Distinct Dual C-Cl Isotope Fractionation Patterns during Anaerobic Biodegradation of 1,2-Dichloroethane: Potential To Characterize Microbial Degradation in the Field.

This study investigates, for the first time, dual C-Cl isotope fractionation during anaerobic biodegradation of 1,2-dichloroethane (1,2-DCA) via dihaloelimination by Dehalococcoides and Dehalogenimonas-containing enrichment cultures. Isotopic fractionation of 1,2-DCA (εbulkC and εbulkCl) for Dehalococcoides (-33.0 ± 0.4‰ and -5.1 ± 0.1‰) and Dehalogenimonas-containing microcosms (-23 ± 2‰ and -12.0 ± 0.8‰) resulted in distinctly different dual element C-Cl isotope correlations (Λ = Δδ13C/Δδ37Cl ≈ εbulkC/εbulkCl), 6.8 ± 0.2 and 1.89 ± 0.02, respectively. Determined isotope effects and detected products suggest that the difference on the obtained Λ values for biodihaloelimination could be associated with a different mode of concerted bond cleavage rather than two different reaction pathways (i.e., stepwise vs concerted). Λ values of 1,2-DCA were, for the first time, determined in two field sites under reducing conditions (2.1 ± 0.1 and 2.2 ± 2.9). They were similar to the one obtained for the Dehalogenimonas-containing microcosms (1.89 ± 0.02) and very different from those reported for aerobic degradation pathways in a previous laboratory study (7.6 ± 0.1 and 0.78 ± 0.03). Thus, this study illustrates the potential of a dual isotope analysis to differentiate between aerobic and anaerobic biodegradation pathways of 1,2-DCA in the field and suggests that this approach might also be used to characterize dihaloelimination of 1,2-DCA by different bacteria, which needs to be confirmed in future studies.

[Approach of the unilateral cleft lip with Meara's cheiloplasty technique]. / Abordaje de la fisura labial unilateral mediante la queiloplastia de Meara.

INTRODUCTION: Isolated cleft lip is the mildest form of the cleft lip and palate spectrum; however those patients are often treated with the same surgical techniques that are used for the more severe cases (advancement-rotation flaps, quadrangular flaps). Meara's cheiloplasty technique may be a less aggressive option for lip repair in isolated cleft lip or whenever the gap between labial segments is not wide. MATERIAL AND METHODS: All children that had their cleft lip repaired following Meara's cheiloplasty between May 2014 and December 2015 were retrospectively reviewed. Duration of the surgical procedure, time to hospital discharge and complications were noted. Aesthetic results were evaluated in terms of lip height and symmetry, nose shape and symmetry, and scar appearance. RESULTS: Thirteen patients underwent Meara's cheiloplasty during this period. The average age was 6.11 months (5 to 12 months). A primary rhinoplasty was done at the same time in case of nasal asymmetry. Duration of the lip repair averaged 85 minutes. Oral feeding was started 4 hours after the procedure; bottle-feeding was withheld for 2 weeks postoperatively, as our protocol recommends after other lip repair techniques. In all 13 cases the result was a symmetrical, adequately high upper lip and a well-balanced nose, except for one case of lip scar retraction that was solved with triamcinolone infiltration. There were no other intra or postoperative complications. CONCLUSIONS: Meara's cheiloplasty corrects small or moderate gap cleft lip (usually cleft lip without cleft alveolus). Benefits over other teccniques are a shorter procedure and less geometric, undulate flaps that produce a harmonic lip.

