DWI-Based Algorithm to Predict Disability in Patients Treated with Thrombectomy for Acute Stroke.

BACKGROUND AND PURPOSE: The reasons for poor clinical outcome after thrombectomy for acute stroke, concerning around half of all patients, are misunderstood. We developed a hierarchic algorithm based on DWI to better identify patients at high risk of disability. MATERIALS AND METHODS: Our single-center, retrospective study included consecutive patients with acute ischemic stroke who underwent thrombectomy for large anterior artery occlusion and underwent pretreatment DWI. The primary outcome was the mRS at 3 months after stroke onset. Multivariable regression was used to identify independent clinical and imaging predictors of poor prognosis (mRS > 2) at 3 months, and a hierarchic algorithm predictive of disability was developed. RESULTS: A total of 149 patients were analyzed. In decreasing importance, DWI lesion volume of >80 mL, baseline NIHSS score of >14, age older than 75 years, and time from stroke onset to groin puncture of >4 hours were independent predictors of poor prognosis. The predictive hierarchic algorithm developed from the multivariate analysis predicted the risk of disability at 3 months for up to 100% of patients with a high predictive value. The area under the receiver operating characteristic curve was 0.87. CONCLUSIONS: The DWI-based hierarchic algorithm we developed is highly predictive of disability at 3 months after thrombectomy and is easy to use in routine practice.

Pertinence of electronic death certificates for real-time surveillance and alert, France, 2012-2014.

OBJECTIVES: In France, the early mortality monitoring, conducted by Santé publique France, the French National Public Health agency (SpFrance) (formerly French Institute for public health surveillance-InVS), is based on the administrative data provided by the National Institute for Statistic and Economic Studies (INSEE) and consequently does not allow analyses on medical causes of death. Since 2007, the physicians can certify deaths electronically. In this electronic system (Electronic Death Registration System; EDRS), the medical causes of death, in free-text format, are directly transmitted to SpFrance. In the future, these data could be used in a real-time surveillance system by medical causes of death. The objective of this study was to evaluate the pertinence of e-death certification using the following assessment criteria: timeliness, representativeness, and completeness of sociodemographic and medical information included in the e-death certificates. STUDY DESIGN: This study consisted of a descriptive analysis of the information collected by e-death certificates recorded between January 1, 2012 and July 31, 2014. METHODS: The study quantified the temporal and geographical evolution of the deployment of the EDRS between 2012 and 2014. The timeliness of the system was estimated by calculating the delay between the dates of death and of data availability for analysis. Sociodemographic and death-related characteristics were described. The frequency of missing data was measured for each variable. The number of completed fields per certificate and the number of words per field and per certificate were calculated for the medical causes of death. RESULTS: Between January 2012 and July 2014, 77,776 e-death certificates were collected. A slight increase in the use of the e-death certification was observed during the study period, reaching 6.1% of the total number of deaths in 2014. Good national coverage was noted. Nearly 79% of e-certificates were submitted to SpFrance on the day of the death. We observed a high completeness of the e-certificates. The rate of missing data did not exceed 2.7% for sociodemographic variables. On average, 10 words, distributed in three fields, were used to describe the medical causes of death. CONCLUSIONS: E-death certificates constitute a reactive source of information on medical causes of death. The deployment of EDRS is of major public health interest for the development of a real-time warning surveillance system of mortality by cause.

Experiencia de un programa de donación en asistolia Maastricht II en una ciudad de pequeño tamaño: resultados preliminares / Experience of a Maastrich type II non heart beating donor program in a small city: preliminary results

