Patients 80 + have similar medication initiation rates to those aged 50-79 in Ontario FLS.

Among individuals presenting to an Ontario FLS, we compared bone active medication initiation rates of patients 80 years and older with those 50-79 years old. After accounting for fracture risk status, there was no statistically significant difference in medication initiation rates between the two age groups INTRODUCTION: A Fracture Liaison Service (FLS) offers post-fracture services to individuals over the age of 50 years and could potentially address age inequities in pharmacotherapy often observed for older adults. Among individuals presenting to an Ontario FLS and classified as being at high risk for future fracture, our objective was to compare bone active medication initiation rates of patients 80 years and older with those 50-79 years old. METHODS: In 39 FLS fracture clinics across Ontario, Canada, fracture prevention coordinators identified, assessed, and facilitated the referral of eligible patients for bone densitometry, fracture risk assessment, and implementation of pharmacotherapy in patients classified as high risk for future fracture. Variables assessed at baseline included age, sex, marital status, living location, fracture location, history of previous fracture, parent's history of hip fracture, history of falls, and fracture risk status. At 6 months, bone active medication initiation was assessed in patients classified as high risk for future fracture. The Chi-square test of independence was used to compare medication initiation rates between patients 80 + and those 50-79 years old. RESULTS: Our sample size consisted of 808 patients aged 50-79 years and 346 aged 80 + years. After accounting for fracture risk status, there was no statistically significant difference in medication initiation rates of patients 50-79 and 80 + years old (76.9% versus 73.7%, p = 0.251). CONCLUSION: A systematic approach to identifying patients at high risk for future fracture and tailoring treatment recommendations to these patients appeared to eliminate differences in treatment initiation rates based on older age.

Few fragility fracture patients perceive that their bone health is affected by their comorbidities and medications.

We examined fragility fracture patients' perceptions of associations between bone health and other chronic conditions and medications. Awareness of the associations between bone health and these conditions and medications was low. Providers should increase patients' awareness of these associations in order to minimize the risk of future fracture. INTRODUCTION: Among patients with a fragility fracture presenting with at least one other chronic health condition, we examined (1) perceptions of the association between bone health and their other health conditions, and (2) perceptions of the association between bone health and prescribed medications taken for other health conditions. METHODS: We identified fragility fracture patients presenting to a Canadian urban fracture clinic with at least one self-reported chronic health condition (in addition to bone fragility). In-depth interviews, 60-90 min in duration, were conducted. Our qualitative methodology was informed by saliency analysis. RESULTS: We interviewed 26 patients (21 females, 5 males) aged 45 to 84 years old. Participants were taking 1-13 medications each and presented with a variety of comorbidities (range 1-7). All participants described at least one condition or medication they were currently taking for which there existed evidence of a negative effect on bone health (increased risk of fracture, bone loss, falling). Two participants perceived a correct association between their other health conditions and compromised bone health, and four participants perceived a correct association between their medications and compromised bone health. CONCLUSION: All patients reported a chronic health condition and/or were taking at least one medication that potentially compromised their bone health. Patient awareness of the association between bone health and other health conditions and prescribed medications was low. Health care providers should increase patients' awareness of the bone health significance of their chronic conditions and medications in order to minimize the risk of future fracture.

Educational booklet reinforces knowledge of osteoporosis and influences intentions to improve bone health in previously diagnosed and treated patients.

We examined individuals' experiences using an educational booklet developed by the Ontario Osteoporosis Strategy. The booklet appeared to motivate individuals to make changes to their existing management of their bone health and served as a reference tool reaffirming current practices and beliefs for others. INTRODUCTION: The purpose of this study was to examine individuals' experiences of the educational booklet and explore the influence of the booklet on individuals' beliefs and actions regarding their bone health. METHODS: Eligible individuals were those who had been prescribed medication to treat low bone mass. One-on-one telephone interviews were conducted over an 18-month period. Participants were interviewed for approximately 1 hour and asked to provide their feedback on the booklet, and to discuss what they were doing with respect to the recommendations made in the booklet. RESULTS: We interviewed 50 participants who ranged in age from 58 to 89. The overall impression of the booklet was positive. Participants described the language in the booklet as clear and easy to understand. Participants stated that they would have appreciated receiving this tool at the onset of their diagnosis. Forty-two participants had already taken action, or expressed an intention to make changes, to their existing routines to improve their bone health. In contrast, eight participants used the booklet to reaffirm current practices and beliefs. For these individuals, the recommendations made in the booklet were consistent with what they had already been doing. CONCLUSION: The booklet can engage patients in discussions about bone health. The booklet appeared to motivate individuals to make changes to their existing routines in an effort to achieve better health outcomes for their bone health. Providing a tool like this to people recently diagnosed with a bone health issue may prove to be beneficial.