INTRODUCCION: La fisura labial aislada es la forma menos grave de presentación del espectro de las fisuras labiopalatinas; sin embargo, para tratarla, usamos las mismas técnicas quirúrgicas que para las formas más graves (colgajos de avance-rotación, cuadrangulares). Presentamos la técnica de queiloplastia publicada por Meara, como alternativa menos agresiva para la reconstrucción del labio, en la fisura labial aislada o cuando los segmentos labiales están próximos entre sí. MATERIAL Y METODOS: Se realizó una revisión retrospectiva de las queiloplastias con técnica de Meara de mayo 2014 a diciembre 2015. Se revisó el tiempo quirúrgico, tiempo medio de ingreso, complicaciones y resultados estéticos, evaluando la altura y simetría del labio superior, la forma y simetría nasal y el aspecto de la cicatriz. RESULTADOS: Trece pacientes han sido intervenidos. La edad media al momento de la intervención fue de 6,11 meses (rango 5-12 meses). Se asoció una rinoplastia en casos con asimetría nasal. El tiempo quirúrgico medio de la queiloplastia aislada fue de 85 minutos. Se reinició alimentación oral a las 4 horas de la intervención, reanudando la alimentación mediante biberón a las 2 semanas, siguiendo el mismo protocolo que con las otras técnicas. En los 13 casos se consiguió un labio superior simétrico con altura adecuada y nariz armónica (excepto 1 que presentó retracción, tratada con infiltración de triamcinolona). No hubo otras complicaciones intra/postoperatorias. CONCLUSIONES: La queiloplastia de Meara corrige de forma muy armónica la fisura labial con poca o moderada separación de los segmentos labiales (habitualmente la fisura labial sin fisura alveolar). Como ventajas frente a otras técnicas permite, en una intervención más corta, la queiloplastia utilizando colgajos ondulados, que son menos geométricos y aportan armonía al resultado.

An updated protocol for mandibular reconstruction in nongrowing patients with craniofacial microsomia with temporomandibular joint total prosthesis.

The authors aim to present an updated protocol for mandibular reconstruction in nongrowing patients with Pruzansky/Kaban type IIb/III congenital craniofacial microsomia with customized temporomandibular joint (TMJ) prosthesis to reduce facial nerve (FN) damage and improve surgical accuracy. This is illustrated (using 3 cases) and is based on preoperative mapping of the FN using MRI for better virtual surgical planning of custom-made TMJ prosthesis. Intraoperative FN mapping and monitoring, as well as verification of the final result with intraoperative cone-beam computed tomography (CBCT) and 3D-reconstructed images is also achieved. All 3 patients presented mild transient postoperative facial palsy due to surgical soft tissue stretching which resolved within 2 months of surgery. All patients presented proper occlusion and mouth opening without pain, with an average incisal opening of 38.8 mm (range 35.5-42 mm) at two months of follow-up. Moreover, superposition of intraoperative and preoperative 3D reconstruction images ensured surgical accuracy and avoided the need for a potential reintervention. In conclusion, the proposed surgical protocol for mandibular reconstruction with customized alloplastic TMJ prosthesis in nongrowing patients with type IIb/III Pruzansky-Kaban congenital mandibular hypoplasia may reduce FN morbidity, improve surgical accuracy and final outcomes.

Usefulness of Video-EEG monitoring in patients with drug-resistant epilepsy.

OBJECTIVE: To evaluate the characteristics of patients on whom long-term Video-EEG monitoring is performed in a specialist centre and to assess its suitability to study refractory epilepsy patients. METHODS: A prospective analysis and study of Video-EEG monitoring was performed in a series of 100 refractory epilepsy patients from a single centre. The analysis included demographic data, the time until the first seizure, the methods used to provoke seizures, and the outcome (usefulness, change in the management, pharmacological and surgical improvement). A subgroup analysis based on diagnosis was performed. RESULTS: The study was performed mainly on young people (mean 34.4 years) and the first seizure appeared in a mean of 30hours, requiring most of the patients to withdraw the medication. Nevertheless, there were no cases of status epilepticus. The usefulness of the test was high in all the groups. The management was changed in 65% of the patients with pharmacological and surgical improvement. CONCLUSION: Long-term Video-EEG monitoring is a suitable test to study refractory epilepsy patients. The main problem in our country is accesibility.

Amblyopia due a dentigerous cyst. Case report and literature review.

