Specific discrimination of pathogenic bacteria causing septic arthritis using Raman spectroscopy: In-vitro study.

In this study we performed preliminary experiments using Raman spectroscopy as an evolving technology in biofluid and microbial characterization, to explore its potential for rapid diagnosis of pathogenic bacteria in an in-vitro synovial fluid infection model. Normal human synovial fluids samples were collected from patients undergoing knee surgery and the three most common pathogenic bacteria introduced in-vitro into the samples. The bacterial growth was systematically monitored using a Raman spectroscopy. Multivariate regression analysis of acquired spectra showed bacterial characteristic Raman bands related to bacterial cell membranes and DNA structures to increase continuously as the incubation period was increased. Spectra signature recorded from cultured synovial fluid samples showed a significant loss in synovial quality and protein morphology over time compared to control samples. In this study, Raman spectroscopy shows promise for rapid pathogenic bacteria identification in synovial fluid. Marker peaks distinguished inoculated bacteria, while chemical changes reveal infection dynamics.

Enhanced intramolecular charge transfer and near-infrared fluorescence in 4-dimethylamino-chalcone analogues through extended conjugation: synthesis, photophysical properties, and theoretical modelling.

The distinctive characteristics of near-infrared fluorescent organic molecules render them indispensable across diverse applications, from energy harvesting to bioimaging and sensing technologies. In this work, we continue our investigation on the chalcone derivative, 4-dimethylamino-2'-hydroxychalcone (nDHC, n = 1; where n is the number of olefinic bonds), by expanding the number of central double bonds (n = 2 (2DHC) and n = 3 (3DHC)). Additionally, we also synthesized the structurally related chalcones lacking the OH group (DC, 2DC, 3DC) in order to obtain a comprehensive understanding of their effects on the intramolecular charge transfer (ICT). The results show remarkable bathochromic shifts in absorption and fluorescence peaks in solution as n increases. These shifts, 20 nm and 35 nm for absorption and 100 nm and 200 nm for fluorescence in 2DHC and 3DHC, respectively, signify enhanced ICT and a significant increase in the excited state's dipole moment. The presence of OH groups notably amplifies these shifts due to additional electron donation, influencing solute-solvent interactions in solution. Femtosecond fluorescence upconversion and transient absoprtion techniques unraveled distinct dynamics in these derivatives, exhibiting the dominance of vibrational cooling, solvation, and intramolecular motions, particularly in the larger conjugated systems 3DHC and 3DC. The observed changes in the femtosecond transinet absorption spectra suggest the existence of new active states in extended conjugation systems, indicating diverse intramolecular conformational states contributing to their relaxation dynamics. The results of this study provide invaluable insights into excited-state spectroscopy, offering a roadmap for tailoring chalcone derivatives for specific applications.

Isolation and Identification of Phytocompounds from Maytenus dhofarensis and Their Biological Potentials.

Maytenus dhofarensis Sebsebe (Celestraceae) is a naturally growing shrub in Oman. It is not a reputed medicinal plant in Oman, but it is regionally endemic and causes shivering attacks on goats that graze on it. The chemical investigation of the hexane and chloroform extracts of the fruits and stems of M. dhofarensis afforded dihydro-ß-agarofuran-type sesquiterpene pyridine alkaloid (1), lupanyl myristoate (2) and lignanolactone (3). Compounds (1-3) are new isolates from M. dhofarensis. The structures of these compounds were assigned through comprehensive IR, NMR, and ESI-MS analyses, and the relative configurations of compounds 1 and 3 were deduced from density function theory (DFT) calculations and NMR experiments. Compound 1 was assayed against the kinase enzyme and showed no inhibition activity for p38 alpha and delta at a 10 µM test concentration. Compound 3 inhibited the 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) by 69.5%, compared to 70.9% and 78.0% for gallic acid and butylated hydroxyanisole, respectively, which were used as positive controls.

Analysis of Bone Microarchitectural Changes and Structural Damage in Sickle Cell Disease-Induced Avascular Necrosis Using Raman Spectroscopy: Is there potential for medical management?

OBJECTIVES: Bone failure due to avascular necrosis (AVN) is a complex pathological phenomenon. Analysis of molecular changes in the bone matrix may help to shed light on the disease process and guide management. This study aimed to explore changes in bone quality and structural damage caused by sickle cell disease (SCD)-induced AVN using Raman spectroscopy. METHODS: A total of 10 necrotic femoral heads were obtained from seven SCD patients who underwent total hip replacements. The femoral heads were cut in half and scanned using Raman spectroscopy in correlation with preoperative magnetic resonance imaging to identify necrotic and healthy control areas. Subsequently, samples were examined to determine changes in bone mineralisation, crystallinity, carbonate content, collagen cross-linking and mineral and collagen fibril orientation. RESULTS: Significant changes were observed in bone mineral content, mineral-to-organic content and collagen fibril orientation in necrotic compared to control areas (P ≤0.050). CONCLUSION: The necrotic samples displayed severe structural damage and loss of mineral and organic contents. Similar Raman signals have been reported in other metabolic bone diseases such as osteoporosis, thereby potentially supporting the use of medical treatment in AVN to promote bone quality.

