Synthesis of photocatalytic cysteine-capped Cu≈10 clusters using Cu5 clusters as catalysts.

We report an easily scalable synthesis method for the preparation of cysteine-capped Cu≈10 clusters through the reduction of Cu(II) ions with NaBH4, using Cu5 clusters as catalysts. The presence of such catalytic clusters allows controlling the formation of the larger Cu≈10 clusters and prevents the production of copper oxides or Cu(I)-cysteine complexes, which are formed when Cu5 is absent or at lower concentrations, respectively. These results indicate that small catalytic clusters could be involved, as precursor species before the reduction step, in the different methods developed for the synthesis of clusters. The visible light-absorbing Cu≈10 clusters, obtained by the cluster-catalysed method, display high photocatalytic activities for the decomposition of methyl orange with visible light.

Comparison of different vascular risk engines in the identification of type 2 diabetes patients with high cardiovascular risk.

BACKGROUND: Some authors consider that secondary prevention should be conducted for all DM2 patients, while others suggest that the drug preventive treatment should start or be increased depending on each patient's individual CVR, estimated using cardiovascular or coronary risk functions to identify the patients with a higher CVR. The principal objective of this study was to assess three different cardiovascular risk prediction models in type 2 diabetes patients. METHODS: Multicentre, cross-sectional descriptive study of 3,041 patients with type 2 diabetes and no history of cardiovascular disease. The demographic, clinical, analytical, and cardiovascular risk factor variables associated with type 2 diabetes were analysed. The risk function and probability that a cardiovascular disease could occur were estimated using three risk engines: REGICOR, UKPDS and ADVANCE. A patient was considered to have a high cardiovascular risk when REGICOR ≥ 10 % or UKPDS ≥ 15 % in 10 years or when ADVANCE ≥ 8 % in 4 years. RESULTS: The ADVANCE and UKPDS risk engines identified a higher number of diabetic patients with a high cardiovascular risk (24.2 % and 22.7 %, respectively) compared to the REGICOR risk engine (10.2 %). The correlation using the REGICOR risk engine was low compared to UKPDS and ADVANCE (r = 0.288 and r = 0.153, respectively; p < 0.0001). The agreement values in the allocation of a particular patient to the high risk group was low between the REGICOR engine and the UKPDS and ADVANCE engines (k = 0.205 and k = 0.123, respectively; p < 0.0001) and acceptable between the ADVANCE and UKPDS risk engines (k = 0.608). CONCLUSIONS: There are discrepancies between the general population and the type 2 diabetic patient-specific risk engines. The results of this study indicate the need for a prospective study which validates specific equations for diabetic patients in the Spanish population, as well as research on new models for cardiovascular risk prediction in these patients.

Interaction of human serum albumin with monofluorinated phospholipid monolayers.

In this work the interaction between human serum albumin (HSA) and a monofluorinated phospholipid, 1-palmitoyl-2-[16-fluoropalmitoyl-phosphatidylcholine] (F-DPPC), was studied by using Langmuir monolayer and Brewster angle microscopy (BAM) techniques. Different amounts of F-DPPC were spread on a previously formed HSA monolayer located at the air/water interface at 25°C and the mixed monolayers thus obtained showed the existence of a liquid expanded-liquid condensed (LE-LC) phase transition (at 14 mN/m), attributed to the pure F-DPPC monolayer, coexisting with a second transition (at 22-24 mN/m) corresponding to the protein conformational change from an unfolded state to another in "loops" configuration. Relative thickness measurements recorded during the compression of the mixed monolayers showed the existence of an "exclusion" surface pressure (π(exc)), above which the protein is squeezed out the interface, but not totally. BAM images reveal that some protein molecules in a packed "loops" configuration remain at the interface at surface pressures higher than the "exclusion" surface pressure. The application of the Defay-Crisp phase rule to the phase diagram of the F-DPPC/HSA system can explain the existence of certain regions of surface pressure in which the mixed monolayer components are miscible, as well as those others that they are immiscible.

Monolayer and Brewster angle microscopy study of human serum albumin-dipalmitoyl phosphatidyl choline mixtures at the air-water interface.

The aim of this study is to deepen the understanding of the behavior of human serum albumin (HSA) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) mixed monolayers. For this purpose, different amounts of DPPC were spread at 25°C on the water surface containing a monolayer of HSA. Surface film balance and Brewster angle microscopy techniques have been used to analyze the structural and energetic characteristics (structure, topography, thickness, miscibility and interactions) of these mixtures. HSA/DPPC mixed monolayers exhibit two phase transitions evidenced by two discontinuities in the corresponding π-A isotherms and by two minimum values in the compressional modulus (C(s)(-1))-surface pressure (π) curves. The plot of the molecular areas occupied by the mixed monolayers as function of the mass fraction of DPPC shows the absence of deviations from linearity, a typical behavior for ideal or inmiscible system. This result was confirmed from the values calculated for the free energy of excess (ΔG(exc)), which are practically zero whatever the composition of the mixtures and the surface pressures at which ΔG(exc) values were calculated. In addition, relative thickness values of HSA/DPPC mixed monolayers showed the existence of an exclusion surface pressure (π(exc)), below which the monolayer is composed of a mixture of both components, while above π(exc) the HSA molecules are squeezed out the interface, but not totally. In fact, although in this region DPPC domains predominate at the interface, the existence of protein molecules in a packing "loops" configuration can be observed in BAM images. Moreover, relative thickness measurements confirm this hypothesis.