Max Diem

Infrared Spectroscopy of Human Tissue. V. Infrared Spectroscopic Studies of Myeloid Leukemia (ML-1) Cells at Different Phases of the Cell Cycle

Infrared spectra of myeloid leukemia (ML-1) cells are reported for cells derived from an asynchronous, exponentially growing culture, as well as for cells that were fractionated according to their stage within the cell division cycle. The observed results suggest that the cells DNA is detectable by infrared spectroscopy mainly when the cell is in the S phase, during the replication of DNA. In the G1 and G2 phases, the DNA is so tightly packed in the nucleus that it appears opaque to infrared radiation. Consequently, the nucleic acid spectral contributions in the G1 and G2 phases would be mostly that of cytoplasmic RNA. These results suggest that infrared spectral changes observed earlier between normal and abnormal cells may have been due to different distributions of cells within the stages of the cell division cycle.

Infrared spectroscopy of human tissue. I. Differentiation and maturation of epithelial cells in the human cervix

Infrared spectral results for the different epithelial layers of human cervical squamous tissue are reported. The layers, representing different cellular maturation stages, exhibit quite different spectral patterns. Thus, infrared spectroscopy presents a powerful tool to monitor cell maturation and differentiation. Furthermore, a detailed understanding of the spectra of the individual layers of tissue permit a proper interpretation of the state of health of cells exfoliated from such tissue. Part II of this series describes the use of the spectral information presented here to interpret the infrared spectra of exfoliated cells.

FT-IR spectroscopic investigations of single cells on the subcellular level

Abstract Spatially resolved Fourier transform infrared (FT-IR) spectroscopy of single oral mucosa cells and FT-IR spectroscopy of liver cell fractions produced by sucrose density gradient centrifugation have been applied to acquire structural information of cell organelles. For the spatially resolved measurements, mapping as well as mercury cadmium telluride (MCT) focal plane array (FPA) detector techniques were utilized. Surprisingly, infrared spectra of distinct subcellular structures differed only slightly. Aside from a minor intensity increase of the symmetric and the antisymmetric PO2− bands in the spectra of the nucleus, all normalized infrared spectra exhibited a remarkably high degree of similarity. Considering the fact that more than 98% of the DNA and significant amounts of the RNA are concentrated in the nucleus which occupies in oral mucosa cells only 5% of the total cell volume, these findings may be interpreted as a proof of the hypothesis that DNA is partially “invisible” in infrared spectroscopy. The finding of comparably small IR spectroscopic differences between cell organelles was confirmed by measurements on cell fractions specifically enriched by sucrose density gradient centrifugation. Besides variations of the non-specific overall protein:lipid ratio, the IR spectra of the distinct pellets exhibited only slightly differing absorbance values for the PO2− bands. As found for the nuclei by spatially resolved microspectrometry, IR spectra of the nuclear pellet displayed minor increased absorbances of the PO2− band at 1083xa0cm−1 when compared to spectra of the mitochondrial or microsomal pellets.

Infrared Spectroscopy of Human Cells and Tissue. VIII. Strategies for Analysis of Infrared Tissue Mapping Data and Applications to Liver Tissue

Experimental and computational methods of infrared microspectroscopy (IRI-MSP) and infrared spectral mapping (ISM) are presented. These methods are subsequently applied to the analysis of cirrhotic liver tissue. The sensitivity of infrared spectral mapping toward spectral changes caused by disease will be demonstrated. In addition, the excellent agreement between ISM data and histopathological information will be discussed.

Infrared Spectroscopy of Human Tissue. II. A Comparative Study of Spectra of Biopsies of Cervical Squamous Epithelium and of Exfoliated Cervical Cells

A comparison of infrared absorption spectra obtained from the different layers of squamous epithelium from the human cervix, and infrared spectra obtained from exfoliated cervical cells, is presented. Infrared spectroscopy has been shown (in part I of this series) to be a sensitive tool to monitor maturation and differentiation of human cervical cells; therefore, this spectroscopic technique provides new insights into the composition and state of health of exfoliated cells.

