We report direct observation of a spatial distribution of water molecules inside of a living cell using Raman images of the O-H stretching band of water. The O-H Raman intensity of the nucleus was higher than that of the cytoplasm, indicating that the water density is higher in the nucleus than that in the cytoplasm. The shape of the O-H stretching band of the nucleus differed from that of the cytoplasm but was similar to that of the balanced salt solution surrounding cells, indicating less crowded environments in the nucleus. The concentration of biomolecules having C-H bonds was also estimated to be lower in the nucleus than that in the cytoplasm. These results indicate that the nucleus is less crowded with biomolecules than the cytoplasm.

Liquid–liquid phase separation (LLPS) plays an important role in a variety of biological processes and is also associated with protein aggregation in neurodegenerative diseases. Quantification of LLPS is necessary to...

No abstract

Due to its lower critical consolute temperature, we can use a nanosecond laser T-jump to induce spinodal demixing in the triethylamine/water binary mixture. Using a time-resolved Raman probe, we obtained direct molecular level evidence for liquid restructuring in the early stage (<200 ns) of this spinodal decomposition. From these Raman data, we concluded that in this system the early and intermediate stage spinodal dynamics were apparently over within 1 µs. In addition to Raman spectroscopy, we developed a novel shadowgraphic microscopic time-resolved imaging system to get information about morphological changes during demixing, such as phase domain growth rate. In the microsecond time scale, the characteristic scale of length ( ) of phase domains increased with time following a simple power law ∼ t 0.76((0.04) , while the structure maintained its self-similarity. In this case, the onset of late stage spinodal phase change is several orders of magnitude faster than has been reported for other simple binary mixtures because of the depth of the jump into the two-phase region brought about by our heating pulse.

We propose a label-free method for measuring intracellular temperature using a Raman image of a cell in the OÀH stretching band. Raman spectra of cultured cells and the medium were first measured at various temperatures using a Raman microscope and the intensity ratio of the two regions of the O À H stretching band was calculated. The intensity ratio varies linearly with temperature in both the medium and cells, and the resulting calibration lines allow simultaneous visualization of both intracellular and extracellular temperatures in a label-free manner. We applied this method to the measurement of temperature changes after the introduction of FCCP (carbonyl cyanide-p-trifluoromethoxyphenylhydrazone) in living cells. We observed a temperature rise in the cytoplasm and succeeded in obtaining an image of the change in intracellular temperature after the FCCP treatment.Intracellular temperature is an essential parameter for understanding physiological phenomena, since all physiological functions involve the generation or absorption of heat. Cellular events such as respiration and cell division have now been examined and understood from the viewpoint of temperature change. The mechanism by which cells detect extracellular temperature [1,2] and transmit it to cell temperature homeostasis has also been studied extensively. [3] Sensing of intracellular temperature is applicable for the diagnosis of diseases, elucidation of disease onset mechanisms, and development of new target drugs.In recent years, the measurement of intracellular temperature has become one of the main topics of chemistry and biophysics, triggered in part by the development of various thermosensitive fluorescent dye molecules. [4][5][6][7][8][9][10][11] These dyes exhibit marked changes in their fluorescence intensity and/or fluorescence lifetime in response to the surrounding temperature, which can be used for evaluating and visualizing the temperature inside a cell. For example, temperature differences among cellular components [4] and heat production in the endoplasmic reticulum by Ca ions [7] have been reported using appropriate thermosensitive fluorescent dyes. However, temperature measurements using exogenous fluorescent dyes have disadvantages, such as the need for pretreatment for dye staining and changes in the intracellular environment with the introduction of dyes. Photobleaching of stained dyes increases the uncertainty of the evaluated temperature. It should be noted that the fluorescence intensity (lifetime) of these dyes depends not only on the surrounding temperature but also on other environmental factors such as ion concentration, viscosity and interaction with biological molecules. Therefore, careful attention must be paid to the estimation of intracellular temperature by fluorescence, [12] since the intracellular environment varies depending on the state of the cell. Furthermore, it is difficult to measure the temperature outside the region where fluorescent molecules are localized. The temperature of the surrounding medium cannot...

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A chemically synthesized silver nanowire was used for atomic-resolution STM imaging and tip-enhanced Raman scattering (TERS) spectroscopy, yielding excellent reproducibility. This TERS tip will open a new venue to surface analysis, such as molecular finger printing at nanoscales.

Nanocubes (NCs) were found to be produced by the irradiation of nanosecond UV pulses to an aqueous solution of silver nitrate. The photoproduct was turned to nanospheres (NSs) when irradiated with a certain amount of sodium dodecyl sulfate (SDS). The SDS concentration to alter the photoproduct from NCs to NSs was about ten times lower than the critical micellar concentration (CMC) of SDS, which implies that a single layer of SDS adsorbed on silver surfaces assisted the growth of NSs.