PURPOSE: The goal of this article is to present an infrequent clinical case and to review the available literatura, with an emphasis on ophthalmological symptoms. METHODS: We present the case of a 4-year-old girl with a large dentigerous cyst on the maxillary bone, who had long-standing unilateral epiphora associated with progressive ocular dystopia, facial asymmetry and ipsilateral amblyopia. A multidisciplinary approach was taken by the maxillofacial surgery, ophthalmology and optometry teams. This included systemic antibiotic administration, surgical cyst drainage and amblyopia treatment. The literature review was carried out in the MEDLINE database through the free electronic access to PubMed in March 2020. RESULTS: At the 6-month follow-up, the patient was asymptomatic. The most common symptoms of dentigerous cysts are epiphora 36.8%, ocular dystopia 31.2%, diplopia 21.1%, proptosis, nasolacrimal duct obstruction and blurred vision at 10.5%. Amblyopia has not been reported. CONCLUSIONS: Dentigerous cysts are benign odontogenic cysts, which can be found in the jaw and less frequently on the maxillary bone. They are usually asymptomatic, and the occurrence of ophthalmic complications is very infrequent. Multidisciplinary management is essential to avoiding long-term morbidity of maxillary dentigerous cysts and should include an ophthalmologist.

Geochemical and isotopic study of abiotic nitrite reduction coupled to biologically produced Fe(II) oxidation in marine environments.

Estuarine sediments are often characterized by abundant iron oxides, organic matter, and anthropogenic nitrogen compounds (e.g., nitrate and nitrite). Anoxic dissimilatory iron reducing bacteria (e.g., Shewanella loihica) are ubiquitous in these environments where they can catalyze the reduction of Fe(III) (oxyhydr)oxides, thereby releasing aqueous Fe(II). The biologically produced Fe(II) can later reduce nitrite to form nitrous oxide. The effect on nitrite reduction by both biologically produced and artificially amended Fe(II) was examined experimentally. Ferrihydrite was reduced by Shewanella loihica in a batch reaction with an anoxic synthetic sea water medium. Some of the Fe(II) released by S. loihica adsorbed onto ferrihydrite, which was involved in the transformation of ferrihydrite to magnetite. In a second set of experiments with identical medium, no microorganism was present, instead, Fe(II) was amended. The amount of solid-bound Fe(II) in the experiments with bioproduced Fe(II) increased the rate of abiotic NO2- reduction with respect to that with synthetic Fe(II), yielding half-lives of 0.07 and 0.47 d, respectively. The δ18O and δ15N of NO2- was measured through time for both the abiotic and innoculated experiments. The ratio of ε18O/ε15N was 0.6 for the abiotic experiments and 3.1 when NO2- was reduced by S. loihica, thus indicating two different mechanisms for the NO2- reduction. Notably, there is a wide range of the ε18O/ε15N values in the literature for abiotic and biotic NO2- reduction, as such, the use of this ratio to distinguish between reduction mechanisms in natural systems should be taken with caution. Therefore, we suggest an additional constraint to identify the mechanisms (i.e. abiotic/biotic) controlling NO2- reduction in natural settings through the correlation of δ15N-NO2- and the aqueous Fe(II) concentration.

Seasonal differences in SO2 ground-level impacts from a power plant plume on complex terrain.

The objective of this study is to describe the seasonal differences in SO2 ground-level fumigations from a power plant situated on very complex terrain in the Iberian Peninsula within the Western Mediterranean Basin (WMB). The study area extends more than 80 km around the power plant on very complex semi-arid terrain. Considering different plume-rise schemes, by experimentation and modelling this study attempts to characterise the seasonal differences in both the plume footprint 80 km around the power plant and the turbulent regime (diurnal or nocturnal) driving the main contribution to the accumulated plume footprints at different distances from the power plant within a complex terrain region. Two markedly different SO2 ground-level distributions around the power plant are presented for the typical summer and winter dispersive scenarios in the area. Simulations show that the SO2 footprint of a plume being advected more than 450 m above ground level in complex terrain is highly dependent on the prevailing meteorological conditions and on the mesoscale perturbations of the synoptic flows within the lower layers of the troposphere. The results obtained show how on complex terrain, despite seasonal meteorological differences and under stable dispersive conditions, the simulated mechanical turbulence leeward of the mountain ranges reproduces highly concentrated SO2 fumigations on the ground more than 50 km away from the power plant. Besides, under summer convective activity, plume fumigations have been successfully simulated less than 15 km from the power plant. In conclusion, this study shows how measurements from air quality networks together with information obtained from atmospheric transport and diffusion models are able to characterise different transport scenarios. This is a clear advantage for the end-users and decision-makers who manage and optimise the regional air quality networks.

