Mutations of penicillin acylase residue B71 extend substrate specificity by decreasing steric constraints for substrate binding

Two mutant forms of penicillin acylase from Escherichia coli strains, selected using directed evolution for the ability to use glutaryl-L-leucine for growth [Forney, Wong and Ferber (1989) Appl. Environ. Microbiol. 55, 2550-2555], are changed within one codon, replacing the B-chain residue Phe(B71) with either Cys or Leu. Increases of up to a factor of ten in k(cat)/K-m values for substrates possessing a phenylacetyl leaving group are consistent with a decrease in K-s. Values of k(cat/)K(m) for glutaryl-L-leucine are increased at least 100-fold. A decrease in k(cat)/K-m for the CySB71 mutant with increased pH is consistent with binding of the uncharged glutaryl group. The mutant proteins are more resistant to urea denaturation monitored by protein fluorescence, to inactivation in the presence of substrate either in the presence of urea or at high pH, and to heat inactivation. The crystal structure of the Leu(B71) mutant protein, solved to 2 X resolution, shows a flip of the side chain of Phe(B256) into the periphery of the catalytic centre, associated with loss of the pi-stacking interactions between Phe(B256) and Phe(B71). Molecular modelling demonstrates that glutaryl-L-leucine may bind with the uncharged glutaryl group in the S-1 subsite of either the wild-type or the Leu(B71) mutant but with greater potential freedom of rotation of the substrate leucine moiety in the complex with the mutant protein. This implies a smaller decrease in the conformational entropy of the substrate on binding to the mutant proteins and consequently greater catalytic activity

Corporate board and default risk of financial firms

This paper analyses the impact of corporate board structure on default risk of European banking firms. We focus on four core aspects of boards that have been addressed in Directive 2013/36/ EU to strengthen the corporate governance of banks: the size of boards, their independence, the participation of female directors and CEO duality. We employ panel data analysis to study the 109 European listed banks between 2002 and 2019. Default risk is estimated by Merton’s (1974) distance to default. We take into account the presence of unobservable heterogeneity, simultaneity and dynamic endogeneity and estimate the model using the dynamic difference and dynamic system GMM methodologies. The results show that the size of the board influences banks’ default risk. Furthermore, bank size, firm profitability and GDP also exert a considerable influence

Algorithms for identification and categorization

The main features of a family of efficient algorithms for recognition and classification of complex patterns are briefly reviewed. They are inspired in the observation that fast synaptic noise is essential for some of the processing of information in the brain.Comment: 6 pages, 5 figure

Construction of orthonormal wavelet-like bases

A general method for constructing wavelet-like bases in a Hilbert space H starting from any orthonormal basis in H and any periodic orthonormal wavelet basis is presented. With this method we can take advantage of the characteristics of both types of bases to obtain orthonormal wavelet-like bases that are suitable to represent functions and operators efficiently.Fil: Morillas, Patricia Mariela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis; Argentina. Universidad Nacional de San Luis; Argentin

El prisma del lenguaje: cómo las palabras colorean el mundo. [RESEÑA]

Deutscher, Guy El prisma del lenguaje: cómo las palabras colorean el mundo. Trad. Manuel Talens. Barcelona: Ariel, 2011. 344 pp. (ISBN: 978-84-344-6969-3

Flebotomos de las Islas Canarias (España)

La ausencla de datos acerca de la fauna de Phlebotominae en el archiplelago Canario, nos ha llevado B realizar iiltimnmente varlos muestreos en las lslas de Oran Canaria y Tenerlfe. Para los mencionados muestreos se emple6 siempre la técnica del papel adhesivo. En Oran Canaria. de un total de €dete estaciones, s610 hubo capturas en una de ellas En Tenerife se recolectaron ejemplares en un total de slete estaciones pero el numero de capturas fue muy bajo. Los caracteres de los ejemplares machos y hembras capturados son : Macho: Pompa genltal en el tercer Segmento abdominal. Filamentos genitales muy largos, que sobrepasan las valvas del pene. Estas son troncoc6nicas con prolongaci6n basa1 muy desarrollada de aspecto semilunar. El estilo (con cinco esplnasi, coxito y l6bulo lateral no presentan particularidad notable. Hembra: Faringe con tres zonas definidas: la posterior, más ancha que las dos anteriores, ocupa un tercio de esta estructura Espermateca tubullforme con paredes lisas y conductos espermáticos extremadamente largos; el cuerpo. ligeramente más ancho que los conductos, se continua en un cuello cuyo diámetro es similar al de la cabeza, la cual esta rodeada de una corona de pelos. Este conjunto de caracteres confieren a los eiemplares procedentes de las islas Canarias peculiaridades propia

