Heme ligation and redox chemistry in two bacterial thiosulfate dehydrogenase (TsdA) enzyme

Thiosulfate dehydrogenases (TsdA) are bidirectional bacterial di-heme enzymes that catalyze the interconversion of tetrathionate and thiosulfate at measurable rates in both directions. In contrast to our knowledge of TsdA activities, information on the redox properties in the absence of substrates is rather scant. To address this deficit, we combined magnetic circular dichroism (MCD) spectroscopy and protein film electrochemistry (PFE) in a study to resolve heme ligation and redox chemistry in two representative TsdAs. We examined the TsdAs from Campylobacter jejuni, a micro-aerobe human pathogen, and from the purple sulfur bacterium Allochromatium vinosum. In these organisms, the enzyme functions as a tetrathionate reductase and a thiosulfate oxidase respectively. The active site Heme 1 in both enzymes has His/Cys− ligation in the ferric and ferrous states and the midpoint potentials (Em) of the corresponding redox transformations are similar, −185 mV versus standard hydrogen electrode (SHE). However, fundamental differences are observed in the properties of the second, electron transferring, Heme 2. In C. jejuni TsdA Heme 2 has His/Met ligation and an Em of +172 mV. In A. vinosum TsdA, Heme 2 reduction triggers a switch from His/Lys ligation (Em, −129 mV) to His/Met (Em,+266 mV) but the rates of interconversion are such that His/Lys ligation would be retained during turnover. In summary, our findings have unambiguously assigned Em values to defined axial ligand sets in TsdAs, specified the rates of Heme 2 ligand exchange in the A. vinosum enzyme, and provided information relevant to describing their catalytic mechanism(s)

Anglo-Dutch translations of medical and scientific texts

In the seventeenth century the use of vernacular languages became more and more accepted in scientific publications and communications, and began to supplement the traditional language in this field, namely: Latin. The increase in the number of languages used in science and medicine was accompanied by a heightened need for translators. The close relationship between England and the Low Countries in the seventeenth century has led to a focus in the existing research on political and religious issues, and this has been reflected in the study of translations between English and Dutch. Yet one also finds in the fields of medicine and science an exchange of ideas through translation. The language skills of both Dutch and English men and women were often not sufficient to understand each other's language, which means that translations were vital. By considering the examples of how Thomas Browne's Religio medici was translated into Dutch, and how letters by Antoni van Leeuwenhoek and a publication by Jan Baptista van Helmont were translated into English, this essay examines the exchange of scientific and medical ideas across the Channel.Part of this article was written during a visiting fellowship in the Summer of 2016 at the Max Planck Institute for the History of Science in Berlin, and I would like to thank the MPIWG and the Global Knowledge Society Project for hosting me, as well as the Making Visible Project (Arts and Humanities Research Council, grant number AH/M001928/1) for providing me with support and the time to write

High Temperature Thermopower in La_{2/3}Ca_{1/3}MnO_3 Films: Evidence for Polaronic Transport

Thermoelectric power, electrical resistivity and magnetization experiments, performed in the paramagnetic phase of La_{2/3}Ca_{1/3}MnO_3, provide evidence for polaron-dominated conduction in CMR materials. At high temperatures, a large, nearly field-independent difference between the activation energies for resistivity (rho) and thermopower (S), a characteristic of Holstein Polarons, is observed, and ln(rho) ceases to scale with the magnetization. On approaching T_c, both energies become field-dependent, indicating that the polarons are magnetically polarized. Below T_c, the thermopower follows a law S(H) prop. 1/rho (H) as in non saturated ferromagnetic metals.Comment: 10 pages, 5 .gif figures. Phys. Rev B (in press

Assessment of the photoprotective and antimicrobial activity of two dermatological creams based on Mathesia and oil of Curcuma longa L. (Zingiberaceae) on Albinos

Introduction The fragility and sensitivity of the skin in people with albinism (PWA) have necessitated extensive research across molecular genetics, dermatology, and cosmetology. These efforts aim to address the increased susceptibility of albino skin to sun damage and dermatological conditions. Purpose This study investigates the dermatological efficacy of two galenic formulations, one based on Mathesia and the other on Curcuma longa L. (Zingiberaceae) oil, assessing their antimicrobial, anti-inflammatory, and photoprotective properties for the skin of PWA. Methods Using freeze-drying techniques for Mathesia and slight modifications of Sahouli et al.'s method for extracting Curcuma longa L. oil, we developed two creams. Their macroscopic properties, pH levels, and tyrosine concentrations were analyzed. UV-visible spectrophotometry determined their sun protection factor (SPF). An antibiogram test assessed their antimicrobial activity, and a clinical test evaluated their efficacy on PWA with and without skin conditions. Results The study revealed that both creams had good texture and appropriate pH levels. However, neither cream provided sufficient photoprotection for the sensitive skin of PWA. The Mathesia-based cream demonstrated a higher antimicrobial efficacy compared to the turmeric oil-based and neutral creams. Clinical tests showed 75% of participants had very satisfactory results, with the turmeric oil-based cream showing the most significant overall efficacy. Conclusion The creams exhibited beneficial antimicrobial and anti-inflammatory properties but were inadequate for UV protection of albino skin. Future research should focus on increasing active ingredient concentrations or exploring alternative plants to enhance tyrosine content and SPF values, potentially offering better protection and therapeutic effects for PWA

Changing portrayals of medicine and patients in eighteenth-century medical writing : Lexical bundles in Public Health, Methods, and case studies

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Sociohistorical and cultural context of Late Modern English Medical Texts

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Scientific Periodicals : The Philosophical Transactions and the Edinburgh Medical Journal

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Towards new knowledge : The corpus of Late Modern English Medical Texts

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Manual to the LMEMT corpus

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