Lymphoepithelial carcinoma of the accessory parotid gland.

Lymphoepithelial carcinoma of the accessory parotid gland is rare, and to our knowledge, only two cases have previously been reported. It has an association with the Epstein-Barr virus and is usually seen in Asians and Greenland Eskimos. We report a case of lymphoepithelial carcinoma of the left accessory parotid gland in a 59-year-old European man who had been raised in the Belgian Congo. After excision of the left accessory parotid gland with preservation of the facial nerve, he recovered well without complication, and there was no evidence of locoregional recurrence or distant metastases after follow up of 3.5 years.

[Non-invasive diagnosis of cardiac amyloidosis due to transthyretin. Case report]. / Diagnóstico no invasivo de amiloidosis cardiaca por transtirretina. Caso clínico.

Amyloidosis due to deposits of transthyretin (ATTR) is currently considered the most frequent form of cardiac amyloidosis and its incidence is increasing thanks to the advances in diagnostic imaging techniques. Some non-invasive diagnostic criteria have recently been published on this entity that due to the development of new drugs for the specific treatment of cardiac ATTR, have prognostic and therapeutic implications. That is why cardiac ATTR could cease to be a rare disease and become a frequent one, and become potentially treatable instead of incurable. We present the case of an 80-year-old male diagnosed with non-hereditary cardiac ATTR by means of gammagraphy with 99mTc diphosfonate scintigraphy (99mTc-DPD) following the new criteria of non-invasive diagnosis.

Compound-specific carbon isotope analysis of volatile organic compounds in water using solid-phase microextraction.

The compound-specific isotope analysis technique in conjunction with solid-phase microextraction using a carboxen-polydimethylsiloxane fiber was tested and implemented for isotopes analyses of organic compounds aiming for environmental application in contaminated groundwater. delta(13)C values of several chlorinated methanes and ethenes, toluene and chlorobenzene were determined using a gas chromatograph coupled to an isotope ratio mass spectrometer through a combustion interface. Direct and headspace solid-phase microextraction (D-SPME, HS-SPME) methods were tested in order to determine the optimum conditions to obtain reproducible delta(13)C values at very low concentration (microg/L range) and, to elucidate the carbon isotopic effects associated with the competitive extraction. For D-SPME, higher accuracy and precision of delta(13)C results were obtained with no salted aqueous standards. Despite that the delta(13)C of those compounds analyzed with both methods showed similar precision (<0.5 per thousand) and accuracy, the highest sensitivity was reached with HS-SPME. Furthermore, the delta(13)C values of cis-1,2-dichloroethylene, chorinated methanes and aromatic compounds obtained using HS-SPME showed measurable deviations with respect to the isotopic composition of pure phase compounds, however, these deviations are constant according to the analytical uncertainties, indicating that they are not affected by competitive extraction, and they could be corrected using standard correction technique based on internal calibrated standards.

Efficacy and safety of eslicarbazepine-acetate in elderly patients with focal epilepsy: Case series.

