Spectroscopy - Volume 23, issue 3-4

Authors: Porumb, Horea

Article Type: Research Article

Abstract: The AML1-ETO fusion protein is responsible for 15% of the acute myeloid leukaemias due to its interference with transcription activation by E-proteins. The eTAFH region of the AML1-ETO competes for the AD1 domain of E-protein, thereby preventing wild-type transcription activation. The structural details concerning the eTAFH–bound AD1 domain are not known. We have previously shown that the eTAFH–AD1 interaction is strong (Kd =28 nM, H. Porumb, Spectroscopy 22 (2008), 251–260). The secondary structure prediction algorithms are undecided as to the conformation of bound AD1 peptide. Here we demonstrate by circular dichroism that the bound AD1 peptide is fully helical. This …will facilitate modeling of the interaction and launches a challenge as to using synthetic peptides to out compete the eTAFH–E-protein interaction. Show more

Keywords: Circular dichroism, difference spectrum, dissociation constants, fusion protein, helical conformation, leukemia, peptides, secondary structure predictions, transcription activation, transcription repression

DOI: 10.3233/SPE-2009-0390

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 123-129, 2009

Authors: Guo, Yan-Chun | Cao, Shu-Xia | Zong, Xiang-Kun | Liao, Xin-Cheng | Zhao, Yu-Fen

Article Type: Research Article

Abstract: Cyclic dipeptides are relatively simple compounds that can exhibit a great variety of important biological activities. The fragmentation pathways of protonated cyclic dipeptides have been studied by electrospray ionization multistage mass spectrometry (ESI-MSn ). The mass spectra studies of the cyclic dipeptides showed that the cyclic dipeptides with the similar substituents, the side chains of amino acid residues at the diketopiperazine ring, followed the same fragmentation pathway. In the fragmentation spectra of protonated cyclic dipeptides, some characteristic fragment ions were observed and could be used to distinguish the cyclic dipeptides. The hydrogen/deuterium (H/D) exchange experiment and the high-resolution mass spectrometry …(Q-TOF) were used to verify and rationalize the proposed fragmentation pathways. These observations may have some potential applications in the structural elucidation and interpretation of the mass spectra of homologous compounds. Show more

Keywords: Cyclic dipeptides, electrospray ionization mass spectrometry, fragmentation pathway

DOI: 10.3233/SPE-2009-0388

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 131-139, 2009

Authors: Muntean, Cristina M. | Bratu, Ioan | Nalpantidis, Konstantinos | Purcaru, Monica A.P.

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 Zn2+ ions concentration, in the presence of a constant concentration of Na+ ions, respectively. The dependencies of the total half bandwidths and of the global relaxation times, on DNA molecular subgroup structure and on Zn2+ ions concentration, are reported. It is shown that changes in the subpicosecond dynamics of molecular subgroups in ZnDNA complexes can be monitored with Raman spectroscopy. Particularly, the Raman band parameters for the vibrations at 729 cm−1 (dA), 792 cm−1 (dC, …dT and 5′-C–O–P–O–C-3′ network), 1094 cm−1 (DNA backbone PO2 − symmetric stretching), 1377 cm−1 (dA, dT, dC), 1489 cm−1 (the guanine N-7 and adenine rings) and 1581 cm−1 (dG, dA) of ZnDNA complexes, in the presence of Zn2+ ions concentrations that varied between 0 and 250 mM, are presented. In our study, the full widths at half-maximum (FWHM) of the bands in calf-thymus DNA complexes are typically in the wavenumber range from 10 to 50 cm−1 . It can be observed that the molecular relaxation processes studied in this work, have a global relaxation time smaller than 0.94 ps and larger than 0.21 ps. The limit values are characterizing the dA and dG residues, respectively (vibrations at 729 cm−1 and 1489 cm−1 ). Binding of Zn2+ ions to double helical calf-thymus DNA results for some vibrations in smaller global relaxation times and larger bandwidths, respectively, possible as a consequence of the increased interaction of the base moieties with the solvent molecules in unstacked structures. The fastest and the slowest dynamics for different DNA structural subgroups and different Zn2+ ions concentrations, respectively, have been analyzed. A comparison between different time scales of the vibrational energy transfer processes, characterizing the ZnDNA structural subgroups has been given. We have found that metal ion's type and concentration are modulators for the (sub)picosecond dynamics of calf thymus DNA molecular subgroups. Show more

Keywords: Subpicosecond dynamics, calf-thymus DNA, Zn^2+ ions, Raman spectroscopy

DOI: 10.3233/SPE-2009-0384

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 141-154, 2009

Authors: Muntean, Cristina M. | Nalpantidis, Konstantinos | Feldmann, Ingo | Deckert, Volker

