Ring Stretch Research Articles

Evaluation of anthelmintic and antioxidant efficacy of green-synthesized copper nanoparticles derived from Erioglossum rubiginosum leaf and seed aqueous extracts

The green synthesis of copper nanoparticles refers to the preparation of nanoparticles using eco-friendly and sustainable processes, often involving plant extracts, microorganisms, or other natural sources. As a sustainable approach with many potential applications, plant extracts could be used for the green synthesis of copper nanoparticles. The green synthesis of copper nanoparticles from plants, such as Erioglossum rubiginosum, involves using leaf and seed extracts to reduce copper ions to form nanoparticles. Primarily, copper nanoparticles are confirmed by visual observation of the aluminum vessel’s inner wall exhibiting a glossy, reddish-brown precipitate. Further, the UV–Vis spectrophotometer is employed to detect the presence of CuNPs. The peak is at 631 nm, which is unique to CuNPs. FTIR data show the presence of a capping agent which stabilizes copper nanoparticles. The peaks at 3,265 cm−1 for the hydroxy group (H-bonded OH stretch) indicate alcohols and phenols; 1610 cm−1 for aromatic ring stretch; and 1,075 cm−1 for aliphatic fluoro compounds (C–F stretch). DPPH reducing power assay is used to verify the antioxidant activity. Both plant extracts and the synthesized CuNPs showed considerable antioxidant activity. The seed and leaf extract of Erioglossum rubiginosum used for the green synthesis of copper nanoparticles served as a capping agent due to the presence of antioxidant phytoconstituents. Then, we used Paramphistomum cervi to evaluate the anthelmintic activity of aqueous extracts of leaves and seeds of Erioglossum rubiginosum. After that, we assessed the anthelmintic activity of the green synthesized copper nanoparticles (CuNPs). We observed that the extracts showed a significant and dose-dependent decrease in the paralysis time and death time of parasites whereas better activity was found from the synthesized CuNPs. At last, we claim that comprehensive investigation on plant extracts and CuNPs could be carried out for further study and might pave the way for development of novel therapeutic agents that show efficacy against diverse parasitic infections.

A Multi-Wavelength Raman Study of Some Oligothiophenes and Polythiophene

We have measured the Raman spectra of some oligothiophenes (bithiophene, terthiophene, quarterthiophene, sexithiophene and octithiophene) and polythiophene with wavelengths from 325–1064 nm (3.815–1.165 eV). All of the materials give good quality spectra with 1064 nm excitation, although there is weak background fluorescence for some of them. The UV lines of 405 and 324 nm generally provide good-quality spectra, albeit with significant fluorescence for bithiophene and quarterthiophene. Surprisingly, there is little difference between the relative intensities (i.e., the ratio of a band’s intensity as compared to the strongest band) of the spectra with the different excitation wavelengths. However, close inspection of the 2000–3200 cm−1 region of octithiophene and polythiophene with 325 and 405 nm excitation shows several modes in this region that can be assigned to combinations and overtones involving the ~1440 cm−1 C–C ring stretch that do not appear with 1064 nm excitation. The presence of overtones and combinations with anomalously large intensities is a hallmark of resonance Raman spectroscopy.

Evaluation of Mineralogical Composition and Organic Matter Content of Oil Shales by IR Microscopy

Sedimentary rocks with different contents of organic matter (oil shales of the Bazhenov Formation and sandstones of the Tyumen Formation) from the West Siberian oil and gas province were used to demonstrate the simultaneous study of the mineralogical and structural-group composition, as well as semi-quantitative evaluation of mineral and organic matter contents in rocks by Fourier transform infrared (FTIR) microscopy. The following bands characterizing the stretching vibrations were used: Si–O and Al–O–Si of clay minerals (990–1090 cm–1), Si–O–Si of quartz (798 cm–1), CO2−3 of carbonates (1460 cm–1), as well as aliphatic C–H stretch (2800–3000 cm–1) and C=C ring stretch (1600–1650 cm–1) of organic matter. The obtained results are in good agreement with data obtained by traditional methods of bulk rock analysis: programmed pyrolysis, X-ray diffraction (XRD), and X-ray fluorescence (XRF) analyses. FTIR-ATR (attenuation total reflection) microscopy also provides the possibility of the distribution analysis of sample surface with color mapping, demonstrating the heterogeneity of the rock composition using the Bazhenov Formation as an example of unconventional reservoir. In addition, the method makes it possible to estimate the organic matter maturity and the rock residual generation potential based on the ratio of stretching band intensities of aliphatic and aromatic fragments.