Electronic and steric effects of platinum(ii) di-yne and poly-yne substituents on the photo-switching behaviour of stilbene: experimental and theoretical insights.

A series of mono-, di-, and poly(platina-ynes) incorporating stilbene spacer units with the formulae trans-[R-C[triple bond, length as m-dash]C-Pt(PBu3)2-C[triple bond, length as m-dash]C-R] (R = (E)-1,2-diphenylethene), trans-[(Ph)-(Et3P)2PtC[triple bond, length as m-dash]C-R-C[triple bond, length as m-dash]CPt(PEt3)2(Ph)] (R = (E)-1,2-diphenylethene), and trans-[-(PnBu3)2PtC[triple bond, length as m-dash]C-R-C[triple bond, length as m-dash]C-]n (R = (E)-1,2-diphenylethene), respectively, have been synthesized and characterized to explore the effects of ligand topology on the photoisomerization and photophysical properties of these materials. The structural and photophysical properties of the complexes have been investigated and compared with those of the previously reported mono-, di- and poly(platina-ynes) incorporating azobenzene spacers. We found that the organometallic species 1M, 2M and 1P undergo topology-dependent reversible trans-to-cis photoisomerization in CH2Cl2 solution. Computational modelling supported the experimental findings.

Impact of the Alkyne Substitution Pattern and Metalation on the Photoisomerization of Azobenzene-Based Platinum(II) Diynes and Polyynes.

Trimethylsilyl-protected dialkynes incorporating azobenzene linker groups, Me3SiC≡CRC≡CSiMe3 (R = azobenzene-3,3'-diyl, azobenzene-4,4'-diyl, 2,5-dioctylazobenzene-4,4'-diyl), and the corresponding terminal dialkynes, HC≡CRC≡CH, have been synthesized and characterized. The CuI-catalyzed dehydrohalogenation reaction between trans-[Ph(Et3P)2PtCl] and the deprotected dialkynes in a 2:1 ratio in iPr2NH/CH2Cl2 gives the platinum(II) diynes trans-[Ph(Et3P)2PtC≡CRC≡CPt(PEt3)2Ph], while the dehydrohalogenation polycondensation reaction between trans-[(nBu3P)2PtCl2] and the dialkynes in a 1:1 molar ratio under similar reaction conditions affords the platinum(II) polyynes, [-Pt(PnBu3)2-C≡CRC≡C-]n. The materials have been characterized spectroscopically, with the diynes also studied using single-crystal X-ray diffraction. The platinum(II) diynes and polyynes are all soluble in common organic solvents. Optical-absorption measurements show that the compounds incorporating the para-alkynylazobenzene spacers have a higher degree of electronic delocalisation than their meta-alkynylazobenzene counterparts. Reversible photoisomerization in solution was observed spectroscopically for the alkynyl-functionalized azobenzene ligands and, to a lesser extent, for the platinum(II) complexes. Complementary quantum-chemical modeling was also used to analyze the optical properties and isomerization energetics.

Experimental and Theoretical Investigation for the Level of Conjugation in Carbazole-Based Precursors and Their Mono-, Di-, and Polynuclear Pt(II) Complexes.

A series of trimethylsilyl-protected monoalkynes (Me3SiC≡C-R) and bis-alkynes (Me3 SiC≡C-R-C≡CSiMe3) incorporating carbazole spacer groups (R = carbazole-2-yl, carbazole-3-yl, carbazole-2,7-diyl, N-(2-ethylhexyl)carbazole-2,7-diyl, carbazole-3,6-diyl, N-(2-ethylhexyl)carbazole-3,6-diyl), together with the corresponding terminal monoalkynes (H-C≡C-R) and bis-alkynes (H-C≡C-R-C≡C-H), have been synthesized and characterized. The CuI-catalyzed dehydrohalogenation reaction between trans-[(Ph)(Et3P)2PtCl], trans-[(Et3P)2PtCl2], and trans-[(P(n)Bu3)2PtCl2] and the terminal alkynes in (i)Pr2NH/CH2Cl2 affords a series of Pt(II) mono- and diynes, while the dehydrohalogenation polycondensation reactions with trans-[(P(n)Bu3)2PtCl2] under similar reaction conditions yields four Pt(II) poly-ynes of the form trans-[(P(n)Bu3)2Pt-C≡C-R-C≡C-]n. The acetylide-functionalized carbazole ligands and the mono-, di-, and polynuclear Pt(II) σ-acetylide complexes have been characterized spectroscopically, with a subset analyzed using single-crystal X-ray diffraction. The Pt(II) mono-, di-, and poly-ynes incorporating the carbazole spacers are soluble in common organic solvents, and solution absorption spectra show a consistent red-shift between the 2- and 2,7- as well as 3- and 3,6-carbazole complexes. Computational modeling is used to explain the observed spectral shifts, which are related to the enhanced electronic delocalization in the latter systems. These results also indicate that the inclusion of carbazole-2,7-diyl units into rigid-rod organometallic polymers should enhance electronic transport along the chains.

