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Biomedical subjects

C Preston

Publications and source records attributed to C Preston.

At least 19 recordsLinked to original sources
PubMed2005

Medical treatments for the maintenance therapy of reflux oesophagitis and endoscopic negative reflux disease.

BACKGROUND: Gastro-oesophageal reflux disease (GORD) - reflux of stomach contents +/- bile into the oesophagus causing symptoms such as heartburn and acid reflux - is a common relapsing and remitting disease which often requires long-term maintenance therapy. Patients with GORD may have oesophagitis (inflammation of the oesophagus) or a normal endoscopy (endoscopy negative reflux disease or ENRD). OBJECTIVES: To assess the effects of continuous maintenance therapy in adults with GORD (both ENRD and healed oesophagitis). SEARCH STRATEGY: We searched Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 2, 2003), MEDLINE (1966 to 2003), EMBASE (1980 to 2003), CINAHL (1982-2003), and the National Research Register (Issue 2, 2003) and reference lists of articles. We also contacted manufacturers and researchers in the field. SELECTION CRITERIA: Randomised controlled studies comparing PPIs, H2RAs, prokinetics, sucralfate and combinations either in comparison to another treatment regimen or to placebo in adults with reflux oesophagitis and ENRD. DATA COLLECTION AND ANALYSIS: One author extracted data from included trials and a second author carried out an unblinded check. Two authors independently assessed trial quality. Study authors were contacted for additional information. MAIN RESULTS: Maintenance of patients with healed oesophagitis: For a healing dose of PPI (generally the standard dose given by the manufacturer) versus placebo, the relative risk (RR) for oesophagitis relapse was 0.26 (95% confidence interval (CI) 0.19 to 0.36); versus H2RAs the RR was 0.36 (95% CI 0.28 to 0.46) and versus maintenance PPIs the RR was 0.63 (95% CI 0.55 to 0.73). However overall adverse effects were also more common and headaches were more common when comparing healing PPIs to H2RAs. For a maintenance dose of PPI (half of the standard dose) versus placebo, the RR for oesophagitis relapse was 0.46 (95% CI 0.38 to 0.57) and versus H2RAs the RR was 0.57 (95% CI 0.47 to 0.69). Overall adverse effects were more common.H2RAs were of marginal help but beneficial for symptomatic relief. Prokinetics and sucralfate were also more effective than placebo. For ENRD patients: Limited data with one RCT showed benefit for omeprazole 10 mg once daily over placebo (RR 0.4; 95% CI 0.29 to 0.53). AUTHORS' CONCLUSIONS: The findings in this review support the long-term treatment of oesophagitis to prevent relapse, both endoscopically and symptomatically. Healing doses of PPIs are more effective than all other therapies, although there is an increase in overall adverse effects compared to placebo, and headache occurrence compared to H2RAs. H2RAs prevent relapse more effectively than placebo, demonstrating a role for PPI-intolerant patients. Prokinetics and sucralfate both show benefit over placebo, but the former is no longer licenced. There is only limited data for ENRD.

Adult↗
PubMed2004

A systematic review of symptomatic outcomes used in oesophagitis drug therapy trials.

Symptoms are an important outcome for measurement in clinical trials into gastro-oesophageal reflux disease, but the optimal approach to symptom assessment has not been formally evaluated. The authors conducted a systematic review to assess how reflux symptoms have been evaluated and how well these correlate with oesophagitis healing and relapse.

Clinical Trials as Topic↗
PubMed2002

Artemether-lumefantrine for treating uncomplicated falciparum malaria.

