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Poly(dI-dC).poly(dI-dC) was studied using vibrational circular dichroism and IR spectroscopy in both the base deformation C = O and symmetric PO2- stretching regions. VCD spectra of this duplex under low salt conditions are consistent with its having a B-form structure. Addition of 5 M NaCl leads to relatively uniform VCD intensity loss which is consistent with loss of helical structure rather than formation of an intermediate state between the B and Z forms. This duplex polymer under high salt conditions with added NiCl2 shows aggregation effects, but its IR and VCD spectra have characteristic features of the Z-form DNA conformation. The cooperative change of backbone and base pair structure upon thermal denaturation is indicated by the simultaneous collapse of the VCD at 65 degrees C in both the PO2- and C = O stretching regions. This study further demonstrates that the VCD bandshape of a specific localized nucleic acid vibrational transition can be a useful indicator of the helical handedness. The empirical conformational interpretations are supported by simulated VCD spectra, which are in excellent agreement with the experimental results, based on dipole coupling calculations. 相似文献
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T Miyase M Sano H Nakai M Muraoka M Nakazawa M Suzuki K Yoshino Y Nishihara J Tanai 《Phytochemistry》1999,52(2):303-310
The stems of Lespedeza homoloba yielded eight new and three known phenolic compounds. Their structures have been elucidated on the basis of their spectral data. These compounds had strong antioxidative activity against lipid peroxidation in the rat brain homogenate test. 3,9-Dihydroxypterocarp-6a-en and lespedezol A2 showed significant antiallergic activity in allergic (type I) mice. 相似文献
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The solution characterization of poly(Lys-Ala-Glu) is described. This polytripeptide is zwitterionic at neutral pH and is shown to take on a conformation which is dictated by the state of ionization, molecular weight, temperature, and solvent. The polypeptide is almost entirely α-helical at low pH and temperature for polymers of greater than 25,000 molecular weight. Melting profiles for these conditions show tm ~ 20°C. Analysis of circular dichroism curves shows the α-helical content to vary in a linear manner with molecular weight in the range 3000–30,000. At neutral pH the charged polypeptide is essentially random, but substantial α-helix could be induced by addition of methanol or trifluoroethanol. At temperatures where the sequential polypeptide is a random coil, addition of trifluoroethanol produces a polymer which is mostly α-helical but also contains an appreciable ammount of β-structure. The infrared spectrum of a low-molecular-weight fraction assumed to be cyclo(Lys-Ala-Glu)2 was tentatively assigned a β-pleated sheet structure. A comparison of this polytripeptide in various ionization states with other polytripeptides containing L -alanine and L -glutamate or L -lysine shows the α-helix directing properties for the (uncharged) residues to lie in the order Ala > Glu > Lys. 相似文献
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Protonated polynucleotides structures - 23. The acid-base hysteresis of poly(dG).poly(dC). 总被引:4,自引:4,他引:0
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The large hysteresis observed during the acid-base titration of poly(dG). poly (dC) was studied by CD and potentiometric scanning curves. Intermediate scanning loops as well as the equilibrium and metastable branches of the hysteresis loop have been determined. The potentiometric titrations showed, however, that the various complexes were not discrete entities, but were linked in "polycomplexes" as had been already suggested. This prevented a thermodynamic study of the system. The acid-base titration was further investigated as a function of ionic strength and temperature. The pK's showed considerably lower ionic strength dependence than observed for polyribonucleotide complexes. The thermal transitions permitted to establish the relative stabilities of the various complexes between pH 2.5 and pH 12.0. 相似文献
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We present an unusual case of massive dermal cylindroma (turban tumor), occupying the entire scalpand forehead. It was treated by a total scalping procedure and skin grafting in two stages. Additional tumors of the face, neck, chest, shoulders, and back were excised and closed. The nose was treated by shoving and dermabrasion, similar to a rhinophyma. The lip was treated by dermabrasion. There has been no evidence of recurrence in the scalp which was treated by excision and grafting. There is now a papular quality of the skin over the nose and on the uppler lip, indicating that regrowth may occur. The etiology, pathology, and a review of the literature are presented. 相似文献
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S R Burzynski Z Stolzmann B Szopa E Stolzmann O P Kaltenberg 《Physiological chemistry and physics》1977,9(6):485-500
Twenty-one patients with advanced cancer or leukemia were treated with antineoplaston A and followed for up to nine months. Dosage by intravenous, intramuscular, subcutaneous, rectal, intrapleural, intravesical and/or topical administration ranged from 0.6 to 33 U/m2/24 h. Treatment was well tolerated, although side effects included fever of short duration and elevation of platelet and white blood count. In 18 cases some degree of clinical improvement was observed. Complete remission occurred in 4 cases. More than 50% remission occurred in 4 other cases which, along with another 6 cases, are continuing the treatment with high doses of antineoplaston A and show a continuing regression of the tumors although not yet achieving the criteria for complete remission; 2 of these 6 cases seem unlikely to achieve remission. Two patients temporarily discontinued treatment. During treatment, 5 patients expired; in 2 of them, however, was seen significant regression of the neoplastic process. The deaths were not due to cancer or to any toxicity incurred by the treatment. 相似文献
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