Infrared study of the bacterial autoinducer N-hexanoyl-homoserine lactone (C6-HSL) in the gas-phase, water, and octanol solutions

The N-hexanoyl-homoserine lactone (C6-HSL) molecule has been investigated by means of infrared multiphoton dissociation (IRMPD) and Fourier-transform infrared spectroscopy (FT-IR) under different conditions in an attempt to mimic biological situations encountered in communication between bacteria for quorum sensing. The protonated molecular ion was studied in the gas-phase that corresponds to a solvent-free situation somewhat analogous to that encountered in the receptor. The simulation of the IRMPD spectrum of the isolated ion was then conducted by means of quantum chemistry calculations in vacuum. In the case of the neutral species, the FT-IR spectra were recorded in D(2)O, mimicking the cytosolic and extracellular media as well as in 1-octanol that is often used for simulation of cell membranes. The interpretation was conducted by considering a C6-HSL molecule in its endo or exo conformation hydrogen-bonded to, respectively, six D(2)O and four 1-octanol molecules. A satisfying agreement with the experimental FT-IR studies conducted in solution at room temperature was obtained as long as a continuum IEFPCM model was added to the explicit solvent environment.     

Molecular structure and vibrational spectra of 1,3-bis(4-pyridyl)propane by quantum chemical calculations

The experimental and theoretical study on the structures and vibrations of 1,3-bis(4-pyridyl)propane are presented. The FT-IR and Raman spectra of molecule have been measured. The optimized geometric bond lengths have been obtained by DFT show the best agreements with experimental values. The harmonic vibrational frequencies were calculated and scaled values have been compared with experimental FT-IR and FT-Raman spectra. Majority of the computed wavenumbers were found to be in good agreement with experimental observations. A complete assignment of the fundamentals was proposed based on the total energy distribution (TED) calculation.     

Molecular and crystal structure of the sequiterpene lactone austricin

An x-ray structural study has been made of the sesquiterpene lactone austricin: diffractometer, MoK radiation, 1147 reflections, direct method, R=0.045. The spatial structure of the molecule has been determined. The conformation of the pentane carbocycle is 1-envelope, of the heptane ring 1,10, 7-chair, and of the lactone ring 7-envelope. The lactone ring is trans-linked with the guaiane skeleton.Institute of Organic Synthesis and Coal Chemistry, Kazakh SSR Academy of Sciences, Karaganda. A. N. Nesmeyanov Institute of Heteroorganic Compounds, USSR Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 788–791, November–December, 1989.     

Molecular and crystal structure of the sequiterpene lactone austricin

An x-ray structural study has been made of the sesquiterpene lactone austricin: diffractometer, MoK_α radiation, 1147 reflections, direct method, R=0.045. The spatial structure of the molecule has been determined. The conformation of the pentane carbocycle is 1α-envelope, of the heptane ring 1,10β, 7α-chair, and of the lactone ring 7α-envelope. The lactone ring is trans-linked with the guaiane skeleton. Institute of Organic Synthesis and Coal Chemistry, Kazakh SSR Academy of Sciences, Karaganda. A. N. Nesmeyanov Institute of Heteroorganic Compounds, USSR Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 788–791, November–December, 1989.     

Molecular and crystal structure of the sesquiterpene lactone ketopelenolide A

The boat-boat conformation of the germacrane ring of ketopelenolide A has been established by x-ray structural analysis. Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Science, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 342–346, May–June, 1990.     

Molecular and crystal structure of the sesquiterpene lactone ketopelenolide A

The boat-boat conformation of the germacrane ring of ketopelenolide A has been established by x-ray structural analysis.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Science, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 342–346, May–June, 1990.     

Molecular and crystal structure of the sesquiterpene lactone ketopelenolide B

The spatial structure of the sesquiterpene lactone ketopelenolide B has been established.Institute of Phytochemistry, Ministry of Sciences and High Education, Republic of Kazakhstan, Karaganda, Ul. Erzhanova, a/ya 19, fax 433773, arglabin@phyto.karaganda.su. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 481–483, July–August, 1999.     

Molecular structure and vibrational spectra of trimethylarsenite

The molecular structure and vibrational spectra of trimethylarsenite were studied by gas phase electron diffractometry and IR and Raman spectroscopv. The configuration of the O-methyl groups with respect to the lone electron pair of the arsenic atom is established to be close to gosh-gosh-trans. The main geometrical parameters are: bond lengths (r_a, Å) As-O 1.780, C-0 1.451, and C-H 1.101; bond angles (deg) As-O-C 115.0, O-As-0 99.5, and O-C-H 115.3. The experimental IR and Raman spectra were obtained for pure liquid and CCl₄ solution. The frequencies and forms of normal vibrations were calculated.     

