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Biomedical subjects

J C Sutherland

Publications and source records attributed to J C Sutherland.

At least 19 recordsLinked to original sources
PubMed1992

Structural analysis of an outer surface protein from the Lyme disease spirochete, Borrelia burgdorferi, using circular dichroism and fluorescence spectroscopy.

The etiological agent of Lyme disease is the tick-borne spirochete, Borrelia burgdorferi. A major antigen of B. burgdorferi is a 31 kDa lipoprotein called outer surface protein A (OspA). Recently, a truncated form of OspA (lacking 17 amino acids at the N-terminus) was cloned, expressed and purified in large quantities (Dunn, J.J., Lade, B.A. and Barbour, A.G. (1990) Protein Expression and Purification 1, 159-168). The truncated protein (OspA-257) is water-soluble, retains the ability to bind antibodies from the sera of Lyme disease patients and may prove useful in development of a vaccine against Lyme disease. We have used far UV circular dichroism (CD) and fluorescence spectroscopy to characterize the secondary structure of and to study conformational changes in OspA-257. CD spectra from 260 to 178 nm predict five classes of secondary structure: alpha-helix (11%), anti-parallel beta-sheet (32%), parallel beta-sheet (10%), beta-turns (18%) and aperiodic structures (including 'random coil') (30%). Analysis of the primary sequence of OspA yielded the most likely sites for alpha-helical regions (residues 100-107, 121-134, 253-273) and for antigenic determinants (Lys-46, Asp-82, Lys-231). CD spectra of the native protein show little change from pH 3 to 11. Thermal denaturation curves, indicate that 'salt bridges' play a role in stabilizing the native protein. Both thermal and chemical denaturations that eliminate all secondary structure as judged by CD or fluorescence are reversible. Denaturation by guanidine-HCl (gdn-HCl) appears to be a cooperative, two-state transition, as indicated by a sudden change in the CD spectrum at approximately 0.75 M gdn-HCl, and an isodichroic point at 208 nm in all CD spectra measured from 0.0-1.75 M gdn-HCl.

Amino Acid Sequence↗
PubMed1992

Quantitation of supercoiled DNA cleavage in nonradioactive DNA: application to ionizing radiation and synthetic endonuclease cleavage.

Quantitation of the conversion of nonradioactive supercoiled DNA to its open circular or linear forms on ethidium-stained electrophoretic gels has been difficult because of differential binding of ethidium to supercoiled DNA vs other forms under different conditions and the nonlinear response of photographic film. We have developed methods for adding a linear DNA as an internal fluorescence standard to "normalize" the quantity of DNA loaded into each lane of a gel. Inclusion of a linear normalizing DNA in samples before partitioning for individual supercoil cleavage reactions allows the quantitation of the resultant species, is technically easy, and does not require quantitative application of the sample to the gel. If the presence of a normalizing DNA during supercoil cleavage is undesirable, the addition of a normalizing plasmid to each sample after supercoil cleavage (but before electrophoresis) or the quantitative application of samples containing test DNA alone to the gel gives similar data, but with increased variability. We use the normalizing DNA method in cleavage by a physical agent (ionizing radiation) and in a more complex situation, by a protein-based, light-dependent synthetic endonuclease. We show how the fraction of intact supercoiled DNA can be calculated from measurement of the cleaved and normalizing species only. The method also can be used in reactions involving the depletion of one DNA species, whether supercoiled or not, such as protein-DNA interactions as detected by gel retardation assays.

DNA, Superhelical↗
PubMed1992

pH-induced conformational changes in spinach ferredoxin: steady-state and time-resolved fluorescence studies.

Steady-state and time-resolved fluorescence techniques were used to monitor pH-induced conformational changes in spinach ferredoxin. An increase was seen in the wave-length maximum of tryptophan-73 (Trp-73) emission, from 325 nm below pH 6.0 to 342 nm above pH 7.0, indicating significantly diminished hydrophobicity, at pH 7.0, in the environment of the indole ring. Raising the solution pH from 6.0 to 7.6 also decreased the binding of the detergent Brij-96, showing that the ferredoxin molecule as a whole became more hydrophilic at higher pH. Nonionic (acrylamide) and ionic (I- and Cs+) quenchers were used to probe the tryptophan environment. Trp-73 is partially shielded from I-, presumably by negatively charged residues, as predicted from the amino acid sequence and three-dimensional structure of plant-type ferredoxins. Ionic strength and pH effects on tryptophan fluorescence lifetimes follow a pattern common to single-tryptophan proteins: the emission decays can be fit to a biexponential model in which the lifetime of the excited state increases with increasing pH. The indication of a pH-induced conformational change in the range pH 6.0 to 7.6 is discussed with reference to the physiological association of ferredoxin with ferredoxin:NADP+ oxidoreductase and the rise in chloroplast stromal pH in the light.