OBJETIVOS: Analizar los resultados de la implantación de un programa de donación Maastricht II en una ciudad de 200.000 habitantes. Inicialmente solo donación pulmonar y tras 9 meses se amplió a donación renal. DISEÑO: Estudio observacional prospectivo de octubre de 2012 a diciembre de 2013. ÁMBITO: UCI del Hospital Universitario Marqués de Valdecilla y área metropolitana de Santander. POBLACIÓN: Pacientes < 55 años fallecidos por parada cardiaca extrahospitalaria. Intervención: La asistencia extrahospitalaria fue con cardiocompresor mecánico (LUCAS II). El diagnóstico de muerte, la asistencia y preservación de los injertos a donar se realizó íntegramente en la UCI. RESULTADOS: Se recibieron un total de 14 llamadas, descartándose 3. De los 11 potenciales donantes, 7 fueron donantes utilizados con edad mediana de 39,5 años (rango: 32-48). Se realizaron 5 trasplantes unipulmonares, 4 trasplantes renales, además de córneas y tejidos. Los donantes no válidos se debieron a problemas técnicos. No hubo negativas. La supervivencia de los trasplantados pulmonares fue 100% al mes y 80% al año. Todos los trasplantados renales presentaban creatinina al mes < 2 mg/dl. El tiempo parada-preservación renal fue 80 minutos (rango intercuartílico: 71-89) y el tiempo parada-preservación pulmonar fue 84 minutos (rango intercuartílico: 77-94). CONCLUSIONES: Un programa Maastricht II en una ciudad pequeña es viable tanto para órganos abdominales como torácicos. La potencialidad es mejorable al incrementar la edad de valoración y disponer de cardiocompresores mecánicos en todas las ambulancias. El tratamiento íntegro del donante en la UCI reduce los tiempos de isquemia caliente mejorando los resultados postrasplante

OBJECTIVE: To study the results of a non-controlled cardiac death (Maastricht type II) donor program in a city of 200,000 inhabitants. The study was initially focused on lung donation and was extended to kidney donation after 9 months. DESIGN: A prospective observational study was conducted between October 2012 and December 2013. SETTING: The Intensive Care Unit of Marqués de Valdecilla University Hospital in Santander (Spain), and surrounding areas. POPULATIONS: Patients (< 55 years) who died of out-of-hospital cardiac arrest. INTERVENTIONS: All out-of-hospital cardiac arrests were treated with mechanical cardiac compression (LUCAS II). The diagnosis of death and organ preservation were performed in the ICU. RESULTS: A total of 14 calls were received, of which three were discarded. Of the 11 potential donors, 7 were effective donors with a median age of 39.5 years (range: 32-48). A total of 5 single lung transplants and four kidney transplants were performed. In addition, corneas and tissues were harvested. The non-valid donors were rejected mainly due to technical problems. There were no donation refusals on the part of the patient relatives. The lung transplant patient survival rate was 100% after one month and 80% after one year. One month after transplantation, the kidney recipients had a serum creatinine concentration of < 2 mg/dl. The interval from cardiac arrest to renal preservation was 80 minutes (range: 71-89), and the interval from cardiac arrest to lung preservation was 84 minutes (range: 77-94). CONCLUSIONS: A Maastricht type II donation program in a small city is viable for both abdominal and thoracic organs. The program was initially very cautious, but its potential is easily improvable by increasing donor and by equipping mobile ICU ambulances with mechanical cardiac compression systems. Full management of the donor in the ICU, avoiding the emergency department or operating rooms, reduces the warm ischemia time, thereby improving transplant outcomes

Individual and regional factors of access to the renal transplant waiting list in france in a cohort of dialyzed patients.

Several studies have investigated geographical variations in access to renal transplant waiting lists, but none has assessed the impact on these variations of factors at both the patient and geographic levels. The objective of our study was to identify medical and non-medical factors at both these levels associated with these geographical variations in waiting-list placement in France. We included all incident patients aged 18-80 years in 11 French regions who started dialysis between January 1, 2006, and December 31, 2008. Both a multilevel Cox model with shared frailty and a competing risks model were used for the analyses. At the patient level, old age, comorbidities, diabetic nephropathy, non-autonomous first dialysis, and female gender were the major determinants of a lower probability of being waitlisted. At the regional level, the only factor associated with this probability was an increase in the number of patients on the waiting list from 2005 to 2009. This finding supports a slight but significant impact of a regional organ shortage on waitlisting practices. Our findings demonstrate that patients' age has a major impact on waitlisting practices, even for patients with no comorbidity or disability, whose survival would likely be improved by transplantation compared with dialysis.

Experience of a Maastrich type II non heart beating donor program in a small city: preliminary results.

