Determining the relationship between protein folding pathways on and off the ribosome remains an important area of investigation in biology. Studies on isolated domains have shown that alteration of ...the separation of residues in a polypeptide chain, while maintaining their spatial contacts, may affect protein stability and folding pathway. Due to the vectorial emergence of the polypeptide chain from the ribosome, chain connectivity may have an important influence upon cotranslational folding. Using MATH, an all β-sandwich domain, we investigate whether the connectivity of residues and secondary structure elements is a key determinant of when cotranslational folding can occur on the ribosome. From Φ-value analysis, we show that the most structured region of the transition state for folding in MATH includes the N and C terminal strands, which are located adjacent to each other in the structure. However, arrest peptide force-profile assays show that wild-type MATH is able to fold cotranslationally, while some C-terminal residues remain sequestered in the ribosome, even when destabilized by 2–3 kcal mol−1. We show that, while this pattern of Φ-values is retained in two circular permutants in our studies of the isolated domains, one of these permutants can fold only when fully emerged from the ribosome. We propose that in the case of MATH, onset of cotranslational folding is determined by the ability to form a sufficiently stable folding nucleus involving both β-sheets, rather than by the location of the terminal strands in the ribosome tunnel.
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•Adjacent N and C terminal strands are most structured region in the transition state.•Two circular permutants retain the same folding pathway as wild-type MATH.•On the ribosome, early emergence of terminal strands does not promote earlier folding.•Formation of both β-sheets is energetically critical for folding on the ribosome.•Folding pathway minimizes formation of partly structured states prone to mis-folding.
The wide-specificity loading module for the avermectin-producing polyketide synthase was grafted onto the first multienzyme component (DEBS1) of the erythromycin-producing polyketide synthase in ...place of the normal loading module. Expression of this hybrid enzyme in the erythromycin producer Saccharopolyspora erythraea produced several novel antibiotic erythromycins derived from endogenous branched-chain acid starter units typical of natural avermectins. Because the avermectin polyketide synthase is known to accept more than 40 alternative carboxylic acids as starter units, this approach opens the way to facile production of novel analogs of antibiotic macrolides.
Abstract Objectives: To determine the association between ambulance response time and survival from out of hospital cardiopulmonary arrest and to estimate the effect of reducing response times. ...Design: Cohort study. Setting: Scottish Ambulance Service. Subjects: All out of hospital cardiopulmonary arrests due to cardiac disease attended by the Scottish Ambulance Service during May 1991 to March 1998. Main outcome measures: Survival rate to hospital discharge and potential improvement from reducing response times. Results: Of 13 822 arrests not witnessed by ambulance crews but attended by them within 15 minutes, complete data were available for 10 554 (76%). Of these patients, 653 (6%) survived to hospital discharge. After other significant covariates were adjusted for, shorter response time was significantly associated with increased probability of receiving defibrillation and survival to discharge among those defibrillated. Reducing the 90th centile for response time to 8 minutes increased the predicted survival to 8%, and reducing it to 5 minutes increased survival to 10-11% (depending on the model used). Conclusions: Reducing ambulance response times to 5 minutes could almost double the survival rate for cardiac arrests not witnessed by ambulance crews. What is already known on this topic Three quarters of all deaths from myocardial infarction occur after cardiac arrest in the community Survival after out of hospital arrest is much lower in the United Kingdom than the United States What this study adds Ambulance response times are independently associated with defibrillation and survival Decreasing the target for response to 90% of calls from 14 minutes to 8 minutes would increase survival from 6% to 8% A response time of 5 minutes would increase survival to 10-11%
Abstract Objective: To estimate the potential impact of public access defibrillators on overall survival after out of hospital cardiac arrest. Design: Retrospective cohort study using data from an ...electronic register. A statistical model was used to estimate the effect on survival of placing public access defibrillators at suitable or possibly suitable sites. Setting: Scottish Ambulance Service. Subjects: Records of all out of hospital cardiac arrests due to heart disease in Scotland in 1991-8. Main outcome measures: Observed and predicted survival to discharge from hospital. Results: Of 15 189 arrests, 12 004 (79.0%) occurred in sites not suitable for the location of public access defibrillators, 453 (3.0%) in sites where they may be suitable, and 2732 (18.0%) in suitable sites. Defibrillation was given in 67.9% of arrests that occurred in possibly suitable sites for locating defibrillators and in 72.9% of arrests that occurred in suitable sites. Compared with an actual overall survival of 744 (5.0%), the predicted survival with public access defibrillators ranged from 942 (6.3%) to 959 (6.5%), depending on the assumptions made regarding defibrillator coverage. Conclusions: The predicted increase in survival from targeted provision of public access defibrillators is less than the increase achievable through expansion of first responder defibrillation to non-ambulance personnel, such as police or firefighters, or of bystander cardiopulmonary resuscitation. Additional resources for wide scale coverage of public access defibrillators are probably not justified by the marginal improvement in survival.
