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Khorobrykh A. A possible relationship between the effect of factors on photoactivation of photosystem II depleted of functional Mn and cytochrome b 559. Biochim Biophys Acta Bioenerg 2023; 1864:148997. [PMID: 37506995 DOI: 10.1016/j.bbabio.2023.148997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Revised: 06/27/2023] [Accepted: 07/19/2023] [Indexed: 07/30/2023]
Abstract
The photoassembly of the Mn4CaO5 cluster in Mn-depleted photosystem II preparations (photoactivation) was studied under the influence of oxidants, reductants and pH. New data on the effect of these factors on the photoactivation yield are presented. The presence of the oxidant, ferricyanide, negatively affected the photoactivation yield over the entire concentration range studied (0-1 mM). In contrast to ferricyanide, the addition of the reductant, ferrocyanide, up to 1 mM resulted in an increase in the photoactivation yield. Other reductants either did not significantly affect (diphenylcarbazide) or suppressed (ascorbate) the photoactivation yield. The effect of ferrocyanide on photoactivation were found to be similar dichlorophenolindophenol. Investigation of the photoactivation yield as a function of pH revealed that the maximum yield was observed at pH 6.5 in the presence of ferrocyanide and DCPIP, and at pH 5.5 without additives. In addition, the photoactivation yield at pH 5.5 was the same without and with the addition of ferrocyanide or dichlorophenolindophenol. Although ferricyanide suppressed the photoactivation, the photoactivation yield increased in the presence of ferricyanide by shifting the pH to the acidic region. The samples contained approximately 25 % of the HP cyt b559, which was in the reduced state, as the absorbance at 559 nm was decreased upon addition of ferricyanide and subsequent addition of ferrocyanide returned the spectrum to the baseline. A possible relationship between the effect of factors on the photoactivation and the involvement of cyt b559 in the protection of PSII from oxidative damage on the donor side is discussed.
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Affiliation(s)
- Andrey Khorobrykh
- Institute of Basic Biological Problems, FRC PSCBR RAS, Pushchino 142290, Moscow Region, Russia.
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Shin D, Nagarajan R. Enzymatic Assays to Investigate Acyl-Homoserine Lactone Autoinducer Synthases. Methods Mol Biol 2018; 1673:161-176. [PMID: 29130172 PMCID: PMC5766357 DOI: 10.1007/978-1-4939-7309-5_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Bacteria use chemical molecules called autoinducers as votes to poll their numerical strength in a colony. This polling mechanism, commonly referred to as quorum sensing, enables bacteria to build a social network and provide a collective response for fighting off common threats. In Gram-negative bacteria, AHL synthases synthesize acyl-homoserine lactone (AHL) autoinducers to turn on the expression of several virulent genes including biofilm formation, protease secretion, and toxin production. Therefore, inhibiting AHL signal synthase would limit quorum sensing and virulence. In this chapter, we describe four enzymatic methods that could be adopted to investigate a broad array of AHL synthases. The enzymatic assays described here should accelerate our mechanistic understanding of quorum-sensing signal synthesis that could pave the way for discovery of potent antivirulence compounds.
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Affiliation(s)
- Daniel Shin
- Department of Chemistry and Biochemistry, Boise State University, 1910 University Drive, Boise, ID, 83725, USA
| | - Rajesh Nagarajan
- Department of Chemistry and Biochemistry, Boise State University, 1910 University Drive, Boise, ID, 83725, USA.
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Veselỳ M, Dzik P, Veselá M, Kete M, Stangar L. Photocatalytic and Antimicrobial Activity of Printed Hybrid Titania/Silica Layers. J Nanosci Nanotechnol 2015; 15:6550-6558. [PMID: 26716211 DOI: 10.1166/jnn.2015.10870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Stable mixed dispersion of TiO2 and SiO2 was developed and hybrid TiO2/SiO2 layers were fabricated by the direct inkjet patterning technique. The prepared layers were tested for photoinduced hydrophilicity and their photocatalytic activity was tested using stearic acid and dichloroindophenol as model compounds. The antimicrobial activity of prepared layers was tested and evaluated by the traditional plate counting method according to ISO 27447:2009, using Escherichia coli CCM 3988. Material printing proved to be well suited for the deposition of this complex nanoparticulate ink and samples with variable thickness were conveniently fabricated. Printed layers are able to change their surface properties from hydrophobic to superhydrophilic and also decompose the model contaminants rapidly.
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Chaibunruang A, Pornphannukool S, Sae-Ung N, Fucharoen G, Sanchaisuriya K, Fucharoen S. Improvement of alpha(0)-thalassemia screening using combined osmotic fragility, dichlorophenolindophenol and Hb H inclusion tests. Clin Lab 2010; 56:111-117. [PMID: 20476642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
BACKGROUND Screening for alpha(0)-thalassemia is usually done using osmotic fragility (OF) test or reduced erythrocyte indexes, both with high sensitivity, but accurate diagnosis requires PCR analysis. However, a low specificity of screening leads to unnecessary PCR workload during a massive population survey. We have established a more effective screening strategy using a combination of three simple tests. METHODS The study was done on 206 subjects with hypochromic microcytosis. Methods include osmotic fragility (OF) test, a dichlorophenolindophenol (DCIP) test for Hb E, a modified Hb H inclusion test, Hb and PCR analyses. RESULTS Initial screening with combined OF and DCIP tests identified 9 subjects with negative OF and DCIP tests (-/-), 58 with positive OF test but negative DCIP test (+/-), 13 with negative OF but positive DCIP tests (-/+) and 126 subjects with positive in both tests (+/+). Hb H inclusion was observed in 52 of 206 subjects including 1 in OF/DCIP (-/-), 31 in OF/DCIP (+/-) and 20 in OF/DCIP (+/+) groups. Among these 52 subjects, PCR analysis identified alpha(0)-thalassemia in 28 of 31 (+/-) and 16 of 20 (+/+) groups. Five of 106 subjects with negative Hb H inclusion in the (+/+) group were found to be heterozygous (3 of 5) and homozygous (2 of 5) Hb E co-inherited with alpha(0)-thalassemia. CONCLUSIONS Hb H inclusion is not an appropriate screening test for alpha(0)-thalassemia in a region where Hb E is common. However performance of the test in the OF/DCIP (+/-) group would enhance the specificity of screening and result in elimination of almost 50% of cases that would have required further PCR confirmation.
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Affiliation(s)
- Attawut Chaibunruang
- Centre for Research and Development of Medical Diagnostic Laboratories, Thailand
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Leng J, Sakurai I, Wada H, Shen JR. Effects of phospholipase and lipase treatments on photosystem II core dimer from a thermophilic cyanobacterium. Photosynth Res 2008; 98:469-478. [PMID: 18668340 DOI: 10.1007/s11120-008-9335-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2008] [Accepted: 07/17/2008] [Indexed: 05/26/2023]
Abstract
Lipids are important components of transmembrane protein complexes. In order to study the roles of lipids in photosystem II (PSII), we treated the PSII core dimer complex from a thermophilic cyanobacterium Thermosynechococcus vulcanus with phospholipase A(2) (PLA(2)) and lipase, and examined their effects on PSII structure and function. PLA(2)-treatment decreased the content of phospholipid, phosphatidylglycerol (PG) by 59%, leading to a decrease of oxygen evolution by 40%. On the other hand, although treatment with lipase specifically decreased the content of monogalactosyldiacylglycerol (MGDG) by 52%, it decreased oxygen evolution only by 16%. This indicates that PG plays a more important role in PSII than MGDG. Both PLA(2)- and lipase-treatments induced neither the dissociation of PSII dimer, nor any loss of polypeptides. The degradation of PG resulted in a damage to the Q(B)-binding site as demonstrated from photoreduction activity of 2,6-dichlorophenolindophenol and chlorophyll fluorescence yields in the absence or presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and the dependencies of oxygen evolution on various electron acceptors before and after PLA(2)- or lipase-treatments. However, there were approximately three and five molecules of PG and MGDG per PSII reaction center left in the PSII dimeric complex after the PLA(2)- and lipase-treatments. These lipids are therefore bound to the interior of the protein matrix and resistant to the lipase treatments. The resistance of these lipids against PLA(2)- and lipase-treatments may be a specific feature of PSII from the thermophilic cyanobacterium, suggesting a possible correlation between binding of lipids and thermostability of PSII.