BACKGROUND: Artemether-lumefantrine is being promoted by the World Health Organization for treating uncomplicated malaria. It is expensive. We sought evidence of its superiority over existing treatment regimens. OBJECTIVES: To compare artemether-lumefantrine with other antimalarial drugs for treating uncomplicated falciparum malaria. SEARCH STRATEGY: We searched the Cochrane Infectious Diseases Group specialized trials register (April 2002), the Cochrane Controlled Trials Register (Issue 2, 2002), MEDLINE (1966 to April 2002), EMBASE (1988 to April 2002), conference proceedings, and reference lists of articles. We contacted experts in malaria research and the pharmaceutical company that manufactures artemether-lumefantrine. SELECTION CRITERIA: Randomized and quasi-randomized trials comparing artemether-lumefantrine administered orally with standard treatment regimens (single drug or combination). DATA COLLECTION AND ANALYSIS: Two reviewers independently applied inclusion criteria to potentially relevant trials, assessed trial quality, and extracted data. Parasitaemia on day 28 (day 42 for sulfadoxine-pyrimethamine and day 63 for mefloquine) was the primary outcome. Adverse event information was collected from the studies. MAIN RESULTS: Eight trials (2117 participants) met the inclusion criteria. In the four studies against single agents, failure rates for artemether-lumefantrine tended to be higher in comparisons against sulfadoxine-pyrimethamine, halofantrine, and mefloquine. This difference was statistically significant for mefloquine. When compared with chloroquine, artemether-lumefantrine was better in two studies, but the failure rate for chloroquine at these sites was over 50%. All single agent studies used four doses of artemether-lumefantrine. In comparisons against combination treatment, three trials tested artemether-lumefantrine against mefloquine-artesunate and showed that artemether-lumefantrine was inferior for day 28 cure (Relative Risk 6.33, 95% confidence interval 3.08 to 13.01). If this comparison is confined to the two trials where participants received six doses, artemether-lumefantrine was associated with higher cure rates, but this was not statistically significant (Relative Risk 4.20, 95% confidence interval 0.55 to 31.93). REVIEWER'S CONCLUSIONS: Artemether-lumefantrine is more effective than chloroquine in chloroquine resistant areas. Artemether-lumefantrine is less effective than mefloquine or mefloquine combined with artesunate. We found no evidence to confirm or refute whether artemether-lumefantrine was better than sulfadoxine-pyrimethamine.

Antimalarials↗
PubMed2002

Evolution of herbicide resistance in weeds: initial frequency of target site-based resistance to acetolactate synthase-inhibiting herbicides in Lolium rigidum.

The frequency of individuals resistant to two acetolactate synthase (ALS)-inhibiting herbicides in three previously untreated populations of Lolium rigidum was determined. The frequency of individuals resistant to the sulfonylurea herbicide sulfometuron-methyl varied from 2.2 x 10(-5) to 1.2 x 10(-4) and the frequency of individuals resistant to the imidazolinone herbicide imazapyr varied from 1 x 10(-5) to 5.8 x 10(-5) depending on the population. Application of sulfometuron-methyl selected individuals with a herbicide-insensitive ALS, which was also cross-resistant to imazapyr. The high initial frequency of individuals resistant to ALS-inhibiting herbicides in L. rigidumpopulations never previously exposed to these herbicides helps explain the rapid evolution of herbicide resistance in this species once ALS-inhibiting herbicides were used.

Acetolactate Synthase↗
PubMed2001

TRISS methodology: an inappropriate tool for comparing outcomes between trauma centers.

BACKGROUND: The TRISS methodology has been used for comparison of survival outcomes between trauma centers. The purpose of this study was to evaluate the role of TRISS in comparing outcomes between a small and a large trauma center and evaluate its usefulness in various groups of patients. STUDY DESIGN: Trauma registry study that compared the survival outcomes between a large academic level I trauma center and a small community level II center. The comparison was made with the standard TRISS probability of survival, M value, and Z score. In the second part of the study the patients from the small center were matched for age, gender, injury severity score, Glasgow Coma Scale, head Abbreviated Injury Score, BP, prehospital respiratory assistance, and transport mode with an equal number of patients from the large center. The Z scores were calculated for each center. In the third part of the study the TRISS usefulness and limitations were evaluated in various subgroups of patients by calculating its sensitivity, specificity, positive predictive value, negative predictive value, and misclassification rate. RESULTS: The Z value of the large center (3,315 patients) was 2.24, indicating a considerably higher mortality than expected when compared with the Major Trauma Outcomes Study population. The Z value of the small center (331 patients) was -0.92, indicating fewer than the Major Trauma Outcomes Study expected deaths. In the second part of the study, 297 patients from the small center were matched with an equal number from the large center. The Z scores were -0.40 and -0.95, respectively, indicating slightly better outcomes than those of the Major Trauma Outcomes Study. Additional evaluation of the TRISS prediction of survival in various subgroups of patients showed a high misclassification rate in severe trauma, in some groups higher than 25%. CONCLUSIONS: The TRISS methodology is not a reliable tool for comparing outcomes between trauma centers and has an unacceptably high misclassification rate in patients with severe trauma.

