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1.
Sudha Rao Gopalakrishna Kamath Gururaj Maralihalli Anil S. Bhagwat 《Photosynthesis research》1987,12(2):155-164
The -aminolevulinic acid dehydratase activity was irreversibly inactivated by irradiation of the enzyme in presence of flavin mononucleotide. The loss of enzyme activity was dependent on time of irradiation, concentration of FMN and intensity of irradiance. It required oxygen and was markedly enhanced in heavy water. The presence of levulinic acid (a competitive inhibitor of -ALAD) during irradiation prevented the inactivation considerably indicating photooxidative damage at or near the active site. Superoxide dismutase, sodium benzoate and sodium formate offered no protection, but singlet oxygen quenchers like azide and tryptophan were effective. NADH, electron donor to excited flavins, also prevented the loss of enzyme activity. These results indicate that singlet oxygen produced by light absorption of FMN was responsible for the photooxidative inhibition of the enzyme.Abbreviations ALAD
-aminolevulinic acid dehydratase
- FMN
flavin mononucleotide
- O2
-
superoxide
- H2O2
hydrogen peroxide
- 102
singlet oxygen
- LA
levulinic acid
- PBG
porphobilinogen
- BSA
bovine serum albumin
- BME
2-mercaptoethanol
- SOD
superoxide dismutase
- pHMB
para-hydroxymercuribenzoate
- DTT
dithiothreitol
- FAD
flavin adenine dinucleotide
- NADH
nicotinamide adenine dinucleotide 相似文献
2.
The biosynthesis of nucleic acids and proteins was studied in rat uterus by following the incorporation of [3H]-thymidine, [3H]-uridineand[14C]-leucinein control and pregnant rats in the presence and absence of two anti-implantation drugs. One of the drugs, 78/224
caused a significant increase in incorporation whereas the other drug, Centchroman, caused an inhibition in incorporation
of all the three precursors. The implications of these changes in the light of estrogenicity, agonist and antagonist actions
of anti-estrogens have been analysed. The importance of homeostatic mechanisms involved in nucleic acids and proteins for
the maintenance of constant internal milieu for blastocyst attachment has been discussed. 相似文献
3.
Magnetic resonance studies reveal a marked difference between the binding of α-tocopherol and that of the corresponding acetate (vitamin E acetate) with dipalmitoylphosphatidylcholine (DPPC) vesicles. This is reflected in differences in the phase-transition curves of the DPPC vesicles incorporated with the two compounds, as well as in the 13C relaxation times and line widths. A model for the incorporation of these molecules in lipid bilayers has been suggested. α-Tocopherol binds strongly with the lipids, possibly through a hydrogen bond formation between the hydroxyl group of the former and one of the oxygen atoms of the latter. The possibility of such a hydrogen bond formation is excluded in vitamin E acetate, which binds loosely through the normal hydrophobic interaction. The model for lipid-vitamin interaction explains the in vitro decomposition of H2O2 by α-tocopherol. α-Tocopherol in conjuction with H2O2 can also act as a free-radical scavenger in the lipid phase. The incorporation of α-tocopherol and vitamin E acetate in DPPC vesicles enhances the permeability of lipid bilayers for small molecules such as sodium ascorbate. 相似文献
4.
D. Sudha Sundari K. Saradadevi A. S. Raghavendra 《Journal of plant biochemistry and biotechnology.》1994,3(2):137-140
When spinach chloroplast membranes were exposed to osmotic stress in vitro, by incubation in 1.0 M sorbitol + 10 mM MgCl2 their oxygen evolving system was suppressed. The possible reasons for such inactivation of PS II mediated oxygen evolution were examined. There were conformational changes in the chloroplast membranes, as indicated by their absorption spectra. The pattern of sensitivity to DCMU was not altered. The sensitivity of PS II to water stress remained, even after a pre-wash treatment with NaCI (which removed 18 and 24 kD proteins) but not when the thylakoids were pretreated with NH20H or CaCl2 (removed manganese and 33 kD). The manganese content of thylakoid membranes was markedly reduced under osmotic stress in presence of magnesium. We suggest that exposure of chloroplasts to 1.0 M sorbitol in presence of Mg2+ released manganese from thylakoid membranes, thereby leading to a suppression in oxygen evolution. 相似文献
5.