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Affiliation(s)
- Jing Leng
- Graduate School of Natural Science and Technology, Department of Biology, Faculty of Science, Okayama University, Okayama 700-8530, Japan
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Wiwanitkit V. Using of osmotic fragility (OF) and dichlorophenol-indolephenol (DCIP) tests screening for antenatal clinic: appraisal of usefulness of the program in rural Thai communities. Rural Remote Health 2006; 6:587. [PMID: 16671839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023] Open
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Abstract
BACKGROUND Haemoglobin E is a variant haemoglobin that can lead to considerable morbidity in compound heterozygous states with beta thalassaemia. Therefore, its detection is important because it permits antenatal counselling. The parts of the world where haemoglobin E is prevalent are resource poor and detection can therefore be problematical. A simple visual test using 2,6-dichlorophenolindophenol (DCIP) has been developed in Thailand, but its use has not become widespread. This test has now become available in kit form. AIMS/METHODS To evaluate the new DCIP test kit for the detection of haemoglobin E. RESULTS Seventeen of 18 samples from individuals with haemoglobin E gave positive results and one gave an equivocal result. False positive or equivocal results were seen in three of 21 individuals with other disorders of globin chain synthesis but were not seen in normal subjects. CONCLUSIONS This study evaluated the sensitivity, specificity, and reproducibility of the kit and confirmed the usefulness of the DCIP test as a screening test for haemoglobin E. In countries with limited health resources, its use would reduce the number of samples requiring referral to a central laboratory for definitive tests.
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Affiliation(s)
- L Chapple
- Department of Haematology, St Mary's Hospital, Praed Street, London W2 1NY, UK
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Sangkitporn S, Sangkitporn S, Sangnoi A, Supangwiput O, Tanphaichitr VS. Validation of osmotic fragility test and dichlorophenol indophenol precipitation test for screening of thalassemia and Hb E. Southeast Asian J Trop Med Public Health 2005; 36:1538-42. [PMID: 16610659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The strategy for screening of thalassemia and Hb E by a combination of osmotic fragility (OF) test and dichlorophenol indophenol precipitation (DCIP) test was validated with 436 unrelated Thai subjects. Hemoglobin (Hb) typing, Hb A2 quantitation, PCR and DNA sequence analysis were used as confirmatory methods for diagnosis of thalassemia and hemoglobinopathy. The sensitivity and specificity of this strategy was 100% and 79.7%, respectively. The results assessed by two medical scientists were exactly the same with 93.3% accuracy in comparison with the confirmatory methods. A combination of OF and DCIP has been shown to be a reliable, rapid, simple and sensitive strategy for screening thalassemia and Hb E in the Thai population.
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Affiliation(s)
- Siripakorn Sangkitporn
- National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Nonthaburi, Thailand
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La Porta N, Bertamini M, Nedunchezhian N, Raddi P, Muthuchelian K. Photoinhibition of photosynthesis in needles of two cypress (Cupressus sempervirens) clones. Tree Physiol 2005; 25:1033-9. [PMID: 15929934 DOI: 10.1093/treephys/25.8.1033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Photoinhibition of photosynthesis and photosynthetic recovery were studied in detached needles of cypress (Cupressus sempervirens L.) Clones 52 and 30 under controlled conditions of high irradiation (about 1900 micromol m(-2) s(-1) for 60 min; HL treatment), followed by 60 min in darkness. The degree of photoinhibition was determined based on the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm), which is a measure of the potential efficiency of photosystem II (PSII), and on electron transport measurements. The Fv/Fm ratio declined in needles of both clones in response to the HL treatment. Minimal fluorescence (Fo) increased in HL-treated needles of both clones. The HL treatment decreased rates of whole-chain and PSII activity of isolated thylakoids more in Clone 52 than in Clone 30. In needles of both clones, PSI activity was less sensitive to photoinhibition than PSII activity. In the subsequent 60-min dark incubation, fast recovery was observed in needles of both clones, with PSII efficiencies reaching similar values to those in non-photoinhibited needles. The artificial exogenous electron donors diphenyl carbazide (DPC), hydroxylamine (NH2OH) and manganese chloride (MnCl2) failed to restore the HL-induced loss of PSII activity in needles of Clone 30, whereas DPC and NH2OH significantly restored PSII activity in photoinhibited needles of Clone 52. Quantification of the PSII reaction center protein D1 and the 33-kDa protein of the water-splitting complex following HL treatment of needles revealed pronounced differences between Clone 52 and Clone 30. The large decrease in PSII activity in HL-treated needles was caused by the marked loss of D1 protein and 33-kDa protein in Clone 30 and Clone 52, respectively.
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Affiliation(s)
- Nicola La Porta
- Istituto Agrario di San Michele all'Adige, 38010 San Michele all'Adige, Italy
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Saha T, Chakraborty TK, Saha R, Das N, Mukherjee M. Interference of laccase in determination of cellobiose dehydrogenase activity ofPleurotus ostreatus (Florida) using dichlorophenol indophenol as the electron acceptor. J Basic Microbiol 2005; 45:142-6. [PMID: 15812859 DOI: 10.1002/jobm.200410472] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Pleurotus ostreatus (Florida), ITCC 3308 produces approximately 9.0 U/ml extracellular cellobiose dehydrogenase (CDH) in cellulose medium after 7 days of growth. However, no activity could be detected if the assay was done with cellobiose as the substrate and 2,6-dichlorophenol indophenol (DPIP) as the electron acceptor in absence of any laccase inhibitor. Kinetic study showed that V(max)/K(m) value was very high for rDPIP (reduced 2,6-dichlrophenol indophenol) oxidation by laccase. Oxygen consumption rate of rDPIP oxidation by the enzyme was found to be highest among all the tested substrates. The present study indicated that rDPIP was a good substrate for laccase. Therefore, caution is needed to measure CDH activity by monitoring DPIP reduction in a system where laccase is likely to be present.
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Affiliation(s)
- Tanima Saha
- Indian Institute of Chemical Biology, 4 Raja SC Mullick Road, Calcutta 700 032, India
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Kuznetsov BA, Davydova ME, Shleeva MO, Shleev SV, Kaprelyants AS, Yaropolov AI. Electrochemical investigation of the dynamics of Mycobacterium smegmatis cells' transformation to dormant, nonculturable form. Bioelectrochemistry 2004; 64:125-31. [PMID: 15296785 DOI: 10.1016/j.bioelechem.2004.05.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Revised: 04/19/2004] [Accepted: 05/03/2004] [Indexed: 11/24/2022]
Abstract
Dynamics of transformation of Mycobacterium smegmatis cells by cultivation under nonoptimal conditions (partial starvation) to dormant, nonculturable form has been studied. For this aim, an electrochemical method was developed to detect both viable and 'viable but nonculturable' (VBNC) cells. The current produced by bacteria placed at the electrode surface was measured in the presence of 2,6-dichlorophenol indophenol (DCIP) at the applied potential of 350 mV. It has been established that electrochemical activity changes parallel with the growth of biomass. The transition of M. smegmatis to a dormant, nonculturable state goes along with the decrease of the detection current up to 20% of the maximum level. This means that nonculturable cells have rather high rest metabolic activity. The course of the CFU values has a complicated character during bacterial growth. The placement of the bacterial culture on the solid medium appears to cause a new stress that stops proliferation and stimulates aggregation. Both processes distort CFU measurement results. The quantitative estimation of the viable but nonculturable cells by counting colonies, measuring optical density and current produced by bacteria has been discussed.
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Affiliation(s)
- B A Kuznetsov
- AN Bach Institute of Biochemistry, RAS, Leninsky prospekt 33, 119071 Moscow, Russia.
