The folding of a 93-residue protein, the histidine-phosphocarrier protein of Streptomyces coelicolor, HPr, has been studied using several biophysical techniques, namely fluorescence, 8-anilinonaphthalene-1-sulfate binding, circular dichroism, Fourier transform infrared spectroscopy, gel filtration chromatography and differential scanning calorimetry. The chemical-denaturation behaviour of HPr, followed by fluorescence, CD and gel filtration, at pH 7.5 and 25°C, is described as a two-state process, which does not involve the accumulation of thermodynamically stable intermediates. Its conformational stability under those conditions is DG ¼ 4.0 ± 0.2 kcalAEmol )1 (1 kcal ¼ 4.18 kJ), which makes the HPr from S. coelicolor the most unstable member of the HPr family described so far. The stability of the protein does not change significantly from pH 7-9, as concluded from the differential scanning calorimetry and thermal CD experiments. Conformational studies at low pH (pH 2.5-4) suggest that, in the absence of cosmotropic agents, HPr does not unfold completely; rather, it accumulates partially folded species. The transition from those species to other states with native-like secondary and tertiary structure, occurs with a pK a ¼ 3.3 ± 0.3, as measured by the averaged measurements obtained by CD and fluorescence. However, this transition does not agree either with: (a) that measured by burial of hydrophobic patches (8-anilinonaphthalene-1-sulfate binding experiments); or (b) that measured by acquisition of native-like compactness (gel-filtration studies). It seems that acquisition of native-like features occurs in a wide pH range and it cannot be ascribed to a unique side-chain titration. These series of intermediates have not been reported previously in any member of the HPr family.

This study is devoted to characterizing the operation of the entire photovoltaic system installed in one of the Auger Muons and Infill for the Ground Array (AMIGA) stations, a complimentary detector for the Pierre Auger Observatory, the largest cosmic‐ray air shower array in the world, 3000 km2, powered exclusively by solar energy. To understand charge and discharge cycles, the whole system behavior under different climatic conditions and to determine its limitations, the design of a new prototype for monitoring the whole system online is a fundamental part of this contribution. Also, it is demonstrated that the configuration of solar charge controllers in parallel is able to manage panels of different powers and brands and that the monitoring system allows analyzing periods with adverse weather conditions.