PURPOSE: Eslicarbazepine-acetate (ESL) is a third generation antiepileptic drug licensed as adjunctive therapy in adults with focal seizures. Efficacy and safety of ESL have been established in real-life setting. However, data about outcomes in elderly patients are scarce. Primary endpoint was to evaluate outcomes of ESL in elderly patients. METHOD: This was a retrospective survey that included patients >65years with focal seizures who started ESL between January 2010 and July 2012 at 12 Spanish Hospitals. ESL was prescribed individually according to real-life practice. Efficacy and safety were evaluated over 1year. These patients were included within the bigger study ESLIBASE. RESULTS: We included 29 patients, most of them males (18). Mean age was 71.2 year-old and epilepsy evolution was 20 years. Eighteen were pharmacorresistant at baseline. At 12 months, the mean dose was 850mg/day, the retention rate 69%, the responder rate 62% and 24.1% were seizure-free. At 12 months, 16 patients (55.2%) had ≥1 adverse effect (AE), that led to discontinuation in 7 patients. Dizziness, nausea and ataxia were the most common AEs. The tolerability profile improved in 4/5 patients who switched from carbamazepine (CBZ) or oxcarbazepine (OXC) to ESL due to AEs. CONCLUSIONS: ESL was well-tolerated and effective in elderly patients in a real-life setting over 1year, with a dose around 800mg/day. AE effects improved in most of who switched from CBZ or OXC to ESL.

[Incidence of influenza and influenza vaccine effectiveness in the 2004-2005 season]. / Incidencia de la gripe y efectividad de la vacuna antigripal en la temporada 2004-2005.

BACKGROUND: To quantify the incidence of flu in different groups of the population of Navarra in the 2004-2005 season, and to evaluate the effectiveness of anti-flu vaccination. METHODS: The analysis of influenza cases in the system of compulsory notificable diseases was complemented by the individualised notifications in the network of sentinel doctors that covers a population of 22,339 inhabitants. The coverage and effectiveness of the vaccine was studied. RESULTS: Vaccine coverage in (3)65 year olds reached 62%. The incidence of influenza was 42.6 cases per 1,000 inhabitants. It reached a maximum in mid-January, exceeding 750 weekly cases per 100,000 inhabitants and 1,900 cases per 100,000 children. The highest rate of influenza was observed in under-15 year olds (49.4 cases per 1,000 inhabitants) and the lowest in non-institutionalised (3)65 year olds (2.6 per 1,000 inhabitants), although it was higher in geriatric residences (62.1 per 1,000; p<0.0001). Seventy-nine percent of the cases from 5 to 64 years resulted in absenteeism from school or work. The flu virus was identified in 42/65 (65%) nasopharyngeal smears, 90% being influenza virus A(H3). The incidence of influenza was 3.08% in the unvaccinated and 0.45% in the vaccinated (p<0.001). The global effectiveness of the anti-flu vaccine was 65%, and in (3)65 years old it was 73%. CONCLUSION: Although its effectiveness is not total, the vaccine is the main measure for preventing influenza. The network of sentinel doctors provide useful information for the coordination of care and public health activities against flu.

ESTUDIO DE LAS COINFECCIONES POR OTROS PATÓGENOS RESPIRATORIOS EN PACIENTES PEDIÁTRICOS CON DIAGNÓSTICO DE COVID-19 / STUDY OF COINFECTIONS BY OTHER PATHOGENS RESPIRATORY IN PEDIATRIC PATIENTS WITH DIAGNOSTICS FROM COVID-19

Introducción: La coinfección de COVID-19 con otros patógenos respiratorios en pediatría ha sido poco estudiada. Resulta de interés conocer las características y cuadro clínico de pacientes que presenten coinfecciones con COVID-19. Objetivo: Estudiar la coinfección de SARS-CoV-2 con patógenos incluidos en el Panel RP 2.0 FilmArray® en muestras de pacientes pediátricos en un hospital del tercer nivel. Materiales y métodos: Durante abril a agosto de 2021 se realizó un estudio prospectivo descriptivo sobre 21 muestras de Hisopado Nasofaríngeo de pacientes pediátricos positivos para SARS-CoV-2 (iAMP® COVID-19 Detection Kit de Atila Biosystems). Se procesaron por PCR multiplex Filmarray® RP 2.0. Luego se describieron las características y síntomas de los pacientes. Resultados: 12/21 (60%) fueron pacientes ambulatorios y 8/21 (40%) internados. El 57% de los pacientes fueron mayores de 5 años, el 24% menores de 1 año y el 19% entre 1 y 5 años. El síntoma más frecuente fue fiebre 18/21 (86%). El 90,5% (19/21) de las muestras no mostraron detección de otros patógenos. En una muestra se detectó Rhino/enterovirus y en otra Coronavirus NL63; ambas pertenecieron a dos pacientes con enfermedades de base. Conclusión: La tasa de coinfecciones fue del 9,5%. Este número podría deberse a la baja circulación de patógenos respiratorios en un contexto con medidas de prevención de los contagios. En el estado actual de incremento de circulación de virus respiratorios endémicos, es de interés la búsqueda de coinfecciones con COVID-19

