Low-intensity Band Research Articles

The structure of mimetite, arsenian pyromorphite and hedyphane – A Raman spectroscopic study

The minerals mimetite Pb 5(AsO 4) 3Cl, arsenian pyromorphite Pb 5(PO 4,AsO 4) 3Cl and hedyphane Pb 3Ca 2(AsO 4) 3Cl have been studied by Raman spectroscopy complimented with infrared spectroscopy. Mimetite is characterised by a band at 812–3 cm −1 attributed to the A g mode. For the arsenian pyromorphite this band is observed at 818 cm −1 and for hedyphane at 819 cm −1. For mimetite and hedyphane bands at 788 and 765 cm −1 are attributed to A u and E 1u vibrational modes and are both Raman and infrared active. For the arsenian pyromorphite, Raman bands at 917–1014 cm −1 are attributed to phosphate stretching vibrations. Raman spectroscopy clearly identifies bands attributable to isomorphous substitution of arsenate by phosphate. The observation of low intensity bands in the 3200–3550 cm −1 region are assigned to adsorbed water and OH units, thus indicating some replacement of chloride ions with hydroxyl ions.

DANGER, a Novel Regulatory Protein of Inositol 1,4,5-Trisphosphate-Receptor Activity

We report the cloning and characterization of DANGER, a novel protein which physiologically binds to inositol 1,4,5-trisphosphate receptors (IP(3)R). DANGER is a membrane-associated protein predicted to contain a partial MAB-21 domain. It is expressed in a wide variety of neuronal cell lineages where it localizes to membranes in the cell periphery together with IP(3)R. DANGER interacts with IP(3)R in vitro and co-immunoprecipitates with IP(3)R from cellular preparations. DANGER robustly enhances Ca(2+)-mediated inhibition of IP(3) RCa(2+) release without affecting IP(3) binding in microsomal assays and inhibits gating in single-channel recordings of IP(3)R. DANGER appears to allosterically modulate the sensitivity of IP(3) RtoCa(2+) inhibition, which likely alters IP(3)R-mediated Ca(2+) dynamics in cells where DANGER and IP(3)R are co-expressed.

A novel function of DNA polymerase ζ regulated by PCNA

DNA polymerase zeta (Polzeta) participates in translesion DNA synthesis and is involved in the generation of the majority of mutations induced by DNA damage. The mechanisms that license access of Polzeta to the primer terminus and regulate the extent of its participation in genome replication are poorly understood. The Polzeta-dependent damage-induced mutagenesis requires monoubiquitination of proliferating cell nuclear antigen (PCNA) that is triggered by exposure to mutagens. We show that Polzeta contributes to DNA replication and causes mutagenesis not only in response to DNA damage but also in response to malfunction of normal replicative machinery due to mutations in replication genes. These replication defects lead to ubiquitination of PCNA even in the absence of DNA damage. Unlike damage-induced mutagenesis, the Polzeta-dependent spontaneous mutagenesis in replication mutants is reduced in strains defective in both ubiquitination and sumoylation of Lys164 of PCNA. Additionally, studies of a PCNA mutant defective for functional interactions with Polzeta, but not for monoubiquitination by the Rad6/Rad18 complex demonstrate a role for PCNA in regulating the mutagenic activity of Polzeta separate from its modification at Lys164.

The 5f2→5f16d1 absorption spectrum of Cs2GeF6:U4+ crystals: A quantum chemical and experimental study

