Fourier transform Raman spectroscopy was employed for structural analysis of triacylglycerols and edible oils. Raman spectra sensitively reflected structural changes in oils. Even slight structural ...fluctuation between triacylglycerols and free fatty acids led to obvious differences in Raman bands as shown by C–O–C stretching from 800 to 1000 cm−1 and the band at 1742 cm−1. Structural difference in geometric isomers was easily distinguished as proved by C = C stretching at 1655 cm−1 (cis) shifting to 1668 cm−1 (trans) and by =C–H in-plane bending at 1266 cm−1 in cis disappearing in the trans isomer. Raman intensity at 1266, 1302, and 1655 cm−1 changed concomitantly with the change of double-bond content in oils. It showed that FT-Raman was capable of precisly reflecting the content of double bonds in oils. A linear correlation with high consistency between the Raman intensity ratio (v1655/v1444) and the iodine value was obtained for commercial oils. Based on the results, FT-Raman spectroscopy proved itself a simple and rapid technique for oil analysis since each measurement could be directly completed in 3 min without any sample modifications.
FT-Raman spectroscopy was employed to explore the structural changes of lens proteins in Tilapia lenses affected by dietary vitamin E supplementation. The microenvironment of major lens constituents ...including thiol compounds, tyrosine, and tryptophan exhibited significant change upon vitamin E treatment, while the protein secondary structure was unaltered and remained as an antiparallel β-pleated sheet. These structures in the cortex were more susceptible to vitamin E treatment than in the nucleus. Protein sulfhydryls in the cortex were predominantly in the reduced form, while in the nucleus both the oxidized and reduced forms coexisted as evidenced by the vibrational mode of SH (2580
cm
−1) and SS (507
cm
−1), respectively. Both tyrosine and tryptophan were more accessible to water or more exposed in the cortex than in the nucleus. The symmetrically inverse response of vitamin E, between Raman intensity of 1090
cm
−1 and the glutathione level, was consistent with a close relationship of GSH and vitamin E in defending the lens from external insults.
A feeding trial was conducted to evaluate the effects of dietary vitamin E contents on the growth, ascorbate induced iron-catalyzed lipid peroxidation in post-mortem muscle and liver tissue, and ...Raman spectral changes in lens of juvenile hybrid tilapia (
Oreochromis
niloticus×
O.
aureus). Experimental fish were fed practical diets supplemented with 0, 50, 100, 200, 450 and 700 mg α-tocopheryl acetate/kg diet for 14 weeks. There was no significant difference in weight gain, feed conversion ratio and protein efficiency ratio among fish fed test diets (
P>0.05). Protein content of fish fed diet containing the lowest vitamin E level was the lowest (
P<0.05) among all groups. No difference was found in other body constituents among test fish (
P>0.05). The thiobarbituric acid-reactive substances produced by iron-catalyzed lipid peroxidation in muscle and liver tissue of fish fed the diet without α-tocopheryl acetate supplementation were significantly (
P<0.05) greater than those from fish fed diets containing higher levels of α-tocopheryl acetate. Dietary vitamin E supplementation increased the antioxidant capability of tilapia tissues against lipid peroxidation. Further, dietary vitamin E supplementation also influenced the lens cortical membrane structure of tilapia.