Introduction: The co-infection of COVID-19 with other respiratory pathogens in pediatrics has been little studied. It is of interest to know the characteristics and clinical picture of patients who present co-infections with COVID-19. Objective: To study the co-infection of SARS-CoV-2 with pathogens included in the RP Panel 2.0 FilmArray® in samples from pediatric patients in a third-level hospital. Materials and methods: During April to August 2021, a prospective descriptive study was conducted on 21 Nasopharyngeal Swab samples from pediatrics patients positive for SARS-CoV-2 (iAMP® COVID-19 Detection Kit from Attila Biosystems). They were processed by PCR multiplex Filmarray® RP 2.0. The characteristics and symptoms of the patients were then described. Results: 12/21 (60%) were outpatients and 8/21 (40%) were hospitalized. 57% of patients were older than 5 years, 24% under 1 year and 19% between 1 and 5 years. The most frequent symptom was fever 18/21 (86%). 90,5% (19/21) of the samples showed no detection of other pathogens. Rhino/enterovirus was detected in one sample and NL63 in another Coronavirus; both belonged to two patients with underlying diseases. Conclusion: The rate of co-infections was 9,5%. This number could be dueto the low circulation of respiratory pathogens in a context with measures to prevent contagion. In the current state of increased circulation of endemic respiratory viruses, the search for co-infections with COVID-19 is of interest

Disulphide bridging of calf thymus histone H3 by 5,5'-dithiobis(2-nitrobenzoic acid).

Electrophoretic analysis of the reaction products of calf thymus histone H3 with 5,5'-dithiobis(2-nitrobenzoic acid), under mild conditions, shows that different oxidized forms of this histone are originated by disulphide interchange. One of the species detected is the intramolecular oxidized monomer of histone H3.

Protamines and other basic proteins from spermatozoa of molluscs.

The basic proteins obtained from spermatozoa of different species of the phylum Mollusca have been extracted and fractionated. The amino acid analysis and electrophoretic mobility of these proteins show a considerable variation in the types and relative amounts of the components present in different species. In some case-(Gibbula, Haliotis, Loligo, Octopus) the main components are similar to the protamines found in the salmonid fishes, although they appear to be larger in size (40-80 amino acids) and show significant differences in amino acid composition. In other cases (Mytilus, Chiton) a complex mixture of proteins is present, which including somatic-like histones and proteins intermediate in size and composition betweeln protamines and histones. Other molluscs (Ostrea, Spisula, Patella) also contain proteins intermediate in composition between protamines and histones, but their molecular weight appears to be larger than in histones. In Eledone a complex mixture of proteins containing cystine is obtained, with some components rich in arginine. In most species, somatic-like histones are also present. Their type and relative amount are different in each species. The significance of these results towards an understanding of the evolutionary history of these proteins is discussed. It is suggested that these proteins evolved from histone precursors.

Interactions of histones and histone peptides with DNA Thermal denaturation and solubility studies.