Single crystals of U(4+)-doped Cs2GeF6 with 1% U4+ concentration have been obtained by the modified Bridgman-Stockbarger method in spite of the large difference in ionic radii between Ge4+ and U4+ in octahedral coordination. Their UV absorption spectrum has been recorded at 7 K, between 190 and 350 nm; it consists of a first broad and intense band peaking at about 38,000 cm(-1) followed by a number of broad bands of lower intensity from 39,000 to 45,000 cm(-1). None of the bands observed shows appreciable fine vibronic structure, so that the energies of experimental electronic origins cannot be deduced and the assignment of the experimental spectrum using empirical methods based on crystal field theory cannot be attempted. Alternatively, the profile of the absorption spectrum has been obtained theoretically using the U-F bond lengths and totally symmetric vibrational frequencies of the ground 5f2 - 1A(1g) and 5f16d(t(2g))1 - iT(1u) excited states, their energy differences, and their corresponding electric dipole transition moments calculated using the relativistic ab initio model potential embedded cluster method. The calculations suggest that the observed bands are associated with the lowest five 5f2 - 1A(1g)-->5f16d(t(2g))1 - iT(1u) (i = 1-5) dipole allowed electronic origins and their vibrational progressions. In particular, the first broad and intense band peaking at about 38,000 cm(-1) can be safely assigned to the 0-0 and 0-1 members of the a(1g) progression of the 5f2 - 1A(1g)-->5f16d(t(2g))1 - 1T(1u) electronic origin. The electronic structure of all the states with main configurational character 5f16d(t(2g))1 has been calculated as well. The results show that the lowest crystal level of this manifold is 5f16d(t(2g))1 - 1E(u) and lies about 6200 cm(-1) above the 5f2 level closest in energy, which amounts to some 11 vibrational quanta. This large energy gap could result in low nonradiative decay and efficient UV emission, which suggest the interest of investigating further this new material as a potential UV solid state laser.

A vibrational spectroscopic study of perhamite, an unusual silico-phosphate

The silico-phosphate mineral perhamite has been studied using a combination of electron and vibrational spectroscopy. SEM photomicrographs reveal that perhamite morphology consists of very thin intergrown platelets that can form a variety of habits. Infrared spectroscopy in the hydroxyl-stretching region shows a number of overlapping bands which are observed in the range 3581–3078 cm −1. These wavenumbers enable an estimation to be made of the hydrogen bond distances in perhamite: 3.176(0), 2.880(5), 2.779(6), 2.749(3), 2.668(1) and 2.599(7) Å. Intense Raman bands are observed in the region 1110–1130 and 966–996 cm −1 and are assigned to the SiO 4 and PO 4 symmetric stretching modes. Other bands are observed in the range 1005–1096 cm −1 and are attributed to the ν 3 antisymmetric bending modes of PO 4. Some low intensity bands around 874 cm −1 were discovered and remain unclassified. Bands in the low-wavenumber region are assigned to the ν 4 and ν 2 out-of-plane bending modes of the OSiO and PO 4 units. Raman spectroscopy is a useful tool in determining the vibrational spectroscopy of mixed hydrated multi-anion minerals such as perhamite. Information on such a mineral would be difficult to obtain by other means.

Role of Sequence and Conformation on the Photochemistry and the Photophysics of A−T DNA Dimers: An Experimental and Computational Approach

The role of base sequence and conformation on the photochemistry and photophysics of thymidylyl (3'-5')-2'-deoxyadenosine sodium salt (TpdA) and 2-deoxyadenylyl (3'-5')-thymidine ammonium salt (dApT) was studied. To this end, nanosecond transient absorption at 266 nm, steady-state irradiation at 254 nm, and quantum chemical calculations were used. The transient absorption spectra show the solvated electron broad band in the visible region for each dinucleotide. In addition, low-intensity absorption bands are observed in the UV region, which are attributed to the deprotonated and protonated neutral radicals of adenine and thymine bases. Photoionization (PI) occurs by one- and two-photon pathways; the latter accounting for approximately 70% of the net PI yield. A diffusion-limited rate constant of 2.0 x 10(10) M(-1) s(-1) was obtained for the reaction of the neutral molecule with the photoejected electron in both sequences. The photodestruction yield, measured from the chromophore loss at 260 nm, decreases in the presence of well-known electron scavengers. This suggests the participation of base radical anions as one of the photodegradation pathways, which is higher in TpdA than in dApT. The intermediacy of a radical ion pair (charge separated state) between the adjacent adenine and thymine bases is proposed in the formation of the [2 + 2] cycloadduct intermediate. The [2 + 2] cycloadduct intermediate is known to be the precursor of the thymine-adenine eight-member ring photoproduct (TA*). Conformational constrains in the radical ion pair are suggested to explain the absence of the TA* photoproduct in dApT. This hypothesis is supported by semiempirical calculations performed on all relevant reactive intermediates proposed to participate in the mechanism of formation of TA*. Altogether, the results show that sequence and conformation profoundly influence the photochemistry and the photophysics of these DNA model systems.