Vibrational relaxation by methylated xanthines in solution: Insights from 2D IR spectroscopy and calculations.

Two-dimensional infrared (2D IR) spectroscopy, infrared pump-infrared probe spectroscopy, and density functional theory calculations were used to study vibrational relaxation by ring and carbonyl stretching modes in a series of methylated xanthine derivatives in acetonitrile and deuterium oxide (heavy water). Isotropic signals from the excited symmetric and asymmetric carbonyl stretch modes decay biexponentially in both solvents. Coherent energy transfer between the symmetric and asymmetric carbonyl stretching modes gives rise to a quantum beat in the time-dependent anisotropy signals. The damping time of the coherent oscillation agrees with the fast decay component of the carbonyl bleach recovery signals, indicating that this time constant reflects intramolecular vibrational redistribution (IVR) to other solute modes. Despite their similar frequencies, the excited ring modes decay monoexponentially with a time constant that matches the slow decay component of the carbonyl modes. The slow decay times, which are faster in heavy water than in acetonitrile, approximately match the ones observed in previous UV pump-IR probe measurements on the same compounds. The slow component is assigned to intermolecular energy transfer to solvent bath modes from low-frequency solute modes, which are populated by IVR and are anharmonically coupled to the carbonyl and ring stretch modes. 2D IR measurements indicate that the carbonyl stretching modes are weakly coupled to the delocalized ring modes, resulting in slow exchange that cannot explain the common solvent-dependence. IVR is suggested to occur at different rates for the carbonyl vs ring modes due to differences in mode-specific couplings and not to differences in the density of accessible states.

Concentration dependent SERS study of a bioactive methylsulfonyl derivative

Concentration dependent surface enhanced Raman scattering (SERS) studies of biologically active methylsulfonyl derivative (BMSP) are reported. Out of various concentrations, SERS at 10-3 M gives maximum enhancement. The experimental results are supported by theoretical investigations. BMSP exhibited selective micro molar activity against Staphylococcus aureus. The interaction of charge transfer between Ag and S atoms is confirmed by the enhanced bond length values. Reduction in ionization potential suggests that the BMSP-Ag6 system has stronger electron donating characteristics than BMSP. The electrophilicity index of the adsorbed system containing BMSP and silver cluster represent biological activity and the adsorption process is chemisorption. Presence of CH3 modes in the SERS spectrum suggest that the molecule adopts a tilted orientation, and that para-substituted phenyl ring is more slanted than poly-substituted phenyl ring. Presence of ring stretches, bending modes for all concentrations suggest that the BMSP molecule may tilt, resulting in an interaction with the metal surface and there is an orientation change for the molecule with respect to the metal surface as concentration changes.

CHROMATOGRAPHIC, INFRARED SPECTRAL AND ANTI-INFLAMMATORY STUDIES OF ETTHYL ACETATE AND METHANOL EXTRACT OF THE SEED OF D. EDULIS