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Fucharoen G, Sanchaisuriya K, Sae-ung N, Dangwibul S, Fucharoen S. A simplified screening strategy for thalassaemia and haemoglobin E in rural communities in south-east Asia. Bull World Health Organ 2004; 82:364-72. [PMID: 15298227 PMCID: PMC2622836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023] Open
Abstract
OBJECTIVE To evaluate a simple screening strategy for thalassaemia and haemoglobin (Hb) E in a prevention and control programme for thalassaemia in rural communities with limited resources. METHODS Blood samples from 301 Thai-Khmer participants were screened for thalassaemia and Hb E using a combined modified one-tube osmotic fragility (OF) test and a modified dichlorophenolindophenol (DCIP) precipitation test. Results were evaluated with standard haematological analyses including erythrocyte indices, Hb typing and quantification and polymerase chain reaction (PCR) analysis of alpha-globin and beta-globin genes. FINDINGS Participants were divided into four groups according to the results of the combined tests. Altogether, 104 of 301 participants (34.6%) had negative results on both tests; 48 (15.9%) were positive on the OF test but not the DCIP test; 40 (13.3%) were negative on the OF test but positive on DCIP test; and 109 (36.2%) were positive on both tests. No carrier of clinically significant forms of thalassaemia (alpha(o)-thalassaemia, beta-thalassaemia) or Hb E was found among the group that had negative results for both tests. All participants with Hb E had positive DCIP tests. Carriers of alpha+-thalassaemia or Hb Constant Spring could generate either positive or negative OF test results but they all had negative DCIP tests. Using both tests as a preliminary screening for the three important groups of carriers gave a sensitivity of 100% and a specificity of 69.8%. The positive predictive value of the combined test was 77.2%. The negative predictive value was 100%. Further evaluation of the screening system by local staff at three community hospitals found a sensitivity of 98.1-100% and a specificity of 65.4-88.4% with positive predictive values of 75.0-86.9% and negative predictive values of 98.1-100%. CONCLUSION A combined test using OF and DCIP could be used as an effective preliminary screening alternative to an electronic blood cell count for identifying carriers with alpha(o)-thalassaemia, beta-thalassaemia and Hb E. The strategy should prove useful for population screening in prevention and control programmes in rural communities in south-east Asia where laboratory facilities and economic resources are limited.
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Affiliation(s)
- Goonnapa Fucharoen
- Department of Clinica Microscopy, Khon Kaen University, Khon Kaen, Thailand
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Bertamini M, Nedunchezhian N. Photoinhibition and recovery of photosynthesis in leaves of Vitis berlandieri and Vitis rupestris. J Plant Physiol 2004; 161:203-210. [PMID: 15022835 DOI: 10.1078/0176-1617-00838] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Photoinhibition of photosynthesis was studied in Vitis berlandieri and Vitis rupestris leaves under controlled conditions (irradiation of detached leaves to about 1900 micromol m(-2) s(-1)). The degree of photoinhibition was determined by means of the ratio of variable to maximum chlorophyll (Chl) fluorescence (Fv/Fm) and electron transport measurements. The potential efficiency of PS2, Fv/Fm declined, Fo increased significantly in leaves of V. berlandieri, while Fo decreased in V. rupestris. In isolated thylakoids, the rate of whole chain and PS2 activity markedly decreased in high light irradiated more in leaves of V. berlandieri than in leaves of V. rupestris. A smaller inhibition of PS1 activity was also observed in both leaves. In the subsequent dark incubation, fast recovery was observed in both leaves and reached maximum PS2 efficiencies similar to those observed in non-photoinhibited leaves. The artificial exogenous electron donors DPC, NH2OH and Mn2+ failed to restore the high light induced loss of PS2 activity in V. berlandieri leaves, while DPC and NH2OH significantly restored in V. rupestris leaves. It is concluded that high light inactivates on the donor side of PS2 and acceptor side of PS2 in V. rupestris and V. berlandieri leaves, respectively. Quantification of the PS2 reaction center protein D1 and 33 kDa protein of water splitting complex following high light exposure of leaves showed pronounced differences between V. berlandieri and V. rupestris leaves. The marked loss of PS2 activity in high light irradiated leaves was due to the marked loss of D1 protein and 33 kDa protein in V. berlandieri and V. rupestris leaves, respectively.
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Affiliation(s)
- Massimo Bertamini
- Istituto Agrario di San Michele all' Adige, 38010 San Michele all' Adige, Italy.
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Wiwanitkit V, Suwansaksri J, Paritpokee N. Combined one-tube osmotic fragility (OF) test and dichlorophenol-indolphenol (DCIP) test screening for hemoglobin disorders, an experience in 213 Thai pregnant women. Clin Lab 2003; 48:525-8. [PMID: 12389713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
OBJECTIVE Hemoglobin disorders are an important health problem in Thailand. Therefore, screening tests for abnormal genotypes offer an effective method for coping with this problem. This study has been designed to study basic screening tests for inherited hemoglobin disorders in Thai pregnant women. METHODS This study was designed as a diagnostic test. EDTA blood specimens from 213 pregnant women were used in this study. The screening methods studied were the one-tube osmotic fragility (OF) test and the dichlorophenol-indolphenol (DCIP) test. The standard method used in this study was hemoglobin typing applying the cellulose acetate hemoglobin electrophoresis method. Diagnostic properties such as sensitivity, specificity and predictive value were used for data analysis. RESULTS The results obtained from this study demonstrated the sensitivity, specificity, positive and negative predictive value for Hb E disorders screened by the DCIP test to be 100%, 97.2%, 94.4% and 100%, respectively. For beta thalassemia disorder screened by the OF test, the sensitivity, specificity, positive and negative predictive value were 100%, 83.7%, 10.5% and 100%, respectively. Evaluation for combining both methods as screening tools for all hemoglobin disorders revealed a sensitivity, specificity, positive and negative predictive value of 100%, 97.1%, 94.9% and 100%, respectively. CONCLUSION The combination of both the OF and the DCIP test as a screening tool for hemoglobin disorders in pregnant women is an effective method and should be used in the antenatal clinic.
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Affiliation(s)
- V Wiwanitkit
- Department of Laboratory Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
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Frébort I, Sebela M, Galuszka P, Werner T, Schmülling T, Pec P. Cytokinin oxidase/cytokinin dehydrogenase assay: optimized procedures and applications. Anal Biochem 2002; 306:1-7. [PMID: 12069407 DOI: 10.1006/abio.2002.5670] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Spectrophotometric methods for determining the activity of cytokinin oxidase/cytokinin dehydrogenase (EC 1.5.99.12) were developed and optimized. A sensitive end-point method based on a combination of the electron acceptor 2,6-dichlorophenolindophenol and Schiff base formation of the reaction product with 4-aminophenol under acidic conditions can be applied to crude cell and tissue extracts. The assay was also adapted for other substrates than N6-(2-isopentenyl)adenine, such as zeatin and the aromatic cytokinins, although an enzyme which degrades the latter compounds has not yet been identified. The second novel method is an initial rate method based on the coupled redox reaction of phenazine methosulfate and 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide resulting in the formation of a formazan dye. This method can be used for kinetic studies with purified enzyme and is entirely substrate independent.
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Affiliation(s)
- Ivo Frébort
- Department of Biochemistry, Faculty of Science, Palacký University, Slechtitelů 11, Olomouc, Czech Republic.
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Abstract
Defects in the mitochondrial genome have been associated with Parkinson's and Alzheimer's disease, and apoptosis can be triggered by the presence of energetically compromised mitochondria. Thus, in this study we have examined whether the divalent cations Cu2+ and Mn2+ could influence mitochondrial function in vitro. Mitochondrial electron transport was dose and time dependently reduced by Cu2+ to a greater extent with succinate as a substrate. Following a 60 min preincubation period, Mn2+ dose dependently inhibited electron transport to a greater extent with lactate and malate. In contrast, paradoxical effects were seen following a 5 min preincubation period with Mn2+. Cu2+ dose-dependently reduced NADH-dependent lactate dehydrogenase (LDH) activity, with almost complete inhibition apparent at 10 microM. An initial induction of LDH by 10 microM Mn2+ was partially reversed by higher concentrations of the metal. Cu2+ dose-dependently reduced flavin adenine dinucleotide (FAD)-dependent monoamine oxidase A (MAO-A) activity in a time-independent manner, with an IC50 value approximately 20 microM, whereas Mn2+ had no effect. In conclusion, it is proposed that Cu2+ and Mn2+ have differential effects on nicotinamide adenine dinucleotide (NAD) and FAD-dependent mitochondrial enzymes at the level of the essential cofactors. Cu2+ appears to exert an inhibitory effect on both NAD and FAD-dependent enzymes, but predominantly against the latter, including MAO-A and succinate dehydrogenase. The complex responses to Mn2+ may be due to dose-related effects on the interconversion of NAD and NADH and reversible enzymatic reactions employing this nucleotide cofactor.
