Eficacia analgésica del bloqueo del grupo de nervios pericapsulares (PENG) en comparación con el bloqueo de la fascia ilíaca (FIB) en pacientes mayores con fractura de fémur proximal en la unidad de urgencias. Ensayo controlado aleatorizado / Analgesic efficacy of Pericapsular Nerve Group (PENG) block compared with Fascia Iliaca Block (FIB) in the elderly patient with fracture of the proximal femur in the emergency room. A randomised controlled trial

Introducción y objetivos: Son escasos los datos relativos a la eficacia del bloqueo PENG (grupo de nervios pericapsulares) para el dolor por traumatismo de cadera. Formulamos la hipótesis de que el bloqueo PENG era más efectivo que el bloqueo FIB (fascia ilíaca) ecoguiado (infrainguinal) para controlar el dolor en los pacientes de 65 o más, con fractura de fémur proximal traumática en la unidad de urgencias hospitalarias (UUH). Materiales y métodos Realizamos un ensayo controlado aleatorizado exploratorio y doble ciego, siendo diferentes el anestesiólogo que realizó el bloqueo y el que evaluó los resultados. Se asignó aleatoriamente a los pacientes al grupo PENG con 20ml de ropivacaína al 0,375% o al grupo FIB (infrainguinal) con 40ml de ropivacaína al 0,2%. Se realizaron las pruebas de hipótesis estándar (prueba t o prueba χ2) para analizar las características basales y los parámetros del resultado. El objetivo primario del estudio fue el éxito analgésico de PENG evaluado como «puntuación NRS de dolor incidental≤4» 30min tras la colocación del bloqueo en comparación con FIB, también a los 30min del bloqueo. Los objetivos secundarios fueron el dolor en reposo («puntuación NRS de dolor en reposo≤4» 30min tras la colocación de los bloqueos), la duración de los bloqueos (tiempo transcurrido antes de la primera solicitud de analgesia del paciente), incidencia de administración de medicación de rescate en caso de fracaso del bloqueo, complicaciones relativas a la colocación del bloqueo. Resultados Tras la obtención de la aprobación del comité ético y el consentimiento informado escrito, se incluyó a 60 pacientes. Considerando el resultado primario, se logró el objetivo en el grupo PENG en 16 de entre 30 pacientes (53,3%), y en 15 de entre 28 casos en el grupo FIB (53,6%). La comparación entre ambos grupos no demostró la superioridad del bloqueo PENG frente a FIB (valor p=0,98). Conclusiones El bloqueo PENG no es superior ... . (AU)

Introduction and objectives: Data on the efficacy of PENG (Pericapsular Nerve Group) block in hip trauma pain are scarce. We hypothesized that PENG block was more effective than infra-inguinal ultrasound-guided FIB (Fascia Iliaca block) for pain control in patients aged 65 years or older presenting in the emergency room (ER) with traumatic proximal femoral fracture. Materials and methods We conducted an exploratory, double-blind, randomized controlled trial. One anaesthesiologist performed the block and another assessed outcomes. Patients were randomly allocated to the PENG group (20ml ropivacaine 0.375%) or the infrainguinal FIB group (40ml ropivacaine 0.2%). Standard hypothesis tests (t test or χ2 test) were performed to analyse baseline characteristics and outcome parameters. The primary end-point of the study was analgesic success, defined as «NRS pain score≤4» 30min after blockade, with PENG vs to FIB. Secondary outcomes were pain at rest («pain at rest NRS score≤4» 30min after blockade), duration of analgesia (time to first request for analgesia), need for rescue medication in case of block failure, and complications during blockade. Results After obtaining ethical committee approval and written informed consent, 60 patients were included.The primary endpoint was achieved in 16 out of 30 patients (53.3%) in the PENG group and in 15 out of 28 patients (53.6%) in the FIB group. Comparison between groups did not show superiority of the PENG vs FIB (p=0.98). Conclusions PENG block does not provide better pain than FIB in proximal femoral fracture in elderly patients treated in the ER. (AU)

Analgesic efficacy of Pericapsular Nerve Group (PENG) block compared with Fascia Iliaca Block (FIB) in the elderly patient with fracture of the proximal femur in the emergency room. A randomised controlled trial.