Objective To determine the cost effectiveness and cost utility of locating defibrillators in all major airports, railway stations, and bus stations throughout Scotland. Design Economic modelling ...exercise with data from Heartstart (Scotland). Parameters used in economic model included direct costs derived for increased accident and emergency attendances, increased hospital bed days, purchase and maintenance of defibrillators, and training in their use; life years gained calculated from increased discharges from hospital and mean survival after discharge; utility (quality of life) obtained from published data. Sensitivity analyses tested the robustness of model. Future gains discounted at 1.5% a year and future costs at 6%. Setting Whole of Scotland. Subjects Records of all prehospital cardiac arrests due to presumed heart disease that occurred in a major airport, railway, or bus station between May 1991 and March 1998 and were not witnessed by ambulance or medical staff. Main outcome measures Observed survival to hospital admission and observed survival to discharge. Predicted survival calculated by applying observed survival in patients attended by ambulance staff within three minutes to those who waited longer. Results The total discounted direct costs were £18 325 a year. The cost per life year gained was £29 625 ($49 625, €;43 151) and the cost per quality adjusted life year (QALY) gained was £41 146 ($68 924, €;59 932). More widespread provision of public place defibrillators would increase these figures. Conclusions The cost per QALY calculated for public place defibrillators represents poorer value for money than some alternative strategies for improving survival after prehospital cardiopulmonary arrest, such as the use of other trained first responders. The figure exceeds the commonly discussed cut off levels for funding in the United Kingdom and United States of £30 000 and $50 000 per QALY, respectively.
During assembly of complex polyketide antibiotics like erythromycin A, molecular recognition by the multienzyme polyketide synthase controls the stereochemical outcome as each successive ...methylmalonyl-coenzyme A (CoA) extender unit is added. Acylation of the purified erythromycin-producing polyketide synthase has shown that all six acyltransferase domains have identical stereospecificity for their normal substrate, (2S)-methylmalonyl-CoA. In contrast, the configuration of the methyl-branched centers in the product, that are derived from (2S)-methylmalonyl-CoA, is different. Stereoselection during the chain building process must, therefore, involve additional epimerization steps.
