Spectroscopic Characterization of i-motif Forming c-myc Derived Sequences Double-Labeled with Pyrene

In current studies we use the oligonucleotides based on c-myc sequence: CCC CAC CCT CCC CAC CCT CCC C (cmyc22) and CCC CAC CCT CCC CAC CCT CCC CA (cmyc22A) functionalized by pyrene moieties at both termini. Results of the circular dichroism (CD), UV absorption melting experiments, and steady-state fluorescence measurements of pyrene-modified i-motifs as well as their unlabeled precursors are presented and discussed here. The pyrene labels have a remarkable influence on i-motif stability which was deduced from CD spectra and confirmed by UV melting experiments. Both probes emit fluorescence band of pyrene monomer with intensity decreasing upon pH lowering. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10895-013-1184-z) contains supplementary material, which is available to authorized users

Steady-State Fluorescence and Lifetime Emission Study of pH-Sensitive Probes Based on i-motif Forming Oligonucleotides Single and Double Labeled with Pyrene

Cytosine-rich nucleic acids undergo pH-stimulated structural transitions leading to formation of an i-motif architecture at an acidic pH. Thus, i-motifs are good foundation for designing simple pH-sensitive fluorescent probes. We report here steady-state and time-resolved fluorescence studies of pyrene-labeled probes based on RET sequence: C4GC4GC4GC4TA (RET21), AC4GC4GC4GC4TA (RET21A) and C4GC4GC4GC4T (RET20). Comparative studies with single- and double-labeled i-motif probes were carried out. For each probe, we have measured fluorescence spectra and decays for emission wavelength of 390 nm over a wide range of pH (from 4.0 to 8.0). Effect of the oligonucleotide sequence and the number of pyrene labels on the spectral characteristics of probes were discussed

Mössbauer measurements of ordinary chondrites type H confirm their level of weathering determined by scale W

Mössbauer measurements of ordinary chondrites type H performed in room temperature are presented. Three investigated meteorites: Carancas, Juancheng and Gao-Guenie are new falls with different terrestrial history. Results of weathering in different conditions during terrestrial life are well seen in their Mössbauer spectra. The level of weathering determined by scale W is in perfect agreement with Mössbauer measurements of these three ordinary chondrites

An example of the application of Mössbauer spectroscopy for determination of concentration of iron in lyophilized brain tissue

Mössbauer spectroscopy is not routinely used for the determination of the concentration of iron. However, as this method does not need any pre-treatment of samples before measurements, it may be of extreme importance for the assessment of iron in samples, which can then be used for further investigations. Biological samples are a good example, however, as the concentrations of iron are very low in these, it is important to exclude possible artefacts from the background spectrum related to iron present in the counter and cryostat windows. The aim of this study was to compare two methods of determination of the amounts of iron in investigated sample: one, in which the background spectrum was subtracted from the sample spectrum measured, and the other, in which the obtained non-elaborated spectrum was fitted with two doublets - a doublet for the measured sample and a doublet for the background spectrum. Three samples containing known amounts of natural iron (400, 800 and 1600 μg) and a sample of lyophilized human brain tissue obtained from globus pallidus were assessed. Both methods led to the creation of a very good calibration curve with a correlation coefficient of 0.99. Although both methods gave similar results for the concentration of iron in the sample, the subtraction of the background spectrum had a significantly lower error of the final result

Application of Mossbauer spectroscopy, multidimensional discriminant analysis, and Mahalanobis distance for classification of equilibrated ordinary chondrites

Mossbauer spectra of equilibrated ordinary chondrites consist of two doublets due to paramagnetic iron present in olivines and pyroxenes and two sextets due to magnetically ordered iron present in metallic phases and troilite. The spectral areas of the different mineralogical phases found by M€ossbauer spectroscopy in meteorites are proportional to the number of iron atoms in this mineralogical phase. This property of M€ossbauer spectra can be the basis for constructing a method for the classification of ordinary chondrites. This idea was first explored at the M€ossbauer Laboratory in Kanpur. This group suggested a qualitative method based on 2-dimensional plots of M€ossbauer spectral areas and thus classified properly some meteorites. We constructed a quantitative method using M€ossbauer spectral areas, multidimensional discriminant analysis, and Mahalanobis distance (4M method) to determine the probability of a meteorite to be of type H, L, or LL. Based on 59 M€ossbauer spectra, we calculated by the 4M method, Scluster, the level of similarity of the Goronyo meteorite to the clusters. On the plot of ferrosilite versus fayalite, the point representing Goronyo is located on the border between H and L areas. Calculated by the 4M method, the meteorite Goronyo is 32% similar to type H, 75% to type L, and 11% to type LL. Additional mineralogical analyses suggested that the Goronyo meteorite would be classified as type L, although it was originally reported as type H in the Meteoritical Bulletin Database

Mössbauer studies of iron sulphides present in ordinary chondrites type LL

Mössbauer measurements of three ordinary chondrites type LL were performed at room temperature. Values of spectral areas (SA) connected with troilite were different for investigated meteorites: for Oued el Hadjar – 4.8%, for Bjurböle – 10.6%, for NWA 8590 – 14.9%. Mössbauer spectra were fitted with the use of Recoil program. In all samples values of internal magnetic field and theta angle for subspectrum of troilite were the same: H = 31 T, theta=62°. In the sample of Bjurböle meteorite the signal from pyrrhotite was also noticed (SA = 1.7%, H = 25 T, theta = 33°). For meteorite NWA 8590 two subspectra of pyrrhotite were fitted with following parameters: for pyrrhotite I (SA = 1.1%, H = 27 T, theta= 41°), for pyrrhotite II (SA = 0.7%, H = 22 T, theta = 33°). It is easy to notice that the presence of pyrrhotite is correlated with higher amount of troilite in the samples of ordinary chondrites type LL