Direct observation of fast protein folding: the initial collapse of apomyoglobin.

The rapid refolding dynamics of apomyoglobin are followed by a new temperature-jump fluorescence technique on a 15-ns to 0.5-ms time scale in vitro. The apparatus measures the protein-folding history in a single sweep in standard aqueous buffers. The earliest steps during folding to a compact state are observed and are complete in under 20 micros. Experiments on mutants and consideration of steady-state CD and fluorescence spectra indicate that the observed microsecond phase monitors assembly of an A x (H x G) helix subunit. Measurements at different viscosities indicate diffusive behavior even at low viscosities, in agreement with motions of a solvent-exposed protein during the initial collapse.

Polímeros de coordenação à base de cobalto(II) e N,N'-bis(4-piridil)-1,4,5,8-naftaleno diimida como ligante e suas propriedade estruturais, espectroscópicas e fotoelétricas

Polímeros de coordenação têm atraído a atenção de pesquisadores na última década por conta de sua incrível versatilidade e virtualmente infinito número de possibilidades de combinação de ligantes orgânicos e centros metálicos. Estes compostos normalmente herdam as características magnéticas, eletrônicas e espectroscópicas de seus componentes base. Entretanto, apesar do crescente número de trabalhos na área, ainda são raros os polímeros de coordenação que apresentem condutividade elétrica. Para este fim, utilizou-se a N,N\'-bis(4-piridil)-1,4,5,8-naftaleno diimida, ou NDI-py, que pertence a uma classe de compostos rígidos, planares, quimicamente e termicamente estáveis e que já foram extensamente estudados por suas propriedades fotoeletroquímicas e semicondução do tipo n. O primeiro polímero de coordenação sintetizado, MOF-CoNDI-py-1, indicou ser um polímero linear, de estrutura 1D. O segundo, MOF-CoNDI-py-2, que conta com ácido tereftálico como ligante suporte, é um sólido cristalino com cela unitária monoclínica pertencente ao grupo espacial C2/c, determinado por difração de raios-X de monocristal. A rede apresenta um arranjo trinuclear de íons Co(II) alto spin com coordenados em uma geometria de octaedro distorcido, enquanto os ligantes NDI-py se encontram em um arranjo paralelo na estrutura, em distâncias apropriadas para transferência eletrônica. Com o auxílio de cálculo teóricos a nível de DFT, foi realizado um estudo aprofundado dos espectros eletrônicos e vibracionais, com atribuição das transições observadas, tanto para o MOF-CoNDI-py-2 quanto para o ligante NDI-py livre. A rede de coordenação absorve em toda a região do espectro eletrônico analisada, de 200 nm a 2500 nm, além de apresentar luminescência com característica do ligante. Dispositivos eletrônicos fabricados com um cristal do MOF-CoNDI-py-2 revelaram condutividades da ordem de 7,9 10-3 S cm -1, a maior já observada para um MOF. Além de elevada, a condutividade elétrica dos cristais demonstrou-se altamente anisotrópica, sendo significativamente menos condutor em algumas direções. Os perfis de corrente versus voltagem foram analisados em termos de mecanismos de condutividade, sendo melhores descritos por um mecanismo limitado pelo eletrodo to tipo Space-Charge Limited Current, concordando com a proposta de condutividade através dos planos de NDI-py na rede. A condutividade dos cristais também é fortemente dependente de luz, apresentando fotocondução quando irradiado por um laser vermelho, de 632 nm, enquanto apresenta um comportamento fotorresistivo frente a uma fonte de luz branca. Estes resultados, combinados, trazem um MOF em uma estrutura incomum e com elevada condutividade elétrica, modulada por luz, em medidas diretas de corrente. Não existem exemplos conhecidos de MOFs na literatura com estas características.

Detectivity comparison of bolometric optical antennas

The practical application of optical antennas in detection devices strongly depends on its ability to produce an acceptable signal-to-noise ratio for the given task. It is known that, due to the intrinsic problems arising from its sub-wavelength dimensions, optical antennas produce very small signals. The quality of these signals depends on the involved transduction mechanism. The contribution of different types of noise should be adapted to the transducer and to the signal extraction regime. Once noise is evaluated and measured, the specific detectivity, D*, becomes the parameter of interest when comparing the performance of antenna coupled devices with other detectors. However, this parameter involves some magnitudes that can be defined in several ways for optical antennas. In this contribution we are interested in the evaluation and comparison of D_ values for several bolometric optical antennas working in the infrared and involving two materials. At the same time, some material and geometrical parameters involved in the definition of noise and detectivity will be discussed to analyze the suitability of D_ to properly account for the performance of optical antennas.