The seed powder of Dacryodes edulis were extracted using n-hexane, ethyl acetate and methanol by the cold maceration method. The crude Methanol and ethyl acetate extracts were then biologically assayed for acute toxicity (LD50) using the method of Lorke (1983). Anti-inflammatory activities of the crude were also assayed using male albino rats. The most biologically active (methanol extract) was separated using series of column chromatography (CC) and thin layer chromatography (TLC). The extractives coded DEF, DEH, DEJ and DEK, respectively were then characterized using infra-red (IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). All the results obtained were statistically analyzed using analysis of variance. The acute toxicity studies showed that even at higher concentration of 5000mg/kg, the extracts were not lethal to all the animals used. The anti-inflammatory analysis showed that the methanol extract had the highest anti-inflammatory activities. The IR for the methanol extractives showed the following λ max: (3500-3200) for the O-H stretch of alcohols and phenols, 3391.9 and 3354.6 for the N-H stretch of amines and amides, 3261.4 for the O-H stretch of carboxylic acids, 2948.3 and 2847.7 for the C-H stretch of alkanes, 1431.3 and 1386.6 for the C-H bend of alkanes and 1364.2 for C-H rocking of alkanes. Also 2836.5 for the C-H stretch of aldehydes, 2210.3 for the C=N stretch of nitriles,1736.9 1699.7 and 1013.8 for the C=O stretch of aldehydes, ketones and carboxylic acids. Equally 1643.2 and1636.9 for the C=C stretch of alkenes and 1576.7 for the C=C stretch of aromatic ring. These functional groups correspond to some of the compounds listed in the GC-MS library suggestions such as tetra- decanoic acid, hexa-decanoic acid, octadecanoic acid, vaccenic acid, catechol, 2, 4-di-tert- butylphenol and others. Presence of N-H group of amines and amides the GC-MS suggested presence of tri-(2-aminoethylamine,3,3,3-trifluoro-N-(2-fluoro-phenyl-2-(trifluoro methyl)methyl propionamide etc. The C=C of alkenes agreed with the suggested presence of cetene and bi-cyclo (10,10) tridec-1-ene and others. The non- toxic nature of the seed and its ability to reduce inflammations gives credence to its use in traditional medicine practice.

Comparative geochemical and pyrolytic study of coals, associated kerogens, and isolated vitrinites at the limit between subbituminous and bituminous coal

A sample set consisting of coal, overlying and intercalating siliciclastic rocks and kerogen concentrated from these rocks of nine Pennsylvanian subbituminous to bituminous coal seam intervals from the German Ruhr Basin was analysed in order to detect chemical structural differences of the organic matter. Vitrinites from the coal seams and the kerogen concentrates were isolated to study effects of maceral group composition on chemical properties of typical type III kerogen. Rock-Eval Tmax values of sediment samples are higher than both those of the kerogen concentrated from them and associated coal samples. This is a result of the mineral matrix effect. Higher OI values of the sediment and kerogen samples as compared to those of the bulk coal samples cannot be explained by the abundance of carbonyl/carboxyl groups as reflected by results obtained by attenuated total reflectance (ATR) FT-IR spectroscopy. Ratios of the areas of the aromatic γCH out of plane, the aliphatic νCHx stretching, and the aromatic νC=C ring stretch regions imply a lower degree of aromaticity and at the same time higher degree of condensation of vitrinites originated from the sedimentary layers, respectively. Upon Curie Point (CP) pyrolysis at 590 °C, these vitrinite samples generate higher amounts of long-chained normal alkanes and n-alkenes than the bulk samples or the vitrinite originating from the coals. While reflectance values of vitrinites from coals and sedimentary layers are within the standard deviation of values expected for the narrow maturity window, only the vitrinites of the coal seams show some correlation with depth. Clearly, the relative abundance of phenols is decreasing with increasing maturity, as well as the ratio of benzenes over higher condensed aromatic moieties as revealed by their pyrolysis products generated at 764 °C.