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Affiliation(s)
- P Heron
- Division of Pharmacology, Faculty of Pharmacy, Rhodes University, Grahamstown, South Africa
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Abstract
Rhodococcus erythropolis DCL14 assimilates all stereoisomers of carveol and dihydrocarveol as sole source of carbon and energy. Induction experiments with carveol- or dihydrocarveol-grown cells showed high oxygen consumption rates with these two compounds and with carvone and dihydrocarvone. (Dihydro)carveol-grown cells of R. erythropolis DCL14 contained the following enzymic activities involved in the carveol and dihydrocarveol degradation pathways of this micro-organism: (dihydro)carveol dehydrogenase (both NAD+- and dichlorophenolindophenol-dependent activities), an unknown cofactor-dependent carvone reductase, (iso-)dihydrocarvone isomerase activity, NADPH-dependent dihydrocarvone monooxygenase (Baeyer-Villiger monooxygenase), epsilon-lactone hydrolase and an NAD+-dependent 6-hydroxy-3-isopropenylheptanoate dehydrogenase. Product accumulation studies identified (4R)-carvone, (1R,4R)-dihydrocarvone, (4R,7R)-4-isopropenyl-7-methyl-2-oxo-oxepanone, (3R)-6-hydroxy-3-isopropenylheptanoate, (3R)-3-isopropenyl-6-oxoheptanoate, (3S,6R)-6-isopropenyl-3-methyl-2-oxooxepanone and (5R)-6-hydroxy-5-isopropenyl-2-methylhexanoate as intermediates in the (4R)-carveol degradation pathway. The opposite stereoisomers of these compounds were identified in the (4S)-carveol degradation pathway. With dihydrocarveol, the same intermediates are involved except that carvone was absent. These results show that R. erythropolis DCL14 metabolizes all four diastereomers of carveol via oxidation to carvone, which is subsequently stereospecifically reduced to (1R)-(iso-) dihydrocarvone. At this point also dihydrocarveol enters the pathway, and this compound is directly oxidized to (iso-)dihydrocarvone. Cell extracts contained both (1R)-(iso-)dihydrocarvone 1,2-monooxygenase and (1S)-(iso)-dihydrocarvone 2,3-monooxygenase activity, resulting in a branch point of the degradation pathway; (1R)-(iso-)dihydrocarvone was converted to 4-isopropenyl-7-methyl-2-oxo-oxepanone, while (1S)-(iso)-dihydrocarvone, which in vivo is isomerized to (1R)-(iso-)dihydrocarvone, was converted to 6-isopropenyl-3-methyl-2-oxo-oxepanone. 4-Isopropenyl-7-methyl-2-oxooxepanone is hydrolysed to 6-hydroxy-3-isopropenylheptanoate, which is subsequently oxidized to 3-isopropenyl-6-oxoheptanoate, thereby linking the (dihydro)carveol degradation pathways to the limonene degradation pathway of this micro-organism. 6-Isopropenyl-3-methyl-2-oxo-oxepanone is, in vitro, hydrolysed to 6-hydroxy-5-isopropenyl-2-methylhexanoate, which is thought to be a dead-end metabolite.
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Affiliation(s)
- Mariët J van der Werf
- Division of Industrial Microbiology, Department of Food Technology and Nutritional Sciences, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands1
| | - Anneke M Boot
- Division of Industrial Microbiology, Department of Food Technology and Nutritional Sciences, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands1
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19
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Muszalska I, Zajac M, Wróbel G, Nogowska M. Redox methods validation of paracetamol and ascorbic acid in pharmaceutical preparations. Acta Pol Pharm 2000; 57:27-32. [PMID: 10846794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The contents of active substances were determined in a preparation TP-4 (tablets) containing paracetamol, ascorbic acid, caffeine and phenylephrine hydrochloride. For the determination of paracetamol and ascorbic acid a non-specific (cerometric and titration of 2,6-dichloroindophenol) method based on a redox reaction was used. Validation of the methods, performed on model mixtures, proved those methods to be accurate, precise, reproducible and linear within the range from 50% to 150% of the amount declared in the preparation. The content of paracetamol and ascorbic acid in TP-4, Thompayrin, Panadol Extra, Ring N, Polopiryna C, Efferalgan Vitamin C and Vitaminum C 0.2 satisfies the FP V demands (+/- 10% of the declared amount).
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Affiliation(s)
- I Muszalska
- Department of Pharmaceutical Chemistry, K. Marcinkowski University of Medical Sciences, Poznań, Poland
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20
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García-Castiñeiras S. [Hydrogen peroxide in the aqueous humor: 1992-1997]. P R Health Sci J 1998; 17:335-43. [PMID: 10028541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Ideas prevailing in 1991 on hydrogen peroxide in the aqueous humor are outlined. They are critically examined under the light of our finding that the method used to establish aqueous humor levels of peroxide generates itself peroxide during the short time span of the analysis. This is due to the fact that the probe used, dichlorophenol indophenol (DCPIP), spontaneously auto-oxidizes in the presence of oxygen. It was concluded then that the level of hydrogen peroxide in the aqueous humor cannot be higher than about 0.3 microM, the detection limit of the DCPIP method. It was also concluded that the statement commonly made in the literature that aqueous humor hydrogen peroxide derives from the oxidation of ascorbate, an abundant component of that fluid, is based solely on the use of the DCPIP method, and so could easily be due to a methodological artifact. The same applies to the statement that the levels of hydrogen peroxide are very high in human senile cataracts. The surprising resistance to accept the results and conclusions of our 1992 publication is documented. Finally, the content is discussed of an oral presentation made at the 1997 ARVO Annual Meeting in which an important portion of our results and conclusions was confirmed, perhaps signaling a shift towards a wider acceptance of our findings.
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Affiliation(s)
- S García-Castiñeiras
- Departamentos de Oftalmologia y Bioquímica, Escuela de Medicina, Universidad de Puerto Rico, San Juan
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21
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Auer BL, Auer D, Rodgers AL. The effect of ascorbic acid ingestion on the biochemical and physicochemical risk factors associated with calcium oxalate kidney stone formation. Clin Chem Lab Med 1998; 36:143-7. [PMID: 9589801 DOI: 10.1515/cclm.1998.027] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The present study was undertaken to determine the effect of ingestion of large doses of vitamin C on urinary oxalate excretion and on a number of other biochemical and physicochemical risk factors associated with calcium oxalate urolithiasis. A further objective was to determine urinary ascorbate excretion and to relate it qualitatively to ingested levels of the vitamin and oxalate excretion. Ten healthy males participated in a protocol in which 4 g ascorbic acid was ingested for 5 days. Urines (24 h) were collected prior to, during and after the protocol. The urine collection procedure was designed to allow for the analysis of oxalate in the presence and absence of an EDTA preservative and for the analysis of ascorbic acid by manual titration using 2,6 dichlorophenolindophenol. Physicochemical risk factors such as the calcium oxalate relative supersaturation and Tiselius risk index were calculated from urine composition. The results showed that erroneously high analytical oxalate levels occur in the asence of preservative. In the preserved samples there was no significant increase in oxalate excretion at any stage of the protocol. Ascorbate excretion increased when vitamin C ingestion commenced but levelled out after 24 hours suggesting that saturation of the metabolic pool is reached within 24 hours after which ingested ascorbic acid is excreted unmetabolized in the urine. While transient statistically significant changes occurred in some of the biochemical risk factors, they were not regarded as being clinically significant. There were no changes in either the calcium oxalate relative supersaturation or Tiselius risk index. It is concluded that ingestion of large doses of ascorbic acid does not affect the principal risk factors associated with calcium oxalate kidney stone formation.