The interactions of DNA with the five histone components (H1, H2B, H2A, H3 and H4) and with a number of histone fragments (N-H1 (1--72), C-H1 (73--216), N-H2B (l--59), C-H2B, (63--125), N-H2A (1-39), C-H2A (58--129), N-H4 (1--84) and C-H4 (85--102) have been studied by using the techniques of thermal denaturation and solubility behaviour. Complexes in 10(-3) M phosphate buffer, 2 - 10(-5) M Na(2)-EDTA, pH 7.0 were prepared by the direct mixing method. For lysine-rich histones (H1 and H2B) it has been found that the main characteristics which governs the interaction with DNA are located in the very lysine-rich part of the molecules, i.e. in the C-H1 and N-H2B segments. These regions are also responsible for a cooperative distribution of the histone along the DNA molecules in the artificial complexes. It appears from our studies that the tertiary structure of the moderately, arginine-rich histone (H2A) is an essential feature for its interaction with DNA. The two arginine-rich histones (H3 and H4) complexed with DNA behave in a similar way, both in thermal denaturation and in DNA precipitation. In the case of C-H4, a marked shift of the melting profile has been observed which is correlated with the presence in the peptide of the hydrophilic cluster Lys-Arg-Gln-Gly-Arg-Thr. Our results suggest that large segments rich in lysine and basic clustering within histones give rise to different modes of electrostatic interaction with DNA.

The interaction of histone H3 with histone H4 and with other histones studied by 19F nuclear magnetic resonance.

The behaviour, upon variations in ionic strength, pH and temperature of 19F nuclear nuclear magnetic resonance signals of the trifluoroacetonylated derivative of histone H3 is compared with those of the H3-H4 complex and of the Hv fraction (an equimolar mixture of H2A, H2B, H3 and h4). The line width of the 19F-labelled histone H3 signals increases with ionic strength or pH, an effect consistent with aggregation of the protein. In the case of H3-H4 complex or Hv the line width decreases at intermediate ionic strengths (0.1-0.25 M NaCl). This effect is interpreted as the consequence of the formation of a well defined structure with ionic strength. At high salt concentrations the line width increases as a consequence of the final rigid quaternary structure or of the formation of higher aggregates.

Characterization of antigenic polypeptides of the RNP, Sm and SS-B nuclear antigens from calf thymus.

Antinuclear autoantibodies are a hallmark of autoimmune diseases. The RNP, Sm and SS-B nuclear antigens from calf thymus in whole tissue, nuclear extracts and fractions have been studied by using different techniques including immunodiffusion, counterimmunoelectrophoresis and protein blotting. Such studies were done in order to obtain a precise characterization of the polypeptide components of those antigens. From our results it can be established that: one 69.8 Kd polypeptide (for whole tissue and nuclei) and a number of well-defined 32-38-Kd polypeptides (for nuclear extracts and ammonium sulfate fractions) show an antigenic character against anti-RNP sera; anti-Sm sera from different patients show in all cases a variable component of antigenic polypeptides, including one 28.8, 29.7 Kd doublet and two singlets of 14.8 and 11.0 Kd; and a 52.0-Kd SS-B antigenic polypeptide is found for whole tissue, which is gradually degraded in nuclei and nuclear extracts to a more stable 47.1-Kd polypeptide.

Molecular mimicry of substrate oxygen atoms by water molecules in the beta-amylase active site.

Soybean beta-amylase (EC 3.2.1.2) has been crystallized both free and complexed with a variety of ligands. Four water molecules in the free-enzyme catalytic cleft form a multihydrogen-bond network with eight strategic residues involved in enzyme-ligand hydrogen bonds. We show here that the positions of these four water molecules are coincident with the positions of four potential oxygen atoms of the ligands within the complex. Some of these waters are displaced from the active site when the ligands bind to the enzyme. How many are displaced depends on the shape of the ligand. This means that when one of the four positions is not occupied by a ligand oxygen atom, the corresponding water remains. We studied the functional/structural role of these four waters and conclude that their presence means that the conformation of the eight side chains is fixed in all situations (free or complexed enzyme) and preserved from unwanted or forbidden conformational changes that could hamper the catalytic mechanism. The water structure at the active pocket of beta-amylase is therefore essential for providing the ligand recognition process with plasticity. It does not affect the protein active-site geometry and preserves the overall hydrogen-bonding network, irrespective of which ligand is bound to the enzyme. We also investigated whether other enzymes showed a similar role for water. Finally, we discuss the potential use of these results for predicting whether water molecules can mimic ligand atoms in the active center.