Identification of Bioactive Chemical Constituents Presents in the Aqueous Extract of Telfairia Occidentalis and Its in vitro Antioxidant Activities

Medicinal plants are utilized as complementary and alternative medicine in different kinds of diseases. The present study was designed to evaluate phytochemical components, of aqueous leaf extract of Telfairia occidentalis and its antioxidant potentials against free radicals. The phytochemical component of the extract was determined by standard methods while the functional groups of the phytochemicals were carried out using FTIR techniques. The antioxidant abilities of aqueous leaf extract of Telfairia occidentalis were evaluated by various antioxidant assays, including 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydrogen peroxide, hydroxyl radicals, scavenging activities. These various antioxidant activities were compared with standard antioxidants such as ascorbic acid and Gallic acid. Qualitative analysis of the extract revealed that the extract is rich in phenol, coumarins, saponin, tannin, anthraquinone, betacyanin, glycosides, oils and resin, quinones, flavonoids, alkaloids, sterols, vitamin C, terpenoids, sterols and phytosterols. Moreover, the results of FTIR analysis confirmed the presence of aromatic CH bend, C-O stretch, phenol, aromatic ring stretch, alkenyl stretch, hydroxyl group (alcohol) in the extract. The extract exhibited high reduction capability and powerful free radical scavenging, especially against DPPH radical and hydrogen peroxide. The extract shows higher inhibition activities than both ascorbic and Gallic acid. The results obtained in the present study clearly established the antioxidant potency of aqueous leaf extract of Telfairia occidentalis, which may account for some of the medical claims attributed to this plant.

Mechanisms of lobed jet mixing: About circularly alternating-lobe mixers

Two configurations of circularly arranged alternating-lobe nozzles were adopted to form lobed mixers with/without a mixing duct. The jet mixing of each mixer was numerically simulated with the unchanged initial conditions of the primary and secondary streams, except the altered initial velocity of the secondary stream. The jet-mixing mechanisms of the circularly alternating-lobe mixers were synthetically analysed by combining the evolution of the flow field structures and the process of heat and mass transfer in the mixing field. It is found that the transverse flow is usually caused by the lobed geometry, and the entrainment of the primary stream also plays a role in certain circumstances. There are two mechanisms for the deflection of the transverse flow at the lobe peaks and troughs. One of these mechanisms is to be suppressed to deflect the flow while the other is deflected by the reaction force and induction effect. The primary and secondary streams deflect to bring the transverse interval between them, and subsequently, the streamwise vortex core appears at the transverse interval. The deflected flow consistently “digging” in the radial and circumferential radiation increases the dimension of the streamwise vortices. The transverse flow velocity decreases and the direction becomes unstable leading to the breakdown of the streamwise vortices. The transverse flow brings the heat and mass transfer. Under the two mechanisms, the frontiers of the primary and secondary streams deflect. Initially, the primary and secondary streams flow around the streamwise vortex core. Subsequently, the mixed stream flows around the vortex core, and the mixing stream area gradually expands outward. The heat and mass transfer decrease in scale when the streamwise vortices break down. Because of the velocity gradient at the interface, shear instability occurs to generate the normal vortex ring. The heat and mass transfer pushes the interface, which leads to the stretch of the normal vortex ring. The mixing speed varies due to the heat and mass transfer. The velocity gradient decreases fast in the rapid mixing segment, where the normal vortex ring breaks first.

Insights on the Molecular Characteristics of Molecularly Imprinted Polymers as Monitored by Sum Frequency Generation Spectroscopy.

Sensing in molecularly imprinted polymers (MIPs) requires specific interactions of the imprinted polymer and the approaching template molecule. These interactions are affected by the morphology of the polymer surface, the affinity of the template molecule to the polymer network, and the steric approach. In this particular study, a template molecule, metronidazole, is studied with respect to the typically used methacrylic acid-based imprinted polymer using a combination of bulk and surface techniques. The resulting infrared (IR) spectra exhibited the presence of the template molecule in the polymer matrix as well as their efficient removal after washing. Dipping of the MIP according to what is expected of facile sensing in an aqueous solution of metronidazole did not show any presence of the template molecule in the bulk of the MIP, as observed by IR spectroscopy. However, using sum frequency generation (SFG) spectroscopy, the CH aromatic stretch of the imidazole ring positioned at ∼3100 cm-1 was observed at the polymer surface, including its inner pores or cavities, and at the buried polymer-fused silica interface after dipping. SFG studies have also shown the vibrational signatures of the polymer matrix, the presence of the template molecule on the surface, and the detection of residual template molecules after washing. Increasing the washing time to 50 min has proven to be less effective than increasing the washing cycles to three. However, after the third cycle, reorganization of the polymer matrix was evident as also the complete removal of the template molecule. The observed changes from the acquired images using scanning electron microscopy and atomic force microscopy show the structural morphologies of MIPs and a good distribution of the pores across the MIP surface. The study demonstrates the importance of combining both bulk and surface characterization in providing insight into the template molecule-polymer network interactions.

