Spectroscopy - Volume 21, issue 4

Authors: Yu, Peiqiang

Article Type: Research Article

Abstract: Synchrotron-based Fourier transform infrared microspectroscopy (S-FTIR) has been developed as a rapid, direct, non-destructive, bioanalytical technique. This technique takes advantage of synchrotron light brightness and small effective source size and is capable of exploring the molecular chemical features and make-up within microstructures of a biological tissue without destruction of inherent structures at ultra-spatial resolutions within cellular dimension. To date there has been very little application of this advanced synchrotron technique to the study of plant and animal tissues' inherent structure at a cellular or subcellular level. In this article, a novel approach was introduced to show the potential of the …newly developed, advanced synchrotron-based analytical technology, which can be used to reveal molecular structural-chemical features of various plant and animal tissues. Show more

Keywords: Synchrotron, infrared microspectroscopy, imaging, molecular chemistry, plant, animal

Citation: Spectroscopy, vol. 21, no. 4, pp. 183-192, 2007

Authors: Muntean, Cristina M. | Bratu, Ioan

Article Type: Research Article

Abstract: In this paper the Raman total half bandwidths of calf-thymus DNA vibrations have been measured as a function of pH, monovalent and divalent cations' type and concentration. The dependence of different band parameters on DNA molecular subgroup structure, on pH and on Na+ , Ca2+ and Mg2+ ions concentrations, respectively, are reported. It is shown that changes in (sub)picosecond dynamics of molecular subgroups in calf-thymus DNA can be monitored with confocal Raman microspectroscopy. The half bandwidths and the global relaxation times for the vibrations at 728 cm−1 (dA), 785 cm−1 (dC), 1094 cm−1 (PO2 …− ), 1377 cm−1 (dA, dG, dT, dC), 1488 cm−1 (dG, dA) and 1580 cm−1 (dG, dA) of calf-thymus DNA are presented. The full-widths at half-height (FWHH) of the bands in calf-thymus DNA are typically in the wavenumber range from 7.4 to 31 cm−1 . The bandwidths in the Raman spectra are sensitive to a dynamics active on a time scale from 0.34 to 1.44 ps. Low pH-induced melting of double helical structure in calf-thymus DNA results for some bands in shorter global relaxation times, as a consequence of the increased interaction of the base moieties with the solvent molecules. The molecular dynamics characterizing the 785, 1094, 1377 and 1580 cm−1 vibrations, is faster in the case of high divalent cations DNA sample (pH 7), as compared to the respective low divalent cations DNA sample (pH 7), for both Ca2+ and Mg2+ ions. The vibrational energy transfer process of the guanine band at 1488 cm−1 is slower for the high salt DNA sample, pH 7 as compared to the corresponding low salt DNA sample, pH 7, for both Ca2+ and Mg2+ . Molecular dynamics characterizing the vibration at 1488 cm−1 is faster for DNA sample at high Na+ ions (pH 7), as compared to the DNA sample at low Na+ ions (pH 7). As far as the CaDNA and MgDNA complexes are concerned (pH 7), the global relaxation times of some base vibrations decrease for the case of magnesium ions, as compared to the case of the same concentration of calcium ions. The different ionic radius of the two types of metal cations (0.72 Å for Mg and 0.99 Å for Ca) were considered in explaining these results. Molecular relaxation processes of DNA subgroups, upon lowering the pH, in the presence of Na+ , Ca2+ and Mg2+ ions are presented. Particularly, at low Ca2+ concentration, upon lowering the pH, the molecular dynamics of DNA subgroups corresponding to vibrations at 728, 1376, 1488 and 1580 cm−1 is much faster, probably due to the denaturation process of the double helical DNA. Show more

Keywords: (Sub)picosecond dynamics, calf-thymus DNA, monovalent and divalent cations, pH, Raman microspectroscopy

Citation: Spectroscopy, vol. 21, no. 4, pp. 193-204, 2007

Authors: Maqbool, M. | Ahmad, Iftikhar

Article Type: Research Article

Abstract: Intense ultraviolet emission from gadolinium doped amorphous aluminum nitride thin films deposited on Si (111) substrate is studied with cathodoluminescence and photoluminescence. The purpose of the study is to find the merits or demerits of gadolinium ions if added intentionally or present as unintentionally added impurity in tissue compensators or collimators in radiation treatment planning. These films are deposited by reactive sputtering at liquid nitrogen temperature, using 100–200 W RF power, 5–8 mTorr nitrogen, and a metal target of aluminum and gadolinium. Thermal annealing was performed at a temperature of 900°C. A sharp ultraviolet peak is observed at 314 nm …corresponding to 6 P7/2 →8 S7/2 transition. The ultraviolet emission is intense enough to harm human tissues if it is used as tissue compensator. Intense ultraviolet emission is observable even if the concentration of gadolinium is less than 0.5%. Thermal annealing further enhances the intensity of ultraviolet emission, indicating that longer use of such tissue compensators or collimators containing gadolinium ions will provide more harm and damage to human body. Radiation Therapists, Oncologist and industries making tissue compensators and collimators are strongly suggested to test any compensator or collimator for gadolinium impurities. Show more