Ground state spectroscopy of hydroxyquinolines: evidence for the formation of protonated species in water-rich dioxane-water mixtures.

We have recently used 6-, 7-, and 8-hydroxyquinolines (HQs) as fluorescent probes to study the binding mechanism in one of the drug binding sites of human serum albumin. In the present work we study the absorption spectra of the HQ molecules in neat and binary mixtures of dioxane and water in order to identify the different tautomeric species in the ground state. This study should help in identifying the environment in nanocavities of macromolecules when HQs are used as local reporters. The enol form is shown to be the only tautomer for the three HQs in dioxane and water, with the exception of 7HQ in which both the enol and the zwitterion tautomers exist in equilibrium in water. The results are confirmed by the density functional theory (DFT) calculations using the B3LYP method with a 6-311++G(2d,p) basis set. In water-rich dioxane mixtures, all HQs are protonated. The results were confirmed by comparing the absorption spectra in binary solvents with those in acidic and basic aqueous solutions, and by DFT calculations of the Franck-Condon S1 ← S0 transitions. The number of water molecules solvating the polar sites in each HQ molecule was estimated from the spectral change in the binary solvent mixtures, and structures were calculated by DFT. Mapping the water density around the polar sites in each HQ using molecular dynamics (MD) simulations shows well-defined hydrogen bonds around the N-heteroatom in each HQ molecule. Water density is only well-defined around the hydroxyl group in 8HQ. The MD simulations indicate free rotation of the OH group in 6HQ and 7HQ, and the stability of the cis-isomer in 8HQ. The results point to the unique spectral signatures of 7HQ in water which make this molecule a potential probe to detect the presence of water in nanocavities of macromolecules, and to the ability of the three HQs to detect acidic media in binding sites.

Solvent effect on anthranilic acid spectroscopy.

The spectroscopy of anthranilic acid (AA) was examined in neat and binary solvents of varying polarity and hydrogen bonding strength in order to understand the role of water in solvating the polar sites of the molecule. With the exception of water, the Stokes shift of AA in different solvents was found to be linearly correlated with the normalized molar transition energy of solvent polarity (ETN), indicating the major role of the hydrogen bonding effect in solution. Analysis of the absorption and fluorescence spectra reveals that AA exists as an anion in neutral water. The pKa (4.50) and pKa* (4.44) values were estimated from the spectral shift in the absorption and fluorescence spectra measured in different pH solutions. The shortest fluorescence lifetime was measured in cyclohexane and is attributed to intramolecular hydrogen dislocation/transfer in the excited state. The lifetime values in polar solvents point to the dominant effect of the hydrogen-bond donating strength (α value) of the solvent. The number of water molecules solvating the polar region of the neutral form of AA was estimated to be three from the absorbance change in dioxane/buffer (pH 3.5) binary mixtures. The structures of AA:water complexes were calculated from density functional theory using the B3LYP method with a 6-311++G(2d,p) basis set. A stepwise addition of water molecules (1­3) to the polar region of AA leads to a preferential solvation of the COOH group of the molecule in a closed-cyclic geometry. It is worth noting that the spectral shift as a function of pH suggests the suitability of AA as a probe to estimate the local acidity of binding sites in macromolecules in the pH range 3.0­7.0.

Analysis of UV and vibrational spectra (FT-IR and FT-Raman) of hexachlorocyclotriphosphazene based on normal coordinate analysis, MP2 and DFT calculations.