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Affiliation(s)
- B L Auer
- Chemistry Department, University of Cape Town, South Africa
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22
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Vassiliev IR, Jung YS, Mamedov MD, Golbeck JH. Near-IR absorbance changes and electrogenic reactions in the microsecond-to-second time domain in Photosystem I. Biophys J 1997; 72:301-15. [PMID: 8994615 PMCID: PMC1184319 DOI: 10.1016/s0006-3495(97)78669-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The back-reaction kinetics in Photosystem I (PS I) were studied on the microsecond-to-s time scale in cyanobacterial preparations, which differed in the number of iron-sulfur clusters to assess the contributions of particular components to the reduction of P700+. In membrane fragments and in trimeric P700-FA/FB complexes, the major contribution to the absorbance change at 820 nm (delta A820) was the back-reaction of FA- and/or FB- with lifetimes of approximately 10 and 80 ms (approximately 10% and 40% relative amplitude). The decay of photoinduced electric potential (delta psi) across a membrane with directionally incorporated P700-FA/FB complexes had similar kinetics. HgCl2-treated PS I complexes, which contain FA but no FB, retain both of these kinetic components, indicating that neither can be assigned uniquely to a specific acceptor. These results suggest that FA- reduces P700+ directly and argue for a rapid electron equilibration between FA and FB, which would eliminate their kinetic distinction in a back-reaction. In PsaC-depleted P700-Fx cores, as well as in P700-FA/FB complexes with chemically reduced FA and FB, the major contribution to the delta A820 and the delta psi decay is a biphasic back-reaction of F-X (approximately 400 microseconds and 1.5 ms) with some contribution from A-1 (approximately 10 microseconds and 100 microseconds), the latter of which is variable depending on experimental conditions. The delta A820 decay in a P700-A1 core devoid of all iron-sulfur clusters comprises two phases with lifetimes of 10 microseconds and 130 microseconds (2.7:1 ratio). The biexponential back-reaction kinetics found for each of the electron acceptors may be related to existence of different conformational states of the PS I complex. In all preparations studied, excitation at 532 nm with flash energies exceeding 10 mJ gives rise to formation of antenna 3Chl, which also contributes to delta A820 decay on the tens-of-microsecond time scale. A distinction between delta A820 components related to back-reactions and to 3Chl decay can be made by analysis of flash saturation dependencies and by measurements of kinetics with preoxidized P700.
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Affiliation(s)
- I R Vassiliev
- Department of Biochemistry, G. W. Beadle Center, University of Nebraska, Lincoln 68588-0664, USA
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23
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24
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Sancesario G, Reiner A, Figueredo-Cardenas G, Morello M, Bernardi G. Differential distribution of nicotinamide adenine dinucleotide phosphate-diaphorase and neural nitric oxide synthase in the rat choroid plexus. A histochemical and immunocytochemical study. Neuroscience 1996; 72:365-75. [PMID: 8737407 DOI: 10.1016/0306-4522(95)00538-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
This study used NADPH diaphorase (NADPHd) histochemistry and neuronal nitric oxide synthase immunocytochemistry to examine the localization of nitric oxide synthase in the choroid plexus of the lateral ventricles and the fourth ventricle of rat brain. That the NADPHd reaction product in choroid plexus was specific to nitric oxide synthase was evaluated: (i) by comparison to immunocytochemical labelling for nitric oxide synthase; and (ii) by comparing NADPHd histochemical staining in choroid plexus and brain (rich in nitric oxide synthase-positive and NADPHd-positive neurons) in the presence or absence of iodonium diphenyl or dichlorophenolindophenol, two potent albeit non-selective inhibitors of nitric oxide synthase activity. In brain, NADPHd histochemistry homogeneously stained neuronal cell bodies, axons and dendrites, while it produced particulate cytoplasmic staining of all epithelial cells in the choroid plexuses of the lateral and fourth ventricles. Within the choroid plexus of the lateral ventricles, NADPHd-positive nerve fibres were also observed around blood vessels and coursing among the epithelial cells. The distribution of immunoreactivity for nitric oxide synthase in brain and in nerve fibres in the choroid plexuses of the lateral ventricles resembled the distribution of histochemical labelling for NADPHd. Choroid plexus epithelial cells were, however, devoid of nitric oxide synthase immunoreactivity. Consistent with this, iodonium diphenyl and dichlorophenolindophenol (0.1 mM) inhibited NADPHd histochemical staining in brain neurons and in choroid plexus nerve fibres, but not in choroid plexus epithelial cells. These results demonstrate that the choroid plexus of the lateral ventricles in rat brain is innervated by nitric oxide synthase-positive nerve fibres. These nitric oxide synthase-positive nerve fibres may have an important role in the regulation of cerebrospinal fluid balance. Although choroid plexus epithelial cells contain an enzyme with NADPHd activity, this enzyme is not nitric oxide synthase.
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Affiliation(s)
- G Sancesario
- Department of Neurology, University of Rome Tor Vergata
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25
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Abstract
The formal potentials (E0') and electron transfer numbers (n) of imidazole (Im), 1-methylimidazole (1-MeIm), and 1-ethylimidazole (1-EtIm) complexes of cytochrome c have been determined for the first time using optically transparent thin-layer spectroelectrochemistry. In comparing these results with the E0' value of the cytochrome c, their potentials at infinite dilution have been calculated, which indicate that axial replacement of methionine-80 by Im, 1-MeIm, and 1-EtIm gives rise to 426, 359, and 327 mV negative shifts relative to that of native cytochrome c, respectively. Thereby, the origins of the effects of axial substitution on redox potential are discussed.
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Affiliation(s)
- G Liu
- State Key Laboratory of Coordination Chemistry, Nanjing University, China
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26
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Sun ZY, Dowd SR, Felix C, Hyde JS, Ho C. Stopped-flow kinetic and biophysical studies of membrane-associated D-lactate dehydrogenase of Escherichia coli. Biochim Biophys Acta 1995; 1252:269-77. [PMID: 7578233 DOI: 10.1016/0167-4838(95)00120-j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The enzyme kinetics of the FAD-containing membrane-associated D-lactate dehydrogenase (D-LDH) of Escherichia coli have been investigated by stopped-flow spectroscopy. The reduction of D-LDH by the substrate, D-lactate, exhibits a two-stage behavior as observed by the absorbance change for the enzyme-bound FAD. The fast stage with a maximum rate of 400 s-1 represents the rapid formation of the enzyme-substrate complex and the formation of the equilibrium between the oxidized and the reduced enzyme-substrate complexes. The slow stage, which occurs on the order of 0.36 s-1, represents the slow release of the product, pyruvate, from the reduced enzyme. The formation of a D-LDH semiquinone radical was not observed during the oxidation of D-lactate by D-LDH at 25 degrees C. However, during the subsequent electron transfer from the reduced enzyme to a nitroxide spin-label, a one-electron acceptor, an enzyme intermediate has been observed and identified by both optical and EPR spectroscopies as an anionic semiquinone. Results from 1H-NMR spectroscopic studies suggest the possible formation of a substrate carbanion when D-lactate is bound at the active site of D-LDH.
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Affiliation(s)
- Z Y Sun
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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27
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Yao H, Halsall HB, Heineman WR, Jenkins SH. Electrochemical dehydrogenase-based homogeneous assays in whole blood. Clin Chem 1995; 41:591-8. [PMID: 7720252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
An electrochemical method has been developed for determining NADH in whole blood for dehydrogenase-based assays by flow-injection analysis. NADH generated by dehydrogenase is oxidized by an electron-transfer coupling reagent, 2,6-dichloroindophenol (DCIP). The reduced form of DCIP (DCIPH2) is measured amperometrically by flow-injection analysis. Endogenous interferents were inhibited by p-hydroxymercuribenzoate. Electrode fouling by proteins was not observed under assay conditions. The Emit theophylline enzyme immunoassay and the hexokinase glucose assay were used as models. For the glucose assay, the intraassay CVs were 15% at 0.31 g/L and 3.5% at 1.82 g/L. Recoveries of glucose from whole blood (compared with that for aqueous standards) were 109%, 97.9%, and 101% at 0.050, 2.00, and 5.00 g/L glucose, respectively, and 104%, 101%, and 102% for theophylline at concentrations of 5.0 (low), 16.4 (medium), and 30.2 (high) mg/L, respectively, with corresponding precisions of 12%, 9.5%, and 8.8%. Both assays correlated well with results by reference methods. These studies demonstrate that this method can measure NADH in whole blood without prior separation and that it is potentially applicable to other dehydrogenase-based assays in whole blood.
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Affiliation(s)
- H Yao
- Biomedical Chemistry Research Center, University of Cincinnati, OH 45221-0172, USA
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28
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Abstract
Hydrogen peroxide levels have been determined in rat lenses by using two methods, a chemiluminescent and a radioisotopic method. The average content was found to be 155 +/- 20 and 127 +/- 18 nmol/g wet weight of the tissue, respectively, by the two methods. The reaction of H2O2 with dichlorophenol-indophenol in the presence of peroxidase was also studied. However, this was found to be less suitable. The results of the chemiluminescent determinations are similar to the results with the radioisotopic methods demonstrating the feasibility of determining H2O2 by chemiluminescence measurement as well.