Magnetic charachterization of surface sediments in the South Atlantic

Surface sediment samples representative for the tropical and subtropical South Atlantic (15°N to 40°S) were investigated by isothermal magnetic methods to delineate magnetic mineral distribution patterns and to identify their predominant Holocene climatic and oceanographic controls. Individual parameters reveal distinct, yet frequently overlapping, regional sedimentation characteristics. A probabilistic ('fuzzy c-means') cluster analysis was applied to five concentration independent magnetic properties assessing magnetite to hematite ratios and diagnostic of bulk and fine-particle magnetite grain size and coercivity spectra. The resultant 10 cluster structures establish an oceanwide magnetic sediment classification scheme tracing the major terrigenous eolian and fluvial fluxes, authigenic biogenic magnetite accumulation in high-productivity areas, transport by ocean current systems, and effects of bottom water velocity on depositional regimes. Distinct dissimilarities in magnetic mineral inventories between the eastern and western basins of the South Atlantic reflect prominent contrasts of both oceanic and continental influences.

Macular atrophy in patients with long-term anti-VEGF treatment for neovascular age-related macular degeneration.

PURPOSE To identify the prevalence and progression of macular atrophy (MA) in neovascular age-related macular degeneration (AMD) patients under long-term anti-vascular endothelial growth factor (VEGF) therapy and to determine risk factors. METHOD This retrospective study included patients with neovascular AMD and ≥30 anti-VEGF injections. Macular atrophy (MA) was measured using near infrared and spectral-domain optical coherence tomography (SD-OCT). Yearly growth rate was estimated using square-root transformation to adjust for baseline area and allow for linearization of growth rate. Multiple regression with Akaike information criterion (AIC) as model selection criterion was used to estimate the influence of various parameters on MA area. RESULTS Forty-nine eyes (47 patients, mean age 77 ± 14) were included with a mean of 48 ± 13 intravitreal anti-VEGF injections (ranibizumab:37 ± 11, aflibercept:11 ± 6, mean number of injections/year 8 ± 2.1) over a mean treatment period of 6.2 ± 1.3 years (range 4-8.5). Mean best-corrected visual acuity improved from 57 ± 17 letters at baseline (= treatment start) to 60 ± 16 letters at last follow-up. The MA prevalence within and outside the choroidal neovascularization (CNV) border at initial measurement was 45% and increased to 74%. Mean MA area increased from 1.8 ± 2.7 mm(2) within and 0.5 ± 0.98 mm(2) outside the CNV boundary to 2.7 ± 3.4 mm(2) and 1.7 ± 1.8 mm(2) , respectively. Multivariate regression determined posterior vitreous detachment (PVD) and presence/development of intraretinal cysts (IRCs) as significant factors for total MA size (R(2) = 0.16, p = 0.02). Macular atrophy (MA) area outside the CNV border was best explained by the presence of reticular pseudodrusen (RPD) and IRC (R(2) = 0.24, p = 0.02). CONCLUSION A majority of patients show MA after long-term anti-VEGF treatment. Reticular pseudodrusen (RPD), IRC and PVD but not number of injections or treatment duration seem to be associated with the MA size.

Proceedings of the International Symposium on Remote Sensing of Environment

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Researches in physical optics

pt. I. Researches in physical optics with especial reference to the radiation of electrons. 1913.--pt. II. Resonance radiation and resonance spectra. 1919.

