Development of an automatic phase-contrast microscopic system capable of determining the microbial density and distribution inside an immobilized carrier

The cell-immobilization technique is used for the physical and chemical fixation of cells onto a solid support in order to increase their stability and capacity of substrate uptake. However, there is no apparatus to observe the microbial community's structure inside cell immobilizing polymeric carrier. In order to satisfy the demand of monitoring for the microbial distribution inside the carrier, we developed an automatic phase contrast microscopic monitoring system capable of determining the microbial density and distribution inside a cell-entrapped carrier automatically.

Behaviors of the "raman spectroscopic signature of life" in single living fission yeast cells under different nutrient, stress, and atmospheric conditions

Time- and space-resolved Raman spectra of mitochondria in single living fission yeast cells have been measured under various nutrient, stress, and atmospheric conditions. A focus is placed on the behavior of the Raman band located at 1602 cm(-1), which sensitively reflects the metabolic activity in mitochondria and which has been called by us the "Raman spectroscopic signature of life". Addition of nutrients increases the intensity of this band by approximately 1.5 times, confirming its correlation with the metabolic activity in mitochondria. The spectra of cells cultured under 100% N(2), 100% O(2), and N(2)/O(2) (V(N2):V(O2) congruent with approximately = 4:1) atmospheres have been measured for both (16)O(2) and (18)O(2). Yeast cells have been found to lose their metabolic activity after the culture under 100% N(2) and 100% O(2) atmospheres. Cells cultured under a N(2)/(16)O(2) ((16)O(2) = 20%) atmosphere show strong "Raman spectroscopic signature of life". No (18)O isotopic shift has been found for the wavenumber 1602 cm(-1), indicating that the origin of this signature is neither O(2) nor an O-containing small molecule. Addition of H(2)O(2) causes a quick decrease of the "Raman spectroscopic signature of life", followed by the cis-trans isomerization in the unsaturated phospholipid chain. The "Raman spectroscopic signature of life" has thus been proved to be a reliable real-time and in vivo indicator for monitoring the metabolic activity in living cells.

Local structure formation in alkyl-imidazolium-based ionic liquids as revealed by linear and nonlinear Raman spectroscopy

We show several pieces of Raman spectroscopic evidence that are indicative of local structure formation in imidazolium-based ionic liquids. Low-frequency Raman spectra of C n mimX, where C n mim stands for 1-alkyl(C n H 2 n+1 )-3-methylimidazolium cation and X represents the anion, exhibit broad bands assignable to collective modes of local structures. Spatial distributions of coherent anti-Stokes Raman scattering (CARS) signals from C n mim[PF 6] are consistent with local structures whose size increases with increasing n. Picosecond Raman spectra of S 1 trans-stilbene as a "picosecond Raman thermometer" show microscopic thermal inhomogeneity ascribable to local structure formation in C 2mimTf 2N and C 4mimTf 2N. We also describe two novel phenomena that we believe are relevant to extraordinary nanoenvironments generated by local structures in a magnetic ionic liquid C 4mim[FeCl 4].

Intra- and intermolecular vibrational energy transfer in tungsten carbonyl complexes W(CO)5(X) (X=CO, CS, CH3CN, and CD3CN)

Vibrational energy relaxation of degenerate CO stretches of four tungsten carbonyl complexes, W(CO)6, W(CO)5(CS), W(CO)5(CH3CN), and W(CO)5(CD3CN), is observed in nine alkane solutions by subpicosecond time-resolved infrared (IR) pump-probe spectroscopy. Between 0 and 10 ps after the vibrational excitation, the bleaching signal of the ground-state IR absorption band shows anisotropy. Decay of the anisotropic component corresponds either to the rotational diffusion of the molecule or to the intramolecular vibrational energy transfer among the degenerate CO stretch modes. The time constant of the anisotropy decay, tauaniso, shows distinct solvent dependence. By comparing the results for the T1u CO stretch of W(CO)6 and the A1 CO stretch of W(CO)5(CS), the time constant of the rotational diffusion, taur, and the time constant of the intramolecular energy transfer among the three degenerate vibrational modes, taue, are determined as 12 and 8 ps, respectively. The tauaniso value increases as the number of carbon atoms in the alkane solvent increases. After 10 ps, the recovery of the bleaching becomes isotropic. The isotropic decay represents the vibrational population relaxation, from v=1 to v=0. In heptane, the time constant for the isotropic decay, tau1, for W(CO)5(CS) and W(CO)6 was 140 ps. The tau1 for the two acetonitrile-substituted complexes, however, shows a smaller value of 80 ps. The vibrational energy relaxation of W(CO)5(CH3CN) and W(CO)5(CD3CN) is accelerated by the intramolecular energy redistribution from the CO ligand to the acetonitrile ligand. In the nine alkane solutions, the tau1 value of W(CO)6 ranges between 124 and 158 ps, showing the apparent V-shaped solvent dependence with its minimum in decane, while the tau1 value shows little solvent dependence for W(CO)5(CH3CN) and W(CO)5(CD3CN).