Assessing the dispersion of supported H3PW12O40 catalysts: No longer a hurdle thanks to in situ IR upon pyridine adsorption

Pyridine is since a long time used as an infrared (IR) molecular probe to characterize the acidity of solids, in particular of heteropolyacids (HPAs). The latter are metal-oxygen-clusters nowadays widely used in acid catalysis. Indeed, thanks to their exceptionally strong Brönsted acidity, they allow operating chemical reactions under significantly milder conditions than required by conventional catalysts. In the case of H3PW12O40, the most acidic Keggin-type HPA, it is well-known that the exposure to pyridine leads to an unusual IR spectrum. Indeed, the band at about 1540 cm−1 associated to the ν19b pyridinium ring stretch mode is split in two. Up to now, this phenomenon was studied with the only aim of understanding its origin, which was proposed to be a tunneling effect related to a frustrated rotation of the pyridinium cation within the solid bulk of H3PW12O40. Here, we demonstrate for the first time that it can actually be used as an analytical tool, namely to probe the degree of dispersion of supported H3PW12O40 units, a key parameter dictating their catalytic performance. We support H3PW12O40 on TiO2 P25 (hydrophilic) and TiO2 T805 (hydrophobic), so yielding samples with different degrees of dispersion, as qualitatively assessed through X-ray photoelectron spectroscopy. Through in situ Fourier-transform IR spectroscopy upon pyridine adsorption, we show that the ν19b pyridinium vibration band only and systematically splits in the presence of agglomerated Keggin units. More precisely, the higher the fraction of agglomerated Keggin units, the more marked the band splitting. So, the latter appears as a fingerprint of agglomerated H3PW12O40. Furthermore, following an easy treatment, the IR spectra allow quantitatively evaluating the fractions of dispersed vs. agglomerated Keggin units within the samples, which is very difficult to achieve through any other technique.

Direct dynamics simulations of the unimolecular dissociation of dioxetane: Probing the non-RRKM dynamics.

In a previous UB3LYP/6-31G* direct dynamics simulation, non-Rice-Ramsperger-Kassel-Marcus (RRKM) unimolecular dynamics was found for vibrationally excited 1,2-dioxetane (DO); [R. Sun et al., J. Chem. Phys. 137, 044305 (2012)]. In the work reported here, these dynamics are studied in more detail using the same direct dynamics method. Vibrational modes of DO were divided into 4 groups, based on their characteristic motions, and each group excited with the same energy. To compare with the dynamics of these groups, an additional group of trajectories comprising a microcanonical ensemble was also simulated. The results of these simulations are consistent with the previous study. The dissociation probability, N(t)/N(0), for these excitation groups were all different. Groups A, B, and C, without initial excitation in the O-O stretch reaction coordinate, had a time lag to of 0.25-1.0 ps for the first dissociation to occur. Somewhat surprisingly, the C-H stretch Group A and out-of-plane motion Group C excitations had exponential dissociation probabilities after to, with a rate constant ∼2 times smaller than the anharmonic RRKM value. Groups B and D, with excitation of the H-C-H bend and wag, and ring bend and stretch modes, respectively, had bi-exponential dissociation probabilities. For Group D, with excitation localized in the reaction coordinate, the initial rate constant is ∼7 times larger than the anharmonic RRKM value, substantial apparent non-RRKM dynamics. N(t)/N(0) for the random excitation trajectories was non-exponential, indicating intrinsic non-RRKM dynamics. For the trajectory integration time of 13.5 ps, 9% of these trajectories did not dissociate in comparison to the RRKM prediction of 0.3%. Classical power spectra for these trajectories indicate they have regular intramolecular dynamics. The N(t)/N(0) for the excitation groups are well described by a two-state coupled phase space model. From the intercept of N(t)/N(0) with random excitation, the anharmonic correction to the RRKM rate constant is approximately a factor of 1.5.