Benchmarking↗
PubMed2001

Iron and protein sufficiency and red cell indices in phenylketonuria.

OBJECTIVE AND METHODS: We reviewed records of 41 children with treated phenylketonuria (PKU) in order to evaluate hematopoiesis and the effect of iron and protein sufficiency. RESULTS: Six children (15%) were found to have anemia. Combined depletion of iron and protein stores was most likely to result in anemia, and two of the three children with this finding were anemic. Four children (10%) had evidence of iron deficiency without anemia (a precursor stage of iron deficiency anemia). Clinically significant iron depletion was found in older as well as younger children (well beyond the traditional infant/toddler deficient years). Plasma albumin was normal in all children and was not adequately sensitive to detect protein depletion sufficient to cause anemia or decreased growth. However, low plasma prealbumin (a more sensitive marker of protein sufficiency) correlated significantly with altered hematopoiesis or poor growth. CONCLUSION: Compared to non-affected individuals, children with treated PKU make fewer red cells that have normal volume but increased hemoglobin per cell, resulting in a lower calculated hematocrit when measured by electronic cell counting. In the presence of iron or protein depletion, anemia may result. Routine monitoring of ferritin, complete blood counts and prealbumin are recommended for children with PKU at all ages.

Adolescent↗
PubMed1999

A comparison of the pharmacological properties of carbohydrate remodeled recombinant and placental-derived beta-glucocerebrosidase: implications for clinical efficacy in treatment of Gaucher disease.

The objective of these studies was to characterize the macrophage mannose receptor binding and pharmacological properties of carbohydrate remodeled human placental-derived and recombinant beta-glucocerebrosidase (pGCR and rGCR, respectively). These are similar but not identical molecules that were developed as enzyme replacement therapies for Gaucher disease. Both undergo oligosaccharide remodeling during purification to expose terminal mannose sugar residues. Competitive binding data indicated carbohydrate remodeling improved targeting to mannose receptors over native enzyme by two orders of magnitude. Mannose receptor dissociation constants (Kd) for pGCR and rGCR were each 13 nmol/L. At 37 degrees C, 95% of the total macrophage binding was mannose receptor specific. In vivo, pGCR and rGCR were cleared from circulation by a saturable pathway. The serum half-life (t1/2) was 3 minutes when less than saturable amounts were injected intravenously (IV) into mice. Twenty minutes postdose, beta-glucocerebrosidase activity increased over endogenous levels in all tissues examined. Fifty percent of the injected activity was recovered. Ninety-five percent of recovered activity was in the liver. Parenchymal cells (PC), Kupffer cells (KC), and liver endothelium cells (LEC) were responsible for 75%, 22%, and 3%, respectively, of the hepatocellular uptake of rGCR and for 76%, 11%, and 12%, respectively, of the hepatocellular uptake of pGCR. Both molecules had poor stability in LEC and relatively long terminal half-lives in PC (t1/2 = 2 days) and KC (t1/2 = 3 days).

Animals↗
PubMed1999

Complications of emergency intubation with and without paralysis.

Expert and definitive airway management is fundamental to the practice of emergency medicine. In critically ill patients, rapid sedation and paralysis, also known as rapid-sequence intubation, is used to facilitate endotracheal intubation in order to minimize aspiration, airway trauma, and other complications of airway management. An alternative method of emergent endotracheal intubation, intubation minus paralysis, is performed without the use of neuromuscular blocking agents. The present study compared complications of these two techniques in the emergency setting. Sixty-seven intubations minus paralysis were prospectively compared with 166 rapid-sequence intubations. Complications were greater in number and severity in the nonparalyzed group and included aspiration (15%), airway trauma (28%), and death (3%). None of these difficulties were observed in the rapid-sequence group (P < .0001). These results show that rapid-sequence intubation when compared with intubation minus paralysis significantly reduces complications of emergency airway management and should be made available to emergency physicians trained in its use.

Adult↗
PubMed1999

Left in limbo: patients' views on care across the primary/secondary interface.

