Rapid localized crystallization of lysozyme by laser trapping.

Confining protein crystallization to a millimetre size was achieved within 0.5 h after stopping 1 h intense trapping laser irradiation, which shows excellent performance in spatial and temporal controllability compared to spontaneous nucleation. A continuous-wave near-infrared laser beam is tightly focused into a glass/solution interfacial layer of a supersaturated buffer solution of hen egg-white lysozyme (HEWL). The crystallization is not observed during laser trapping, but initiated by stopping the laser irradiation. The generated crystals are localized densely in a circular area with a diameter of a few millimetres around the focal spot and show specific directions of the optical axes of the HEWL crystals. To interpret this unique crystallization, we propose a mechanism that nucleation and the subsequent growth take place in a highly concentrated domain consisting of HEWL liquid-like clusters after turning off laser trapping.

Short-term exposure to fluconazole induces chromosome loss in Candida albicans: an approach to produce haploid cells.

Candida albicans is considered to be an obligate diploid fungus. Here, we describe an approach to isolate aneuploids or haploids induced by the short-term (12-16 h) exposure of diploid reference strains SC5314 and CAI4 to the most commonly used antifungal drug, fluconazole, followed by repeated single-cell separation among small morphologically distinct colonies in the inhibition zone. The isolated strains had altered cell morphology and LOH events in the MTL and other marker alleles of the analyzed loci at 8 chromosomes of C. albicans with decreased DNA content. The present study employed next-generation sequencing (NGS) combined flow cytometry analysis of the DNA content to analyze the haploid, autodiploid, and aneuploid strains that arose from the fluconazole treatment instead of using the conventional single nucleotide polymorphism/comparative genome hybridization (SNP/CGH) method. A multiple-alignment tool was also developed based on sequenced data from NGS to establish haplotype mapping for each chromosome of the selected strains. These findings revealed that C. albicans experiences 'concerted chromosome loss' to form strains with homozygous alleles and that it even has a haploid status after short-term exposure to fluconazole. Additionally, we developed a new platform to analyze chromosome copy number using NGS.

Self-assembly formation of the magic ion of (H2O)20O+: observation of nanoscale cages of oxygenated water clusters induced from iron nanoparticles.

For the first time, we observed a stable and intense ion (m/z 376) of the oxygenated water cluster ion ((H(2)O)(20)O(+)) produced from simply spraying an aqueous solution of iron nanoparticles (Fe NPs) into an electrospray mass spectrometry (ESI-MS) system. Tandem mass spectrometric (MS/MS and MS/MS/MS) results were applied to identify the assignments of the fragment ions of m/z 376 in order to explore the possible structures of this cluster ion. The possible structures of the (H(2)O)(20)O(+) ions are proposed as pentagonal dodecahedron water clathrate cages from the results of tandem mass spectrometry since eliminations of five water molecules were frequently observed in the MS/MS results for many subsequent fragment ions of m/z 376. The formation of this oxygenated water cluster ion ((H(2)O)(20)O(+)) in ESI-MS is attributed to the high surface reactivity and surface energy of Fe NPs during ESI processes (under high temperature and high voltage (5 kV) of ESI spray environment). We believe that the observation of self-assembly formation of oxygenated water clusters is an important issue in nanoscience as well as in the fields of water clusters.

Synthesis of large-area MoS2 atomic layers with chemical vapor deposition.

Large-area MoS(2) atomic layers are synthesized on SiO(2) substrates by chemical vapor deposition using MoO(3) and S powders as the reactants. Optical, microscopic and electrical measurements suggest that the synthetic process leads to the growth of MoS(2) monolayer. The TEM images verify that the synthesized MoS(2) sheets are highly crystalline.