INTRODUCTION AND OBJECTIVES: Data on the efficacy of PENG (Pericapsular Nerve Group) block in hip trauma pain are scarce. We hypothesized that PENG block was more effective than infra-inguinal ultrasound-guided FIB (Fascia Iliaca block) for pain control in patients aged 65 years or older presenting in the emergency room (ER) with traumatic proximal femoral fracture. MATERIALS AND METHODS: We conducted an exploratory, double-blind, randomized controlled trial. One anaesthesiologist performed the block and another assessed outcomes. Patients were randomly allocated to the PENG group (20 ml ropivacaine 0.375%) or the infrainguinal FIB group (40 ml ropivacaine 0.2%). Standard hypothesis tests (t test or χ2 test) were performed to analyse baseline characteristics and outcome parameters. The primary end-point of the study was analgesic success, defined as "NRS pain score ≤ 4" 30 min after blockade, with PENG vs to FIB. Secondary outcomes were pain at rest ("pain at rest NRS score ≤ 4" 30 min after blockade), duration of analgesia (time to first request for analgesia), need for rescue medication in case of block failure, and complications during blockade. RESULTS: After obtaining ethical committee approval and written informed consent, 60 patients were included. The primary endpoint was achieved in 16 out of 30 patients (53.3%) in the PENG group and in 15 out of 28 patients (53.6%) in the FIB group. Comparison between groups did not show superiority of the PENG vs FIB (P-value .98). CONCLUSIONS: PENG block does not provide better pain than FIB in proximal femoral fracture in elderly patients treated in the ER.

Knowledge, attitudes and adherence towards influenza and other vaccinations among healthcare workers at the University Hospital of Palermo, Italy, during the first COVID-19 pandemic season (2020/2021).

Background: Increasing adherence to influenza vaccination among healthcare workers is a public health priority, stated that actually remains far below than international recommendations. During the 2020/2021 pandemic season, COVID-19 vaccines were not yet available until the end of December 2020, and influenza vaccines were the only one available to protect against seasonal respiratory diseases. The main objective of the present study was to assess knowledge, attitudes and adherence to influenza and other vaccinations recommended by the National Immunization Plan 2017-2021 for healthcare workers. Methods: Enrollment lasted from October and December 2020 at the vaccination unit of the University Hospital of Palermo. Data were collected through an anonymous and self-administered questionnaire, divided into 5 sections and 31 items. Results: Among 734 healthcare professionals that completed the survey, a significantly higher adherence to influenza vaccination was observed among healthcare workers that were more prone to receive COVID-19 vaccination (OR=4.02; 95% CI: 1.63-9.91). Moreover, higher influenza vaccination rates were observed among healthcare professionals that received influenza vaccination during previous 2019/2020 season (OR=15.3; 95% CI: 5.17-45.1) and that were favorable to the possible impact on increasing adherence of influenza mandatory vaccination (OR=4.88; 95% CI: 2.43-9.80). Conclusions: Propensity of healthcare workers to undergo vaccinations recommended in the National Immunization Plan increased during the first pandemic season. At the end of the vaccination season, flu vaccination coverage reached highest rates ever at the University Hospital of Palermo (around 60%), remaining anyway below the recommended minimum value of 75%. During next seasonal flu vaccination campaigns, it becomes essential to promote communication and information strategies to increase flu vaccination among healthcare workers, also focusing on co-administration with the anti-COVID-19 booster/seasonal doses.

Time trend in the surgical management of obstructed defecation syndrome: a multicenter experience on behalf of the Italian Society of Colorectal Surgery (SICCR).