OBJECTIVES: To discover the views of patients about their experiences across the interface between primary and secondary health care, including referral from general practitioners, outpatient and inpatient care, discharge, and aftercare. DESIGN: A qualitative study involving individual and focus group interviews of patients and interviews of carers. SUBJECTS: 33 patients who had attended at least one outpatient appointment or had been an inpatient between two and four months previously, and eight carers of patients with chronic conditions. SETTING: Three acute hospitals and one community health service in Leicestershire. MAIN OUTCOME MEASURES: Common themes in the views of patients and carers towards their experiences of care. RESULTS: Five themes emerged. The first four were: "getting in" (access to appropriate care), "fitting in" (orientation of care to the patient's requirements), "knowing what's going on" (provision of information), and "continuity" (continuity of staff and coordination and communication among professionals). The fifth theme was "limbo" (difficulty in making progress through the system), which was influenced by failures in care in relation to the other four themes. CONCLUSIONS: The concept of progress is central to patients' views of care. It involves both progress through the healthcare system and progress towards recovery or adjustment to an altered health state. Patients' views on how well they progress through the healthcare system may be an appropriate indicator for monitoring health service performance.

Continuity of Patient Care↗
PubMed1999

Measuring patients' attitudes to care across the primary/secondary interface: the development of the patient career diary.

BACKGROUND: A growing number of new ways of organising services across the primary/secondary interface are being introduced and evaluated. The principal motive for such reorganisation is to improve the efficiency of health care. However, unless the impact of the new services on patients is investigated and taken into account, it is possible that patients' reactions could be negative, a factor that could lead to unexpected consequences in the use and costs of services. OBJECTIVE: To develop a measure of patients' attitudes towards care across the interface between primary and secondary care. DESIGN: Generation of questions to be included in the measure from a qualitative study of patients' experiences of care across the interface; administration of pilot versions of the measure to samples of patients referred to secondary care; refinement of questions guided by analysis of response patterns, principal components analysis and internal consistency; administration of the final version of the patient career diary in complete form retrospectively to patients referred to secondary care, and one section alone to patients attending outpatient departments for follow up appointments. Face validity was assessed by analysis of open comments in a sample of 50 diaries, and review of the diary by 34 health professionals. Construct validity was assessed by investigation of levels of correlation between components of each section of the diary and the components of the healthcare section overall. SETTING: In the final field test, patients were attending various hospital services, including cardiology, dermatology, neurology, gynaecology, general surgery, general medicine, ophthalmology, trauma and orthopaedics, and gastroenterology. RESULTS: The final version of the diary included 109 questions in seven sections: general practitioner (GP) visits and referral, other GP visits, first outpatient visit, other outpatient visits, inpatient stay and discharge, care after discharge, and care overall. Response rates were poor for retrospective completion of the entire diary, but excellent when a section was given separately. Principal components analysis confirmed that components relating to issues identified as important to patients in the qualitative study had been included in the diary. Levels of internal consistency were good, and comments of patients and health professionals supported validity. CONCLUSION: The patient career diary is a valid and reliable measure of patients' attitudes to care across the interface. It should be given in sections to ensure adequate response rates, and is suitable for use in the evaluation or quality of patterns of care across the interface. In future, the impact on patients of new ways of organising services across the interface should be investigated by use of measures such as the patient career diary.

Attitude↗
PubMed1998

Use of a novel histidyl modifier to probe for residues on Tris-treated photosystem II membrane fragments that may bind functional manganese.