Having caregiving responsibilities affects management of fragility fractures and bone health.

In this secondary analysis of six qualitative studies, we found that approximately one-quarter of individuals with fragility fracture were serving as informal caregivers. The caregiving role appeared to be a cause of the fracture for some and was prioritized over bone health, acting as a barrier to bone health management. INTRODUCTION: Among fragility fracture patients serving as informal caregivers, our objective was to examine how caregiving responsibilities were associated with, and possibly impacted by, the fracture experience and the resulting management of bone health. METHODS: We conducted a secondary analysis (amplified analysis) of six qualitative studies to understand caregiver responsibilities and the relationship between these responsibilities and patients' management of the fracture and bone health. The primary studies and the secondary analysis were conducted from a phenomenological approach. Eligible individuals in the primary studies were English-speaking men and women who were 45+ years old recruited from three settings (local, provincial, and national). RESULTS: Without being prompted to talk about their experience of caregiving, 33 of 145 (23%) individuals reported they were providing care to a family member or friend at the time of their fracture or during recovery post-fracture. The experience of having caregiving responsibilities was related to the fracture and bone health in two ways: (1) the caregiving role appeared to be a cause of the fracture in some participants and (2) caregiving was prioritized over participants' own bone health and was a barrier to bone health management. CONCLUSION: Fragility fracture is associated with, and potentially leads to an impairment of, an important social role in patients providing physical and emotional support and supervision for dependents as caregivers. Further, an important cause of fragility fracture can occur in the act of caregiving.

Men's health-seeking behaviours regarding bone health after a fragility fracture: a secondary analysis of qualitative data.

UNLABELLED: In our qualitative study, men with fragility fractures described their spouses as playing an integral role in their health behaviours. Men also described taking risks, preferring not to dwell on the meaning of the fracture and/or their bone health. Communication strategies specific to men about bone health should be developed. INTRODUCTION: We examined men's experiences and behaviours regarding bone health after a fragility fracture. METHODS: We conducted a secondary analysis of five qualitative studies. In each primary study, male and female participants were interviewed for 1-2 h and asked to describe recommendations they had received for bone health and what they were doing about those recommendations. Maintaining the phenomenological approach of the primary studies, the transcripts of all male participants were re-analyzed to highlight experiences and behaviours particular to men. RESULTS: Twenty-two men (50-88 years old) were identified. Sixteen lived with a wife, male partner, or family member and the remaining participants lived alone. Participants had sustained hip fractures (n = 7), wrist fractures (n = 5), vertebral fractures (n = 2) and fractures at other locations (n = 8). Fourteen were taking antiresorptive medication at the time of the interview. In general, men with a wife/female partner described these women as playing an integral role in their health behaviours, such as removing tripping hazards and organizing their medication regimen. While participants described giving up activities due to their bone health, they also described taking risks such as drinking too much alcohol and climbing ladders or deliberately refusing to adhere to bone health recommendations. Finally, men did not dwell on the meaning of the fracture and/or their bone health. CONCLUSIONS: Behaviours consistent with those shown in other studies on men were described by our sample. We recommend that future research address these findings in more detail so that communication strategies specific to men about bone health be developed.

Patients do not have a consistent understanding of high risk for future fracture: a qualitative study of patients from a post-fracture secondary prevention program.

UNLABELLED: We examined fracture patients' understanding of "high" fracture risk after they were screened through a post-fracture secondary prevention program and educated about their risk verbally, numerically, and graphically. Our findings suggest that messages about fracture risk are confusing to patients and need to be modified to better suit patients' needs. INTRODUCTION: The aim of this study was to examine fracture patients' understanding of high risk for future fracture. METHODS: We conducted an in-depth qualitative study in patients who were high risk for future fracture. Patients were screened through the Osteoporosis Exemplary Care Program where they were educated about fracture risk: verbally told they were "high risk" for future fracture, given a numerical prompt that they had a >20 % chance of future fracture over the next 10 years, and given a visual graph highlighting the "high risk" segment. This information about fracture risk was also relayed to patients' primary care physicians (PCPs) and specialists. Participants were interviewed at baseline (within six months of fracture) and follow-up (after visit with a PCP and/or specialist) and asked to recall their understanding of risk and whether it applied to them. RESULTS: We recruited 27 patients (20 females, 7 males) aged 51-87 years old. Fractures were sustained at the wrist (n = 7), hip (n = 7), vertebrae (n = 2), and multiple or other locations (n = 11). While most participants recalled they had been labeled as "high risk" (verbal cue), most were unable to correctly recall the other elements of risk (numerical, graphical). Further, approximately half of the patients who recalled they were high risk did not believe that high risk applied, or had meaning, to them. Participants also had difficulty explaining what they were at risk for. CONCLUSIONS: Our results suggest that health care providers' messages about fracture risk are confusing to patients and that these messages need to be modified to better suit patients' needs.