BACKGROUND: Surgical management of obstructed defecation syndrome (ODS) is challenging, with several surgical options showing inconsistent functional results over time. The aim of this study was to evaluate the trend in surgical management of ODS in a 10-year timeframe across Italian referral centers. METHODS: Surgeons from referral centers for the management of pelvic floor disorders and affiliated to the Italian Society of Colorectal Surgery provided data on the yearly volume of procedures for ODS from 2010 to 2019. Six common clinical scenarios of ODS were captured, including details on patient's anal sphincter function and presence of rectocele and/or rectal intussusception. Perineal repair, ventral rectopexy (VRP), transanal repair (internal Delorme), stapled transanal rectal resection (STARR), Contour Transtar, and transvaginal repair were considered in each clinical scenario. RESULTS: Twenty-five centers were included providing data on 2943 surgical patients. Procedure volumes ranged from 10-20 (54%) to 21-50 (46%) per year across centers. The most performed techniques in patients with good sphincter function were transanal repair for isolated rectocele (243/716 [34%]), transanal repair for isolated rectal intussusception (287/677 [42%]) and VRP for combined abnormalities (464/976 [48%]). When considering poor sphincter function, these were perineal repair (112/194 [57.8%]) for isolated rectocele, and VRP for the other two scenarios (60/120 [50%] and 97/260 [37%], respectively). The use of STARR and Contour Transtar decreased over time in patients with impaired sphincter function. CONCLUSIONS: The complexity of ODS treatment is confirmed by the variety of clinical scenarios that can occur and by the changing trend of surgical management over the last 10 years.

Representaciones sociales sobre salud y acceso a la salud en las localidades del plan AHI / Social representations on health and access to health in the localities of the AHI plan

INTRODUCCIÓN El estudio de las representaciones sociales (RS) resulta fecundo no sólo como una herramienta de comprensión de la realidad, sino también como una vía de acción. El presente trabajo busca profundizar el conocimiento sobre las RS en torno a la salud y el acceso a ella, puesto que la temática es relativamente poco estudiada en Argentina, a diferencia de otros países de Latinoamérica. OBJETIVOS Describir y analizar las RS sobre la salud y el acceso a la salud de habitantes de tres localidades en las que interviene el Plan AHÍ. MÉTODOS Se diseñó una estrategia metodológica de carácter cualitativo, exploratorio y descriptivo. Se seleccionó la muestra a través del método bola de nieve y se realizaron 40 entrevistas semiestructuradas en las localidades. Para el análisis de las entrevistas se tomaron las siguientes dimensiones RS sobre salud y RS sobre el acceso a la salud. RESULTADOS Las RS en torno a la salud de la muestra refieren a ideas sobre el bienestar, la ausencia de enfermedad o de tratamiento médico, el cuidado y la prevención, el estado anímico o psicológico, la capacidad funcional, la relación con el ambiente social y ecológico y, en algunos casos, una concepción más integral, que incorpora las dimensiones de política y/o género. Las representaciones más relevantes respecto del acceso a la salud refieren a las dimensiones geográfica, económica, sociocultural, organizacional, burocrática y simbólica, observando que las RS sobre salud pueden influir en el acceso a ella. DISCUSIÓN Cabe esperar que los resultados sean útiles para el estudio, diseño y planificación de una intervención territorial de los programas de abordaje socio-sanitario, que contemple las especificidades de las comunidades beneficiarias y mejore el desempeño de los agentes e instituciones de salud.

tst1-positive ST22-MRSA-IVa in healthy Italian preschool children.

A survey was performed in May 2013 to assess methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization in healthy children attending 26 municipal daycare centres in Palermo, Italy. Of the 500 children, ten (2 %) tested positive. Eight MRSA isolates were tst1-positive ST22-MRSA-IVa, spa t223; the other two isolates were identified as ST1-IVa and ST398-V, respectively. tst1-positive ST22-MRSA, spa t223 has been previously identified only in the Middle Eastern area.

The burden of hospitalization related to diabetes mellitus: a population-based study.

