Visible, near‐infrared, and ultraviolet laser‐excited Raman spectroscopy of the monocytes/macrophages (U937) cells

Abstract

Raman spectra of the monocytes were recorded with laser excitation at 532, 785, 830, and 244 nm. The measurements of the Raman spectra of monocytes excited with visible, near-infrared (NIR), and ultraviolet (UV) lasers lad to the following conclusions.(1) The Raman peak pattern of the monocytes can be easily distinguished from those of HeLa and yeast cells; (2) Positions of the Raman peaks of the dried cell are in coincidence with those of the monocytes in a culture cell media. However, the relative intensities of the peaks are changed: the peak centered around 1045 cm −1 is strongly intensified. (3) Raman spectra of the dead monocytes are similar to those of living cells with only one exception: the Raman peak centered around 1004 cm −1 associated with breathing mode of phenylalanine is strongly intensified. The Raman spectra of monocytes excited with 244-nm UV laser were measured on cells in a cell culture medium. A peak centered at 1485 cm −1 dominates the UV Raman spectra of monocytes. The ratio I 1574 /I 1613 for monocytes is found to be around 0.71. This number reflects the ratio between proteins and DNA content inside a cell and it is found to be twice as high as that of E. coli and 5 times as high as that of gram-positive bacteria. Copyright

A micro-Raman spectroscopic investigation of leukemic U-937 cells treated with Crotalaria agatiflora Schweinf and the isolated compound madurensine

“…In accordance with results reported in the literature is was found that for the 514.7 nm laser line the power should be less than 5 mW at the samples to avoid morphological changes in the cells [5] and [6]. The laser power used for the control samples (untreated, DMSO and actinomycin D) was 3 mW, but was reduced to 2 mW for the treated samples due to an increase in sensitivity to the laser light.…”

“…In and phospholipids (∼860 cm −1 ) [5], [6], [7] and [10]. The band centred at ∼783 cm −1 was also previously found in bacteria and HeLa cells and assigned to the C-C breathing vibrations of cytosine, thymine and uracil [7].…”

“…The strongest band in the spectrum of a specific compound cannot always be used as a marker as it may overlap with bands from other molecules and not all the constituents can always be identified through their Raman spectra as some of the bands may be hidden. [6] 783 wn Cytosine, Thymine, Uracil, O-P-O backbone [5], [6] and [10] 830 mn Tyrosine [6] 855 mn Tyrosine [5] 860 wn Phospholipids [9] 920 sb α-helix conformation (C-C stretch of proline ring, valine and protein backbones [7] and [10] Peak position (cm −1 )…”

“…1003 sn Phenylalanine (ring breathing mode) [5], [6] and [10] 1031 mn Cell culture medium [7] 1096 mb DNA (O-P-O-stretch) [7] and [10] 1125 mn C-C stretching [5] 1172 wn Tyrosine, Phenylalanine [5] and [7] 1193-1207 mn Tyrosine, Phenylalanine [6] and [7] 1255-1268 wn Amide III [6] and [7] 1309 wn Adenine [14] 1340 wn C-H deformation, Tryptophan [6] and [7] Polynucleotide chain (DNA purine bases, specially Adenine) [5] and [10] 1361 mn Thymine and adenine [7] 1447 sb CH 2 stretching [6] and [7] CH 2 stretching [6] and [7] 1490 wn Adenine [11] 1555 mn Amide III (C-N stretching mode) [15] 1573-1580 mn Guanine, Adenine ring stretch [8] and [10] 1607 wn Phenylalanine and tyrosine [5] 1657 sb Amide I [16] C C stretch [6] Abbreviations regarding Raman peaks: s, strong; m, medium; w, weak; n, narrow; b, broad.…”

“…It is therefore possible to differentiate between normal and abnormal cells in tissues; for example the detection of cancerous cells. The distribution of chemicals, induced by a change in physical or chemical conditions, can be measured within the cells at sub-cellular levels as recent research focussing on drug interactions with proteins and DNA has illustrated [5].…”