Article Type: Research Article

Abstract: The influence of Zn2+ ions on the structure of natural calf thymus DNA was studied by Raman spectroscopy. Measurements were done at room temperature and pH 6.2±0.1, in the presence of 10 mM Na+ , and of Zn2+ in a concentration range varying between 0 and 250 mM, respectively. No condensation of DNA was observed. As judging from the marker bands near 681 cm−1 (dG), 729 cm−1 (dA), 752 cm−1 (dT), and 787 cm−1 (dC, dT) altered nucleoside conformations in these residues are supposed to occur, in different intervals of Zn2+ ions …concentration. Changes in the conformational marker centered around 835 cm−1 , upon Zn2+ binding to DNA, were detected. Binding of zinc(II) ions to the charged phosphate groups of DNA, stabilizing the double helical structure, is indicated in the spectra. We have found that binding of metal ions at N3 of cytosine takes place at zinc(II) concentrations between 150–250 mM and interaction of Zn2+ ions with adenine is observed in a concentration range from 10 to 250 mM. Binding of zinc(II) ions to N7 of guanine and, possibly, in a lesser extent to adenine was also observed as indicated by the Raman marker bands near 1490 and 1581 cm−1 . There is no intensity change of the band at 1668 cm−1 , suggesting no change in their base pairing and no change induced in the structure of water by Zn2+ cations. No evidence for DNA melting was identified. Show more

Keywords: Zn^2+ ions, DNA structure, Raman spectroscopy, difference spectra

DOI: 10.3233/SPE-2009-0382

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 155-163, 2009

Authors: Mysliwiec, Tami H. | Tierno, Anthony F. | Aurentz, David J.

Article Type: Research Article

Abstract: A comparative analysis on cultures from wild-type and sporulation mutants of Bacillus subtilis infected with pseudotemperate spore-converting bacteriophages was performed to discern differences in the chemical functionality of the cellular population. Variations in the cell surface chemistry of B. subtilis cultures were analyzed using attenuated total reflectance (ATR) Fourier transform infrared (FT-IR) spectroscopy of dried sample films on optical plates. Comparison of wild-type and phage infected cultures revealed an increase in the amount of aliphatic ester in the infected populations. Spectral analysis of cultures from bacteriophage infected sporulation mutants, spo0K and spo0J revealed varying levels of ester linkages.

Keywords: Bacillus subtilis, FT-IR spectroscopy, sporulation, cell surface composition, bacteriophages

DOI: 10.3233/SPE-2009-0389

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 165-174, 2009

Authors: Liaqat, Iram

Article Type: Research Article

Abstract: Fourier transform-infrared (FT-IR) spectroscopy has become an important tool for rapid analysis of complex biological samples. The infrared absorbance spectrum could be regarded as a “fingerprint” which is a feature of biochemical substances. The FT-IR spectra of fresh and stored dried samples of six bacterial isolates (Klebsiella sp., Bacillus cereus, Bacillus subtilis, Pseudomonas aeruginosa, Achromobacter xylosoxidans and Achromobacter sp.) were observed by variation in sample preparation. The results indicated that variation in sample preparation did not affect the spectra of isolates. However, less promiment/absence of a small shoulder peak at 1738 cm−1 was evident in fresh dried samples of …Achromobacter sp. and A. xylosoxidans compared to prominent and broad shoulder band at 1724 cm−1 in stored dried samples of these two isolates. In addition to the established KBr pellet technique, attenuated total reflectance (ATR) spectroscopy was used to analyse the spectra of planktonic growth (−80°C liquid cultures) and biofilm growth of six isolates. ATR spectroscopy of −80°C planktonic and biofilm growth showed variation in absorption spectra in fingerprint (1200–900 cm−1 ) region. Two clear absorption bands were prominent in biofilm at 1175 and 1143 cm−1 whereas, one prominent broad band at 1075 cm−1 resulting from the overlapping of two band was noted in planktonic cultures. Biofilm forming capability of the six isolates was also determined by acridine orange staining method. The microscopic analysis of biofilms formed on glass slides revealed the presence of a matrix of exopolysaccharides and microcolonies typical of biofilm architecture. Maximum biofilm formation was observed after 175 h in P. aeruginosa and Klebsiella sp. Show more

Keywords: FT-IR analysis, planktonic, biofilm, DUWL bacterial isolates, acridine orange staining

DOI: 10.3233/SPE-2009-0374

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 175-189, 2009

Authors: Olaru, Alexandra | Borodi, Gh. | Kacsó, Iren | Vasilescu, M. | Bratu, I. | Cozar, O.

Article Type: Research Article

Abstract: The inclusion compounds of lisinopril with β-cyclodextrin, prepared by different methods: kneading, co-precipitation and freeze-drying were investigated by XRD, FTIR, DSC and solid-state NMR techniques. It was established by these methods that the complexation process was successfully. The degree of crystallinity for the product obtained by kneading was also determined. The kneaded product has a certain crystallinity degree, so it is possible that the inclusion process is less effective in this case. In the case of freeze-dried and co-precipitated products only amorphous phase exists, i.e. the complexation was produced with a higher efficiency.

Keywords: FTIR, X-ray powder diffraction, DSC, 13C NMR, molecular modeling, inclusion compounds, β-cyclodextrin

DOI: 10.3233/SPE-2009-0386

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 191-199, 2009

Authors: Córdoba-Díaz, D. | Córdoba-Díaz, M. | Elorza, B.