BACKGROUND AND AIMS: To estimate the impact of diabetes and its complications, overall and in different age classes, on the likelihood of hospital admission for specific causes. METHODS AND RESULTS: We carried out a record-linkage analysis of administrative registers including data on 8,940,420 citizens in 21 Local Health Authorities in Italy. Individuals with pharmacologically treated diabetes (≥2 prescriptions of antidiabetic agents during the year 2008) were paired in a 1:1 proportion with those who did not receive such drugs (controls) based on propensity-score matching. Odds Ratios (ORs) of hospitalization for macro and microvascular conditions in individuals with diabetes as compared to controls were estimated. The system identified 498,825 individuals with diabetes pharmacologically treated (prevalence of 5.6%). Prevalence of diabetes in people aged <14 years, 14-39 years, 40-65 years, and ≥65 years was 0.1%, 0.6%, 6.4%, and 18.2%, respectively. Overall, 23.9% of subjects with diabetes and 11.5% of controls had had at least a hospital admission during 12 months for the causes considered. Diabetes increased the likelihood of hospitalization by two to six times for the different causes examined. In absolute terms, diabetes was responsible for an excess of over 12,000 hospital admissions per 100,000 individuals/year. CONCLUSION: Despite the availability of effective treatments to prevent or delay major complications, diabetes still places an enormous burden on both patients and the health care system. Given the continuous rise in diabetes prevalence both in middle-aged and elderly individuals, we can expect an additional, hardly sustainable increase in the demand for health care in the near future.

MR in the evaluation of new anterior cruciate ligament and tibial tunnel position: correlation with clinical and functional features.

PURPOSE: This study aimed to evaluate correlations between the position of the tibial tunnel, its alignment with the ligament-screw system, presence of intratunnel fluid, position of the tibial tunnel with respect to the Blumensaat line and clinical knee stability in patients who underwent arthroscopic reconstruction of the anterior cruciate ligament (ACL), by using magnetic resonance (MR) imaging. MATERIALS AND METHODS: Forty-eight patients (40 men, eight women; mean age, 31 years) underwent arthroscopic reconstruction of the ACL using double-strand semitendinosus and gracilis tendons. The new ACL was fixed to the tibial tunnel using Bio-Intrafix (Mitek). All patients underwent MR imaging 12 months after surgery and clinical evaluation at 6 and 12 months using the International Knee Documentation Committee (IKDC) scoring system. MR imaging and clinical features were correlated using the Mann-Whitney U test for continuous variables and Fisher's exact test for categorical variables. RESULTS: Forty-one patients were clinically stable (groups A and B according to the IKDC test) and seven were unstable (group C). Mean values of tibial tunnel position in clinically unstable vs stable patients were, respectively, -3.6 ±3.8 mm vs. -2.8±3.8 mm in relation to the Blumensaat line (p=0.5712) and 77.3°±11.3 vs. 72.5°±5.5 as concerned the angle measured on the coronal view of the new ACL (p=0.3248); fluid was present in the tibial tunnel in 42.9% and 9.8% of cases, respectively (p=0.2104). MR imaging showed misalignment of ligament screw and tibial tunnel in 57.1% of patients in group C and in 12.2% in groups A and B (p=0.017). CONCLUSIONS: Misalignment of the ligament-screw system and the tibial tunnel and the presence of fluid in the tibial tunnel appear to be directly correlated with clinical instability.

A novel germline mutation in peroxisome proliferator-activated receptor gamma gene associated with large intestine polyp formation and dyslipidemia.

We report a novel PPARG germline mutation in a patient affected by colorectal cancer that replaces serine 289 with cysteine in the mature protein (S289C). The mutant has impaired transactivation potential and acts as dominant negative to the wild type receptor. In addition, it no longer restrains cell proliferation both in vitro and in vivo. Interestingly, the S289C mutant poorly activates target genes and interferes with the inflammatory pathway in tumor tissues and proximal normal mucosa. Consistently, only mutation carriers exhibit colonic lesions that can evolve to dysplastic polyps. The proband presented also dyslipidemia, hypertension and overweight, not associated to type 2 diabetes; of note, family members tested positive for the mutation and display only a dyslipidemic profile at variable penetrance with other biochemical parameters in the normal range. Finally, superimposing the mutation to the crystal structure of the ligand binding domain, the new Cys289 becomes so closely positioned to Cys285 to form an S-S bridge. This would reduce the depth of the ligand binding pocket and impede agonist positioning, explaining the biological effects and subcellular distribution of the mutant protein. This is the first PPARG germline mutation associated with dyslipidemia and colonic polyp formation that can progress to full-blown adenocarcinoma.