Characterization of Growth Patterns of Nanoscale Organic Films on Carbon Electrodes by Surface Enhanced Raman Spectroscopy.

Electrochemical deposition of aromatic organic molecules by reduction of diazonium reagents enables formation of molecular layers with sufficient integrity for use in molecular electronic junctions of interest to microelectronics. Characterization of organic films with thicknesses in the 1-10 nm range is difficult with Raman spectroscopy, since most molecular structures of electronic interest have Raman cross sections which are too small to observe as either thin films on solid electrodes or within intact molecular junctions. Layer formation on a 10 nm thick Ag island film on a flat carbon surface (eC/Ag) permitted acquisition of structural information using surface enhanced Raman spectroscopy (SERS), in many cases for molecules with weak Raman scattering. Raman spectra obtained on eC/Ag surfaces were indistinguishable from those on carbon without Ag present, and the spectra of oligomeric molecular layers were completely consistent with those of the monomers. Layer growth was predominantly linear for cases where such growth was sterically allowed, and linear growth correlated strongly with the line width and splitting of the C═C phenyl ring stretches. Molecular bilayers made by successive reduction of different diazonium reagents were also observable and will be valuable for applications of 1-20 nm organic films in molecular electronics.

27P Pectin-Chitosan conjugates novel biomaterial as platform for colon cancer drug delivery

Background In comparison to injectable, oral delivery of chemotherapeutic agents, especially in the form of a colon specific delivery system is expected to increase drug bioavailability at target site, reduce drug dose and systemic adverse effects. Pectin (PEC) and Chitosan (CS) are suitable and well documented independently drug delivery polymers for use as colon specific drug delivery as it is selectively digested by colonic microflora to release drug with minimal degradation in upper gastrointestinal tract. Pectin chitosan bioconjugate has not been synthesized and well studied for their suitability in colon cancer drug delivery applications; hence we have attempted to synthesize PEC-CS conjugate system. Methods Pectin-chitosan conjugate system was developed by conjugating the free carboxyl group of moiety of pectin and primary amine group of CS. Synthesized material was characterized by FTIR, XRD, DSC, TGA and SEM. Cancer cell toxicity study of the synthesized material were done in HT29 colon adeno- carcinoma cell lines using MTT assay. Results Pectin reacts with -NHS to form an ester in presence of DCC in anhydrous conditions along with the side product dicyclohexylurea, and finally CS reacts with this mixture replacing NHS to form the conjugate. The peaks in the region 1709 cm-1 and 1641 cm-1 corresponds to weak carbonyl stretch due to H-bonding and the amide-I band of the formed conjugate. Also seen in the FTIR spectrais the peak belongingt o amide-II band of secondary amides at 1554 cm-1 and C-C ring stretch at 1509 cm-2. The conjugate showed significantly low weight loss till 300 C (23.6%) as comparedto PEC.TheaboveresultopinedthatPEC-CSexhibitedhighthermalstabilityascompared to its native precursor. The plain PEC showed its Tgat69.55 C, while in PEC-CS itwas observed at55.13 C. This result confirmsthat movementof molecule in PEC-CS is unhindered as compared to in PEC. The conjugation was confirmed by FTIR, and XRD. TheDSCandTGAanalysisexhibitedformationofamorethermostablematerialas compared to its native precursors. The conjugated material did not exhibit any cytotoxicity in HT29 cells. Conclusions The results showed a potential to be used this novel conjugate material for colon cancer drug delivery application. Legal entity responsible for the study Akhilesh Vikram Singh Funding UGC-MHRD, New Delhi, India Disclosure A.V.Singh: The presented work is purely academic research and funded by Government of India (UGC-MHRD,NewDelhi).