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Affiliation(s)
- P S Devamanoharan
- Department of Ophthalmology, University of Maryland at Baltimore 21201, USA
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29
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Gaume B, Sharp RE, Manson FD, Chapman SK, Reid GA, Lederer F. Mutation to glutamine of histidine 373, the catalytic base of flavocytochrome b2 (L-lactate dehydrogenase). Biochimie 1995; 77:621-30. [PMID: 8589072 DOI: 10.1016/0300-9084(96)88177-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Flavocytochrome b2 catalyzes the two-electron oxidation of L-lactate. Reducing equivalents are transferred first to FMN then to heme b2 in the same subunit, finally to cytochrome c or a non-physiological acceptor. The enzyme's three-dimensional structure, when analyzed in the light of existing mechanistic knowledge, suggested that His 373 is the active site base which initiates the substrate chemical transformation by abstracting the lactate alpha-proton. We report here the properties of a mutant enzyme with glutamine substituted histidine at position 373. The mutated enzyme preparations show a 10(4)-fold decrease in catalytic activity. We find that most of this residual activity can be eliminated by treatments with: 1) fluoropyruvate, an affinity label for His 373; and 2) 2- hydroxy-3-butynoate, a suicide reagent which normally forms an adduct with FMN but in this case leaves the bulk of the prosthetic group intact. Furthermore, although spectral titrations do not detect any binding of oxalate, this reagent inhibits the mutant enzyme with the same kinetic behaviour as for the wild-type enzyme. We conclude that the enzyme preparations contain about 1 in 10(4) molecules of wild-type flavocytochrome b2; this is probably due to codon misreading during biosynthesis. Thus the H373Q enzyme displays at most 10(5)-fold less activity than the wild-type enzyme. We report values for the spectrally determined binding constants of sulfite, pyruvate and D-lactate for the mutant enzyme. Finally, we show that 2,6-dichlorophenol indophenol, which is a 10-fold more sensitive routine electron acceptor than ferricyanide, accepts electrons only from heme b2 and not from the flavin.
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Affiliation(s)
- B Gaume
- CNRS-URA 1461, Hôpital Necker, Paris, France
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30
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Ignatov SG. [A new method for determining the complement-mediated bacteriolytic action of serum on Escherichia coli cells]. Zh Mikrobiol Epidemiol Immunobiol 1994:99-100. [PMID: 7879570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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31
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Trach VV, Shvartau VV, Dmitrenko NP, Chmil' VD. [Use of chloroplasts for herbicide detection after thin layer chromatography]. Ukr Biokhim Zh (1978) 1994; 66:100-4. [PMID: 7747335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The procedure of spreading of native pea (Pisum sativum L.) chloroplasts and 2,4-dichlorophenolindophenol on thin-layer chromatographical plates is used to detect herbicides. The sensitivity of photosystem 2 inhibitors detecting ureas and simm-triazines, is 10 ng. Dinitroaniline, thiocarbamate and chloroacetamide herbicides may be detected on 100 ng level. The method may by used for the screening of new physiologically active compounds for phototoxicity.
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Shishoo DM, Shah RC, Desai CA, Joshi KF. Dental chairside test for the diagnosis of ascorbic acid deficiency. Indian J Dent Res 1994; 5:19-24. [PMID: 9495147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
There is a strong correlation between gingival inflammation and clinical and sub-clinical ascorbic acid deficiency. This has created a demand for a handy diagnostic test to detect the ascorbic acid deficiency. The aim of this work was to find out the efficacy of one such test, i.e. the modified Lingual Ascorbic Acid Test (LAAT). To find out the significance of ths LAAT, it was compared with plasma ascorbic acid levels and then confirmed statistically. Our findings suggest that with this simple, reliable and inexpensive method, the dental practitioners can conveniently assess the ascorbic acid status of their patients.
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Affiliation(s)
- D M Shishoo
- Dept. of Physiology, Government Dental College, Ahmedabad
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33
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Yamano T, Kuroda K, Fujii S, Miura R. Characterization of the electron acceptors of old yellow enzyme: mechanistic approach to the mode of one electron transfer from the enzyme to menadione or dyestuffs. J Biochem 1993; 114:879-84. [PMID: 8138546 DOI: 10.1093/oxfordjournals.jbchem.a124271] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Molecular oxygen or cytochrome c has been described as the electron acceptor of the reaction of old yellow enzyme with NADPH. In this study, menadione was found to be a sensitive electron acceptor of the reaction under aerobic as well as anaerobic conditions. The Km value of menadione for old yellow enzyme is as low as 2-3 x 10(-7) M in the presence or absence of superoxide dismutase. The rate enhancement of the cytochrome c reduction of old yellow enzyme with NADPH was about eight times in the presence of menadione. The rate increment was slightly higher under aerobic than anaerobic conditions. The rate enhancement by menadione enabled sensitive determination of the enzyme activity in the assay system, which contained NADPH, cytochrome c, menadione, and old yellow enzyme. In the reaction course, the semiquinone species of menadione was trapped by the reaction with t-butyl-alpha-phenylnitrone. The radical adduct was detected on EPR. The dyestuff, 2,6-dichlorophenolindophenol, was found to be reduced ineffectively even in the presence of menadione; moreover, it was inhibitory in the NADPH consumption reaction. Methylene blue or Lauth's violet, known to be capable of semiquinone formation, also behaved, like menadione, as a mediator of electron transport to cytochrome c. On the basis of the experimental results, the occurrence of the one electron transfer of the old yellow enzyme reaction was emphasized.
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Affiliation(s)
- T Yamano
- Laboratory of Chemistry, Kansai Medical University, Osaka
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34
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Oosthuizen HM, Ungerer JP, Bissbort SH. Kinetic determination of serum adenosine deaminase. Clin Chem 1993; 39:2182-5. [PMID: 8403405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A new kinetic method for the determination of serum adenosine deaminase (EC 3.5.4.4) is described, with adenosine as the substrate and nucleoside phosphorylase and xanthine oxidase as the reaction enzymes. Inosine is produced, which is converted to hypoxanthine. The hypoxanthine is oxidized to xanthine, which is further oxidized to uric acid. In these two reactions, blue 2,6-dichlorophenolindophenol is reduced to a colorless compound and the decrease in color is measured spectrophotometrically at 606 nm. The assay was automated by using a Cobas Mira analyzer. The automated assay had a CV of < 7%, and the calibration curve was linear from 10 to 120 U/L. The assay correlates well with an established method, based on detection of liberated NH3 with Berthelot's reaction. The reference interval (mean +/- 2 SD) was 14-34 U/L (mean 24 U/L, n = 84). The enzymatic method described is easily automated and seems to be suitable for the routine determination of adenosine deaminase in serum.
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Affiliation(s)
- H M Oosthuizen
- Department of Chemical Pathology, Medical Faculty, University of Pretoria, South Africa
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35
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Muiño-Blanco T, Enríquez JA, Laveaga MJ, López-Pérez MJ. Use of a resolving density gradient created with dextran and poly(ethylene glycol) to purify brain synaptosomes. J Biochem Biophys Methods 1993; 27:1-10. [PMID: 7691917 DOI: 10.1016/0165-022x(93)90063-t] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Poly(ethylene glycol) and dextran are exclusion agents which when mixed above critical concentrations account for phase separation. In this work, we have used a density gradient created by mixing dextran (denser) and PEG (lighter) solutions to achieve a further purification of synaptosomes by centrifugation. When a brain synaptosomal preparation, containing about 40% of contaminating material, is sedimented in such gradient, two bands of material were obtained. Glutamate decarboxylase activity and glucose-dependent DCIP reduction (an improved marker of the metabolic performance of synaptosomes) were preferentially located in the lower band. These results, together with the electron micrographs of the bands, proved the synaptosomal nature of this lower band. The upper band contained myelin, membranes, vesicles and some synaptosomes. The gradient used shows a high resolution for isopycnic separation of sedimenting material and could be of general interest for subcellular fractionation.
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Affiliation(s)
- T Muiño-Blanco
- Departamento de Bioquímica, Biología Molecular y Celular, Facultad de Veterinaria, Zaragoza, Spain
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36
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Abstract
Both phenylbutazon and mofebutazon inhibit oxidative fragmentation of the methionine derivative, 2-keto-4-methylthio-butyric acid (KMB) by xanthine oxidase--or diaphorase mediated OH radical production. Differentiation of the two non-steroidal antiinflammatory drugs is possible by means of determining oxygen reduction by xanthine oxidase or diaphorase in the presence of the naphthoquinone, juglone, where only mofebutazon shows an inhibitory effect.