Estudo espectroscópico do equilíbrio entre espécies hexacoordenada e pentacoordenada dos monômero d nativo e reconstituído da hemoglobina extracelular gigante de Glossoscolex paulistus em meio alcalino

UV-Vis and fluorescence spectroscopic studies of native and reconstituted d monomers from Glossoscolex paulistus were performed in alkaline pH. In addition to the presence of aquomet and hemichrome hexacoordinated species, a pentacoordinated species occurs. This latter species, which presents an imidazolate group of axial histidine as fifth ligand, is identified by the blue-shifted low-intensity Soret band and LMCT band. The pentacoordinated species must occur due to partial polypeptide unfolding.

Subchondral insufficiency fracture of the femoral head after total knee arthroplasty in a patient with rheumatoid arthritis

We report an 80-year-old woman with rheumatoid arthritis (RA) who was found to have subchondral insufficiency fracture of the right femoral head after total knee arthroplasty (TKA). Initially, plain radiographs showed no obvious changes, but magnetic resonance imaging (MRI) revealed an irregular, discontinuous, low-intensity band on T1-weighted images of the right hip. She underwent hemiarthroplasty of the hip. This report describes a rare case of subchondral insufficiency fracture of the femoral head after TKA in a patient with RA.

Magnetic Resonance Imaging Appearance of a Double Anterior Cruciate Ligament Associated With a Displaced Tear of the Lateral Meniscus

The aim of this study is to report a novel description of a displaced tear of the lateral meniscus as a curvilinear low signal intensity band parallel and posteroinferior to the anterior cruciate ligament (ACL) on midline oblique sagittal magnetic resonance (MR) images, resulting in the appearance of a "double ACL." The appearance of a double ACL may potentially be a specific indicator for a lateral meniscal displaced tear. Increased awareness of this characteristic MR finding may increase accuracy in the diagnosis of displaced tears of the lateral meniscus.

Method for large-scale isolation and purification of R-phycoerythrin from red alga Polysiphonia urceolata Grev

R-phycoerythrin was isolated and purified from a red alga, Polysiphonia urceolata Grev, using Streamline column combined with ion-exchange chromatography or hydroxyapatite chromatography. The purity of R-phycoerythrin isolated by Streamline column was up to 1.66 and the yield of R-phycoerythrin could be as high as 0.68 mg/g frozen P. urceolata. All the eluates from Streamline column were divided into two equivalent parts, respectively. One part was pumped into the ion-exchange column loaded with Q-Sepharose and the other was applied to the adsorption column loaded with hydroxyapatite. The purities of R-phycoerythrin purified using these two methods were both up to 3.26, more than 3.2 the commonly accepted criterion. The yield of purified R-phycoerythrin from the ion-exchange chromatography was 0.40 mg/g frozen P. urceolata and that from the hydroxyapatite chromatography could reach 0.34 mg/g frozen P. urceolata. The purified protein had three absorption peaks at 498, 535, and 565 nm and displayed a fluorescence maximum at 580 nm, which was consistent with the typical spectrum of R-phycoerythrin. The purified R-PE was also identified with electrophoresis. Only one single protein band appeared on native-PAGE with silver staining. SDS–PAGE demonstrated the presence of one 20 kDa major subunit, and one low intensity band corresponding to 33 kDa subunit. The results indicate that using the expanded bed adsorption combined with ion-exchange chromatography or hydroxyapatite chromatography, R-phycoerythrin can be purified from frozen P. urceolata on large scale.