Patient perceptions of provider barriers to post-fracture secondary prevention.

UNLABELLED: We examined patients' experiences regarding bone mineral density (BMD) testing and bone health treatment after being screened through Ontario's Fracture Clinic Screening Program. Provider-level barriers to testing and treatment appeared to be as significant as patient-level barriers and potentially had more of an impact on treatment than on testing. INTRODUCTION: Post-fracture secondary prevention programs have had modest effects on bone densitometry rates and osteoporosis (OP) treatment initiation. Few studies have examined in depth the reasons that patients choose to seek or avoid investigation and treatment after screening through such a program. Our purpose was to examine patients' experiences regarding bone mineral density (BMD) testing and bone health treatment after screening through Ontario's Fracture Clinic Screening Program (FCSP). METHODS: We conducted a prospective qualitative study in fragility fracture patients screened through one site of the FCSP. Eligible patients not on antiresorptive medication at the time of fracture were assessed by an osteoporosis screening coordinator and advised to follow up with their primary care physician for a BMD test and appropriate treatment. Participants were interviewed within 6, and within 18, months of their clinic visit. Fracture risk was assessed by the study team. Interviews were transcribed verbatim and analyzed by two researchers. RESULTS: We conducted 51 interviews with 25 patients (22 females, 3 males) aged 50-79 years old, of whom 8 were deemed high risk for future fracture. Eighteen participants had a BMD test between baseline and follow-up and three reported receiving a prescription for pharmacotherapy. We categorized 21 participants as experiencing at least one barrier to BMD testing and appropriate treatment including health care providers telling participants that the fracture was not a fragility fracture, using participants' appearance/demographic information and X-rays to judge bone density, telling participants that a BMD test was not appropriate, failing to discuss fracture risk status, and giving unclear or incorrect information about treatment. CONCLUSION: We identified modifiable barriers to post-fracture secondary prevention from the patient's perspective. Provider-level barriers appeare to be as significant as patient-level barriers and potentially had more of an impact on treatment than on BMD testing.

Non-pharmacological strategies used by patients at high risk for future fracture to manage fracture risk--a qualitative study.

UNLABELLED: We examined patients' self-management of bone health and fracture risk, particularly behaviors other than medication use and seeking diagnostic testing. Awareness of fracture risk was accompanied by positive lifestyle changes in participants' lives such as being careful. Future research should evaluate how lifestyle changes mitigate fracture risk. INTRODUCTION: We examined patients' understanding of bone health and self-management decisions regarding bone health and fracture risk, particularly behaviors other than medication use and seeking diagnostic testing. METHODS: A phenomenological (qualitative) study was conducted. English-speaking patients, 65+ years old, who were "high risk" for future fracture and prescribed pharmacotherapy after being screened through a post-fracture osteoporosis initiative were eligible. Patients were interviewed for 1-2 h and were asked to discuss perceptions of bone health status (bone densitometry results and perceived fracture risk), recommendations received for bone health, and lifestyle changes since their most recent fracture. We analyzed the data guided by Giorgi's methodology. RESULTS: We interviewed 21 fracture patients (6 males and 15 females), aged 65 to 88 years old. With the exception of one participant, all participants appeared to understand that they had low bone mass and were at risk of sustaining another fracture. Most participants (n = 20) were predominantly concerned about being careful, and they focused their responses on personal and environmental factors that they perceived to be modifiable. Participants also spoke about strategies to manage their bone health such as exercise, having a healthy diet and taking supplements, and using aids and devices. Non-pharmacological strategies used by patients appeared to be independent of current use of pharmacotherapy. CONCLUSIONS: Awareness of fracture risk was accompanied by a number of positive lifestyle changes in participants' lives such as being careful and engaging in exercise. Future research needs to evaluate how lifestyle changes such as being careful mitigate fracture risk.