OBJECTIVE: To study the results of a non-controlled cardiac death (Maastricht type II) donor program in a city of 200,000 inhabitants. The study was initially focused on lung donation and was extended to kidney donation after 9 months. DESIGN: A prospective observational study was conducted between October 2012 and December 2013. SETTING: The Intensive Care Unit of Marqués de Valdecilla University Hospital in Santander (Spain), and surrounding areas. POPULATIONS: Patients (< 55 years) who died of out-of-hospital cardiac arrest. INTERVENTIONS: All out-of-hospital cardiac arrests were treated with mechanical cardiac compression (LUCAS II). The diagnosis of death and organ preservation were performed in the ICU. RESULTS: A total of 14 calls were received, of which three were discarded. Of the 11 potential donors, 7 were effective donors with a median age of 39.5 years (range: 32-48). A total of 5 single lung transplants and four kidney transplants were performed. In addition, corneas and tissues were harvested. The non-valid donors were rejected mainly due to technical problems. There were no donation refusals on the part of the patient relatives. The lung transplant patient survival rate was 100% after one month and 80% after one year. One month after transplantation, the kidney recipients had a serum creatinine concentration of<2mg/dl. The interval from cardiac arrest to renal preservation was 80minutes (range: 71-89), and the interval from cardiac arrest to lung preservation was 84minutes (range: 77-94). CONCLUSIONS: A Maastricht type II donation program in a small city is viable for both abdominal and thoracic organs. The program was initially very cautious, but its potential is easily improvable by increasing donor and by equipping mobile ICU ambulances with mechanical cardiac compression systems. Full management of the donor in the ICU, avoiding the emergency department or operating rooms, reduces the warm ischemia time, thereby improving transplant outcomes.

[REIN Report 2011--summary]. / Rapport Rein 2011--Synthèse.

INCIDENT PATIENTS: In 2011, in France, we estimate that 9 400 patients started a treatment by dialysis (incidence of dialysis: 144 per million inhabitants) and 335 patients with a pre-emptive graft without previous dialysis (incidence of pre-emptive graft: 5 per million inhabitants). As in 2010, incidence rate seems to stabilize. Elders provide the majority of new patients (median age at RRT start: 71 years old). New patients present a high rate of disabilities especially diabetes (41% of the new patients) and cardiovascular disabilities (>50% of the new patients) that increase with age. Considering treatment and follow-up, the first treatment remains center's hemodialysis and we do not notice any progression of self-dialysis. RRT started in emergency in 33% of the patients. This finding contrasts with the fact that 56% of patients started hemodialysis on a catheter. This, together with the major inter-region variability, suggests that different strategies of management exist. Finally, the hemoglobin level at RRT start seems to be an interesting indicator of good management and follow-up since 13% of patients presenting an underprovided follow-up have a hemoglobin level under 10g/dl, whereas only 2.5% of patients with an appropriate follow-up presented such a condition. PREVALENT PATIENTS: On December 31, 2011, in France, we estimate that 70.700 patients were receiving a renal replacement therapy, 39.600 (56%) on dialysis and 31.100 (44%) living with a functional renal transplant. The overall crude prevalence was 1091 per million inhabitants. It was 1.6 higher in males. Prevalence was subject to regional variations with 5 regions (3 overseas) above the national rate. Renal transplant share varied from 33% in Nord-Pas de Calais to 53% in Pays de Loire, and from 16 to 25% in overseas regions. The study of temporal variations for 18 regions contributing to the registry since 2007 demonstrated a +4% increase in standardized prevalence of ESRD patients with a functional transplant vs. +2% increase for dialysis, resulting in a decreasing gap between dialysis and transplantation prevalence, due to an increase number of renal transplant and a longer survival of transplanted patients. The main dialysis technique was hemodialysis (93.3% of patients). Even if an important inter-region variability remains considering the choices of treatment, more than 50% of the patients are undergoing hemodialysis in a hospital-based incenter unit, and we noticed an increase in