Short peptide alpha helices induced by multiple metal clips

Alpha helices are key structural components of proteins and important recognition motifs in biology. New techniques for stabilizing short peptide helices could be valuable for studying protein folding, modeling proteins, creating artificial proteins, and may aid the design of inhibitors or mimics of protein function. We previously reported* that 5-15 residue peptides, corresponding to the Zn-binding domain of thermolysin, react with [Pd(en)(ONO,),]in DMF-d’ and 90% H,O 10% DzO to form a 22-membered [Pd(en)(H*ELTH*)]2+ macrocycle that is helical in solution and acts as a template in nucleating helicity in both Cand N- terminal directions within the longer sequences in DMF. ~f~~&g7$$& d&qx~m ~. y AC&q& In water, however, there was less a-helicity observed, testifying to #..q,& &$--Lb &l-- &.$;,J~p?:~~q&~+~~ ’ w w the difficulty of fixing intramolecular amide NH...OC H-bonds in 6,“;;” ( k.$ U”C.a , p d$. competition with the H-bond donor solvent water. To expand the utility of [Pd(en)(H*XXXH*)]*+ as a helix- @r4”8 & oJ#:& &G& @-qd ,‘d@-gyp promoting module in solution, we now report the result that Ac- ‘$4: %$yyy + H*ELTH*H*VTDH*-NH,(l), AC-H*ELTH*AVTDYH*ELTH*- NH, (2) and AC-H*AAAH*H*ELTH*H*VTDH*-NH* (3) react with multiple equivalents of [Pd(en)(ONO,),] to produce exclusively 4-6 respectively in both DMF-d7 and water (90% Hz0 10% D,O). Mass spectrometry, 15N- and 2D ‘H- NMR spectroscopy, and CD spectra were used to characterise the structures 4-6, and their three dimensional structures were calculated from NOE restraints using simulated annealing protocols. Results demonstrate (a) selective coordination of metal ions at (i, i+4) histidine positions in water and DMF, (b) incorporation of 2 and 3 a turn-mimicking modules [Pd(en)(HELTH)]2+ in lo-15 residue peptides, and (c) facile conversion of unstructured peptides into 3- and 4- turn helices of macrocycles, with well defined a-helicity throughout and more structure in DMF than in water.

The cell wall galactans from Australian representatives of the genus Meristotheca (solieriaceae, rhodophyta)

The Solieriaceae, has the largest number of genera (16-18) of any family in the carrageenophyte order Gigartinales. One of these genera, Meristotheca, consists of three or four species of foliose, erect to prostrate plants sporadically recorded from the tropics of both hemispheres. The hot-water-soluble polysaccharides from Australian representatives of the type species, M. papulosa, and M. procumbens from Lord Howe Island have been characterized by compositional assays, linkage analysis, and Fourier transform infrared and C-13-nuclear magnetic resonance spectroscopy. The results show that polysaccharides from both species are similar, being predominantly composed of 4-linked 3,6-anhydro-alpha-D-galactopyranose 2-sulphate alternating with 3-linked beta-D-galactopyranose 4-sulphate, as is typical of iota-carrageenan. Small proportions of the 3-linked units occur as the pyruvated residue 4,6-O-(1-carboxyethylidene)-beta-D-galactopyranose, and other minor variations from idealized iota-carrageenan were also detected. The polysaccharides from representatives of Meristotheca are comparable to those of other solieriacean algae analysed to date, but the minor structural variations suggest a closer chemotaxonomic affinity with noneucheumoid genera of the Solieriaceae, such as Sarconema, Solieria, and Tikvahiella, than to the eucheumoid genera Eucheuma, Kappaphycus and Betaphycus (tribe Eucheumatoideae) from which most kappa- and iota-carrageenans are commercially extracted.

Single turn peptide alpha helices with exceptional stability in water

Cyclic pentapepticles are not known to exist in a-helical conformations. CD and NMR spectra show that specific 20-membered cyclic pentapepticles, Ac-(cyclo-1,5) [KxxxD]-NH2 and Ac-(cyclo-2,6)R[KxxxD]-NH2, are highly a-helical structures in water and independent of concentration, TFE, denaturants, and proteases. These are the smallest a-helical peptides in water.

The effect of local galaxy surface density on star formation for HI selected galaxies

We present the result of investigations into two theories to explain the star formation rate (SFR)-density relationship. For regions of high galaxy density, either there are fewer star-forming galaxies or galaxies capable of forming stars are present but some physical process is suppressing their star formation. We use H I Parkes All-Sky Survey's (HIPASS) HI detected galaxies and infrared and radio fluxes to investigate SFRs and efficiencies with respect to local surface density. For nearby (vel < 10 000 km s(-1)) H I galaxies, we find a strong correlation between H I mass and SFR. The number of H I galaxies decreases with increasing local surface density. For H I galaxies (1000 < vel < 6000 km s(-1)), there is no significant change in the SFR or the efficiency of star formation with respect to local surface density. We conclude that the SFR-density relation is due to a decrease in the number of H I star-forming galaxies in regions of high galaxy density and not to the suppression of star formation.