Osteoarthritis patients' perceptions of "appropriateness" for total joint replacement surgery.

OBJECTIVE: To understand patients' perspectives on 'appropriateness' for hip and knee total joint arthroplasty (TJA). METHODS: Focus groups were conducted, stratified by history of a previous TJA, in English-speaking men and women aged 40+ years with moderate to severe hip and knee osteoarthritis. Participants discussed: their appropriateness for TJA; the ideal candidate; patients' role in TJA decision making; and the relationship between appropriateness and willingness to consider TJA. Participants self-completed a questionnaire assessing demographics, arthritis severity (Western Ontario McMaster University Osteoarthritis index - WOMAC), perceived TJA candidacy and willingness to consider TJA. Focus groups were audio-taped and transcribed verbatim. Content analysis was performed. RESULTS: Eleven focus groups were conducted with 58 participants in total: mean age 72 years; 79% female; 25 (43%) with prior TJA; mean WOMAC summary score 43.1. Half reported willingness to consider TJA and 43% felt they were appropriate for TJA. Appropriateness was equated with candidacy for the procedure. Pain intensity and the ability to cope with pain were identified as the most important factors determining surgical candidacy, but felt to be inadequately evaluated by physicians. TJA appropriateness and willingness were felt to be distinct, yet related, concepts; those unwilling had stricter criteria about candidacy than those who were willing. CONCLUSIONS: Participants equated appropriateness for TJA with surgical candidacy. Patients' pain experience (intensity, impact on quality of life, ability to cope) was seen as most important in determining appropriateness, but felt to be inadequately evaluated currently. Enhanced patient-physician communication, possibly through use of patient decision aids, has potential to improve patient selection for TJA.

Patients reject the concept of fragility fracture--a new understanding based on fracture patients' communication.

UNLABELLED: We examined patients' communication about fragility fractures to gain insight into why patients do not connect fractures to bone health. The term "fragility" fracture was a misnomer to patients who perceived the event as physically and emotionally traumatic. Improved communication about such fractures could facilitate awareness of bone health. INTRODUCTION: We examined patients' communication about fragility fractures to gain insight into why patients do not perceive the connection between their fracture and low bone mass. METHODS: A descriptive phenomenological (qualitative) study was conducted. During face-to-face interviews, the participants described the experience of their fracture in detail and the circumstances surrounding the fracture. Data analysis was guided by Giorgi's methodology. English-speaking male and female patients aged 65+ years and "high" risk for future fracture were eligible and screened for osteoporosis through an established screening program at an urban teaching hospital. RESULTS: We recruited 30 participants (9 males, 21 females), aged 65-88, who presented with a hip (n = 11), wrist (n = 11), shoulder (n = 6), or other (n = 2) fracture. Ten of the 30 fractures occurred inside the home and the remaining fractures occurred outside the home. Sustaining a fragility fracture was perceived as a traumatic event, both physically and emotionally. In general, participants used forceful, action-oriented words and referred to hard surfaces to describe the experience. Explanations for the fracture, other than bone quality, were often reported, especially that falls were "freak" or "fluke" events. Patients who sustained a fracture under more mundane circumstances seemed more likely to perceive a connection between the fracture and their bone health. CONCLUSIONS: The term fragility fracture was a misnomer for many older adults. By reexamining how this term is communicated to fracture patients, health care providers may better facilitate patients' awareness of bone health.

p53-independent upregulation of miR-34a during oncogene-induced senescence represses MYC.

Aberrant oncogene activation induces cellular senescence, an irreversible growth arrest that acts as a barrier against tumorigenesis. To identify microRNAs (miRNAs) involved in oncogene-induced senescence, we examined the expression of miRNAs in primary human TIG3 fibroblasts after constitutive activation of B-RAF. Among the regulated miRNAs, both miR-34a and miR-146a were strongly induced during senescence. Although members of the miR-34 family are known to be transcriptionally regulated by p53, we find that miR-34a is regulated independently of p53 during oncogene-induced senescence. Instead, upregulation of miR-34a is mediated by the ETS family transcription factor, ELK1. During senescence, miR-34a targets the important proto-oncogene MYC and our data suggest that miR-34a thereby coordinately controls a set of cell cycle regulators. Hence, in addition to its integration in the p53 pathway, we show that alternative cancer-related pathways regulate miR-34a, emphasising its significance as a tumour suppressor.

Group A streptococcal meningitis: report of a case and review of literature since 1976.

