Protein Condensation at Nanopore Entrances as Studied by Differential Scanning Calorimetry and Small-Angle Neutron Scattering.

The condensation of globular myoglobin (Mb) at the pore entrances of mesoporous silica (MPS) with a series of pore diameters (4.2, 6.4, 7.7, and 9.0 nm) was examined by differential scanning calorimetry (DSC) and contrast-matching small-angle neutron scattering (CM-SANS) experiments. The DSC measurements were performed to estimate the amount of Mb adsorbed at two different adsorption sites, namely, the pore interior and the pore entrance regions. The CM-SANS measurements were conducted to observe condensation of Mb molecules at the pore entrance regions. Notably, the nanopore entrance with a diameter close to twice that of the Mb diameter was found to be the specific cavity to facilitate the condensation of globular Mb. The Mb condensation occurred at the entrances of the 6.4 nm pore during the adsorption uptake from concentrated Mb solutions, whereas the adsorption uptake from diluted Mb solutions induced the condensation of Mb at the entrances of the 7.7 nm pore.

Structural Characterization of Proteins Adsorbed at Nanoporous Materials.

A nanoporous material has been applied for the development of functional nanobiomaterials by utilizing its uniform pore structure and large adsorption capacity. The structure and stability of biomacromolecules, such as peptide, oligonucleotide, and protein, are primary factors to govern the performance of nanobiomaterials, so that their direct characterization methodologies are in progress. In this review, we focus on recent topics in the structural characterization of protein molecules adsorbed at a nanoporous material with uniform meso-sized pores. The thermal stabilities of the adsorbed proteins are also summarized to discuss whether the structure of the adsorbed protein molecules can be stabilized or not.

Differential Scanning Calorimetry Study on the Adsorption of Myoglobin at Mesoporous Silicas: Effects of Solution pH and Pore Size.

In the present study, pore adsorption behavior of globular myoglobin (Mb) at mesoporous silicas was examined utilizing the low-temperature differential scanning calorimetry (DSC) method. The DSC method relies on a decrease in heat of fusion for the pore water upon adsorption of Mb. The amount and structure of Mb adsorbed into the mesoporous silica were examined by DSC and optical absorption spectroscopy. The results indicated that the pore adsorption behavior of Mb strongly depended on the solution pH and pore size of mesoporous silica. For the adsorption of Mb (diameter = 3.5 nm) into mesoporous silica with narrow pores (pore diameter = 3.3 nm) at a pH ranging from 7.0 to 3.7, the penetration of both folded and denatured Mb molecules was confirmed. The folded Mb could penetrate into large mesoporous silica pores (pore diameter = 5.3 and 7.9 nm), whereas the penetration of the denatured Mb molecules was completely inhibited. The distribution of folded Mb at mesoporous silica depended on the pore size; almost all folded Mb molecules located inside mesoporous silica pores of diameters 3.3 and 5.3 nm, whereas the Mb molecules distributed at bot internal and external pore surfaces of mesoporous silica with 7.9 nm in pore diameter. These pore adsorption behaviors suggest that aggregation or stacking of the Mb molecules at the pore entrance regions of the large pores affected the pore adsorption behavior.

Antioxidant properties of rare sugar D-allose: Effects on mitochondrial reactive oxygen species production in Neuro2A cells.

The anti-oxidative activity of the rare sugar D-allose has recently been reported, but the mechanism is largely unclear. In this study, we evaluated the reactive oxygen species (ROS) scavenging activities of D-allose and then examined the effects of D-allose on ROS production in mitochondria to clarify the antioxidant properties of D-allose. While D-allose did not scavenge hydrogen peroxide and superoxide anions, it eliminated hydroxyl radicals to the same extent as D-glucose. Rotenone, an uncoupler of mitochondrial respiratory complex I, induces ROS production in mouse neuroblastoma Neuro2A cells in the presence of D-glucose. However, in the presence of D-allose, there was no change in the ROS levels in Neuro2A cells following rotenone treatment. Furthermore, treatment with D-allose attenuated the D-glucose-dependent ROS generation induced by rotenone. Whereas treatment with D-glucose enhanced ATP synthesis in Neuro2A cells, D-allose was less effective in producing intracellular ATP than D-glucose. Treatment with D-allose inhibited the ATP synthesis stimulated by D-glucose. These results suggest that D-allose suppresses ROS production in the mitochondria due to competition with D-glucose at the cellular level.

Synthesis and characteristics of graphene oxide-derived carbon nanosheet-Pd nanosized particle composites.

Carbon nanosheet (CNS)-Pd nanosized particle (NP) composites were synthesized by using graphite oxide (GO) and bis(ethylenediamine)palladium(II) (Pd(en)(2)(2+)) as the precursors, and their structure and adsorption properties were examined. It was found that the Pd(en)(2)(2+) complex ions can be intercalated into GO layers highly efficiently to form a layered structure containing a large amount of Pd (approximately 12 wt %). By the subsequent chemical reduction, Pd NPs (2-6 nm in size) are well dispersed between CNS to form a CNS-Pd NP composite and serve as spacers to increase the porosity of the composite. Hydrogen adsorption results demonstrate that both Pd NPs and CNS play important roles in hydrogen adsorption, particularly at a lower temperature and for CNS with deficient sites, which bring about a H(2) adsorption greater than those on other Pd-loaded nanocarbon materials reported so far. The unique composite nanostructure having large contents of Pd NPs (20-25 wt %) stabilized by CNSs is hopeful to be applied to the fields of H(2)-related catalysis, sensing, and so forth.

Comparative examination of titania nanocrystals synthesized by peroxo titanic acid approach from different precursors.

Titanium dioxide nanocrystalline particles were synthesized by peroxo titanium acid (PTA) approach from titanium alkoxide and inorganic salt precursors, and their structural and surface properties, porosities, and photocatalytic activities were comparatively examined by XRD, TG/DTA, DRIFT, UV-vis, low temperature N(2) adsorption, and methyl orange (MO) degradation. It was found that nanoparticles with single anatase phase can be obtained from alkoxide precursor even near room temperature if synthesis conditions are appropriately controlled. PTA-derived anatase nanoparticles from titanium alkoxide precursor have smaller crystalline sizes and better porosities, and contain less amount of peroxo group and no organic impurities as compared to those from TiCl(4) precursor. The advantages in structural property, porosity, and surface properties (few deficiencies) lead to a much better photocatalytic activity for TiO(2) nanoparticles from titanium alkoxide precursor in comparison with those from TiCl(4) precursor.