An Investigation of the Cytotoxicity and Caspase-Mediated Apoptotic Effect of Green Synthesized Zinc Oxide Nanoparticles Using Eclipta prostrata on Human Liver Carcinoma Cells.

Cancer is a leading cause of death worldwide and sustained focus is on the discovery and development of newer and better tolerated anticancer drugs, especially from plants. In the present study, a simple, eco-friendly, and inexpensive approach was followed for the synthesis of zinc oxide nanoparticles (ZnO NPs) using the aqueous leaf extract of Eclipta prostrata. The synthesized ZnO NPs were characterized by UV-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), High-resolution transmission electron microscopy (HRTEM), and Selected area (electron) diffraction (SAED). The HRTEM images confirmed the presence of triangle, radial, hexagonal, rod, and rectangle, shaped with an average size of 29 ± 1.3 nm. The functional groups for synthesized ZnO NPs were 3852 cm−1 for H-H weak peak, 3138 cm−1 for aromatic C-H extend, and 1648 cm−1 for Aromatic ring stretch. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT), caspase and DNA fragmentation assays were carried out using various concentrations of ZnO NPs ranging from 1 to 100 mg/mL. The synthesized ZnO NPs showed dose dependent cytopathic effects in the Hep-G2 cell line. At 100 mg/mL concentration, the synthesized ZnO NPs exhibited significant cytotoxic effects and the apoptotic features were confirmed through caspase-3 activation and DNA fragmentation assays.

Directly probing redox-linked quinones in photosystem II membrane fragments via UV resonance Raman scattering

In photosynthesis, photosystem II (PSII) harvests sunlight with bound pigments to oxidize water and reduce quinone to quinol, which serves as electron and proton mediators for solar-to-chemical energy conversion. At least two types of quinone cofactors in PSII are redox-linked: QA, and QB. Here, we for the first time apply 257-nm ultraviolet resonance Raman (UVRR) spectroscopy to acquire the molecular vibrations of plastoquinone (PQ) in PSII membranes. Owing to the resonance enhancement effect, the vibrational signal of PQ in PSII membranes is prominent. A strong band at 1661cm−1 is assigned to ring CC/CO symmetric stretch mode (ν8a mode) of PQ, and a weak band at 469cm−1 to ring stretch mode. By using a pump-probe difference UVRR method and a sample jet technique, the signals of QA and QB can be distinguished. A frequency difference of 1.4cm−1 in ν8a vibrational mode between QA and QB is observed, corresponding to ~86mV redox potential difference imposed by their protein environment. In addition, there are other PQs in the PSII membranes. A negligible anharmonicity effect on their combination band at 2130cm−1 suggests that the ‘other PQs’ are situated in a hydrophobic environment. The detection of the ‘other PQs’ might be consistent with the view that another functional PQ cofactor (not QA or QB) exists in PSII. This UVRR approach will be useful to the study of quinone molecules in photosynthesis or other biological systems.

Angle-Dependent Polarized Raman Spectroscopy of TIPS Pentacene Single-Crystalline Domains Deposited on Au-Striped Substrates

ABSTRACT6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was deposited on SiO2/Si substrates with Au stripes using electrostatic spray deposition (ESD). We observed that crystalline domains on the substrates were preferentially oriented. To elucidate this phenomenon, the correlation between the orientation direction and stripe direction was investigated by angle-dependent polarized Raman spectroscopy. Since the acene planes in TIPS pentacene take an edge-on orientation on the substrates, C-C ring stretch modes can be used to probe the in-plane orientation. We found that the long molecular axis of acene planes is inclined at about 50° or 110° from the stripe direction. This result suggests that the molecular orientation of the crystalline domains can be controlled by the stripes.