Article Type: Research Article

Abstract: Isoniazid, one of the most important drugs for the chemotherapy of tuberculosis, can react with some widely used pharmaceutical excipients, like lactose, leading to the formation of hydrazones. This interaction can dramatically modify the oral bioavailability of the drug, what could lead to a failure of the treatment. Some analytical methods, including techniques like HPLC, can be used to quantify this type of products, but all of them are tedious and time-consuming. In this sense, the aim of the present work is to develop a sensitive, rapid and cheap alternative to other published methods. For this reason, two spectrophotometric methods …were developed and validated. In the first one, isoniazid and its lactosyl-hydrazone were measured together. The second one involved a reaction between not bound to lactose isoniazid and 2,3-dichloro-1,4-naphthoquinone. Lactosyl-hydrazone is quantified by comparison of the results obtained from both methods. The linearity is confirmed to be within a range of 1.5–30.0 μg/ml of total isoniazid and 0.5–30.0 μg/ml of “free” isoniazid. Limits of quantification of 1.2 μg/ml and 0.3 μg/ml were obtained for bound and free isoniazid respectively. These results indicated that the here described methods are at least, as sensitive and accurate as the vast majority of the previously published chromatographic methods. This methodology shows a good repeatability (RSD below 2.0%) as well as good accuracy (average recoveries of 100.83% and 99.96% for total and free isoniazid respectively). The results obtained from the assay of isoniazid tablets demonstrated that the proposed method constitutes a clear alternative to chromatographic methods and also to the official titration method. It would be of interest for the routine quality control of oral dosage forms containing isoniazid and lactose and for stability studies. Show more

Keywords: Isoniazid, assay, lactosyl-hydrazone, validation, UV-Vis spectrophotometry, derivatization

DOI: 10.3233/SPE-2009-0385

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 201-208, 2009

Authors: Shao, Xiaodong | Li, Ying | Liu, Yangqin | Song, Zhenghua

Article Type: Research Article

Abstract: Levofloxacin{(–)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid} is a synthetic fluorinated quinolone derivative, having activity against both Gram (+) and Gram (−) bacteria (aerobic and anaerobic) through inhibition of their DNA gyrase. In this paper, a simple flow injection chemiluminescence with luminol–hydrogen peroxide system was described for determining levofloxacin. The chemiluminescence intensity in the presence of levofloxacin was remarkably enhanced compared with that in the absence of it. Under the optimum reaction conditions the chemiluminescence increment produced was proportional to the concentration of levofloxacin in the range of 1.0–700.0 ng ml−1 (R2 =0.9992), with a detection limit of 0.3 ng ml−1 (3σ). At …the flow rate of 2.0 ml min−1 , the whole process including sampling and washing could be completed in 0.5 min offering the sampling efficiency of 120 times h−1 accordingly, and the relative standard deviation (RSD) was less than 3.0% (n=5). The recovery for the levofloxacin samples was from 95.9% to 104.5%. It was satisfactory for the application to determine levofloxacin in pharmaceutical preparations, human urine and serum samples. Show more

Keywords: Levofloxacin, chemiluminescence, flow injection, human serum and urine

DOI: 10.3233/SPE-2009-0379

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 209-216, 2009

Authors: Silveira Jr., Landulfo | Moreira, Leonardo Marmo | Conceição, Viviane G.B. | Casalechi, Heliodora L. | Muñoz, Ingrid S. | da Silva, Fabiano Fernandes | Silva, Marcos Augusto S.R. | de Souza, Renato Aparecido | Pacheco, Marcos Tadeu T.

Article Type: Research Article

Abstract: The objective of this study was to quantify the sucrose amount in commercial lemon-type soft drinks through dispersive Raman spectroscopy, comparing the amount listed in the nutritional table of each product to the predicted by a least-square model, in order to obtain a method for quality assurance applied to soft drinks. A dispersive Raman spectrometer was employed using 830 nm laser and imaging spectrograph coupled to a CCD camera, and a total of 48 samples from four brands of lemon-type soft drinks were analyzed. A calibration curve using sucrose from refined sugar (sugarcane) diluted in spring water was elaborated in …the range between 0 and 15.0 g/100 ml, and a quantification model based on Partial Least Squares (PLS) regression was developed to correlate the Raman spectra and the amount of sucrose in each dilution. Then, the sucrose in each soft drink sample was predicted employing the calibration curve. The mean error of calibration for the PLS method was 0.30 g/100 ml (3.0%). Results indicated that soft drinks samples have predicted sugar content ranging from 8.1 to 10.9 g/100 ml, with an error of the predicted value compared to the nutritional table ranged from 1.1% to 5.5%. Therefore, Raman spectroscopy in association with PLS regression was an effective method for quantifying the sucrose, with small prediction error. Thus, the present work allows to infer auspicious possibilities of Raman spectroscopy application in the quantification of relevant nutritional facts in beverages. Show more

Keywords: Sucrose quantification, soft drinks, industrialized food, Raman spectroscopy, PLS

DOI: 10.3233/SPE-2009-0383

Citation: Spectroscopy, vol. 23, no. 3-4, pp. 217-226, 2009