Detergents↗
PubMed1992

Circular dichroism user facility at the National Synchrotron Light Source: estimation of protein secondary structure.

The ultraviolet circular dichroism of a protein can be used to estimate the net fraction of its amino acids in different classes of secondary structure. Recent advances in the accuracy of such calculations have resulted from improved computational techniques, as well as extension of the spectral region analyzed to wavelengths less than 180 nm, a wavelength range beyond the limit of most laboratory-based circular dichroism spectrometers. We describe a spectrometer that uses UV radiation from the National Synchrotron Light Source at the Brookhaven National Laboratory to record circular dichroism spectra of proteins (and other biologically important molecules) in aqueous solution over the optimum wavelength range required for calculation of secondary structures. This instrument is available for use by scientists from academic, commercial and research institutions.

Animals↗
PubMed1992

Quantitation of pyrimidine dimers in DNA from UVB-irradiated alfalfa (Medicago sativa L.) seedlings.

Depletion of stratospheric ozone will increase the solar ultraviolet radiation in the range from 290-320 nm (UVB) that reaches the surface of the earth, placing an increased UV burden on exposed organisms. One consequence of increased UVB may be decreased productivity of crop plants. A principal lesion caused by UV in DNA is the cyclobutyl pyrimidine dimer. We have adapted a method for measuring these dimers in nanogram quantities of non-radioactive DNA for use in UV-irradiated plants. We find that biologically relevant doses of broad band UVB radiation induce easily detectable frequencies of pyrimidine dimers in the DNA of irradiated alfalfa sprout leaves and that the dose response for dimer formation is linear up to doses of at least 690 J m-2. We also find easily measurable frequencies of dimers in the leaves of seedlings grown in glass filtered sunlight but not exposed to additional UVB, suggesting that significant numbers of dimers are formed in plants exposed to normal sunlight.

DNA↗
PubMed1979

Synthesis and pharmacology of a prohormone angiotensin antagonist.

A prohormone angiotensin antagonist, Sarcosyl1-Alanyl8-angiotensin I (Sar1-Ala8-A-I) was synthesized and its pharmacological properties were evaluated in three biological systems. It was found to be a good inhibitor in vivo in the rat blood pressure assay, somewhat less active in guinea pig ileum and a relatively weak antagonist in rat uterus. In vivo the inhibitory effect was greatly attenuated by the presence of the converting enzyme inhibitor BPP5alpha.

Angiotensin I↗
PubMed1978

Magnetic circular dichroism of netropsin and natural circular dichroism of the netropsin-DNA complex.

We report the first measurement of the magnetic circular dichroism (MCD) of the basic polypeptide antibiotic netropsin (Nt). The MCD shows that the longest wavelength absorption band of Nt is the sum of more than one component and permits a radically new interpretation of the circular dichroism of the complex which Nt forms with DNA. We conclude that Nt has no major effect on the CD and thus the helical structure of the bases of the DNA to which it is bound. Thus the ability of Nt to inhibit the function of DNA polymerase, RNA polymerase, and the photoreactivating enzyme must be mediated by factors other than a distortion of the helical structure of the bases.

Animals↗
PubMed1976

Photoreactivation of pyrimidine dimers in the DNA of normal and xeroderma pigmentosum cells.

Photoproducts formed in the DNA of human cells irradiated with ultraviolet light (uv) were identified as cyclobuytl pyrimidine dimers by their chromatographic mobility, reversibility to monomers upon short wavelength uv irradiation, and comparison of the kinetics of this monomerization with that of authentic cis-syn thymine-thymine dimers prepared by irradiation of thymine in ice. The level of cellular photoreactivation of these dimers reflects the level of photoreactivating enzyme measured in cell extracts. Action spectra for cellular dimer photoreactivation in the xeroderma pigmentosum line XP12BE agree in range (300 nm to at least 577 nm) and maximum (near 400 nm) with that for photoreactivation by purified human photoreactivating enzyme. Normal human cells can also photoreactivate dimers in their DNA. The action spectrum for the cellular monomerization of dimers is similar to that for photoreactivation by the photoreactivating enzyme in extracts of normal human fibroblasts.