Abstract Objectives: To determine the short and long term outcome of patients admitted to hospital after initially successful resuscitation from cardiac arrest out of hospital. Design: Review of ...ambulance and hospital records. Follow up of mortality by “flagging” with the registrar general. Cox proportional hazards analysis of predictors of mortality in patients discharged alive from hospital. Setting: Scottish Ambulance Service and acute hospitals throughout Scotland. Subjects: 1476 patients admitted to a hospital ward, of whom 680 (46%) were discharged alive. Main outcome measures: Survival to hospital discharge, neurological status at discharge, time to death, and cause of death after discharge. Results: The median duration of hospital stay was 10 days (interquartile range 8-15) in patients discharged alive and 1 (1-4) day in those dying in hospital. Neurological status at discharge in survivors was normal or mildly impaired in 605 (89%), moderately impaired in 58 (8.5%), and severely impaired in 13 (2%); one patient was comatose. Direct discharge to home occurred in 622 (91%) cases. The 680 discharged survivors were followed up for a median of 25 (range 0-68) months. There were 176 deaths, of which 81 were sudden cardiac deaths, 55 were non-sudden cardiac deaths, and 40 were due to other causes. The product limit estimate of 4 year survival after discharge was 68%. The independent predictors of mortality on follow up were increased age, treatment for heart failure, and cardiac arrest not due to definite myocardial infarction. Conclusion: About 40% of initial survivors of resuscitation out of hospital are discharged home without major neurological disability. Patients at high risk of subsequent cardiac death can be identified and may benefit from further cardiological evaluation. Key messages Nearly 70% of patients discharged after cardiac arrest are alive four years after the event Patients whose cardiac arrest is not due to definite myocardial infarction require further cardiological assessment
Aims To determine whether survival after discharge following pre-hospital cardiopulmonary arrest has improved. Methods and results The Heartstart Register was used to identify all 1659 patients ...discharged alive from Scottish hospitals during 1991–01 following pre-hospital arrest due to cardiac aetiology. The cohort was split into tertiles using year of arrest. A Cox proportional hazards model was used to determine risk of death relative to 1991–93. Patients who survived cardiopulmonary arrest in 1997–01 were less likely to die from any cause (unadjusted HR 0.60, 95% CI 0.48–0.75, P<0.001) or cardiac disease (unadjusted HR 0.50, 95% CI 0.38–0.65, P<0.001). After adjustment for case-mix, there remained significant declines in all-cause (adjusted HR 0.62, 95% CI 0.50–0.78, P<0.001) and cardiac death (adjusted HR 0.52, 95% CI 0.39–0.68, P<0.001). Clinical management had improved, with increased use of thrombolysis (47–63%, χ2 trend, P<0.001), beta-blockers (28–53%, χ2 trend, P<0.001), ACE-inhibitors (48–69%, χ2 trend, P<0.001), and anti-thrombotics (79–88%, χ2 trend, P<001). Adjustment for recorded changes in management attenuated the decline in all-cause death (adjusted HR 0.77, 95% CI 0.60–0.98, P=0.03). Conclusion Survival following cardiopulmonary arrest has improved after adjusting for changes in case-mix. Better clinical management has contributed to this improvement.
To determine the incidence, predisposing factors, and costs of emergency treatment of severe hypoglycemia in people with type 1 and type 2 diabetes.
Over a 12-month period, routinely collected ...datasets were analyzed in a population of 367,051 people, including 8,655 people with diabetes, to measure the incidence of severe hypoglycemia that required emergency assistance from Ninewells Hospital and Medical School (NHS) personnel including those in primary care, ambulance services, hospital accident and emergency departments, and inpatient care. Associated costs with these episodes were calculated.
A total of 244 episodes of severe hypoglycemia were recorded in 160 patients, comprising 69 (7.1%) people with type 1 diabetes, 66 (7.3%) with type 2 diabetes treated with insulin, and 23 (0.8%) with type 2 diabetes treated with sulfonylurea tablets. Incidence rates were 11.5 and 11.8 events per 100 patient-years for type 1 and type 2 patients treated with insulin, respectively. Age, duration, and socioeconomic status were identified as risk factors for severe hypoglycemia. One in three cases were treated solely by the ambulance service with no other contact from health care professionals. The total estimated cost of emergency treatment of severe hypoglycemia was </= pound 92,078 in one year.
Hypoglycemia requiring emergency assistance from health service personnel is as common in people with type 2 diabetes treated with insulin as in people with type 1 diabetes. It is associated with considerable NHS resource use that has a significant economic and personal cost.
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