Group A streptococcal (GAS) invasive disease has become increasingly common in recent years. However, acute bacterial meningitis caused by this pathogen is unusual. We report a case of GAS meningitis in a previously healthy 21/2-year-old child associated with a dramatically rapid course and fatal outcome. A literature review of previously reported cases is presented. This case serves as a reminder that GAS can cause severe meningitis in otherwise healthy hosts.

A phase I study of cranial radiation therapy with concomitant continuous infusion paclitaxel in children with brain tumors.

BACKGROUND: The prognosis of children with high-grade astrocytomas of the central nervous system is grim and has not been substantially improved by conventional chemoradiotherapy. We performed a multi-institutional phase I study to determine the toxicities and tolerance of concurrent external beam radiation of the brain and a unique dose-schedule of paclitaxel as a radiation sensitizer. PROCEDURE: Paclitaxel was delivered intravenously as a continuous 24 h/day, 7 days/week infusion during the entire 6-week course of fixed schedule standard radiation therapy. The dose of paclitaxel was escalated in patient cohorts in standard phase I design. RESULTS: Eleven patients (eight brain stem gliomas, one glioblastoma multiforme, and two gliomatosis cerebri) were treated. Dose-limiting toxicity was encountered in the two patients treated at 6 mg/(m(2)/24 h), both of whom developed severe obstipation requiring prolonged hospitalization. CONCLUSIONS: We have shown in this first study of its kind that paclitaxel can be administered safely to children as a 6-week continuous infusion concurrent with cranial irradiation. The maximally tolerated and recommended phase II dose is 4 mg/(m(2)/day). The benefits of taxanes as clinical radiation sensitizers for children with high-grade gliomas, if any, remain to be determined.

Alterations of the oxygen-evolving apparatus in a (448)Arg --> (448)S mutant in the CP47 protein of photosystem II under normal and low chloride conditions.

We have shown previously that a mutant which contained the alteration (448)R --> (448)S (R448S) in the CP47 protein of photosystem II exhibited a defect in its ability to grow and assemble functional photosystem II reaction centers under chloride-limiting conditions [Wu, J., Masri, N., Lee, W., Frankel, L. K., and Bricker, T. M. (1999) Plant Mol. Biol. 39, 381-386]. In this paper we have examined the function of the oxygen-evolving complex under chloride-sufficient (480 microM) and chloride-limiting (< 20 microM) conditions. When placed under chloride-limiting conditions, both the control strain K3 and R448S cells exhibit a loss of steady-state oxygen evolution, with t(1/2) of 16 and 17 min, respectively. Upon the addition of chloride, both recover their oxygen-evolving capacity relatively rapidly. However, R448S exhibits a much slower reactivation of oxygen evolution than does K3 (t(1/2) of 308 and 50 s, respectively). This may indicate a defect at the low-affinity, rapidly exchanging chloride-binding site [Lindberg, K., and Andréasson, L.-E. (1996) Biochemistry 35, 14259-14267]. Additionally, alterations in the distribution of S states and S-state lifetimes were observed. Under chloride-sufficient conditions, the R448S mutant exhibits a significant increase in the proportion of reaction centers in the S(3) state and a greatly increased lifetime of the S(3) state. Under chloride-limiting conditions, the proportion of reaction centers in both the S(2) and S(3) states increases significantly, and there is a marked increase in the lifetime of the S(2) state. These alterations are not observed in the control strain K3. Our observations support the hypothesis that (448)R of CP47 may participate in the formation of the binding domain for chloride in photosystem II and/or in the functional interaction with the 33 kDa protein with the photosystem.

Human alveolar macrophages induce functional inactivation in antigen-specific CD4 T cells.

BACKGROUND: Alveolar macrophages (AMCs) are the most abundant phagocytic cells in the lung, but they present antigen poorly to T cells. OBJECTIVES: The objectives of our studies were to more clearly define the mechanisms by which AMCs present antigen to T cells and to determine whether AMCs actively inhibit T-cell activation. METHODS: We studied purified human CD4 T cells and compared the capacity of allogeneic AMCs and peripheral blood monocytes to induce T-cell proliferation and cytokine production. RESULTS: We previously demonstrated that human AMCs fail to upregulate expression of B7-1 and B7-2 on stimulation with IFN-gamma. We now demonstrate that AMCs actively induce T-cell unresponsiveness (functional inactivation) in an antigen-specific manner and reduce the capacity of CD4 T cells to respond on secondary stimulation. The induction of unresponsiveness was reversed by the addition of CD28 costimulation or IL-2. However, interruption of Fas/Fas ligand interactions or of B7/CTLA-4 interactions did not prevent unresponsiveness, indicating that neither CTLA-4 triggering nor Fas-induced apoptosis was involved in the induction of T-cell unresponsiveness. CONCLUSIONS: These studies indicate that AMCs actively tolerize CD4 T cells in an antigen-specific fashion. We propose that AMCs mediate a form of immune privilege in the lungs that effectively limits immune responses in the pulmonary compartment but has little effect on systemic immunity.

