The C-terminal domain is sufficient for endonuclease activity of Neisseria gonorrhoeae MutL

The mutL gene of Neisseria gonorrhoeae has been cloned and the gene product purified. We have found that the homodimeric N. gonorrhoeae MutL (NgoL) protein displays an endonuclease activity that incises covalently closed circular DNA in the presence of Mn2+, Mg2+ or Ca2+ ions, unlike human MutL alpha which shows endonuclease activity only in the presence of Mn2+. We report in the present paper that the C-terminal domain of N. gonorrhoeae MutL (NgoL-CTD) consisting of amino acids 460-658 exhibits Mn2+-dependent endonuclease activity. Sedimentation velocity, sedimentation equilibrium and dynamic light scattering experiments show NgoL-CTD to be a dimer. The probable endonucleolytic active site is localized to a metal-binding motif, DMHAX(2)EX(4)E, and the nicking endonuclease activity is dependent on the integrity of this motif. By in vitro comparison of wild-type and it mutant NgoL-CTD protein, we show that the latter protein exhibits highly reduced endonuclease activity. We therefore suggest that the mode of excision initiation in DNA mismatch repair may be different in organisms that lack MutH protein, but have MutL proteins that harbour the D[M/Q]HAX(2)EX(4)E motif.

Enhanced efficiency of tri-layered dye solar cells with hydrothermally synthesized titania nanotubes as light scattering outer layer

In the present study dye sensitized solar cells (DSSCs) have been fabricated with a tri-layer photo anode consisting of hydrothermally prepared titania nano tubes (TNT) having a diameter of 9-10 nm and length of several micrometers as outer layer, P25 TiO2 powder as transparent light absorbing middle layer and a compact TiO2 inner layer to improve the adhesion of different layers on a transparent conducting oxide coated substrate. In comparison to cells fabricated using TNTs or P25 alone, the tri-layer DSSCs exhibit an enhanced efficiency of 7.15% with a current density of 17.12 mA cm(-2) under AM 1.5 illumination. The enhancement is attributed to the light scattering generated by TNTs aggregates, reduction in electron transport resistance at the TiO2/dye/electrolyte interface and an improvement in electron life-time. (c) 2012 Elsevier B.V. All rights reserved.

Tripodal Bile Acid Architectures Based on a Triarylphosphine Oxide Core Obtained by Copper-Catalysed 1,3]-Dipolar Cycloaddition: Synthesis and Preliminary Aggregation Studies

We report the synthesis and aggregation behaviour of new water-soluble, bile acid derived tripodal architectures based on a core derived from triphenylphosphine oxide. We employed the well-established copper-catalysed 1,3]-dipolar cycloaddition (CuAAC) for the construction of these tripodal molecules. The aggregation behaviour of these molecules in aqueous media was studied by different analytical methods such as dye solubilisation, dynamic light scattering, NMR and AFM. These molecular architectures also offer an additional advantage in aiding understanding of the influence of the nature of the bile acid backbone and of the configuration at the steroid C-3 position in these architectures; to the best of our knowledge this has not been reported in the literature. The unique gelation properties of the -derivatives were explained through molecular modelling studies and the mechanical behaviour of these gels was studied by rheology experiments.

Synthesis of self-light-scattering wrinkle structured ZnO photoanode by sol-gel method for dye-sensitized solar cells

A special morphological zinc oxide (ZnO) photoanode for dye-sensitized solar cell was fabricated by simple sol-gel drop casting technique. This film shows a wrinkled structure resembling the roots of banyan tree, which acts as an effective self scattering layer for harvesting more visible light and offers an easy transport path for photo-injected electrons. These ZnO electrode of low thickness (similar to 5 mu m) gained an enhanced short-circuit current density of 6.15 mA/cm(2), open-circuit voltage of 0.67 V, fill factor of 0.47 and overall conversion efficiency of 1.97 % under 1 sun illumination. This shows a high conversion efficiency and a superior performance than that of ZnO nanoparticle-based photoanode (eta similar to 1.13 %) of high thickness (similar to 8 mu m).