hemodialysis in a medical satellite unit with time whereas the rate of self-care hemodialysis decreases. The rate of peritoneal dialysis remains stable. When comparing guidelines to real-life treatments, 77.5% of patients receive adequate dose of treatment (12 H/week, KT/ V>1.2), the rate of patients with a hemoglobin blood-level lower than 10g/dl and without erythropoietin treatment is 1.3%, which confirmed a good management of anemia. On the contrary, 34% of patients have a BMI lower than 23kg/m(2) and only 23% have an albumin blood-level over 40g/l, which underlines that nutritional management of ESRD patients can be improved. MORTALITY: Age strongly influences survival on dialysis. Thus, one year survival of patients under age 65 is over 90%. After 5 years, among patients over 85 years, it is more than 15%. The presence of diabetes or one or more cardiovascular comorbidities also significantly worse patient survival. In terms of trend, we do not find significant improvement in the 2-year survival between patients in the cohort 2006-2007 and the 2008-2009 cohort. Cardiovascular diseases account for 27% of causes of death to infectious diseases (12%) and cancer (10%). Life expectancy of patients is highly dependent on their treatment. Thus, a transplant patient aged 30 has a life expectancy of 41 years versus 23 years for a dialysis patient. ESRD PEDIATRIC PATIENTS: In 2011, the incidence and the prevalence of ESRD among patients under 20 years old remained stable at 8 and 53 per million inhabitants respectively. The first causes of ESDR remain uropathies and hypodysplasia followed by glomerulonephritis and genetic diseases. Considering the initial treatment, we found a high rate of hemodialysis and a low rate of peritoneal dialysis that is mainly used in younger children. In 2011, 31 preemptive transplantations were performed accounting for 27.7% of new patients. Finally, survival analysis confirm that younger children (under 4 years old) have the highest risk of death (88% survival rate at 2 years vs. 98% in patients over 4 years old) and that the treatment of choice remains the renal transplantation since it increases the expected remaining lifetime of 20 to 40 years depending on the considered age. TRANSPLANTATION: Access to the waiting list is evaluated on a cohort of 51,846 new patients who started dialysis between 2002 and 2011 in 25 regions. The probability of first wait-listing was of 3.7% at the start of dialysis (pre-emptive registrations), 15% at 12, 22% at 36 and 24% to 60 months. Patient older than 60 had a very poor access to the waiting list, whatever their diabetes status was. Among 13,653 patients less than 60 years old, the probability of being registered was 11% at the start of dialysis, 43% to 12 months, 62% to 36 months and 66% to 60 months (median dialysis duration: 16 months). Seventeen regions with up to 5 years follow-up show an increase of 8 to 15% in pre-emptive registrations between 2007 and 2001, without change at 1 year. Access to kidney transplant is evaluated on a cohort of 53,301 new patients who started a renal replacement therapy (dialysis or pre-emptive renal transplant) between 2002 and 2011 in 25 regions. The probability of first kidney transplant was of 7% at 12, 17% at 36 and 21% at 60 months. 8,633 patients (16,2%) had received a first renal transplant within 14.7 month median time; 1,455 (2.7%) had received a pre-emptive graft. Among the 14.770 new patients less than 60 years old, the probability of being transplanted was of 21% at 12, 46% at 36 and 58% at 60 months (median dialysis duration: 42 months). When pre-emptive graft were excluded, the probability of being transplanted was of 5% at 12, 15% to 36 and 19% to 60 months FLOW BETWEEN TREATMENT MODALITIES: Among the 36.849 patients on dialysis at 31/10/2010, 79% were already on RRT at 31/12/2009. Respectively 91%, 85% and 93% of the patients on HD in-center, HD self-care unit and peritoneal dialysis were in the same modality of treatment the year before. Among the 29.758 patients with a functioning graft at 31/12/2010, 98% were already on RRT at 31/12/2009, 95% of them with a functioning graft.72%, 72% and 74% of the patients with in-center HD, out-center HD and self-care unit were in the same modality of treatment at 31/12/2011. But 37% of the patients on PD at 31/12/2010 were not on PD at 31/12/2011. In 2011, new patients represented 89% of the entries in peritoneal dialysis. Renal transplantation represented 10% of the outcomes of the HD patients in self-care unit or at home.