Susan L. Brandow David C. Turner Banahalli R. Ratna Bruce P. Gaber 《Biophysical journal》1993,64(3):898-902
The atomic force microscope (AFM) was used to structurally modify supported lipid bilayers in a controlled quantitative manner. By increasing the force applied by the AFM tip, lipid was removed from the scanned area, leaving a cut through the lipid bilayer. Cuts were repaired with the AFM by scanning the region with a controlled force and driving lipid back into the cut. A slow self-annealing of cuts was also observed. 相似文献
6.
K. Sudha Rani M. V. Swamy D. Sunitha D. Haritha G. Seenayya 《World journal of microbiology & biotechnology》1996,12(1):57-60
Two Clostridium thermocellum strains were improved for ethanol tolerance, to 5% (v/v), by gradual adaptation and mutation. The best mutant gave an ethanol yield of 0.37 g/g substrate, with a growth yield 1.5 times more than its parent. Accumulation of acids and reducing sugars by the mutant strain with 5% (v/v) ethanol was lower than that of the parent strain with 1.5% (v/v) ethanol. 相似文献
7.
Prof. H. S. Randhawa Sudha Chaturvedi Z. U. Khan V. P. Chaturvedi S. K. Jain R. C. Jain G. Bazaz-Malik 《Mycopathologia》1995,131(3):173-177
An autochthonous case of epididymal histoplasmosis masquerading as tuberculosis in a 55-year-old male patient is reported from India. It was diagnosed by culture ofHistoplasma capsulatum from semen and by demonstration of the fungus upon re-examination of epididymal biopsy sections previously misinterpreted as tuberculous granuloma. The patient's main complaints were painful epididymal swelling, occasional fever and cough. He was treated successfully by excision of epididymis and vas deferens combined with amphotericin B therapy. This is believed to be the first case of epididymal histoplasmosis to be reported outside the American continent and the fourth of its type reported in the English literature. The case is also noteworthy in thatH. capsulatum was isolated for the first time from semen, and it underlines the importance of mycological culture of semen specimens for diagnosis of genitourinary infections of obscure etiology.Presented at the XII Congress of the International Society for Human and Animal Mycology, Adelaide, Australia, March 13–18, 1994. 相似文献
8.
Shridhara Alva Swati Sen Gupta Ratna S. Phadke Girjesh Govil 《Biosensors & bioelectronics》1991,6(8):663-668
Glucose oxidase has been immobilized onto a thin platinum strip, by co-crosslinking with bovine serum albumin and glutaraldehyde. The retention of redox characteristics of glucose oxidase has been verified by cyclic voltammetry. The activity of the immobilized enzyme reduces to a quarter of its value when the enzyme is in solution but improves when coimmobilized with 1
urea. The potentiometric response builds up and remains stable after 100 s. It is sensitive to the thickness of the immobilizing matrix, pH and temperature. An improvement in the performance of the electrode has been achieved by coimmobilizing 2
urea and metal ions such as Mg2+ and Mn2+. The presence of Cu has been proved to be detrimental. The electrode has been calibrated in the 0.1–5.0 mM glucose concentration range. It gives a stable response for more than 50 independent assays and can be stored for 60 days without significant loss of function. 相似文献
9.
The site of inhibition of chlorophyll biosynthesis by α′,α′-dipyridyl was found to be at the level of conversion of chlorophyllide (672 nm) to chlorophyll (678 nm) during greening of groundnut leaves. This inhibition was partially reversed by certain divalent cations. 相似文献
10.
Mycobacillin non-producers, whether sporogenous or asporogenous, possess less exoprotease, but effective exoprotease producers are not always good mycobacillin yielders. There might exist a minimum level of exoprotease formation for elaboration of mycobacillin. 相似文献