In this paper, we investigate the effects of histidyl amino acid modification on high-affinity Mn binding to photosystem II (PSII) using methods similar to those used in the preceding paper [Ghirardi et al. (1998) Biochemistry 37, 0000] for carboxyl amino acid modification. Given the rather low specificity of diethyl pyrocarbonate (DEPC) for histidine modification, we modified Tris-washed PSII membranes with a novel and more specific histidyl modifier, platinum(II) (2,2':6',2"-terpyridine) chloride (Pt-TP). Both the "diphenylcarbazide (DPC)-inhibition assay" and single-turnover flash approaches were used. The concentration dependence of Pt-TP modification on steady-state measurements shows two types of interactions, each accounting for about half of the full effect. At concentrations <50 microM, Pt-TP modifies mostly histidyls and abolishes half of the observed Mn inhibition of DPC-mediated 2,6-dichlorophenolindophenol (DCIP) photoreduction (equivalent to two high-affinity, Mn-binding ligands). This effect can be blocked by addition of Mn2+ during Pt-TP modification. Double-modification experiments with DEPC and Pt-TP demonstrate that both modifiers affect the same observable histidyl residues in PSII. Above 50 microM, Pt-TP modifies mostly cysteines (or histidines in a more hydrophobic environment) and has an additional effect on the reducing side of PSII that (a) does not involve Mn binding and (b) results in the apparent abolishment of all four of the Mn-binding ligands detected by the DPC-inhibition assay. Single-flash experiments show that histidyl modification does not eliminate the binding of the high-affinity, photooxidizable Mn2+ to Asp170 on D1 (nor does it significantly affect high-affinity DPC photooxidation), but it does decrease the binding affinity (Kd) of that Mn from 0.6 to 1.5 microM, particularly at lower (<50 microM Pt-TP) concentrations. Double-modification experiments also demonstrate that the lower affinity, photooxidizable Mn-binding site, uncovered when the high-affinity site is modified with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride (EDC) [see Ghirardi et al. (1998)], is not associated with a histidyl ligand. Three nonphotooxidizable, high-affinity Mn2+ ions bind to a second carboxyl and two histidyl ligands, and these Mn are not photooxidized by a flash even when the ligand to the photooxidizable Mn is modified by EDC. Proteolytic enzyme studies indicate that the two histidyl ligands identified by the DPC-inhibition assay are probably His337 on D1 and His 339 on D2, but His 332 on D1 is not eliminated.

2,6-Dichloroindophenol↗
PubMed1998

Time to publication as full reports of abstracts of randomized controlled trials in cystic fibrosis.

OBJECTIVES: To determine 1) what proportion of abstracts of randomized controlled trials (RCTs) presented at international conferences on cystic fibrosis (CF) are published as full reports, 2) time to publication, and 3) factors that might delay or prevent publication. METHODS: At the end of 1995, the Cochrane CF Group's register of RCTs contained 199 abstracts describing 180 RCTs. Abstracts were identified by handsearching 44 abstract books of three international CF conferences over a 30-year period. We searched the register for subsequent full reports of these RCTs and used survival analysis to investigate time to publication. Using the log-rank test, we examined 1) whether there is a difference in time to publication between reports where the investigators concluded that the test treatment was as effective as or better than the control treatment, and reports where it was not, and 2) whether there is a difference in time to publication according to sample size. RESULTS: Thirty-two percent of the 178 abstracts analyzed were subsequently published in full. Survival analysis indicated that the proportions published before 12 months, 2 years, and 5 years were 8.1%, 29%, and 40% respectively. No difference in time to publication was identified when the abstracts were stratified according to conclusions or sample size; no significant association (P > 0.05) existed between time to publication and both sample size and conclusions together. CONCLUSION: Only a small proportion of abstracts of RCTs presented at international conferences on CF are followed by full publication, and usually only after several years. Therefore, many potentially valuable studies do not reach a wide audience. However, we found no consistent factors which might delay or prevent publication.

Abstracting and Indexing↗
PubMed1994

Heart failure therapy with cilazapril: an overview.

The efficacy and safety of cilazapril in chronic heart failure have been extensively investigated in an international clinical program in patients with underlying chronic heart failure with ischemic heart disease or dilated cardiomyopathy. Cilazapril in single doses of 1.25-5 mg produced a significant dose-dependent reduction in pulmonary capillary wedge pressure and systemic vascular resistance and a significant increase in cardiac index. In placebo-controlled studies, 1-5 mg of cilazapril once daily for 12 weeks prolonged predose exercise test duration and improved New York Heart Association classification status and signs and symptoms of chronic heart failure, including paroxysmal nocturnal dyspnea. Up to 86% of patients receiving these dosages had improvement, with only 12% of patients requiring the higher dose, 5 mg. These data indicate that cilazapril is effective when administered once daily to patients with chronic heart failure receiving concomitant therapy with digitalis and/or a diuretic. The safety of cilazapril in patients with chronic heart failure has been evaluated in 1,163 patients administered from 0.5 to 15 mg once daily for treatment periods ranging from 1 day to 57 months. Cilazapril was administered to 500 patients for at least 6 months, 264 patients for at least 1 year, and 101 patients for at least 2 years. The most frequently occurring adverse events were dizziness, coughing, dyspnea, fatigue, angina pectoris, and headache. Cilazapril was equally well tolerated by young and elderly patients. Treatment was discontinued due to adverse events in 12.9% of patients, mainly as a result of coughing (1.7%) and dizziness (1%). Forty-four patients (3.8%) died during cilazapril therapy or during a period without treatment. Of these deaths, 93% were due to cardiac causes, especially rhythm disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathy, Dilated↗
PubMed1992

On the Mechanism of Resistance to Paraquat in Hordeum glaucum and H. leporinum: Delayed Inhibition of Photosynthetic O(2) Evolution after Paraquat Application.