A high sensitivity refractometer based upon a long period grating Mach-Zehnder interferometer

A low cost interrogation scheme is demonstrated for a refractometer based on an in-line fiber long period grating (LPG) Mach–Zehnder interferometer. Using this interrogation scheme the minimum detectable change in refractive index of ?n ~ 1.8×10-6 is obtained, which is the highest resolution achieved using a fiber LPG device, and is comparable to precision techniques used in the industry including high performance liquid chromatography and ultraviolet spectroscopy.

Cyclodextrin complexes of antimicrobial agents

Poorly water-soluble drugs show an increase in solubility in the presence of cyclodextrins (CyD) due to the formation of a water-soluble complex between the drug and dissolved CyD. This study investigated the interactions of -Cyd and hydroxypropyl--CyD (HP--CyD, M.S. = 0.6) with antimicrobial agents of limited solubility in an attempt to increase their microbiological efficacy. The agents studied were chlorhexidine dihydrochloride (CHX), p-hydroxybenzoic acid esters (methyl, ethyl, proply and butyl) and triclosan. The interactions between the antimicrobials and CyDs were studied in solution and solid phases. Phase solubility studied revealed an enhancement in the aqueous drug solubility in the presence of the CyD and also gave an indication of the complex stability constant (Ks). The temperature-dependence of the stability constant of the complex was modelled by the van't Hoff plot which yielded the thermodynamic parameters for complexation. Further confirmation of the inclusion of the antimicrobials within the cavity of the CyDs in aqueous solution was obtained from proton magnetic resonance and ultraviolet absorption spectroscopies. The former method indicated that the chlorophenyl moiety of the CHX was included within the -CyD cavity and the stoichiometry of the complex formed was 1:1. The solid-phase complexes were prepared by freeze-drying. The inclusion complex of triclosan with HP--CyD was obtained from aqueous solution with the addition of ammonia. Evidence to confirm complex formation was obtained from DSC, IR and X-ray powder diffraction studies. Dissolution studies of the solid inclusion complexes using the dispersed powder technique illustrated their superior solubilities as compared to the equimolar physical mix of the guest and CyD. It was shown that these solutions of the complex were supersaturated with respect to the free guest. This was further demonstrated by diffusion studies which showed the flux of free drug from donor solutions of the antimicrobial-CyD complex to be significantly greater than the flux from donor suspensions of drug alone.

A low-cost remote sensing system for agricultural applications

This research develops a low cost remote sensing system for use in agricultural applications. The important features of the system are that it monitors the near infrared and it incorporates position and attitude measuring equipment allowing for geo-rectified images to be produced without the use of ground control points. The equipment is designed to be hand held and hence requires no structural modification to the aircraft. The portable remote sensing system consists of an inertia measurement unit (IMU), which is accelerometer based, a low-cost GPS device and a small format false colour composite digital camera. The total cost of producing such a system is below GBP 3000, which is far cheaper than equivalent existing systems. The design of the portable remote sensing device has eliminated bore sight misalignment errors from the direct geo-referencing process. A new processing technique has been introduced for the data obtained from these low-cost devices, and it is found that using this technique the image can be matched (overlaid) onto Ordnance Survey Master Maps at an accuracy compatible with precision agriculture requirements. The direct geo-referencing has also been improved by introducing an algorithm capable of correcting oblique images directly. This algorithm alters the pixels value, hence it is advised that image analysis is performed before image georectification. The drawback of this research is that the low-cost GPS device experienced bad checksum errors, which resulted in missing data. The Wide Area Augmented System (WAAS) correction could not be employed because the satellites could not be locked onto whilst flying. The best GPS data were obtained from the Garmin eTrex (15 m kinematic and 2 m static) instruments which have a highsensitivity receiver with good lock on capability. The limitation of this GPS device is the inability to effectively receive the P-Code wavelength, which is needed to gain the best accuracy when undertaking differential GPS processing. Pairing the carrier phase L1 with the pseudorange C/A-Code received, in order to determine the image coordinates by the differential technique, is still under investigation. To improve the position accuracy, it is recommended that a GPS base station should be established near the survey area, instead of using a permanent GPS base station established by the Ordnance Survey.

Efficiency enhancement of components based on talbot effect

Two ways to improve efficiency of components based on Talbot effect are considered in the present paper. One way is based on optimization of waveguide wall impedance, another one consists in modification of waveguide cross-section shape. Both methods allow correction of waveguide modes spectrum and lead to efficiency enhancement. For the important application of Talbot effect-remote steering antenna of a wavebeam in plasma-the steering band is expanded by 40-50%. © 2007 Springer Science+Business Media, LLC.