[Survival and mortality in ESRD patients]. / Survie et mortalité des patients en IRCT.

This chapter provides a set of indicators on survival, life expectancy and causes of death of patients in chronic renal failure treated by dialysis or transplantation beginning a first replacement therapy between 2002 and 2011. Age strongly influences survival on dialysis. Thus, one year survival of patients under age 65 is over 90%. After 5 years, among patients over 85 years, it is more than 15%. The presence of diabetes or one or more cardiovascular comorbidities also significantly worse patient survival. In terms of trend, we do not find significant improvement in the 2-year survival between patients in the cohort 2006-2007 and the 2008-2009 cohort. Cardiovascular diseases account for 27% of causes of death to infectious diseases (12%) and cancer (10%). Life expectancy of patients is highly dependent on their treatment. Thus, a transplant patient aged 30 has a life expectancy of 41 years versus 23 years for a dialysis patient. Transplant patients have a mortality rate much lower than those of dialysis patients. Thus, between 60 and 69 years, for 1000 patients in dialysis in 2011, 127 died within the year. For 1000 patients of the same age, who have a functioning kidney transplant, 24 died within the year.

Targeted Vpr-derived peptides reach mitochondria to induce apoptosis of alphaVbeta3-expressing endothelial cells.

The HIV-1 encoded apoptogenic protein Vpr induces mitochondrial membrane permeabilization (MMP) via interactions with the voltage-dependent anion channel (VDAC) and the adenine nucleotide translocator (ANT). We have designed a peptide, TEAM-VP, composed of two functional domains, one a tumor blood vessel RGD-like 'homing' motif and the other an MMP-inducing sequence derived from Vpr. When added to isolated mitochondria, TEAM-VP interacts with ANT and VDAC, reduces oxygen consumption and overcomes Bcl-2 protection to cause inner and outer MMP. TEAM-VP specifically recognizes cell-surface expressed alpha(V)beta(3) integrins, internalizes, temporarily localizes to lysosomes and progressively co-distributes with the mitochondrial compartment with no sign of lysosomal membrane permeabilization. Finally TEAM-VP reaches mitochondria of angiogenic endothelial cells to induce mitochondrial fission, dissipation of the mitochondrial transmembrane potential (DeltaPsi(m)), cytochrome c release and apoptosis hallmarks. Hence, this chimeric peptide constitutes the first example of a virus-derived mitochondriotoxic compound as a candidate to kill selectively tumor neo-endothelia.

Filling a cavity dramatically increases pressure stability of the c-Myb R2 subdomain.

Cavities or packing defects in proteins may generally be related with the dynamics and function of a protein. In the c-Myb R2 subdomain, its single cavity has been shown to be crucial for its DNA recognition. Cavities are also considered important in determining the pressure stability of a protein. In the present work, high-pressure proton nuclear magnetic resonance ((1)H NMR) spectroscopy at 750 MHz is used to study the effect of a cavity-filling mutation (V103L) on the stability of the c-Myb R2 subdomain in the pressure range between 1 and 3,700 bar at 5 degrees C. A dramatic increase in the pressure stability of the c-Myb R2 subdomain is attained, from which we estimate the cavity size to be 35.3 A(3), in good agreement with literature values. We also evaluated the increase in thermodynamic stability DeltaG(0)(1bar) from 5.35 kJ/mol to 7.34 kJ/mol by the mutation, giving a clear example of the effect of a cavity on the global stability of a globular protein.

The pressure-temperature free energy-landscape of staphylococcal nuclease monitored by (1)H NMR.

The thermodynamic stability of staphylococcal nuclease was studied against the variation of both temperature and pressure by utilizing (1)H NMR spectroscopy at 750 MHz in 20 mM Mes buffer containing 99.9 % (2)H(2)O, pH 5.3. Equilibrium fractions of folded and unfolded protein species were evaluated with the proton signals of two histidine residues as monitor in the pressure range of 30-3300 bar and in the temperature range of 1.5 degrees C-35 degrees C. From the multi-parameter fit of the experimental data to the Gibbs energy equation expressed as a simultaneous function of pressure and temperature, we determined the compressibility change (Deltabeta), the volume change at 1 bar (DeltaV degrees ) and the expansivity change (Deltaalpha) upon unfolding among other thermodynamic parameters: Deltabeta=0.02(+/-0.003) ml mol(-1) bar(-1); Deltaalpha=1.33(+/-0.2) ml mol(-1) K(-1); DeltaV degrees =-41.9(+/-6. 3) ml mol(-1) (at 24 degrees C); DeltaG degrees =13.18(+/-2) kJ mol(-1) (at 24 degrees C); DeltaC(p)=13.12(+/-2) kJ mol(-1) K(-1); DeltaS degrees =0.32(+/-0.05) kJ mol(-1) K(-1 )(at 24 degrees C). The result yields a three-dimensional free energy surface, i.e. the free energy-landscape of staphylococcal nuclease on the P-T plane. The significantly positive Deltabeta and Deltaalpha values suggest that, in the pressure-denatured state, staphylococcal nuclease forms a loosely packed and fluctuating structure. The slight but statistically significant difference between the unfolding transitions of the His8 and His124 environments is considered to reflect local fluctuations in the native state, leading to pre-melting of the His124 environment prior to the cooperative unfolding of the major part of the protein.

Refolding studies on the tetrameric loop deletion mutant RM6 of ROP protein.

