majority of amide hydrogens were readily accessible to solvent. The kinetics of the conformational transition coincided with an increase in solution viscosity and turbidity. An initiation phase preceded the conformational transition during which only minor spectral changes were observed by infrared spectroscopy. The initiation phase and reaction kinetics were consistent with a highly cooperative nucleation ultimately leading to a network of intermolecular beta-sheet structure and gel formation. Increased temperature accelerated the conformational transition. The conformational transition was thermally irreversible but the beta-sheet structure of aggregated or gelled peptide could be disrupted by dilution and agitation.

Deuterium↗
PubMed1989

Investigations of protein structure with optical spectroscopy: bovine growth hormone.

Optical spectroscopy provides a wealth of information about protein structure that is difficult to obtain from other methods. Investigations of changes in primary, secondary, tertiary, and quaternary structure are particularly well-suited for optical techniques such as UV absorption, circular dichroism, fluorescence, Raman and infrared spectroscopy, as well as light scattering methods. Each method has unique areas of applicability and contributes to structure determination in a different manner. The application of these methods is demonstrated with examples of studies performed on bovine growth hormone. Some of these include: determination of solution-state structure, monitoring differences between solution- and solid-state structure, determination of molecular size distribution, and investigations of protein folding mechanisms. It is demonstrated that by judicious choice of methods, a reasonably complete description of protein structure can be obtained.

Animals↗
PubMed1982

Normal coordinate analysis of the copper center of azurin and the assignment of its resonance Raman spectrum.

Normal coordinate analysis that utilizes a general valence force field and the Wilson FG matrix method has been applied to several structural models representing the active site of the blue copper protein, azurin. The models included tetrahedral and square planar CuN2SS', trigonal CuN2S, and trigonal bipyramidal CuN2SS'O structures in which the Ns are imidazole nitrogens of histidines, S is the thiolate sulfur of cysteine, S' is the thioether sulfur of methionine, and O is a peptide carbonyl oxygen. For constant Cu--ligand bond lengths and initial force constants, the force field was refined against the most intense of the observed frequencies (424, 404, 369, and 261 cm-1) in the resonance Raman spectrum of Pseudomonas aeruginosa azurin. The most satisfactory fit between observed and calculated frequencies occurs for tetrahedral and trigonal structures. The calculations provide detailed assignments for the resonance Raman spectrum of azurin and reveal considerable mixing of Cu--S(Cys) and Cu--N(His) vibrational modes. The trigonal model is favored because it is shown that the approximately equal to 260-cm-1 vibration is an invariant feature in the resonance Raman spectra of blue copper proteins, even those lacking a methionine in the vicinity of the copper atom. The present analysis ascribes the high frequencies of the Cu--ligand stretching modes and the resonance enhancement to the coupled nature of their vibrations and the Franck-Condon overlaps with predominant (Cys)S leads to Cu(II) charge transfer bands in the visible region.

Azurin↗
PubMed1981

The high salt form of poly(dG-dC).poly(dG-dC) is left-handed Z-DNA: Raman spectra of crystals and solutions.

The laser-Raman spectra of crystalline d(CpGpCpGpCpG) and of aqueous poly(dG-dC).poly(dG-dC) in high salt (4M NaCl) and low salt (0.1M NaCl) solutions have been measured and compared. The spectra of the crystal and the high-salt solution show a striking congruence, which indicates clearly that the high-salt form of the aqueous polymer has the left-handed Z-DNA structure of the crystalline oligomer. These two spectra differ substantially from that of the low-salt form of the polymer, which has been found previously to have spectral characteristics of the B-form of DNA. The high salt spectrum shows a unique line due to guanine residues at 625 cm-1 which should be useful for qualitative and possibly quantitative assessment of the amount of Z-structure present in a sample of DNA.

Crystallization↗