Genome classification of banana cultivars from South India using IRAP markers

The banana cultivars are originated from the intra- and inter-specific hybridization of two wild diploid species, Musa acuminata Colla and Musa balbisiana Colla, contributing the A and B genomes, respectively. They are classified into genomic groups by scoring morphological features. Molecular markers provide a quick and reliable system of genome characterization and manipulation in breeding lines. In the present study a PCR based molecular marker specific for B genomes is been reported. The IRAP primer, designed based on the LTR sequence of banana Ty3-gypsy-like retroelement (Musa acuminata Monkey retrotransposon, AF 143332), was used to identify the B genome in the banana cultivars. Further a primer pair designed from B specific bands of Musa balbisiana `Pisang Gala' was used to classify AAB and ABB cultivars in the collection. Among the 36 cultivars tested with this primer, the B specific band was absent in the AA and AAA cultivars (except in one AAA and AAB cultivar) but present in all other AB, AAB and ABB cultivars. Among the triploid AAB/ABB, the PCR products with B specific primers showed restriction pattern polymorphism with AluI. In ABB genomes the band intensity was high whereas low intensity band observed in AAB genomes. Four cultivars reported to have the ABB genome showed a pattern similar to AAB, and one cultivar reported to have AAA genome showed a pattern similar to ABB genome, suggesting missampling or misidentification. The primers used in this study are useful to identify the presence of B genome in banana cultivars, and band intensity may be a preliminary indicator of ploidy level of the B genome but needs further studies with competitive PCR for clarification.

Visible photoluminescence from Ge nanoclusters implanted in nanoporous aluminum oxide films

Nanoporous aluminum oxide (Al2O3) films with uniform porous size of 45nm prepared by the electrochemical process in inorganic acid medium were implanted at room temperature (RT) with 120keV Ge+ ions with a fluence of 1.2×1016cm−2. The nucleation and growths of Ge nanoparticles, were obtained by thermal annealing of the implanted samples at the temperature range of 200–600°C. The size and distribution of the nanoparticles were characterized by photoluminescence (PL) measurements. The photoluminescence measurements as a function of the annealing temperature shows that at low annealing temperature (200°C), the sample presents a low intensity and broad emission band centered at 5456Å consistent with emission band characteristics of nanocluster of Ge with diameter in the range of 4–8nm, as the annealing temperature increases to 400°C the PL intensity increases by a factor of almost 20 and the emission band suffers a small red shift. The intensity increases can be related to the increase of the number of Ge nanocluster. At the annealing temperature of 600°C, the emission band is considerably red shifted by almost 172Å and the emission intensity decreases significantly, strongly suggesting that nanocrystalline Ge having a character of direct optical transitions exhibits the visible photoluminescence.

Thermochromic and Spectral Properties of Perimidinespirocyclohexadienones: A DFT and ab initio Studies

ABSTRACT The ring-opening reactions of perimidinespirocyclohexadienones in the ground and first excited singlet and triplet states were studied at the DFT B3LYP/6-31G**, UB3LYP/6-31G** and CIS/3-21G** levels of theory . It has been found that the thermal isomerization is governed by the non-adiabatic mechanism involving excitation in the triplet state. The irreversible character of the ring-opening photoreaction can be explained by the absence of a local minimum corresponding to the opened form at the S1 potential energy surface. According to the TD DFT calculations the low intense long-wavelength absorption band at 436 nm inherent in perimidinespirocyclohexadienones belongs to a charge-transfer electronic transition involving the frontier orbitals located at different spiroconjugated moieties.

Bilateral subchondral insufficiency fracture of the femoral head after renal transplantation: A case report

This report describes the case of a 47-year-old woman who was found to have subchondral insufficiency fractures in both femoral heads after renal transplantation. Initially, plain radiographs showed no obvious changes, but magnetic resonance imaging (MRI) revealed an irregular, discontinuous, low-intensity band on the T1-weighted image of both hips. The patient was treated nonsurgically. Ten months after onset, the pain in both hips disappeared, and plain radiographs and MRI showed no abnormalities. Subchondral insufficiency fracture should be considered in the diagnosis of patients who have hip pain after renal transplantation.