Bacterial signal C10-HSL stimulates spore germination of Galactomyces geotrichum by transboundary interaction

The coevolution and coexistence of bacterial–fungal consortium have been widely reported in various natural ecosystems. The transboundary communication mediated by bacterial acyl–homoserine lactone signals probably is the driving force of fungal spore germination. This study aimed to report a functional bacterial signal molecule, C10-acyl homoserine lactone, which could be sensed by Galactomyces geotrichum. The spore germination rates of G. geotrichum increased by 22%. Meanwhile, carbohydrate production improved by 1.0- to 2.5-fold. G. geotrichum signaled to C10-HSL through receptor gene Rho1 and made a response in cell wall assembly and carbohydrate biosynthesis by the upregulated expression (above 1-fold) of functional genes, such as Smi1, Utr2, and Chs2. It contributed to spore germination and morphology transformation together. This study provides a novel perspective for understating the transboundary cooperation between fungi and bacteria by cell-to-cell communication.     

Molecular structure and vibrational characteristics of thorium tetrafluoride

The molecular structure of ThF₄ is studied by synchrotron electron diffractometry and mass spectrometry. The thermally mean values of internuclear distances are found at a temperature of 1370±20 K: r_g(Th-F) = 2.124(5) å, r_g(F-F) = 3.418(31) å, δ(F-F) = 0.049(32) å, and LF-Th-F = 107.2(1.7)?. These distances agree with the tetrahedral structure of the molecule. The missing vibration frequencies of the ThF₄ molecule are calculated in a combined analysis of electron diffraction and spectroscopic data: v₁ = 620(30) cm^-1 and v₂ = 115(15) cm^-1.     

Crystal structure and vibrational spectra of piperazinium bis(4-hydroxybenzenesulphonate) molecular-ionic crystal

The piperazinium bis(4-hydroxybenzenesulphonate) crystallizes from water solution at room temperature in P2(1)/c space group of monoclinic system. The crystals are built up of doubly protonated piperazinium cations and ionized 4-hydroxybenzenesulphonate anions that interact through weak hydrogen bonds of O-H...O and N-H...O type. Mutual orientation of anions is determined by non-conventional hydrogen bonds of C-Hcdots, three dots, centeredpi type. Room temperature powder FT IR and FT Raman measurements were carried out. The vibrational spectra are in full agreement with the structure obtained from X-ray crystallography. The big single crystals of the title salt can be grown.     

Molecular structure and vibrational spectra of 4-, 5-, 6-chloroindole

The molecular geometry, IR intensities, harmonic and anharmonic vibrational frequencies of 4-, 5-, 6-chloroindole in the ground state were calculated by DFT/B3LYP level of theory using the 6-31G (d, p) basis set. To give complete and reasonable vibrational assignments, the normal coordinate analysis has been performed for 4-chloroindole, 5-chloroindole and 6-chloroindole. The effect of position of chloro atom on the molecular properties (electron density, dipole moments and energies) of the indole aromatic system is examined on the basis of calculation data for 4-, 5- and 6-chloroindoles.     

Molecular structure of hafnium and zirconium acetylacetonates M(C5H7O2)4

Electron diffraction and spectral data for hafnium and zirconium tetrakis(acetylacetonates) Hf(C₅H₇O₂)₄ and Zr(C₅H₇O₂)₄ are analyzed in terms of D₂ symmetry of the geometrical configuration. Structural parameters and rms amplitudes of vibrations are determined. It is found that r_g(Zr-O)=227.1(5) pm and r_g(Hf-O)=226.5(5) pm. United Institute of High Temperatures, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 1, pp. 46–54, January–February, 1998.     

Crystal structure, differential scanning calorimetry and vibrational low temperature investigation of C(NH2)3 x HSeO4

The first X-ray and vibrational spectroscopic analysis of a new molecular complex between guanidinium and selenic acid is reported. The crystal of guanidinium hydrogenselenate at room temperature belongs to P2(1)/n space group of the monoclinic system with Z=4, a=8.330A, b=5.109A, c=14.855A and beta=92.65 degrees . Room temperature powder infrared and Raman spectra for the titled complex (1:1) were measured. The observed IR and Raman spectra are in accordance with this crystallographic structure. The differential scanning calorimetric (DSC) experiment on powder samples indicates on continuous phase transition at ca. 160K. To explain in detail the behavior of the crystal during the phase transition the infrared and Raman powder spectra in low temperature range (10-300K) were measured. The temperature dependencies of bands position and intensities for obtained spectra are analysed.