Fiber Optic Accessory Research Articles

Spectroscopic study of fluorescent probes based on G-quadruplex oligonucleotides labeled with ethynylpyrenyldeoxyuridine

The design, synthesis, and spectral properties of four pyrene labeled oligonucleotide probes with G-quadruplex structure (Tel22–Tpy, Tel22–Upy, Tel22–6Upy, Tel22–18Upy) based on the 22-mer human telomeric sequence (Tel22) have been reported. Pyrene labels in the form of ethynylpyrenyldeoxyuridine have been inserted efficiently into oligodeoxynucleotides probes using phosphoramidite chemistry. The probes exhibited abilities to fold into G-quadruplex structures and to bind metal cations (Na+ and K+). Folding properties of probes and their spectral behavior were examined by recording the UV–vis, fluorescence, and CD spectra as well as by analyzing melting profiles. Fluorescence characteristics and G-quadruplex folding of probes were also studied at the interface of cationic dioctadecyldimethylammonium bromide (DODAB) monolayer. Investigations included film balance measurements (π–A isotherms) and fluorescence spectra recording using a fiber optic accessory interfaced with a spectrofluorimeter.

FRET study of G-quadruplex forming fluorescent oligonucleotide probes at the lipid monolayer interface

Spectral properties and G-quadruplex folding ability of fluorescent oligonucleotide probes at the cationic dioctadecyldimethylammonium bromide (DODAB) monolayer interface are reported. Two oligonucleotides, a 19-mer bearing thrombin binding aptamer sequence and a 21-mer with human telomeric sequence, were end-labeled with fluorescent groups (FAM and TAMRA) to give FRET probes F19T and F21T, respectively. The probes exhibited abilities to fold into a quadruplex structure and to bind metal cations (Na+ and K+). Fluorescence spectra of G-quadruplex FRET probes at the monolayer interface are reported for the first time. Investigations included film balance measurements (π-A isotherms) and fluorescence spectra recording using a fiber optic accessory interfaced with a spectrofluorimeter. The effect of the presence of DODAB monolayer, metal cations and the surface pressure of monolayer on spectral behavior of FRET probes were examined. Adsorption of probe at the cationic monolayer interface resulted in the FRET signal enhancement even in the absence of metal cations. Variation in the monolayer surface pressure exerted rather modest effect on the spectral properties of probes. The fluorescence energy transfer efficiency of monolayer adsorbed probes increased significantly in the presence of sodium or potassium ion in subphase, which indicated that the probes retained their cation binding properties when adsorbed at the monolayer interface.

Spatially-Resolved Radial Scanning of Tree Increment Cores for near Infrared Prediction of Microfibril Angle and Chemical Composition

A fibre-optic accessory with a linear drive transport system has been coupled to a near infrared (NIR) instrument to enable solid samples, in this instance increment cores from standing trees, to be scanned at 1 mm increments along the length of the sample. This allows the NIR prediction of wood properties (oven-dry chemical composition and microfibril angle) to be undertaken so that the radial profile of chemistry or microfibril angle can be determined from the pith to the bark. Calibration models provided prediction errors for microfibril angle in Pinus radiata softwood of 4.1° while for Eucalyptus globulus the error is 3.9°. The errors for prediction of chemical composition in Pinus radiata are 0.2% (arabinose) 1.1% (galactose), 2.3% (glucose), 0.7% (mannose), 0.7% (xylose) and 1.6% (lignin).

Primary bioreceptivity: A comparative study of different Portuguese lithotypes

The current condition of many historical monuments clearly reveals that they are not immune to “weathering” factors such as biological decay or biodeterioration. In the present study, Portuguese lithotype samples were inoculated in the laboratory with the microalga Stichococcus bacillaris and the cyanobacterium Gloeocapsa alpina in order to study their primary bioreceptivity and to establish an index of bioreceptivity. The types of building stones used were Ançã and Lioz limestone, Portalegre granite and Vila Viçosa white marble, which are materials renowned in Portuguese architecture. Microbial growth, including the area of the stone surface covered, was evaluated by visual examination and measurement of in vivo chlorophyll a fluorescence using a spectrofluorometer fitted with a fibre-optic accessory. It was possible to verify that 4 months after inoculation, colonization had led to development of biofilms similar to those occurring on stone monuments located outdoors. The results showed that Ançã limestone had the highest primary bioreceptivity, followed by Lioz limestone, with Portalegre granite being weakly colonized or not colonized at all. White marble was not taken into account for the bioreceptivity index, since ANOVA results of microbial growth showed greater internal variance among replicates than between these and the other lithotypes.

NIR spectroscopy: A non-destructive fast technique to verify heat treatment of fish-meat gel

Attempts have been made to assess previous heat treatment of fish-meat gels prepared from walleye pollack and horse mackerel surimi, since surimi-based products have been gaining popularity for their protein quality, law fat content and convenience in consumption. Visible–NIR spectra of gels (30–90 °C) were collected from 650 to 1100 nm with a surface interactance fibre optic accessory. Partial least squares (PLS) and multiple linear regression (MLR) techniques were employed for data analysis. Spectral changes upon heat treatment were related to the heating temperature which reflected the changes in the environment of the secondary structure due to the denaturation of proteins, and to changes in the state of water. A promising linear relationship ( R = 0.98) was observed between NIR-predicted temperatures and the actual heating temperatures with prediction error of 1.85 °C.

Nondestructive determination of water and protein in surimi by near-infrared spectroscopy

Nondestructive near-infrared spectroscopy (NIRS) between 400 and 1100 nm regions was employed directly on surimi using a surface interactance fibre optic accessory, to investigate the potential of NIRS as a fast method to determine water and protein contents. The reason why NIRS is well suited when assessing the presence of water or protein is due to the specificity of O–H and N–H bindings. At 980 nm only one broad peak in the original spectra can be seen due to the absorption of water since it contained nearly 80% of surimi. Predictive equations were developed using partial least squares (PLS) regression where excellent predictions for protein and water are noticed. Regression coefficients are higher than 0.98, errors are small and RPD value for protein is well over 8 and that for water is very close to it which can be used for any analytical purpose.

Grazing-Angle Fiber-Optic IRRAS for in Situ Cleaning Validation

Grazing-angle Fourier transform infrared reflection−absorption spectrometry (IRRAS) using a fiber-optic accessory has been investigated as a potential in situ technique for the detection and quantification of contamination by active pharmaceutical agents on glass and metal surfaces. Two methods were used for contamination preparation: one based on smearing a known amount of sample, in solution, onto the substrate and the other by spraying the substrate with an aerosol of the analyte in a volatile solvent. Chemometric calibrations using partial least-squares (PLS) regression are presented and evaluated for acetaminophen on aluminum and glass, and ibuprofen on aluminum and stainless steel. The results indicate that surface loadings of 0.05 μg/cm2 is a readily achievable limit of detection for the IRRAS technique.