Lattice Boltzmann Study of a Vortex Ring Impacting Spheroidal Particles

AbstractInteraction of vortex rings with solid is an important research topic of hydrodynamic. In this study, a multiple-relaxation time (MRT) lattice Boltzmann method (LBM) is used to investigate the flow of a vortex ring impacting spheroidal particles. The MRT-LBM is validated through the cases of vortex ring impacting a flat wall. The vortex evolution due to particle size, the aspect ratio of a prolate particle, as well as Reynolds (Re) number are discussed in detail. When the vortex ring impacting a stationary sphere, the primary and secondary vortex rings wrap around each other, which is different from the situation of the vortex ring impacting a plate. For the vortex ring impacting with a prolate spheroid, the secondary vortex ring stretches mainly along the long axis of the ellipsoid particle. However, it is found that after the vortex wrapping stage, the primary vortex recovers along the short axis of the particle faster than that in the long axis, i.e., the primary vortex ring stretches mainly along the short axis of the particle. That has never been address in the literature.

Mode-specific vibrational relaxation of photoexcited guanosine 5′-monophosphate and its acid form: a femtosecond broadband mid-IR transient absorption and theoretical study

UV-pump/broadband-mid-IR-probe transient absorption (TA) experiments and ab initio quantum mechanical (QM) calculations were used to investigate the photophysics in heavy water of the neutral and acid forms of guanosine 5'-monophosphate (GMP and GMPD(+), respectively). Excited GMP undergoes ultrafast internal conversion (IC) and returns to the electronic ground state in less than one picosecond with a large amount of excess vibrational energy. The spectroscopic signals are dominated by vibrational cooling - a process in which the solute dissipates vibrational energy to the solvent. For neutral GMP, cooling proceeds with a time constant of 3 ps. Following IC, at least some medium-frequency modes such as the carbonyl stretch and an in-plane ring vibration are excited, suggesting that the vibrational energy distribution is non-statistical. This is consistent with predicted structural changes upon passage through the S1/S0 conical intersection. GMPD(+) differs from GMP by a single deuteron at the N7 position, but has a dramatically longer lifetime of 200 ps. Vibrational cooling of the S1 state of GMPD(+) was monitored via several medium-frequency modes that were assigned using QM calculations. These medium-frequency modes are also vibrationally excited in a non-statistical fashion. Excitation of these modes is in line with the change in geometry at the S1 minimum of GMPD(+) predicted by QM calculations. Furthermore, these modes relax at different rates, fully consistent with QM calculations, which predict that excited vibrational states of the carbonyl stretch couple strongly to the D2O solvent and thus deactivate via intermolecular energy transfer (IET). In contrast, the ring stretch couples strongly to other ring modes of the guanine chromophore and appears to decay via intramolecular vibrational energy redistribution (IVR).

Temperature-dependent dynamic response to flash heating of molecular monolayers on metal surfaces: vibrational energy exchange.

An ultrafast nonlinear coherent laser spectroscopy termed vibrational sum-frequency generation (SFG) was used to monitor vibrational transitions of a self-assembled monolayer (SAM) of 4-nitrobenzenethiolate (NBT) on Au after Au flash heating. Ultrafast thermoreflectance measurements showed the surface temperature jumps ΔT were in the 35-250 K range. The NBT symmetric and antisymmetric nitro stretches νsNO2 and νasNO2 and a phenyl ring stretch νCC were probed. Flash heating caused these transitions to lose intensity, shift, and broaden. The time dependences all had overshoot-decay-plateau structures. In the long-lived plateau, the SAM was in thermal equilibrium with the hot Au surface. The SFG plateau intensity losses of νsNO2 and νCC, two vibrations with parallel transition moments, were identical, indicating that the SFG intensity loss was caused by thermally induced SAM orientational disorder. The T-jump-induced frequency shifts of νsNO2 and νasNO2 were identical and opposite in sign. The rise times of the shifts were identical and equal to the ∼3.5 ps time constant for the rise of Au surface temperature, which indicates that both shifts were caused by anharmonic coupling to the same lower-energy vibration. The temperature dependence of the νsNO2 shift and width indicated that this vibration was the ∼480 cm(-1) nitro bend. The νsNO2 temperature dependence was interpreted using a vibrational energy exchange mechanism between the nitro stretch and bend.