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Affiliation(s)
- I Schneider
- Institut für Botanik und Mikrobiologie, Biochemisches Labor, Technische Universität, München
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37
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Argall ME, Smith GD. The use of trehalose-stabilized lyophilized methanol dehydrogenase from Hyphomicrobium X for the detection of methanol. Biochem Mol Biol Int 1993; 30:491-7. [PMID: 8401307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The enzyme methanol dehydrogenase (EC 1.1.99.8) from Hyphomicrobium X was used in an attempt to develop a rapid colorimetric test for methanol. The enzyme was stabilized for storage by lyophilization in the presence of the disaccharide trehalose. It was found that the enzyme retained significantly greater activity in the dried state with trehalose than without. The enzyme was partially purified by ammonium sulphate fractionation, after which it was found to be more stable in solution at pH 9 than at pH 7. A procedure is given which involves mixing a defined amount of enzyme with the methanol-containing water together with phenazine methosulphate (PMS), 2-6-dichlorophenol-indophenol (DCPIP) and cyanide, and observing the resultant colour change from blue to yellow if methanol is present. The sensitivity of the procedure is such that 9 mg L-1 of methanol can be readily detected.
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Affiliation(s)
- M E Argall
- Division of Biochemistry and Molecular Biology, School of Life Sciences, Australian National University, Canberra
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38
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Abstract
We have developed a simple reversed-phase high-performance liquid chromatographic method for determining plasma ascorbic acid level and studied the relationship between its plasma concentration and fruit and vegetable intake and plasma dopamine-beta-hydroxylase activity. The samples were pretreated by precipitating the proteins and injected onto the column. Elution with a methanol gradient in sodium phosphate buffer was carried out by monitoring the absorbance at 265 nm, and the peak corresponding to ascorbic acid was well separated from other peaks of reagents used for pretreatment and from plasma endogenous components. The proposed method correlated well with the conventional dichlorophenol-indophenol method. Mean levels of ascorbic acid in normal human plasma were 0.86 +/- 0.36 mg/dl for males (twenty subjects, 19-28 years old) and 1.01 +/- 0.30 mg/dl for females (twenty subjects, 19-21 years old). There was good correlation between plasma ascorbic acid levels and dopamine-beta-hydroxylase levels, reflecting activities of daily living, but no correlation was found between these levels and dietary consumption of vegetables or fruits.
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Affiliation(s)
- K Tanishima
- Department of Clinical Laboratory Science, School of Allied Medical Professions, Kanazawa University, Ishikawa, Japan
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39
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Abstract
Hydrogen peroxide is now reported to be a normal aqueous humor component present, in the low microM concentration range, in the animal species which have been studied. This finding was established with the exclusive use of the dichlorophenol-indophenol method of analysis. In this procedure, aqueous humor is added to a blue, oxidized dichlorophenol-indophenol solution. The 605 nm absorbance of this solution immediately decreases in response to the reducing action of ascorbate present in the sample. The extent of reoxidation of the solution upon the addition of peroxidase, as measured by the increase in its 605 nm absorbance, can be quantitatively related to the concentration of H2O2 in the sample. A close examination of this method revealed that reduced dichlorophenol-indophenol spontaneously reoxidizes at a rate of 0.03 nmol min-1 microM-1, with generation of H2O2. H2O2 generation was unequivocally established by analysis of the temporal dependency of the absorbance increase produced by peroxidase in the absence of added H2O2 and by the sensitivity of this phenomenon to catalase. This spontaneous production of H2O2, on the other hand, cannot be attributed to ascorbate auto-oxidation because added ascorbate quantitatively reacts with dichlorophenol-indophenol, provided that an excess of the latter is maintained. This method then has an enormous potential to overestimate H2O2 in any sample. On the other hand, the response of the assay system to a given level of H2O2 depends on the level of reduction previously produced by ascorbate. This results in an artifactual positive correlation between ascorbate and H2O2 levels in samples containing variable amounts of ascorbate. In spite of these serious limitations the method can still be useful to measure H2O2 if appropriate precautions are taken. When using it for the analysis of rabbit aqueous humor H2O2 without correcting for the H2O2 generated during the assay and ignoring differences in the level of ascorbate in the samples, we obtained an average value of 25.3 microM H2O2, which coincides with that reported in the literature for the rabbit, but is obviously incorrect. When analysing aqueous humor there was the additional variable of the aqueous humor itself inhibiting the rate of dichlorophenol-indophenol auto-oxidation and so the final, corrected figure for H2O2 concentration in the aqueous humor became uncertain, since the auto-oxidation of the substrate could not be properly subtracted.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- S García-Castiñeiras
- Department of Ophthalmology, School of Medicine, University of Puerto Rico, San Juan
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Scholte HR, Ross JD, Blom W, Boonman AM, van Diggelen OP, Hall CL, Huijmans JG, Luyt-Houwen IE, Kleijer WJ, de Klerk JB. Assessment of deficiencies of fatty acyl-CoA dehydrogenases in fibroblasts, muscle and liver. J Inherit Metab Dis 1992; 15:347-52. [PMID: 1405467 DOI: 10.1007/bf02435973] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- H R Scholte
- Department of Biochemistry, Erasmus University Rotterdam, The Netherlands
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41
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Abstract
Automation of the glutathione peroxidase enzyme assay has been problematical. Although such methods have been reported, they do not give equivalent results to the standard manual assay, wherein glutathione oxidation is coupled to NADPH oxidation via glutathione reductase. We report here the development of a fully automated, continuous-flow, colorimetric method for glutathione peroxidase assays in which glutathione oxidation is monitored by its effect on the reaction of glutathione with the colorimetric reagent 2,6-dichloroindophenol. This method has a linear response to glutathione peroxidase over an 800-fold range of enzyme concentrations. Results of assays done by this method in erythrocyte and plasma samples correlate well with the standard manual coupled assay (r = 0.997 and 0.923, respectively), with no evidence of systematic errors. The assay works equally well with hydrogen peroxide or cumene hydroperoxide as substrate and shows the same selectivity toward glutathione S-transferases as the standard coupled assay. The within-day repeatability and the between-day reproducibility were estimated as 1.1 to 6.4% and 1.3 to 7.1% (relative standard deviation), respectively. This method is suitable for enzyme determinations in whole blood, erythrocytes, plasma, and serum from rats, rabbits, monkeys, and humans.
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Affiliation(s)
- W C Hawkes
- Western Human Nutrition Research Center, U.S. Department of Agriculture, Presidio of San Francisco, California 94129
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42
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Abstract
The reducing reaction of 2,6-dichlorophenolindophenol by L-ascorbic acid was used to determine the dead time of a stopped-flow instrument. Because this reaction is irreversible, the dead time could be determined by a simple graphical analysis. The dead time values determined by the present method were comparable to those by other methods previously reported.
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Affiliation(s)
- K Matsumura
- Second Department of Physiology, Nara Medical University, Kashihara, Japan
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43
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Barzana E, Klibanov AM, Karel M. A colorimetric method for the enzymatic analysis of gases: the determination of ethanol and formaldehyde vapors using solid alcohol oxidase. Anal Biochem 1989; 182:109-15. [PMID: 2690675 DOI: 10.1016/0003-2697(89)90726-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A novel enzymatic approach to the direct determination of ethanol vapors in the gas phase is described. The system is composed of alcohol oxidase, peroxidase, and the color indicator 2,6-dichloroindophenol dispersed on microcrystalline cellulose (avicel). Simple devices are developed for the semiquantitative determination of ethanol in the breath. The devices are optimized to produce a sharp color change at a set time of 1 min for ethanol concentrations above the legal limit for driving (kinetic method) or a stable final color after 5 min (equilibrium method). Such color changes are detectable by simple visual observation. Using TLC plastic sheets and a transmittance densitometer, the system can also be used as a quantitative method for the determination of ethanol or formaldehyde vapors. Dehydrated enzymes may be useful for the analysis of hazardous gases.
