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Articles 1 - 8 of 8

Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Cooperative Binding By A Self-Assembled Receptor: Metal In A Structural And Functional Role , Jin-Ho Lee Jan 1994

Cooperative Binding By A Self-Assembled Receptor: Metal In A Structural And Functional Role , Jin-Ho Lee

Retrospective Theses and Dissertations

Metal complexes of the amino acid, 4,4[superscript]'-phosphinylidine bis phenylalanine (PBP*, 1), self-assemble to produce a macrocyclic receptor (Co[subscript]2PBP[subscript]2, 2) with a hydrophobic cavity capable of binding aromatic compounds from water. Here we demonstrate that the metal can play a structural and a functional role: the receptor binds substrates bearing both aromatic and polar functional groups ditopically, using the hydrophobic pocket as well as the metal itself. The doubly anionic Co[superscript]2+ macrocyclic complex binds neutral aromatic guests more tightly than it does most anionic guests, as would be expected. However, carboxylates tethered ...


Photophysics Of A Novel Optical Probe-7-Azatryptophan And Its Application In The Study Of Protein-Protein Interactions , Yu Chen Jan 1994

Photophysics Of A Novel Optical Probe-7-Azatryptophan And Its Application In The Study Of Protein-Protein Interactions , Yu Chen

Retrospective Theses and Dissertations

Time-resolved and steady-state fluorescence study of the biological optical probe, 7-azatryptophan, its chromophoric moiety 7-azaindole are performed in order to explain the observation that the fluorescence spectrum of 7-azaindole (7-azatryptophan) apparently consists of one band in water ([lambda][subscript]sp\max em = 386nm) whereas in alcohols the spectrum is bimodal (eg. for methanol, [lambda][subscript]sp\max em = 374, 505nm). Careful measurements of the fluorescence decay as a function of emission wavelength indicate a small amplitude of an ~70 ps decaying component at the bluer wavelength and a rising component of the same duration at the redder wavelengths. The small ...


Structure And Function Of Unmodified E. Coli Valine-Trna , Dongxian Yue Jan 1994

Structure And Function Of Unmodified E. Coli Valine-Trna , Dongxian Yue

Retrospective Theses and Dissertations

The effects of nucleoside modifications on E. coli tRNA[superscript]Val structure have been probed by imino [superscript]1H NMR. The NMR data shows that the structure of in vitro transcribed (unmodified) and native (modified) tRNA[superscript] Val are very similar in 15 mM Mg[superscript]2+. Temperature dependence of the spectra reveals that nucleoside modifications stabilize tertiary interactions between T and D loops. On removal of Mg[superscript]2+, unmodified tRNA[superscript] Val undergoes remarkable structural changes which are not observed in native tRNA[superscript] Val. There is near total disruption of the D stem and of tertiary interactions ...


Biochemical Characterization Of Plant Biotin-Containing Enzymes , Tomás Alberto Diez Jan 1994

Biochemical Characterization Of Plant Biotin-Containing Enzymes , Tomás Alberto Diez

Retrospective Theses and Dissertations

3-Methylcrotonyl-CoA carboxylase has been purified and characterized from maize leaves. The enzyme is composed of two subunits, a biotin-containing polypeptide of 80 kDa, and a nonbiotin-containing polypeptide of 58 kDa. The native molecular weight of the holoenzyme is estimated at 853,000. The enzyme probably has an [alpha][subscript]6[beta][subscript]6 configuration. The kinetic constants for the substrates of 3-methylcrotonyl-CoA and its pH optimum were determined. The enzyme is allosterically activated by Mg[superscript]2+ and nonessentially activated by monovalent cations. The enzyme is strongly inhibited by acetoacetyl-CoA and by arginyl and sulfhydryl modifying reagents;The effect of ...


Sensitive Detection And Study Of Catalytic Species For Bimolecular Reactions , James William Lane Jan 1994

Sensitive Detection And Study Of Catalytic Species For Bimolecular Reactions , James William Lane

Retrospective Theses and Dissertations

In our lab, we have developed a sensitive and convenient assay for the detection of catalysts for bimolecular reactions. We have shown that catalysis of peptide synthesis by as little as 2.5 fmol (2.5 x 10[superscript]-15 mol) of a damaged enzyme can be detected using our assay. An interesting feature of our procedure is that it requires no complex apparatus, and may be carried out in parallel on many samples. We have used the assay to detect the presence of an enzyme catalyst, however the basic assay design is very versatile and may also be used ...


Dethiolation Of Protein Mixed-Disulfides , Che-Hun Jung Jan 1994

Dethiolation Of Protein Mixed-Disulfides , Che-Hun Jung

Retrospective Theses and Dissertations

The dithiol proteins, glutaredoxin, thioredoxin, and protein disulfide isomerase, were examined as dethiolases (i.e., reductases for protein mixed-disulfides) by studying the specificity and reactivity for an S-glutathiolated protein mixture. The 35S-glutathiolated protein mixture was prepared from 35S-labeled rat hepatocytes by diamide treatment. Dethiolation of individual 35S-labeled proteins was analyzed by combining SDS-PAGE and autoradiography. The dithiol proteins greatly enhanced dethiolation rates and could completely dethiolate all of the S-glutathiolated proteins. The dethiolation rate for individual proteins by each dithiol protein was compared and glutaredoxin was the most effective for every S-glutathiolated hepatocyte protein. When testing the reduction of insulin ...


G-Wires: The Growth And Characterization Of A G4-Dna Nanostructure , Thomas Cosgrove Marsh Jan 1994

G-Wires: The Growth And Characterization Of A G4-Dna Nanostructure , Thomas Cosgrove Marsh

Retrospective Theses and Dissertations

Guanine-rich sequences are vital components in the genomes of many organisms. For example, G-rich sequences are found in telomeres, fragile X locus, promoters, IgG switch regions, recombinational hot spots and the HIV RNA dimerization domain. The functions of these G-rich sequences rely in part on guanine self-recognition. G-rich sequences can adopt a quadruple helical conformation in the presence of specific monovalent and divalent metal cations which are also required for maintaining the quadruplex stability. The structural basis of the quadruplex is a cyclic Hoogsteen hydrogen bonded guanine tetrad known as the G-quartet. Sequences capable of forming G-quartets are classified as ...


Expression, Purification, Characterization, And Site-Directed Mutagenesis Of Phosphorylase Kinase [Upsilon] Subunit , Chi-Ying F. Huang Jan 1994

Expression, Purification, Characterization, And Site-Directed Mutagenesis Of Phosphorylase Kinase [Upsilon] Subunit , Chi-Ying F. Huang

Retrospective Theses and Dissertations

The overall aim was to elucidate the substrate specificity and regulatory properties of the catalytic subunit of phosphorylase kinase (PhK) to better understand how this enzyme works. I have expressed the PhK [gamma] subunit (full-length and seven truncated forms) in E. coli. One of the truncated forms of [gamma], [gamma][subscript]1-300 has a 2-fold higher specific activity than the full-length [gamma], suggesting that an autoinhibitory domain(s) is located at the C-terminus of [gamma], [gamma][subscript]301-386. The truncated [gamma][subscript]1-300 purified to homogeneity has several properties similar to full-length [gamma], including its substrate specificity and metal ion ...