Extended bidirectional reflectance distribution function for polarized light scattering from subsurface defects under a smooth surface

By introducing the scattering probability of a subsurface defect (SSD) and statistical distribution functions of SSD radius, refractive index, and position, we derive an extended bidirectional reflectance distribution function (BRDF) from the Jones scattering matrix. This function is applicable to the calculation for comparison with measurement of polarized light-scattering resulting from a SSD. A numerical calculation of the extended BRDF for the case of p-polarized incident light was performed by means of the Monte Carlo method. Our numerical results indicate that the extended BRDF strongly depends on the light incidence angle, the light scattering angle, and the out-of-plane azimuth angle. We observe a 180 degrees symmetry with respect to the azimuth angle. We further investigate the influence of the SSD density, the substrate refractive index, and the statistical distributions of the SSD radius and refractive index on the extended BRDF. For transparent substrates, we also find the dependence of the extended BRDF on the SSD positions. (c) 2006 Optical Society of America.

Measurements of light scattering from glass substrates by total integrated scattering

A total integrated scattering (TIS) measurement was performed to investigate the surface and volume scattering of K9 glass substrates with low reflectance. Ag layers with thicknesses of 60 nm were deposited on the front and back surfaces of the K9 glass substrates by the magnetron sputtering technique. Surface scattering of the K9 glass substrate was obtained by the TIS measurement of the Ag layers on the assumption that the Ag layers and the K9 substrate had the same surface profile. Volume scattering of the substrates was deduced by subtracting the front and back surface scattering from the total scattering of the substrates. (c) 2005 Optical Society of America.

THE CHAIN STRUCTURE AND LIGHT-SCATTERING-STUDIES FOR ACRYLAMIDE-SODIUM ACRYLIC-ACID (AM-AA) COPOLYMERS

A set of AM-AA copolymer samples with the same comonomer content and different average molecular weight have been characterized by C-13 NMB and light scattering methods in this paper. The chemical composition (comonomer AA, mole content 16.9 +/- 1.1%) of these samples is uniform. the sequence of AA in the macromolecular chain is of alone and random distribution and the light scattering theory from polyelectrolyte in added-salt solutions is suitable for the AM-AA copolymers-0.12 mol/L NaCl water systems. The actual values of M(w), the second Virial coefficient A(2) and the mean square radius of gyration (R(2)), for the studied samples have been obtained. The relationships between the molecular parameters are as follows: A(2)=0.0619 ($) over bar M(w)(-0.24), < R(2) >(1/2)(t)= 0.0210 ($) over bar M(w)(0.54).

Response of chlorophyll fluorescence to dynamic light in three alpine species differing in plant architecture

A study was carried out to examine the effect of dynamic photosynthetically active photon flux density (PPFD) on photoinhibition and energy use in three herbaceous species, prostrate Saussurea superba, erect-leaved S. katochaete, and half-erect-leaved Gentiana straminea, from the Qinghai-Tibet Plateau. Chlorophyll fluorescence response was measured under each of three sets of high-low PPFD combinations: 1700-0, 1400-300, and 1200-500 mu mol m(-2) s(-1), illuminating in four dynamic frequencies: 1, 5, 15, and 60 cycles per 2 h. The total light exposure time was 2h and the integrated PPFD was the same in all treatments. The highest frequency of PPFD fluctuation resulted in the lowest photochemical activity, the highest level of non-photochemical quenching, and the greatest decrease of F-v/F-m (maximal photochemical efficiency of PSII). The 5 and 15 cycles per 2h treatments resulted in higher photochemical activity than the 1 cycle per 2h treatment. The 1700-0 PPFD combination led to the lowest photochemical activity and more serious photoinhibition in all species. S. superba usually exhibited the highest photochemical activity and CO2 uptake rate, the lowest reduction of F-v/F-m,F- and the smallest fraction of energy in thermal dissipation. With similar fractions of thermal dissipation, S. katochaete had relatively less photoinhibition than G. straminea owing to effective F-o quenching. The results suggest that high frequency of fluctuating PPFD generally results in photoinhibition, which is more serious under periods of irradiation with high light intensity. (c) 2005 Elsevier B.V. All rights reserved.

Resonant Rayleigh light scattering response of individual Au nanoparticles to antigen--antibody interaction

A proof-of-concept study was reported on analysis of antigen–antibody recognition based on resonant Rayleigh scattering response of single Au nanoparticles in an imaging chamber. As benefited by a traditional dark-field microscope and a spectrograph, individual Au nanoparticles (30 nm) were observed with high signal-to-noise ratio and they were effectively utilized to monitor changes in refractive index induced by specific binding of the adsorbates. Using PSA antigen as a model, a LSPR ?max shift of about 2.85 nm was recorded for a molecular binding corresponding to 0.1 pg ml-1 of the protein biomarker. This result successfully demonstrates a non-labeling detection system for proteins as well as thousands of different chemical or biological species, and it possesses a great potential as a sensitive, on-chip and multiplexing detection.