Binding Sites↗
PubMed1976

Fungal infection of muscle in acute leukemia.

A patient with acute lymphoblastic leukemia and granulocytopenia developed fever and diffuse muscle pain and weakness while under therapy. Blood cultures grew Candida Krusei and autopsy showed diffuse muscle fungal infestation.

Adult↗
PubMed1976

A comparison of cyclophosphamide, vincristine, and prednisone (COP) with nitrogen mustard, vincristine, procarbazine, and prednisone (MOPP) in the treatment of nodular, poorly differentiated, lymphocytic lymphoma.

This study was designed to test the efficacy and toxicity of COP (cyclophosphamide, vincristine, and prednisone) and MOPP (nitrogen mustard, vincristine, prednisone, and procarbazine) in 13 previously untreated patients with disseminated, nodular, poorly differentiated, lymphocytic lymphoma, and to test for patient cross-resistance to the regimens. Complete remission was initially achieved in six of eight patients on COP and three of five on MOPP. Three patients were crossed over to the alternative induction regimen because of progressive disease after an initial partial response; one was crossed over because of toxicity. On crossover, four patients achieved complete remission, two on either regimen. Durations of unmaintained complete remission range from 6-46+ months, with 8/13 still in their first complete remission. Only one patient has died, while in remission, from progressive Kaposi's sarcoma; one was lost to follow-up while in complete remission at 44 months; the others (85%) remain alive 33-54 months from the initiation of chemotherapy. MOPP was significantly more toxic with respect to thrombocytopenia, duration of myelosuppression, and cumulation of toxicity. Because of its more acceptable toxicity, COP is recommended as initial therapy for patients with nodular, poorly differentiated, lymphocytic lymphoma. MOPP or another regimen of non-crossresistant combination chemotherapy would be more appropriate for primary treatment failures.

Adult↗
PubMed1976

Clinically significant cardiac infiltration in acute leukemia, lymphocytic lymphoma, and plasma cell myeloma.

Cardiac infiltration by hematologic neoplasms leading to clinically significant cardiovascular disease is rare. Three such cases are described in this report, and it is suggested that rare manifestations of hematologic neoplasms may become more common in the future since these diseases are more amenable to therapy than heretofore. Cardiac involvement with hematologic neoplasms is of more than academic interest since this complication is likely to respond to radiotherapy.

Adult↗
PubMed1976

Torulopsis glabrata infections in patients with cancer. Increasing incidence and relationship to colonization.

Torulopsis glabrata, an opportunistic pathogen, was found to be the etiologic agent of infections in patients with cancer. This observation prompted a retrospective review to determine the incidence and underlying factors of infection with this organism. This study showed that T. glabrata had been cultured frequently and that the incidence of infection has been progressively increasing. During a 48-month period (9/70-8/74), T. glabrata was cultured from routine surveillance and diagnostic cultures in 167 patients, 27 of whom had either presumed or documented infection. Review of clinical and necropsy records implicated T. glabrata infections as a contributory factor in the death of 14 of the 27 patients. Etiologic diagnosis of infection was established antemortem in only three patients. Pulmonary isolation in pure growth occurred in 24 of the 27 patients. Seventeen of 19 infected patients who had prior routine surveillance cultures were colonized prior to infection. Infection occurred in the setting of far advanced malignancy or leukopenia and followed the use of systemic, broad spectrum antibiotics. T. glabrata is a frequently overlooked opportunistic pathogen which, in the proper setting, appears to be producing increasing numbers of infections.

Bone Neoplasms↗
PubMed1976

Fluorescence-detected magnetic circular dichroism of fluorescent and nonfluorescent molecules.

We have modified a spectrometer for the measurement of fluorescence-detected magnetic (and natural) circular dichroism (FDMCD). The instrument can be operated either in a direct mode in which the average and polarization-induced differential fluorescent intensities are recorded separately or in a mode which records their ratio. We have measured the FDMCD of tryptophan, which is itself fluorescent. With the aid of an added fluorescent molecule we also measured the FDMCD of Fe(III) cytochrome c, which is nonfluorescent. In both cases, the FDMCD agreed with the conventional transmission-detected magnetic circular dichroism within experimental uncertainty. The FDMCD of both fluorescent and nonfluorescent molecules is potentially a useful technique for investigating optically dense materials and biological molecules in their native environments and systems in which there is inter- or intramolecular energy transfer.

Circular Dichroism↗