Transpedicular eggshell osteotomies for congenital scoliosis using frameless stereotactic guidance.

STUDY DESIGN: Three cases of multiplanar congenital scoliosis corrected by a transpedicular eggshell osteotomy using frameless stereotactic guidance are reported. OBJECTIVE: To show an alternative surgical technique for correcting and fusing complex congenital spinal curves. SUMMARY OF BACKGROUND DATA: Children with congenital scoliosis can have progressive curves causing significant multiplanar deformities. In older children, traditional approaches to spinal corrective surgery including fusion in situ, convex growth arrest, and hemivertebra excision can achieve only limited corrections. METHODS: Three older patients who had congenital scoliosis with significant multiplanar curves underwent one-stage posterior transpedicular eggshell osteotomy. Three-dimensional reconstructive images and frameless stereotactic guidance were used for preoperative selection of osteotomy levels and accurate placement of pedicle screws. After completion of the osteotomy, closure was obtained with extension of the hips. RESULTS: The average coronal correction of the major curve was 28.7 degrees (range, 22-33 degrees ). The average correction of the plumb line or lateral displacement from the center of the trunk was 4.8 cm (range, 3-7.5 cm). A significant kyphotic deformity was corrected 38 degrees, and a pelvic tilt was reduced from 7 to 3 cm. CONCLUSIONS: One-stage posterior reduction eggshell osteotomy can be used to correct a sagittal and/or coronal congenital spinal curve imbalance. Frameless stereotactic guidance for solid pedicle screw fixation was essential to the achievement of rigid spinal stabilization before arthrodesis. Transpedicular eggshell osteotomy is a technique that should be considered for older patients who have congenital scoliosis with multiplanar spinal abnormalities.

Contribution of chain termini to the conformational stability and biological activity of onconase.

Onconase, a member of the RNase A superfamily, is a potent antitumor agent which is undergoing phase III clinical trials as an antitumor drug. We have recently shown that onconase is an unusually stable protein. Furthermore, the protein is resistant to the action of proteases, which could influence its use as a drug, prolonging its biological life, and leading to its renal toxicity. Our investigation focused on the contribution of chain termini to onconase conformational stability and biological activities. We used differential scanning calorimetry, isothermal unfolding experiments, limited proteolysis, and catalytic and antitumor activity determinations to investigate the effect of the elimination of the two blocks at the chain termini, the N-terminal cyclized glutamine and the C-terminal disulfide bridge between the terminal Cys104 and Cys87. The determination of the thermodynamic parameters of the protein led to the conclusion that the two blocks at onconase chain termini are responsible for the unusual stability of the protein. Moreover, the reduced stability of the onconase mutants does not influence greatly their catalytic and antitumor activities. Thus, our data would suggest that an onconase-based drug, with a decreased toxicity, could be obtained through the use of less stable onconase variants.

The use of traction methods to correct severe cervical deformity in rheumatoid arthritis patients: a report of five cases.

STUDY DESIGN: A case series is presented. OBJECTIVES: To describe the methods of correction used in this study for flexible severe cervical deformity, and to report the results in patients with rheumatoid arthritis. SUMMARY OF BACKGROUND DATA: Long-standing rheumatoid arthritis can lead to severe cervical deformity, causing significant functional deficits and poor cosmesis. Information on the use of traction combined with surgical stabilization to achieve correction of flexible deformity in rheumatoid patients is sparse in the English literature. METHODS: A review of five cases, including pertinent history, physical examination, radiographic evaluation, traction techniques, surgical stabilization, and outcomes, was conducted. RESULTS: Excellent correction of deformity and radiographic union were achieved in all the patients. One patient had minimal loss of correction after surgery and thereafter remained stable. Pin tract infections were the only significant complication. CONCLUSIONS: Severe cervical flexible deformity in rheumatoid patients can cause significant disability and can be treated successfully with a combination of traction techniques and surgical stabilization.