Keywords: Gadolinium, cathodoluminescence, photoluminescence, ultraviolet emission, tissue damage, tissue compensator

Citation: Spectroscopy, vol. 21, no. 4, pp. 205-210, 2007

Authors: Zheng, Yiwu | Lai, Xuxin | Ipsen, Henrik | Larsen, Jørgen Nedergaard | Løwenstein, Henning | Søndergaard, Ib | Jacobsen, Susanne

Article Type: Research Article

Abstract: Structural integrity of antigens upon adsorption and release is not only important for investigating vaccine immunogenicity, but also for the epitope specificity of the resulting immune response and hence therapeutic efficacy. Moreover, the structural information is also important for understanding the mechanism of how adjuvants can enhance the immune response. However, little is known about an antigen's structure when it is adsorbed on and subsequently released from aluminium adjuvants. In this study, the structures of two protein antigens, bovine serum albumin and β-lactoglobulin, were investigated using Fourier transform infrared–attenuated total reflection (FTIR–ATR) spectroscopy. The secondary structures of both model antigens …change when adsorbed to aluminium hydroxide. The structural perturbation depends on the amount of adsorbed protein. Maximal adsorption gives a more native-like structure. This may indicate that protein is adsorbed in different manners depending on the concentration. The adsorbed antigens are released using phosphate buffer pH 7.4 (PB). The recovery is approximate 80% after 40 min in the presence of PB. The recovery curves of both proteins also indicate two different adsorption modes. FTIR–ATR and circular dichroism (CD) spectroscopy yield similar results suggesting that the adsorbed antigens refold to their native-like state after release. Show more

Keywords: Antigen, secondary structure, FTIR–ATR, aluminium hydroxide

Citation: Spectroscopy, vol. 21, no. 4, pp. 211-226, 2007

Authors: Bayarı, Sevgi Haman | Utku, Haluk | Ikemoto, Yuka | Celasun, Bülent | Kömürcü, Mahmut | Atik, Aziz

Article Type: Research Article

Abstract: Avascular necrosis (osteonecrosis) is a disease that results from the temporary or permanent loss of blood supply to the bone. Synchrotron FT-IR microspectroscopy has been used to study the changes in mineral and matrix content of necrotic bone. FT-IR spectroscopic analysis revealed that in necrotic bone the relative mineral/matrix ratio decreased. Spectroscopic differences were observed between normal and necrotic bones. The noticeable differences may have important implications for analyzing and evaluating death bone.

Keywords: Avascular necrosis, necrotic bone, synchrotron, FT-IR microspectroscopy

Citation: Spectroscopy, vol. 21, no. 4, pp. 227-234, 2007

Authors: Zhou, J.H. | Wu, X.H. | Yang, C. | Gu, X.T. | Zhou, L. | Song, K.X. | Feng, Y.Y. | Shen, J.

Article Type: Research Article

Abstract: Experimental results of UV-visible absorption spectroscopy and fluorescence spectroscopy indicate that hypocrellin A, which has been studied in photodynamic therapy, can interact with the surface of myoglobin through hydrophobic forces, and form a complex. Based on the Stern–Volmer equation, the quenching constants of the process can be calculated to be 4.81×1012 L mol−1 s−1 (t=25°C) and 4.54×1012 L mol−1 s−1 (t=42°C) respectively, and the binding constant is 5.53×104 M−1 (t=25°C), while the binding sites is 0.94 (t=25°C). In addition, Electron paramagnetic resonance and fluorescence spectroscopic analysis suggests that that the quenching mechanism …of the interaction process occurs through the electron transfer between hypocrellin A and myoglobin. Show more

Keywords: Hypocrellin A, myoglobin, UV-visible absorption spectroscopy, fluorescence spectroscopy, electron paramagnetic resonance spectroscopy

Citation: Spectroscopy, vol. 21, no. 4, pp. 235-243, 2007