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Affiliation(s)
- E Barzana
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge 02139
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44
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Iushchishina AN, Genkin MV, Koroteev SV, Malievskiĭ AD, Davydov RM. [The effect of reversed micelles of cetyltrimethylammonium bromide on equilibrium constants and kinetics of oxidation-reduction reactions with the participation of cytochrome c]. Mol Biol (Mosk) 1988; 22:1650-7. [PMID: 2855257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
To model the effect of membrane environment on the electron transfer reactions we studied the thermodynamics and kinetics of the reactions of cytochrome c and 2,6-dichlorophenolindophenol with ferri- and ferrocyanide in the reversed micelles cetyltrimethylammonium bromide in chloroform/octan mixture. Incorporation of the protein in micelles leads to increasing the equilibrium constant (K1) up to 300 times. This effect is mainly due to a decrease in the ferrocytochrome c oxidation rate constant in the reaction with ferricyanide. Micellar solubilization of the dye also leads to a marked increase in the equilibrium constant K2. The estimations of the values K1 and K2 in water-alcohol mixtures and in aqueous micellar solutions of surfactant together with kinetical and spectral data show that the increase of K1 and K2 in reversed micelles is caused generally by redox potential changes of low-molecular reagents. The latter change their environment after adsorption on the micellar surface.
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45
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Seefeldt LC, Arp DJ. Redox-dependent subunit dissociation of Azotobacter vinelandii hydrogenase in the presence of sodium dodecyl sulfate. J Biol Chem 1987; 262:16816-21. [PMID: 3316226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Hydrogenases catalyze the reversible activation of dihydrogen. We have previously demonstrated that the purified hydrogenase from the nitrogen-fixing microorganism Azotobacter vinelandii is an alpha beta dimer (98,000 Da) with subunits of 67,000 (alpha) and 31,000 (beta) daltons and that this enzyme contains iron and nickel. The enzyme can be purified anaerobically in the presence of dithionite in a fully active state that is irreversibly inactivated by exposure to O2. Analysis of this hydrogenase by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) following boiling in SDS yields two protein staining bands corresponding to the alpha and beta subunits. However, when this enzyme was treated with SDS (25-65 degrees C) for up to 30 min under anaerobic/reductive conditions and then analyzed by anaerobic SDS-PAGE, a protein staining band corresponding to an apparent molecular mass of 58,000 Da was observed that stained for hydrogenase activity. Analysis of the 58,000-Da activity staining band by a Western immunoblot or a second aerobic SDS-polyacrylamide gel revealed that this protein actually consisted of both the alpha and beta subunits. Thus, the activity staining band (apparent 58,000 Da) represents the 98,000-Da dimer migrating abnormally on SDS-PAGE. Treatment of the anaerobically purified hydrogenase with SDS under aerobic conditions or under anaerobic conditions with electron acceptors prior to electrophoresis resulted in no activity staining band and the separated alpha and beta subunits. A. vinelandii hydrogenase was also purified under aerobic conditions in an inactive O2 stable form that can be activated by removal of oxygen followed by addition of reductant. This enzyme (as isolated), the activated form, and the reoxidized form were analyzed for their stability toward denaturation by SDS. We conclude that the dissociation of the A. vinelandii hydrogenase subunits in SDS is controlled by the redox state of the enzyme suggesting an important role of one or more redox sites in controlling the structure of this enzyme.
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Affiliation(s)
- L C Seefeldt
- University of California at Riverside, Department of Biochemistry 92521
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VanderJagt DJ, Garry PJ, Hunt WC. Ascorbate in plasma as measured by liquid chromatography and by dichlorophenolindophenol colorimetry. Clin Chem 1986; 32:1004-6. [PMID: 3708799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Ascorbic acid was measured in 125 plasma samples by an automated colorimetric method involving dichlorophenolindophenol and by a "high-performance" liquid-chromatographic procedure with electrochemical detection. The two methods gave comparable results for samples with ascorbate concentrations of 1 to 20 mg/L (r = 0.97). We also measured the amount of total ascorbate (ascorbic acid + dehydroascorbic acid) in the same samples by a liquid-chromatographic procedure with precolumn derivitization of ascorbic acid. We confirmed that plasma contains little dehydroascorbic acid.
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Leggott PJ, Robertson PB, Rothman DL, Murray PA, Jacob RA. Response of lingual ascorbic acid test and salivary ascorbate levels to changes in ascorbic acid intake. J Dent Res 1986; 65:131-4. [PMID: 3455968 DOI: 10.1177/00220345860650020801] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
This study sought to determine whether the lingual ascorbic acid test (LAAT) and measurement of salivary ascorbate reflect plasma and leukocyte ascorbate levels during controlled periods of ascorbic acid depletion and supplementation. Eleven healthy non-smoking men, aged 19-28 years, ate a diet that was repeated every seven days and was adequate in all nutrients except ascorbic acid (AA). This basal diet, which provided less than 5 mg of AA per day, was supplemented with 60 mg of AA per day for two weeks, 0 mg (placebo) per day for four weeks, 600 mg per day for three weeks, and 0 mg per day for four weeks. Oral examinations, the lingual ascorbic acid test, and measurement of salivary, plasma, and leukocyte ascorbate concentrations were conducted throughout the study. Ascorbic acid concentrations in plasma and leukocytes responded rapidly to changes in vitamin C intake. LAAT-derived ascorbate values were unrelated to ascorbic acid intake and plasma and leukocyte ascorbate concentrations. Salivary ascorbate levels approached the lower limits of detection of the assay and remained constant throughout the investigation. Oral hygiene was consistently excellent, and no severe mucosal or periodontal changes were observed. It was concluded that lingual ascorbic acid test values and salivary ascorbate levels are not related to changes in ascorbic acid intake and are not consistent with plasma or leukocyte ascorbate concentrations.
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Abstract
A slit-type mixer specially designed for stopped-flow X-ray scattering was constructed. It mixes two solutions at a time, allowing a large-sized window to be used immediately after mixing. Dead time of the mixer was 13 ms with 3.5 kg/cm2 of pressure at the piston head. It has been successfully used for studying the tetramer-dimer interconversion of phosphorylase a. The applicability of this mixer to other detection methods, far-UV circular dichroism, light scattering, EXAFS and fluorescence is also indicated.
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49
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Damoder R, Dismukes GC. pH dependence of the multiline, manganese EPR signal for the 'S2' state in PS II particles. Absence of proton release during the S1----S2 electron transfer step of the oxygen evolving system. FEBS Lett 1984; 174:157-61. [PMID: 6088285 DOI: 10.1016/0014-5793(84)81096-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The pH dependence of oxygen evolution rates, 2,6-dichlorophenolindophenol (DCIP) reduction rates and the intensity of the multiline manganese EPR signal associated with the S2K ok state has been studied using oxygen-evolving spinach (PS) II particles. The oxygen evolution and DCIP reduction rates are found to be very sensitive to pH, with the maximal rates occurring at pH 6.5-7.0. Both the rate and yield of the S2 multiline manganese EPR signal intensity, produced by single flash excitation at room temperature or by continuous illumination at 200 K, are found to be independent of pH, indicating that no proton is released from this manganese site during the S1----S2 electron transfer. These results agree with those from other laboratories showing no proton release on this transition, but using techniques monitoring other species.
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50
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Abstract
A stopped-flow instrument operating over temperature and pressure ranges of +30 to -20 degrees C and 10(-3) to 2 kbar , respectively, is described. The system has been designed so that it can be easily interfaced with many commercially available spectrophotometers of fast response time, with the aid of quartz fiber optics. The materials used for the construction are inert, metal free and the apparatus has proven to be leak free at temperatures as low as -20 degrees C under a pressure of 2 kbar . The performance of the instrument was tested by measuring the rate of reduction of cytochrome c with sodium dithionite and the 2,6-dichloroindophenol/ascorbate reaction. The dead time of the system has been evaluated to be 20, 50, and congruent to 100 ms in water at 20 degrees C, in 40% ethylene glycol/water, and at 20 degrees C and -15 degrees C, respectively. These values are rather pressure independent up to 2 kbar . Application of the bomb was demonstrated using the cytochrome c peroxidase/ethyl peroxide reaction. This process occurred in two phases and an increase in pressure decreased the rates of reactions indicating two positive volumes of activation (delta V not equal to app (fast) = 9.2 +/- 1.5 ml X mol-1; delta V not equal to app (slow) = 14 +/- 1.5 ml X mol-1, temperature 2 degrees C). The data suggest that the fast reaction could involve a hydrophobic bond, whereas the slow process could be associated with a stereochemical change of the protein. The problem of temperature equilibrium for high-pressure experiments is also discussed.
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