Deciphering past and present atmospheric metal pollution of urban environments: The role of black crusts formed on historical constructions

Construction materials affected by black crusts (BCs) can be subjected to restoration, demolition, recycling or even to their management as waste products. Therefore, the determination of their chemical features should be considered a crucial step before undertaking any action. In this work, we present the development of an analytical methodology useful to be implemented as a routine screening tool to detect recent and past atmospheric emissions of heavy metals, nowadays superficially deposited or even encapsulated in BCs. For its development, BCs together with the underneath original substrate/construction material were sampled from the historical construction Punta Begona Galleries (Getxo, Basque Country, North of Spain). In order to detect quickly and in a cost-effective way the stratification of the metallic deposits in the BCs over time (surface or external/recent and internal/past), thin sections were analyzed by elemental spectroscopic imaging techniques (SEM-EDS and mu-ED-XRF). In the external part of the BCs, iron particles were mainly identified, whereas in the inner areas (past deposition events) of the most exposed BCs to the atmosphere, lead accumulations together with zinc and copper were identified. Additional Raman imaging studies allowed to perform the molecular speciation study of lead, identifying mainly laurionite (PbClOH) together with hydrocerussite (Pb-3(CO3)(2)(OH)(2)). The presence of the mentioned lead chloride hydroxide confirms the role of the marine aerosol (chloride input) in the formation of the metallic compounds. These experimental evidences were used to assist the chemical equilibrium models developed to explain the reactivity pathway, which lead to the formation of the identified compounds. Through ICP-MS and lead isotopic ratio analysis, more than 3000 mg kg(-1) of lead were quantified in the BCs, probably coming from the old emissions conducted by the old power station close to the construction,. That lead content can be high enough to consider those crusts as a source of metallic contamination and a possible risk to the environment and human health

Non-Adherence in Adult Male Patients with Community-Acquired Pneumonia: Relative Forgiveness of Amoxicillin versus Respiratory Fluoroquinolones

The consequences of non-adherence to treatment (NAT) on antimicrobial efficacy may depend on drug forgiveness—a property that should account for pharmacokinetics (PK) and pharmacodynamics (PD) as well as interindividual variability. In this simulation study, relative forgiveness (RF) in NAT, defined as the probability of a successful PK/PD target (PTA) attained under perfect adherence compared to imperfect adherence, was evaluated for amoxicillin (AMOX) (oral 1000 mg/8 h) and two respiratory fluoroquinolones—levofloxacin (LFX) (oral 750 mg/24 h) and moxifloxacin (MOX) (oral 400 mg/24 h)—in virtual outpatients with community-acquired pneumonia for S. pneumoniae. Several NAT scenarios (delay in dose intake and a missed dose) were considered. PK characteristics of virtual patients, including variability in creatinine clearance (70–131 mL/min) and S. pneumoniae susceptibility variability associated with geographical location, were simulated in NAT. In this regard, in regions of low MIC delays from 1 h to 7 h or omission of dose ingestion would not have negative consequences on the efficacy of AMOX because of its good RF associated with the AMOX PK and PD properties; RF of LFX 750 mg or MOX 400 mg/24 h regimen vs. AMOX 1000 mg/8 h is one. However, in regions of elevated MIC for S. pneumoniae AMOX loses its RF, LFX and MOX vs. AMOX, showing higher RF (>1) depending on the CLCR of patients. These results illustrate the importance of considering the RF of antimicrobial drugs in NAT and provide a framework for further studying its implications for clinical success rates

The current importance of Leishmaniasis in Spain

Se pasa revisión al estado actual de los principales elementos epidemiológicos de las leishmaniosis en España: parásito, reservorio canino, flebotomo vector, y hombre, poniendo de manifiesto la importancia sanitaria, social y económica de la enfermedad. Se termina recogiendo datos recientes sobre el diagnóstico y tratamiento de la enfermedad.A revision is made of the current state of the principal epidemiological elements of leishmaniasis in Spain (the parasite, the canine population, the sandflies vector, and humans), while stating the sanitary, social and economic significance of the disease. Finally, recent information is given regarding the diagnosis and treatment of the disease