Remifentanil- and fentanyl-based anesthesia for intraoperative monitoring of somatosensory evoked potentials.

We sought to compare effects of remifentanil- and fentanyl-based anesthesia on the morphology of somatosensory evoked potentials (SSEPs) and speed of recovery from anesthesia. Forty-one patients undergoing spinal surgery and requiring intraoperative monitoring of SSEPs were randomized into two groups. In Group 1, anesthesia was induced with sodium thiopental and maintained with fentanyl, 50% nitrous oxide in oxygen, and 0.5%--0.75% isoflurane. In Group 2, anesthesia was induced with sodium thiopental and maintained with remifentanil, 50% oxygen in air, and 0.5%--0.75% isoflurane. The variables compared included hemodynamic changes during the induction and intubation, the interval from the end of anesthesia to extubation, intraoperative blood loss and fluid administration, and changes in latency and amplitude of the P37--N45 component of posterior tibial nerve somatosensory evoked potentials and the N20--P24 component of median nerve somatosensory evoked potentials. The two groups were matched for demographics, ASA physical status, and duration of surgery. Hemodynamic profiles after the induction and intubation were similar. There were significant differences between groups in time intervals from the end of anesthesia to extubation (15.3 +/- 12.8 vs 5.3 +/- 2.3 min; P = 0.0001) and ability to follow verbal commands (14.6 +/- 11.9 vs 4.5 +/- 2.4 min; P = 0.0001), with the Remifentanil group showing earlier recovery. Variability (coefficient of variation) of P37--N45 latency was greater (0.026 vs 0.014; P = 0.001) in the Fentanyl group.

Efficacy of the laparoscopic approach for anterior lumbar spinal fusion.

BACKGROUND: This study compares the immediate postoperative outcomes in patients who undergo laparoscopic and open anterior lumbar spinal fusion and describes the learning curve associated with the performance of this procedure. METHODS: The charts of patients who underwent anterior lumbar spinal fusion between January 1995 and July 1999 were reviewed. Data pertaining to the operation and postoperative course were analyzed and compared. RESULTS: Eighty-nine patients underwent anterior lumbar spinal fusion. Fourteen patients were excluded; a full analysis was performed on the records of the remaining 75 patients. Fifty-five patients underwent an attempted laparoscopic procedure, and 20 patients underwent an open procedure. The conversion rate was 38% (21/55 patients) in the group who underwent the laparoscopic procedure. In the 34 patients whose laparoscopic procedure was completed, there was significantly less blood loss and shorter postoperative ileus, but the operative time was longer, when compared with patients who underwent the open procedure. The laparoscopic procedures performed in 1999 resulted in fewer conversions, less blood loss, and a shorter operating room time, when compared with the laparoscopic procedures in 1998. CONCLUSIONS: Laparoscopic anterior lumbar spinal fusion improves immediate postoperative results when compared with open anterior lumbar spinal fusion.

Onconase: an unusually stable protein.

Several members of the RNase A superfamily are endowed with antitumor activity, showing selective cytotoxicity toward tumor cell lines. One of these is onconase, the smallest member of the superfamily, which at present is undergoing phase-III clinical trials as an antitumor drug. Our investigation focused on other interesting features of the enzyme, such as its unusually high denaturation temperature, its low catalytic activity, and its renal toxicity as a drug. We used differential scanning calorimetry, circular dichroism, fluorescence measurements, and limited proteolysis to investigate the molecular determinants of the stability of onconase and of a mutant, (M23L)-ONC, which is catalytically more active than the wild-type enzyme, and fully active as an antitumor agent. The determination of the main thermodynamic parameters of the protein led to the conclusion that onconase is an unusually stable protein. This was confirmed by its resistance to proteolysis. On the basis of this analysis and on a comparative analysis of the (M23L)-ONC variant of the protein, which is less stable and more sensitive to proteolysis, a model was constructed in line with available data. This model supports a satisfactory hypothesis of the molecular basis of onconase stability and low-catalytic activity.