Picosecond Time-Resolved Fluorescence Study on Solute−Solvent Interaction of 2-Aminoquinoline in Room-Temperature Ionic Liquids: Aromaticity of Imidazolium-Based Ionic Liquids

Time-resolved fluorescence spectra and fluorescence anisotropy decay of 2-aminoquinoline (2AQ) have been measured in eight room-temperature ionic liquids, including five imidazolium-based aromatic ionic liquids and three nonaromatic ionic liquids. The same experiments have also been carried out in several ordinary molecular liquids for comparison. The observed time-resolved fluorescence spectra indicate the formation of pi-pi aromatic complexes of 2AQ in some of the aromatic ionic liquids but not in the nonaromatic ionic liquids. The fluorescence anisotropy decay data show unusually slow rotational diffusion of 2AQ in the aromatic ionic liquids, suggesting the formation of solute-solvent complexes. The probe 2AQ molecule is likely to be incorporated in the possible local structure of ionic liquids, and hence the anisotropy decays only through the rotation of the whole local structure, making the apparent rotational diffusion of 2AQ slow. The rotational diffusion time decreases rapidly by adding a small amount of acetonitrile to the solution. This observation is interpreted in terms of the local structure formation in the aromatic ionic liquids and its destruction by acetonitrile. No unusual behavior upon addition of acetonitrile has been found for the nonaromatic ionic liquids. It is argued that the aromaticity of the imidazolium cation plays a key role in the local structure formation in imidazolium-based ionic liquids.

Local Structure at the Air/Liquid Interface of Room-Temperature Ionic Liquids Probed by Infrared−Visible Sum Frequency Generation Vibrational Spectroscopy: 1-Alkyl-3-methylimidazolium Tetrafluoroborates

The air/liquid interface of 1-alkyl-3-methylimidazolium tetrafluoroborates with the general formula [C(n)mim]BF(4) (n = 4-11) was studied using infrared-visible sum frequency generation (SFG) vibrational spectroscopy. The probability of the gauche defect per CH2-CH2 bond in the alkyl chain decreases as the number of carbon atoms in the alkyl chain increases. This observation suggests that the interaction between the alkyl chains is enhanced as the alkyl chain length becomes longer. The frequencies of the C-H stretching vibrational modes observed in the SFG spectra are higher than those of the corresponding peak positions observed in the infrared spectra of the bulk liquids. This shift is consistent with a structure in which the alkyl chain protrudes from the bulk liquid into the air. A local structure, which originates from the intermolecular interaction between the ionic liquid molecules, is proposed to explain these observations.

Excited-State Structure and Dynamics of 1,3,5-Tris(phenylethynyl)benzene as Studied by Raman and Time-Resolved Fluorescence Spectroscopy

Excited-state structure and dynamics of 1,3,5-tris(phenylethynyl)benzene (TPB) have been studied in n-hexane and n-heptane solutions. Time-resolved fluorescence spectra, fluorescence anisotropy, and lifetime of TPB were recorded with femtosecond to nanosecond time resolution. Raman depolarization ratio was also measured to elucidate a nonplanar structure of the ground state. Two fluorescence components, the short-lived component with 150 fs lifetime and the long-lived component with 10 ns lifetime, were observed. The analysis of the fluorescence anisotropy values combined with the Raman depolarization data has led to a conclusion that TPB is primarily excited to a short-lived excited singlet state with a nonplanar structure, and then it relaxes to a long-lived excited singlet state with a 3-fold axis. A rapid structural change from a nonplanar to a planar structure is suggested to take place in the process of relaxation.