Bacillus kaustophilus leucine aminopeptidase (bkLAP) was sensitive to oxidative damage by hydrogen peroxide. To improve its oxidative stability, the oxidation-sensitive methionine residues in the ...enzyme were replaced with leucine by site-directed mutagenesis. The variants, each with an apparent molecular mass of approximately 54 kDa, were overexpressed in recombinant Escherichia coli M15 cells and purified to homogeneity by nickel-chelate chromatography. The specific activity for M282L, M285L, M289L and M321L decreased by more than 43%, while M400L, M426L, M445L, and M485L showed 191, 79, 313, and 103%, respectively, higher activity than the wild-type enzyme. Although the mutations did not cause significant changes in the K^sub m^ value, more than 67.8% increase in the value of k^sub cat^/K^sub m^ was observed in the M400L, M426L, M445L and M485L. In the presence of 50 mM H^sub 2^O^sub 2^, most variants were more stable with respect to the wild-type enzyme, indicating that the oxidative stability of the enzyme can be improved by engineering the methionine residues.PUBLICATION ABSTRACT
Serine/threonine kinase Akt plays a central role in the regulation of cell survival and proliferation. Hence, the search for Akt specific inhibitors constitutes an attractive strategy for anticancer ...therapy. We have previously demonstrated that the proto-oncogene TCL1 coactivates Akt upon binding to its Plekstrin Homology Domain, and we proposed a model for the structure of the complex TCL1:Akt2-PHD. This model led to the rational design of Akt-in, a peptide inhibitor spanning the A beta -strand of human TCL1 that binds Akt2 PH domain and inhibits the kinase activation. In the present report, we used NMR spectroscopy to determine the 3D structure of the peptide free in solution and bound to Akt2-PHD. NMR chemical shift mapping was used to determine the imprint of Akt-in on the PH domain; whereas peptide Ala- scanning revealed which peptide residues were involved in the interaction. Together with the solution structure of Akt2-PHD, these results allowed us to dock Akt-in on the PH domain. The docked complex suggests that while Akt-in binds Akt2-PHD in a region overlapping the binding site of TCL1, its mode of interaction is markedly different. Moreover, the affinity was disappointingly low, contrary to that published previously. Besides providing a description of the interaction between Akt-in an Akt2 PH domain, the present work brings additional clues on the putative peptide mode of action. Instead of behaving as an analog of PtdIns, as previously suggested, Akt-in might act as an "allosteric" inhibitor, maintaining the full-length kinase in its "closed" inactive conformation, rather than disturbing the membrane anchorage of its "open" active conformation.
Modified ionomer films were prepared and their antimicrobial abilities were investigated. The anhydride linkage of the modified films formed by the reaction of acid/base-treated films with benzoyl ...chloride was confirmed by the specific anhydride absorption (-CO-O-CO-, 1807 cm-1 and 1741 cm-1; -C-O-C-, 1009 cm-1) in Fourier-transform infrared (FT-IR) spectra. Release of benzoic acid from the modified ionomer films either immersed in buffer solutions or buried between two layers of potato dextrose agar (PDA) media was detected by high performance liquid chromatography (HPLC). This suggested the feasibility of using the modified ionomer films as antimicrobial food packaging material. The base-treated modified films were better as antimicrobial food packaging materials than the acid-treated ones because of the higher amount of benzoic acid released from the former than from the later. The antimicrobial ability of modified ionomer films was further demonstrated by inhibition of the growth of Penicillium sp. and Aspergillus niger. The modified ionomer films exhibited high efficiency in the inhibition of microbial growth.
Roasted peanut kernels were ground into meal and subjected to supercritical carbon dioxide (SC-CO2) defatting using a semicontinuous process (SCP). The amount of oil recovered from meal increased ...with increased pressures and temperatures from 3000 to 8000 psi and from 40 to 80 °C. When SCP and an intermittently depressurized process (IDP) were applied at 8000 psi and 80 °C, the amount of oil recovered from roasted, deskinned kernels was less than that recovered from roasted peanut meals. When IDP was done at 80 °C and various CO2 pressures, the amount of oil recovered decreased with a pressure reduction from 8000 to 4000 psi and increased with a further reduction to 2000 psi. The breaking intensity of kernels partially defatted by IDP was significantly less than that of full-fat kernels. The fatty acid composition of SCP-extracted oils from peanut meal differed insignificantly, while that of IDP-extracted oils from peanut kernels differed slightly depending on extraction conditions. Infrared and Raman spectra of the oils extracted from kernels using SCP or IDP did not vary significantly. Keywords: Peanut; defatting; SFE; fatty acid composition
We present in this report a detailed structural study of calf gamma-crystallins both in the solid state and in solution by the newly developed technique of near-infrared (IR) Fourier transform ...(FT)-Raman spectroscopy as well as by the conventional Raman method. In comparison with conventional laser Raman spectroscopy, the near-IR FT-Raman approach exhibits several attractive features such as fluorescence rejection capability, frequency accuracy, and the FT's multiplex and throughput advantages. These distinct characteristics combined form the basis for the particular suitability of FT-Raman in crystallin structural analysis and elucidation. We have thus obtained evidence in support of the view that native calf gamma-II crystallin does not contain a disulfide bond either in the lyophilized state or in solution. In addition, conventional Raman spectra are examined for all four gamma-crystallin fractions. gamma-S, gamma-II, gamma-III, and gamma-IV, and the results indicate a high degree of structural similarities among them. It is also found that the sulfhydryl groups in all four gamma-crystallins are highly resistant to air oxidation and are capable of maintaining their reduced state during isolation in the absence of added reductants or such chelating agents as EDTA.
PDF