Infrared Spectroscopy of Human Cells and Tissue: Detection of Disease

An objective method for the analysis of tissue section is described that uses the chemical composition of the tissue, rather than cell morphology, as an indicator for the state of health of the cells in the tissue. The chemical composition of cells and tissue, and small variations therein, are determined by an objective, quantitative spectral measurement carried out in the infrared spectral region. This method does not utilize any stains or chemical treatment of the sample, but uses an inherent optical property of all materials. The spectral information is converted to false color images by unsupervised mathematical methods. The false color maps reveal the same anatomical features of the tissue that can be confirmed using a variety of common histopathological procedures, and may be used to differentiate between normal and diseased areas of the tissue.

Infrared spectroscopy of cultured cells: II. Spectra of exponentially growing, serum-deprived and confluent cells

Abstract Infrared microspectroscopy (IR-MSP) is a spectroscopic technique that is able to monitor cell differentiation, maturation, and progression through the cell cycle. In order to establish this technique as a diagnostic tool in cellular biology and pharmacology, spectral patterns indicative of the stages of cell proliferation need to be collected. Thus, we have embarked on a systematic study of the effects of cell division and cell cycle progression on the infrared spectra of cells. In this paper, we modulated the level of cell proliferation and report the effects of this modulation on the observed infrared spectra of the cells. The modulation was achieved by serum deprivation of the growing cells, or by having the cell culture reach confluence. The progression of the cells through the cell cycle was monitored via flow cytometry, and correlated with changes in IR-MSP features in the spectral signatures due to nucleic acids (1250–1000xa0cm −1 ). In both these experiments, the majority of cells are in the G0/G1 stages, 3 with only a small percentage in the S and G2 phases. Nevertheless, spectral differences could be observed and interpreted in terms of the spectral changes of cellular DNA.

Vibrational circular dichroism in amino acids and peptides. 3. Solution- and solid-phase spectra of alanine and serine

Vibrational circular dichroism (VCD) in solution and solid phases is reported for alanine and serine in vibrational nmodes involving hydrogen and deuterium stretching motions. The quality of the solution-phase VCD spectra was significantly nenhanced by on-line computer averaging techniques. Solid-phase spectra were obtained as mulls in halocarbon oil and this nmethod promises to be a useful new sampling technique in VCD spectroscopy. VCD signals in the solid phase are considerablq nlarger than the solution spectra for the same molecules. The increased magnitude is attributed to such effects as conformational nuniformity, local ordering, and crqstal lattice interactions between molecules. A neb vibrational assignment of solutionphase nalanine in the carbon-hydrogen stretching region is presented as determined from the solid-phase Ranian spectra of alaninc-do nand alanine-C*-dl. The basic features of the observed VCD spectra of alanine and serine are discussed in terms of their nconstituent normal modes and the chiral perturbation of locally symmetric groups.

Design and Performance of an Optimized Dispersive Infrared Dichrograph

The design of a spectrometer for the observation of infrared vibrational circular dichroism (VCD) is reported. This instrument utilizes f/4 aperture, a minimum of optical elements, and a new electronic data acquisition method to improve the sensitivity of previous dispersive units. The instrument described exhibits a level of sensitivity comparable to that of present Fourier transform (FT) VCD instruments, while avoiding some problems which still persist in FT-VCD.

Strategies for the computation of infrared CD and absorption spectra of biological molecules: ribonucleic acids

We report observed and computed infrared (vibrational) circular dichroism spectra of a number of polyribonucleic acids in aqueous solutions in the 1600-1750 cm-1 spectral region, in which C = O and some nucleotide base ring stretching vibrations occur. The experimental data are compared with results calculated using different levels of sophistication within the exciton approach. We find that observed band shapes are generally well reproduced by these models, particularly if care is taken to determine the direction of the vibrational dipole transition moments accurately.