Melting and freezing behaviors of prototype ionic liquids, 1-butyl-3-methylimidazolium bromide and its chloride, studied by using a nano-Watt differential scanning calorimeter

1-Butyl-3-methylimidazolium bromide ([bmim]Br) and its chloride ([bmim]Cl) are representative prototypes of ionic liquids. We investigated the melting and freezing behaviors of [bmim]Br and [bmim]Cl by using a homemade differential scanning calorimeter (DSC) with nano-Watt stability and sensitivity. The measurements were carried out at heating and cooling rates slow enough to mimic quasi-static processes. Their thermal behaviors of melting and freezing show characteristic features such as a wide pre-melting range and excessive supercooling and individual behaviors of single crystals even for the same substance. The melting temperatures of [bmim]Br and [bmim]Cl were determined from the broad DSC traces and discussed in relation to the crystal structure. We suggest that the observed characteristics are due to the dynamics of the cooperative change between gauche-trans (GT) and trans-trans (TT) conformations of the butyl group in the [bmim]+ cation.

Charge Resonance Character in the Charge Transfer State of Bianthryls: Effect of Symmetry Breaking on Time-Resolved Near-IR Absorption Spectra

We study the effects of symmetry breaking on the photogenerated intramolecular charge transfer (CT) state of 9,9'-bianthryl (BA) with femtosecond time-resolved near-IR spectroscopy. The time-resolved near-IR spectra are measured in acetonitrile for a symmetric substituted derivative of 10,10'-dicyano-9,9'-bianthryl (DCBA) and asymmetric substituted derivatives of 10-cyano-9,9'-bianthryl (CBA) and 9-(N-carbazolyl)anthracene (C9A), as well as nonsubstituted BA. The transient near-IR absorption spectrum of each compound at 0 ps has a locally excited (LE) absorption band, which agrees with the transient absorption band of the corresponding monomer unit. At 3 ps after the photoexcitation, the symmetric compounds show a broad charge transfer (CT) absorption band, whereas no absorption peak appears in the spectra of the asymmetric compounds. The broad CT absorption at 1250 nm only observed for the symmetric compounds can be attributed to the charge resonance transition associated with two equivalent charge separated states.

Three-Dimensional Vibrational Imaging of a Microcrystalline J-Aggregate Using Supercontinuum-Based Ultra-Broadband Multiplex Coherent Anti-Stokes Raman Scattering Microscopy

Vibrational properties of a porphyrin J-aggregate microcrystal have been investigated by ultra-broadband multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy using a supercontinuum light source generated from a photonic crystal fiber. Owing to a strong resonance effect due to an excitonic transition, clear spectral and spatial profiles of the CARS signal have been successfully obtained. On the basis of the comparison between the CARS and the fluorescence images, the spatial dependence of the CARS signal can be explained by the spatial inhomogeneity of the excitonic transition energy in the single J-aggregate microcrystal.

Hyper-Raman microspectroscopy: a new approach to completing vibrational spectral and imaging information under a microscope

We have developed hyper-Raman scattering microspectroscopy and applied it to a microcrystal of all-trans-beta-carotene. The hyper-Raman spectrum of all-trans-beta-carotene exhibits a Raman-inactive but infrared-active vibrational mode at 1564 cm(-1). Hyper-Raman imaging of a microcrystal was performed with this band. Infrared-active vibrational imaging was achieved with a spatial resolution much higher than that of conventional infrared microscopy. The combination of Raman and hyper-Raman spectroscopy opens up a new scope for high-spatial-resolution vibrational microspectroscopy that is not restricted by the selection rule.

Effect of Water on the Molecular Structure and Arrangement of Nitrile-Functionalized Ionic Liquids

Water changes the physical properties of ionic liquids (ILs). In this paper, the effect of water on ILs is investigated at the molecular level. The molecular structure and arrangement of 1-butyronitrile-3-methylimidazolium halide, in the presence and absence of the intruded water molecule, have been elucidated by single-crystal X-ray crystallography and near-infrared Raman spectroscopy. Water molecule is found to change the conformation of the n-butyronitrile chain of the cation. The hydrogen bonding interaction between the anion and water molecule, leading to loose molecular packing, is most likely to be responsible for the change. Distinct molecular structures and arrangements of ILs with and without water molecule have been presented here for the first time. As the unique properties of ILs are related to their structures and molecular arrangements, the presence of water, wanted or unwanted, must be carefully examined in any kind of IL research and applications.