Deep photo-lithography characterization of SU-8 resist layers

SU-8 layers of different thickness that were formed by spinning and soft baking or a casting process with a solvent content of not more than 4% were used for experimental investigation of deep UV lithography using modified radiation of a mercury lamp. The specific absorbance of the SU-8 layers have been measured in dependence on the wavelength to calculate the power of the absorbed radiation as a function of depth in the resist layer. The resist layers which were formed on a photo-mask have been exposed with a variation of exposure dose to study the residual thickness of the resist. There are threshold exposures for the formation of insoluble SU-8 resist layer and for the disappearance of shrinkage of the resist layer, which depends on the size of the irradiated area, on microstructure topology and on the resist thickness for fixed parameters of pre- and post-exposure baking. It has been shown that exact filtration of a low-intensity band of exposure radiation at 334 nm allows to reduce strong diffraction distortion in the upper layer of the resist. Microstructures with an aspect ratio of 25 in a SU-8 resist layer of 1 mm thickness have been obtained using a 100 μm thick SU-8 resist layer as a filter for the UV radiation and with optimal dose of exposure.

Fluorescence of Vegetable Oils: Olive Oils

Fluorescence spectra of undiluted extra virgin olive oil obtained with the traditional setup (right-angle fluorescence) show considerable artifacts and deformations due to self-absorption phenomena, even when the spectra are corrected for inner filter effects. On the other side, front-face fluorescence spectra are much less affected by self-absorption. Front-face fluorescence of native olive oil reveals the presence of different fluorophores and can provide information about their amount. From the intense emission at ca. 315-330 nm, it is possible to detect fluorescent polyphenols and pherols and to evaluate their overall content. Low-intensity emission bands at 350-600 nm are correlated to vitamins and other important molecules. Among them, the fluorescence of the riboflavin fluorophore can be used to evaluate its concentration. The intense emission of chlorophyll derivatives, measured in the 640-800 nm spectral region, can provide information on their concentration.

Structural Changes of D1 C-terminal α-Carboxylate during S-state Cycling in Photosynthetic Oxygen Evolution

Changes in the chemical structure of alpha-carboxylate of the D1 C-terminal Ala-344 during S-state cycling of photosynthetic oxygen-evolving complex were selectively measured using light-induced Fourier transform infrared (FTIR) difference spectroscopy in combination with specific [(13)C]alanine labeling and site-directed mutagenesis in photosystem II core particles from Synechocystis sp. PCC 6803. Several bands for carboxylate symmetric stretching modes in an S(2)/S(1) FTIR difference spectrum were affected by selective (13)C labeling of the alpha-carboxylate of Ala with l-[1-(13)C]alanine, whereas most of the isotopic effects failed to be induced in a site-directed mutant in which Ala-344 was replaced with Gly. Labeling of the alpha-methyl of Ala with l-[3-(13)C]alanine had much smaller effects on the spectrum to induce isotopic bands due to a symmetric CH(3) deformation coupled with the alpha-carboxylate. The isotopic bands for the alpha-carboxylate of Ala-344 showed characteristic changes during S-state cycling. The bands appeared prominently upon the S(1)-to-S(2) transition and to a lesser extent upon the S(2)-to-S(3) transition but reappeared at slightly upshifted frequencies with the opposite sign upon the S(3)-to-S(0) transition. No obvious isotopic band appeared upon the S(0)-to-S(1) transition. These results indicate that the alpha-carboxylate of C-terminal Ala-344 is structurally associated with a manganese ion that becomes oxidized upon the S(1)-to-S(2) transition and reduced reversely upon the S(3)-to-S(0) transition but is not associated with manganese ion(s) oxidized during the S(0)-to-S(1) (and S(2)-to-S(3)) transition(s). Consistently, l-[1-(13)C]alanine labeling also induced spectral changes in the low frequency (670-350 cm(-1)) S(2)/S(1) FTIR difference spectrum.