The ultrasensitive detection of prostate cancer biomarker based on resonant Rayleigh light-scattering response of single Au nanoparticle

A proof-of-concept study was reported on analysis of antigen-antibody recognition based on resonant Rayleigh scattering response of single Au nanoparticles on a microimaging chamber. As benefited by a traditional dark-field microscope and a spectrograph, tiny 30 nm Au nanoparticles were effectively used as nanosensors to monitor changes in refractive index induced by every single binding of the adsorbates. The individual Au nanoparticles were observed with very high signal-to-noise ratio, and a LSPR ?max shift of about 2.5 nm accounting for the detection of PSA antigen with concentration as low as 0.1 pg ml-1 was recorded. This resulted in the successful demonstration of a non-labelling detection system for proteins as well as thousands of different chemical or biological species with possibility of miniaturization and multiplexing scheme.

Spin-wave modes in Ni nanorod arrays studied by Brillouin light scattering

Dynamic magnetic properties of arrays of Ni nanorods with a low aspect ratio have been investigated. It has been shown that the spectra of spin-wave resonances localized on nanorods with a low aspect ratio typically feature the presence of zones with high density of states resulting in a characteristic two-peak pattern of Stokes and anti-Stokes lines of magneto-optical (MO) Brillouin light scattering with pronounced Stokes–anti-Stokes (S-AS) asymmetry. A simple theoretical model based on the analysis of the elliptic character of the polarization of the optical wave interacting with a dipole magnetostatic wave has been proposed. It has been shown that the S-AS asymmetry is due entirely to the asymmetry of the MO interaction efficiency with respect to time reversal of the magnetic precession in a magnon.

Brillouin light scattering by spin waves in magnetic metamaterials based on Co nanorods

We report on the investigations of spin wave modes in arrays of densely packed Co nanorods using Brillouin light scattering. We have observed a significant role of spin wave modes along the nanorod axis in contrast to infinite magnetic nanowires. Unusual optical properties featuring an inverted Stokes/anti-Stokes asymmetry of the Brillouin scattering spectra have been observed. The spectrum of spin wave modes in the nanorod array has been calculated and compared with the experiment. Experimental observations are explained in terms of a combined numerical-analytical approach taking into account both the low aspect ratio of individual magnetic nanorods and dipolar magnetic coupling between the nanorods in the array. The optical studies of spin-wave modes in the metamaterials with low aspect ratio nanorods have revealed new magnetic and magneto-optical properties compared to continuous magnetic films or infinite magnetic nanowires. Such magnetic metamaterials are important class of active metamaterials needed for prospective data storage and signal processing applications. (c) 2012 Optical Society of America

Structuring reductive media containing protic ionic liquids and their application to the formation of metallic nanoparticles

Herein, we present a facile method for the formation of monodispersed metal nanoparticles (NPs) at room temperature from M^(III)Cl₃ (with M = Au, Ru, Mn, Fe or V) in different media based on N,N-dimethylformamide (DMF) or water solutions containing a protic ionic liquid (PIL), namely the octylammonium formate (denoted OAF) or the bis(2-ethyl-hexyl)ammonium formate (denoted BEHAF). These two PILs present different structures and redox-active structuring properties that influence their interactions with selected molecular compounds (DMF or water), as well as the shape and the size of formed metal NPs in these solutions. Herein, the physical properties, such as the thermal, transport and micellar properties, of investigated PIL solutions were firstly investigated in order to understand the relation between PILs structure and their properties in solutions with DMF or water. The formation of metal NPs in these solutions was then characterized by using UV–vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and dynamic light scattering (DLS) measurements. From our investigations, it appears that the PILs structure and their aggregation pathways in selected solvents affect strongly the formation, growths, the shape and the size of metal NPs. In fact by using this approach, the shape-/size-controlled metal NPs can be generated under mild condition. This approach suggests also a wealth of potential for these designer nanomaterials within the biomedical, materials, and catalysis communities by using designer and safer media based on PILs.