The Raman (1400-100 cm(-1)) and infrared (4000-400 cm(-1)) of solid hexachlorocyclotriphosphazene, P(3)N(3)Cl(6) (HCCTP) were recorded. The conformational energies were calculated using MP2 and DFT (B3LYP and B3PW91) methods utilizing a variety of basis sets up to 6-311+G(d). On the basis of D(3h) symmetry, the simulated vibrational spectra of P(3)N(3)Cl(6) from MP2 and DFT methods were in excellent agreement with those obtained experimentally. Additionally, Frontier Molecular Orbitals and electronic transitions were predicted using steady state and time dependent DFT(B3LYP)/PCM calculations respectively, each employing the 6-311+G(d,p) optimized structural parameters. The predicted wavelengths were in excellent agreement with experimental values when CH(2)Cl(2) was used as solvent. The (14)N and (31)P chemical shifts were predicted with B3LYP/6-311+G(2d,p) calculations using the GIAO technique with solvent effect modeled using the PCM method. The computed structural parameters of the planar P(3)N(3)Cl(6) (D(3h)) agree well with experimental values from both X-ray and electron diffraction data with slight distortions observed due to lattice defects in the solid phase. The experimental/computational results favor a slightly distorted D(3h) symmetry for the title compound in the gas and solid phases and in solution (τPNPN and τNPNP ranged from 0.018° to 0.90°). Aided by normal coordinate analysis, and the simulated vibrational spectra utilizing MP2, B3LYP and B3PW91 methods at 6-31G(d) basis set, revised and complete vibrational assignments for all fundamentals are provided herein.

Vibrational assignments, normal coordinate analysis, B3LYP calculations and conformational analysis of methyl-5-amino-4-cyano-3-(methylthio)-1H-pyrazole-1-carbodithioate.

The Raman and infrared spectra of solid methyl-5-amino-4-cyano-3-(methylthio)-1H-pyrazole-1-carbodithioate (MAMPC, C7H8N4S3) were measured in the spectral range of 3700-100 cm(-1) and 4000-200 cm(-1) with a resolution of 4 and 0.5 cm(-1), respectively. Room temperature 13C NMR and (1)H NMR spectra from room temperature down to -60 °C were also recorded. As a result of internal rotation around C-N and/or C-S bonds, eighteen rotational isomers are suggested for the MAMPC molecule (Cs symmetry). DFT/B3LYP and MP2 calculations were carried out up to 6-311++G(d,p) basis sets to include polarization and diffusion functions. The results favor conformer 1 in the solid (experimentally) and gaseous (theoretically) phases. For conformer 1, the two -CH3 groups are directed towards the nitrogen atoms (pyrazole ring) and CS, while the -NH2 group retains sp2 hybridization and C-CN bond is quasi linear. To support NMR spectral assignments, chemical shifts (δ) were predicted at the B3LYP/6-311+G(2d,p) level using the method of Gauge-Invariant Atomic Orbital (GIAO) method. Moreover, the solvent effect was included via the Polarizable Continuum Model (PCM). Additionally, both infrared and Raman spectra were predicted using B3LYP/6-31G(d) calculations. The recorded vibrational, 1H and 13C NMR spectral data favors conformer 1 in both the solid phase and in solution. Aided by normal coordinate analysis and potential energy distributions, confident vibrational assignments for observed bands have been proposed. Moreover, the CH3 barriers to internal rotations were investigated. The results are discussed herein are compared with similar molecules whenever appropriate.

Tautomerism in 7-hydroxyquinoline: a combined experimental and theoretical study in water.

Tautomerism in the ground and excited states of 7-hydroxyquinoline (7HQ) was studied in different solvents using steady-state and lifetime spectroscopic measurements, density functional theory (DFT) calculations, and molecular dynamics (MD) simulations. Equilibrium between the enol and the keto/zwitterion tautomers exists in 7HQ, which is solvent-dependent. Of the solvents used in this study, only in water does the absorbance spectrum of 7HQ show absorption from both the enol and zwitterion tautomers. In addition, in aqueous media, fluorescence is observed from the zwitterion tautomer only, which is attributed to self-quenching of the enol fluorescence by energy transfer to the ground-state zwitterion tautomer and energetically favorable excited-state proton transfer. Solvation of the hydrogen bonding sites of 7HQ was studied in binary mixtures of 1,4-dioxane and water, and three water molecules were estimated to connect the polar sites and induce intermolecular proton transfer. The results are confirmed by DFT calculations showing that three water molecules are the minimum number required to form a stable solvent wire. Mapping the water density around the polar sites using MD simulations shows well-defined hydrogen bonds around the amino and hydroxyl groups of the enol tautomer and slightly less well-defined hydrogen bonds for the zwitterion tautomer. The presence of three-member water wires connecting the polar centers in 7HQ is evident in the MD simulations. The results point to the unique spectral signatures of 7HQ in water, which make this molecule a potential probe to detect the presence of water in nanocavities of macromolecules.