The mechanism of resistance to paraquat was investigated in biotypes of Hordeum glaucum Steud. and H. leporinum Link. with high levels of resistance. Inhibition of photosynthetic O(2) evolution after herbicide application was used to monitor the presence of paraquat at the active site. Inhibition of photosynthetic O(2) evolution after paraquat application was delayed in both resistant biotypes compared with the susceptible biotypes; however, this differential was more pronounced in the case of H. glaucum than in H. leporinum. Similar results could be obtained with the related herbicide diquat. Examination of the concentration dependence of paraquat-induced inhibition of O(2) evolution showed that the resistant H. glaucum biotype was less affected by herbicide compared with the susceptible biotype 3 h after treatment at most rates. The resistant H. leporinum biotype, in contrast, was as inhibited as the susceptible biotype except at the higher rates. In all cases photosynthetic O(2) evolution was dramatically inhibited 24 h after treatment. Measurement of the amount of paraquat transported to the young tissue of these plants 24 h after treatment showed 57% and 53% reductions in the amount of herbicide transported in the case of the resistant H. glaucum and H. leporinum biotypes, respectively, compared with the susceptible biotypes. This was associated with 62% and 66% decreases in photosynthetic O(2) evolution of young leaves in the susceptible H. glaucum and H. leporinum biotypes, respectively, a 39% decrease in activity for the resistant H. leporinum biotype, but no change in the resistant H. glaucum biotype. Photosynthetic O(2) evolution of leaf slices from resistant H. glaucum was not as inhibited by paraquat compared with the susceptible biotype; however, those of resistant and susceptible biotypes of H. leporinum were equally inhibited by paraquat. Paraquat resistance in these two biotypes appears to be a consequence of reduced movement of the herbicide in the resistant plants; however, the mechanism involved is not the same in H. glaucum as in H. leporinum.

Journal Article↗
PubMed1991

The carboxyl modifier 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) inhibits half of the high-affinity Mn-binding site in photosystem II membrane fragments.

The diphenylcarbazide(DPC)/Mn2+ assay [Hsu, B.-D., Lee, J.-Y., & Pan, R.-L. (1987) Biochim. Biophys. Acta 890, 89-96] was used to assess the amount of the high-affinity Mn-binding site in manganese-depleted photosystem II (PS II) membrane fragments from spinach and Scenedesmus obliquus. The assay mechanism at high DPC concentration was shown to involve noncompetitive inhibition of only half of the control level of DPC donation to PS II by micromolar concentrations of Mn at pH 6.5 (i.e., one of two DPC donation sites is inhibited). At low DPC concentration both DPC and Mn2+ donate to PS II additively. Treatment with the carboxyl amino acid modifier 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) inhibited half of the high-affinity Mn-binding site in spinach and Scenedesmus WT PS II membranes and all of the available site in Scenedesmus LF-1 mutant PS II membranes. A similar EDC concentration dependence was observed in all cases. Addition of 2 mM MnCl2 to the 10 mM EDC modification buffer provided complete protection for the Mn-binding site from modification. This protection was specific for Mn2+; six other divalent cations were ineffective. We conclude that EDC modifies that half of the high-affinity Mn-binding site that is insensitive to the histidine modifier diethyl pyrocarbonate (DEPC) [Seibert, M., Tamura, N., & Inoue, Y. (1989) Biochim. Biophys. Acta 974, 185-191] and directly affects ligands that bind Mn. The effects of EDC and DEPC that influence the high-affinity site are mutually exclusive and are specific to the lumenal side of the PS II membrane. Removal of the two more loosely bound of the four functional Mn from PS II membranes uncovers that part of the high-affinity site associated with carboxyl but not histidyl residues. We suggest that carboxyl residues on reaction center proteins are associated with half of the high-affinity Mn-binding site in PS II and are involved along with histidine residues in binding Mn functional in the O2-evolving process.

Binding, Competitive↗