Routine chest radiographs in pediatric intensive care units.

OBJECTIVES: To determine whether interventions were performed based on portable routine morning chest x-rays (CXRs) in pediatric intensive care unit (PICU) patients and to identify patient subgroups for whom the routine CXR is most useful. DESIGN: Prospective multiinstitutional study. Setting. PICUs of 15 tertiary care hospitals. Patients. PICU patients who received a routine morning CXR were included in the study. OUTCOME MEASURES: Recorded data included: weight, diagnosis, presence of active cardiopulmonary problems, length of stay, and number and type of devices. The number and types of interventions based on the interpretation of the CXR were recorded. RESULTS: Five hundred twelve routine CXRs were evaluated. The majority of the routine chest radiographs were obtained on patients who were admitted for cardiovascular disease (195/512; 38%) or respiratory failure (186/512; 36%), and 465/512 of the routine CXRs (91%) were performed on patients with one or more devices. Two hundred thirty-one of the 512 routine CXRs (45%) resulted in 1 or more interventions. One hundred fifty-five of the 284 routine CXRs (55%) obtained in children /=40 kg, respectively. The frequency of interventions increased from 19% in children with no devices to >50% in children with 2 or more devices. One or more interventions were performed in 27% of routine CXRs when no active cardiopulmonary problems were present, compared with 51% of routine CXRs when active cardiopulmonary problems were present. Diagnosis and length of intensive care unit stay at the time the routine CXR was obtained did not affect the percentage of CXRs that resulted in interventions. CONCLUSIONS: Routine CXRs are more likely to result in interventions in the smaller, critically ill child with one or more devices and if active cardiopulmonary problems are present.

Isolation of lumenal proteins from spinach thylakoid membranes by triton X-114 phase partitioning.

The proteins present in the thylakoid lumen of higher plant chloroplasts have not been rigorously examined. In this communication we present a simple and rapid procedure for the isolation of the soluble proteins and extrinsic membrane proteins present in the thylakoid lumen from spinach. Our procedure involves extensive washing of the thylakoid membranes followed by Triton X-114 phase partitioning. When analyzed by one-dimensional polyacrylamide gel electrophoresis (PAGE), we obtain results which are very similar to those obtained by Kieselbach et al. using more classical methods [T. Kieselbach, A. Hagman, B. Andersson, W.P. Schroder, J. Biol. Chem. 273 (1998) 6710-6716]. About 25 major proteins are observed upon Coomassie blue staining. Upon two-dimensional isoelectric focusing-sodium dodecyl sulfate-PAGE and either Coomassie blue or silver staining, however, numerous other protein components are resolved. Our findings indicate that the total number of proteins (soluble and extrinsic membrane) present in the lumen may exceed 150.

Carboxylate groups on the manganese-stabilizing protein are required for its efficient binding to photosystem II.

The effects of the modification of carboxylate groups on the manganese-stabilizing protein of photosystem II were investigated. Carboxylate groups (including possibly the C-terminus) on the manganese-stabilizing protein were modified with glycine methyl ester in a reaction facilitated by 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide. The manganese-stabilizing protein that was modified while associated with NaCl-washed photosystem II membranes contained 1-2 modified carboxylates, whereas the protein that was modified while free in solution contained 4 modified carboxylates. Both types of modified protein could reconstitute oxygen evolution at high manganese-stabilizing protein to photosystem II reaction center ratios. However, the protein that had been modified in solution exhibited a dramatically altered binding affinity for photosystem II. No such alteration in binding affinity was observed for the protein that had been modified while associated with the photosystem. Mapping of the sites of modification was carried out by trypsin and Staphylococcus V8 protease digestion of the modified proteins and analysis by matrix-assisted laser desorption/ionization mass spectrometry. These studies indicated that the domains (157)D-(168)D and (212)E-(247)Q (C-terminus) are labeled only when the manganese-stabilizing protein is modified in solution. Modified carboxylates in these domains are responsible for the altered binding affinity of this protein for the photosystem.