Previous DSC and X-ray studies on RM6, a loop deletion mutant of wtROP protein, have shown that removal of five amino acids from the loop causes a dramatic reorganization of the wild-type structure. The new tetrameric molecule exhibits a significantly higher stability (Lassalle, M.W. et al., J. Mol. Biol., 1998, 279, 987-1000) and unfolds in a second order reaction (Lassalle, M.W. and Hinz, H.-J., Biochemistry, 1998, 37, 8465-8472). In the present investigation we report extensive refolding studies of RM6 at different temperatures and GdnHCl concentrations monitored by CD and fluorescence to probe for changes in secondary and tertiary structure, respectively. The measurements permitted us to determine activation parameters as a function of denaturant concentration. The results demonstrate convincingly that the variation with GdnHCl concentration of the activation parameters deltaH#, deltaS# and deltaG# is very similar for unfolding and refolding. For both processes the activation properties approach a maximum in the vicinity of the denaturant concentration, c(K=1), where the equilibrium constant equals 1, i.e. deltaG0 equals zero. CD and fluorescence refolding kinetics are described by identical constants suggesting that the formation of secondary and tertiary structure occurs simultaneously. Refolding is, however, characterized by a more complex mechanism than unfolding. Although the general pattern is dominated by the sequence monomers to dimers to tetramers, parallel side reactions involving dimers and monomers have to be envisaged in the initial folding phase, supporting the view that the native state of RM6 can be reached by several rather than a single pathway.

Unfolding of the tetrameric loop deletion mutant of ROP protein is a second-order reaction.

Comprehensive kinetic studies were carried out on the unfolding properties of RM6 as a function of GdnHCl concentration and temperature. This protein is a mutant resulting from the dimeric wild-type CoLE1-ROP protein by deletion of 5 amino acids (Asp 30, Ala 31, Asp 32, Glu 33, Gln 34) in the loop of each monomer. The deletion has dramatic consequences. The dimeric 4-alpha-helix structure characteristic of the wild-type protein is completely reorganized and the RM6 structure can be described as a tetrameric alpha helix of extended monomers without loops. These extraordinary structural changes are accompanied by an enormous increase in transition temperature from 71 to 101 degreesC. These features have been discussed in a separate publication (1). The remarkable change in thermal stability of RM6 should be reflected in significant changes in the folding rate constants. This was observed in the present unfolding studies. Decay of tetrameric RM6 was monitored by circular dichroism (CD) and fluorescence to probe for changes in both secondary and tertiary structure, respectively. The identity of the kinetic parameters obtained from the two techniques supports the view that secondary and tertiary structure break down simultaneously. However, the most intriguing result is the finding that unfolding of tetrameric RM6 can be described very well by a second-order reaction. The magnitude of the second-order rate constant k2 varies dramatically with both temperature and denaturant concentration. At 25 degreesC and 6.5 M GdnHCl concentration k2 is 4200 L.(mol of dimer)-1.s-1, whereas at 4.4 M GdnHCl a value of k2 = 0.9 L.(mol of dimer)-1.s-1 is observed. Correspondingly, apparent activation enthalpies show a strong increase from DeltaH# = 29.1 kJ.mol-1 at 6. 5 M GdnHCl to Delta H# = 79.7 kJ.mol-1 at 4.4 M GdnHCl. A mechanism involving a dimeric intermediate is suggested which permits a consistent interpretation of the findings.

Dimer-to-tetramer transformation: loop excision dramatically alters structure and stability of the ROP four alpha-helix bundle protein.

The ROP loop excision mutant RM6 shows dramatic changes in structure and stability in comparison to the wild-type protein. Removal of the five amino acids (Asp30, Ala31, Asp32, Glu33, Gln34) from the loop results in a complete reorganization of the protein as evidenced by single crystal X-ray analysis and thermodynamic unfolding studies. The homodimeric four-alpha-helix motif of the wild-type structure is given up. Instead a homotetrameric four-alpha-helix structure with extended, loop-free helical monomers is formed. This intriguing structural change is associated with the acquisition of hyperthermophilic stability. This is evident in the shift in transition temperature from 71 degreesC characteristic of the wild-type protein to 101 degreesC for RM6. Accordingly the Gibbs energy of unfolding is increased from 71.7 kJ (mol of dimer)-1 to 195.1 kJ (mol of tetramer)-1. The tetramer-to-monomer transition proceeds highly cooperatively involving an enthalpy change of DeltaH=1073+/-30 kJ (mol of tetramer)-1 and a heat capacity change at the transition temperature of DeltaDNCp=14.9(+/-)3% kJ (mol of tetramerxK)-1. The two-state nature of the unfolding reaction is reflected in coinciding calorimetric and van't Hoff enthalpy values.