On the temperature-induced coil to globule transition of poly-N-isopropylacrylamide in dilute aqueous solutions.

Poly-N-isopropylacrylamide (PNIPAM) is a chemical isomer of poly-leucine, having the polar peptide group in the side-chain rather than in the backbone. It has been demonstrated experimentally that PNIPAM dissolved in aqueous solution undergoes a collapse transition from coil to globule on increasing temperature above the θ-point. By a careful reviewing of existing experimental data, we emphasize that such coil to globule collapse has to be considered an intramolecular first-order transition, analogous to the cold renaturation of small globular proteins. The main theoretical approaches to the coil to globule collapse in homopolymers are discussed briefly, and a critical comparison between the existing models is performed. We point out that, as a general result, the coil to globule collapse is expected to be a first-order transition for rigid and semi-rigid macromolecules. Finally, taking advantage of the analogy between the coil to globule collapse of PNIPAM and the cold renaturation of small globular proteins, we try to clarify some important and intriguing aspects of protein thermodynamics. This leads to the conclusion that the amphiphilic nature of polypeptide chain plays the fundamental role for the existence of two temperature-induced conformational transitions.

Linkage of proton binding to the thermal unfolding of Sso7d from the hyperthermophilic archaebacterium Sulfolobus solfataricus.

In this study the pH dependence of the thermal stability of Sso7d from Sulfolobus solfataricus is analyzed. This small globular protein of 63 residues shows a very marked dependence of thermal stability on pH: the denaturation temperature passes from 65.2 degrees C at pH 2.5 to 97.9 degrees C at pH 4.5. Analysis of the data points out that the binding of at least two protons is coupled to the thermal unfolding. By linking the proton binding to the conformational unfolding equilibrium, a thermodynamic model, which is able to describe the dependence upon the solution pH of both the excess heat capacity function and the denaturation Gibbs energy change for Sso7d, is developed. The decreased stability in very acid conditions is due to the binding of two protons on identical and noninteracting sites of the unfolded state. Actually, such sites are two carboxyl groups possessing very low pKa values in the native structure, probably involved in salt-bridges on the protein surface.

Hydrophobicity of benzene.

The present work tries to clarify the molecular origin of the poor solubility of benzene in water. The transfer of benzene from pure liquid phase into water is dissected in two processes: transfer from gas phase to pure liquid benzene; and transfer from gas phase to liquid water. The two solvation processes are analyzed in the temperature range 5-100 degrees C according to Lee's Theory. The solvation Gibbs energy change is determined by the balance between the work of cavity creation in the solvent, and the dispersive interactions of the inserted benzene molecule with the surrounding solvent molecules. The purely structural solvent reorganization upon solute insertion proves to be a compensating process. The analysis shows that the work of cavity creation is larger in water than in benzene, whereas the attractive energetic interactions are stronger in benzene than in water; this scenario is true at any temperature. Therefore, both terms act in the same direction, contrasting the transfer of benzene from pure liquid phase into water and determining its hydrophobicity.

Circular dichroism study of ribonuclease A mutants containing the minimal structural requirements for dimerization and swapping.

Four residues Pro19. Leu28, Cys31 and Cys32 proved to be the minimal structural requirements in determining the dimeric structure and the N-terminal segment swapping of bovine seminal ribonuclease, BS-RNase. We analyzed the content of secondary and tertiary structures in RNase A, P-RNase A, PL-RNase A, MCAM-PLCC-RNase A and MCAM-BS-RNase, performing near and far-UV CD spectra. It results that the five proteins have very similar native conformations. Thermal denaturation at pH 5.0 of the proteins. studied by means of CD measurements. proved reversible and well represented by the two-state N<==>D transition model. Thermodynamic data are discussed in the light of the structural information available for RNase A and BS-RNase.