The common effect of hydrophobic and electrophilic types of hydration dependent on protonation in the sec-butylamine/HCl/H 2O system studied by FTIR spectroscopy

Hydration of sec-butylamine in an aqueous solution was studied by FTIR spectroscopy. HDO diluted in H 2O was used as a probe of water environment. Quantitative difference spectra method of data analysis was performed to remove the contribution of bulk water in the solution spectra. As HCl is introduced to the system, the main component band of affected HDO spectrum, ascribed to hydrophobicaly hydrated water, undergoes a gradual shift from ca. 2511 cm −1 for the free amine, to about 2520 cm −1 for the protonated ammonium cation. The process of amine N atom protonation is evidenced by systematic buildup of the ca. 2250 cm −1 band, attributed to N–D oscillators, with decreasing pH. In the case of free amine and neutralized solutions at high pH, a sharp, low intensity band at ca. 2450 cm −1 is also visible and attributed to the HDO molecules forming hydrogen bond directly to the amine's lone electron pair. The hydrophobic effect of alkyl side chain is influenced by the polarizing power exerted on water molecules by the electrophilic amine group. This polarizing effect is cooperatively transmitted to the interactions inside the clathrate-like water ‘cage’ around the alkyl group, effectively strengthening it.

A Raman spectroscopic study of the uranyl sulphate mineral johannite

Raman spectroscopy at 298 and 77 K has been used to study the secondary uranyl mineral johannite of formula (Cu(UO 2) 2(SO 4) 2(OH) 2·8H 2O). Four Raman bands are observed at 3593, 3523, 3387 and 3234 cm −1 and four infrared bands at 3589, 3518, 3389 and 3205 cm −1. The first two bands are assigned to OH − units (hydroxyls) and the second two bands to water units. Estimations of the hydrogen bond distances for these four bands are 3.35, 2.92, 2.79 and 2.70 Å. A sharp intense band at 1042 cm −1 is attributed to the (SO 4) 2− symmetric stretching vibration and the three Raman bands at 1147, 1100 and 1090 cm −1 to the (SO 4) 2− anti-symmetric stretching vibrations. The ν 2 bending modes were at 469, 425 and 388 cm −1 at 77 K confirming the reduction in symmetry of the (SO 4) 2− units. At 77 K two bands at 811 and 786 cm −1 are attributed to the ν 1 symmetric stretching modes of the (UO 2) 2+ units suggesting the non-equivalence of the UO bonds in the (UO 2) 2+ units. The band at 786 cm −1, however, may be related to water molecules libration modes. In the 77 K Raman spectrum, bands are observed at 306, 282, 231 and 210 cm −1 with other low intensity bands found at 191, 170 and 149 cm −1. The two bands at 282 and 210 cm −1 are attributed to the doubly degenerate ν 2 bending vibration of the (UO 2) 2+ units. Raman spectroscopy can contribute significant knowledge in the study of uranyl minerals because of better band separation with significantly narrower bands, avoiding the complex spectral profiles as observed with infrared spectroscopy.

Molecular structure of the uranyl mineral uranopilite—a Raman spectroscopic study

Raman spectroscopy of the mineral uranopilite at 298 and 77 K has been obtained and used to elucidate the structure of the mineral at the molecular level. A single intense band at 1010 cm −1 is assigned to the ν 1 (SO 4) 2− symmetric stretching mode. Three low intensity bands in the 298 K Raman spectrum are observed at 1143, 1117 and 1097 cm −1 and in the 77 K spectrum four bands at 1148, 1130, 1118 and 1106 cm −1. These bands are attributed to the ν 3 antisymmetric stretching modes. A series of infrared bands are found at 1559, 1540, 1526 and 1511 cm −1 attributed to δ UOH bending modes. Three bands are observed at 843, 835 and 819 cm −1 in both 298 and 77 K spectra attributed to the ν 1 symmetric stretching modes of the (UO 2) 2+ units. In the infrared spectra bands are observed at 941, 929 and 910 cm −1 and are assigned to the ν 3 antisymmetric stretching modes of the UO 2 units. These values are used to calculate UO bond distances. Multiple OH stretching modes prove a complex arrangement of OH groupings, i.e. water molecules and OH − ions, and hydrogen bonding in the crystal structure of uranopilite.