Secondary Structure Of Hemoglobin Research Articles

Effect of the bile salt surfactant sodium taurodeoxycholate on the physicochemical properties of a mixed system of Galangin-Hemoglobin and Baicalein-Hemoglobin

A surfactant that can regulate interactions between drugs and proteins would be a material that is medicinally excipient and biomimetic that has great theoretical and practical significance. Thus, the interactions and binding mechanism of flavonoid isomers [galangin (Gal) and baicalein (Bai)] and hemoglobin (HB) under physiological conditions were studied using multispectral methods, dynamic light scattering (DLS), and antioxidant, antibacterial, and cytotoxicity assay techniques. Then, one bile salt biosurfactant [sodium taurodeoxycholate (NaTDC)] was added to explore the effects that it has on the interactions and functional properties of Gal-HB and Bai-HB systems. For Gal-HB and Bai-HB systems, the fluorescence quenching mechanism of flavonoids on HB was always a static quenching. Driven mainly by electrostatic forces, the conformation of HB became loose, and its secondary structure changed as a result of the presence of Gal or Bai. Three adjacent hydroxyl groups on the A-ring had an obvious binding interaction with protein, and thus, Bai had a stronger binding affinity with HB than Gal, and this has a greater influence on the secondary structure of HB than Gal. In the presence of NaTDC, the binding constants were significantly increased for both systems; also, the antioxidant character, stability, solubility, antibacterial properties, and cancer cell growth inhibition of flavonoids were improved to a certain extent. These findings help us understand the pharmacokinetics, pharmacodynamic function and mechanism of Gal and Bai at the molecular level and also lay the scientific foundation for the design of flavonoid-based foods and drugs.

Contrasting spectroscopic response of human hemoglobin in presence of graphene oxides and its reduced form: Comparative approach with carbon quantum dots.

Recently, a considerable amount of research is being directed towards study of graphene oxide (GO) and its reduced form (RGO) since their exposed functional groups make them better candidates in nanobiotechnolgy. In order to assess their biocompatibility, the nature of interactions between Human Hemoglobin (HHb) and GO/RGO are monitored since a comparative spectroscopic approach towards understanding their nature of interactions has not been investigated previously. UV-vis spectroscopy reveals hyperchromicity for HHb-GO system and hypochromicity for HHb-RGO system in the region of absorption of tryptophan/tyrosine residues. Notably, although steady-state fluorescence static quenching of HHb for GO and enhancement of fluorescence for RGO is noticed, but average fluorescence-lifetime is remaining unchanged in presence of GO/RGO. Calorimetric data illustrates three-site and five-site binding model to be the best-fit model for GO and RGO respectively. Also, synchronous fluorescence quenching corresponding to alterations in microenvironment of tryptophan/ tyrosine residues is observed only in presence of GO. Likewise FTIR spectroscopy elucidates involvement of both amide I and amide II bond of HHb backbone through H-bonding interaction only for GO. Furthermore RLS spectra demonstrate an increase and a decrease in signal for GO and RGO respectively. Surprisingly, secondary structure of HHb is maintained upon interaction with both GO/RGO, as revealed by CD spectroscopy, thus supporting their potential application in biological microenvironment. Thus it appears that the spectroscopic properties of HHb upon interaction with GO is altered upon its reduction to RGO. Furthermore the role of HHb as good candidate for bimolecular interaction has been highlighted.

Age–related and atherosclerosis–related erythropathy in ApoE/LDLR−/− mice

In this work we applied a multimodal approach to define the age– and atherosclerosis–related biochemical and functional alterations in red blood cells (RBCs) in ApoE/LDLR−/− mice. Our results revealed that age–related changes in RBCs, such as decreases in RBC deformability and mean height, were more pronounced in ApoE/LDLR−/− mice than in age–matched control mice (C57BL/6J). The decreases in phospholipid content and level of lipid unsaturation were accompanied by an increase in cholesterol esters and esterified lipids in RBC membranes in aged C57BL/6J mice. The age–related decrease in the phospholipid content was more pronounced in ApoE/LDLR−/− mice. In contrast, the increase in the total lipid content in RBC membranes occurred only in ApoE/LDLR−/− mice with advanced atherosclerosis. The age–related alterations also included a decrease in the ratio of turns to α–helices in the secondary structure of hemoglobin (Hb) inside intact RBCs. On the other hand, an increase in the ratio of unordered conformations to α–helices of Hb was observed only in ApoE/LDLR−/− mice and occurred already at the age of 5–weeks. This was related to hypercholesterolemia and resulted in an increased oxygen-carrying capacity. In conclusion, progressive mechanical and functional alterations of RBCs in aged ApoE/LDLR−/− mice were more pronounced than in age–matched C57BL/6J mice. Although, several biochemical changes in RBCs in aged ApoE/LDLR−/− mice recapitulated age–dependent changes observed in control mice, some biochemical features of RBC membranes attributed to hypercholesterolemia were distinct and could contribute to the accelerated deterioration of RBC function in ApoE/LDLR−/− mice.

Effects of the Addition of Sodium Chloride to a Tetrameric Protein in Water Solution During Exposure to High Frequency Electromagnetic Field

Background:Previous studies have shown that exposure to high frequency electromagnetic fields induces alterations in simple organic systems such as proteins in bidistilled water solution.Objective:The aim of this study was to test the shielding action of sodium chloride in bidistilled water solution against exposure to a high frequency electromagnetic field, in order to evaluate if the addition of NaCl in proteins aqueous solution can be considered a valuable bioprotector against electromagnetic fields.Method:Samples of 250 μl of different hemoglobin aqueous solutions, in the absence or presence of sodium-chloride, were exposed for 3 hours to an electromagnetic field at 1750 MHz at a power density around 1 W/m2emitted by an operational mobile phone. Fourier Transform Infrared Spectroscopy was used to study the effects of exposure on the secondary structure of hemoglobin also in the presence of sodium-chloride.Results:Spectral analysis evidenced that significant increase in intensity of the Amide I and II vibration bands in hemoglobin bidistilled water solution occurred after exposure to the electromagnetic field. This result can be due to the increase of dipole moment of the protein due to the alignment of α-helix towards the direction of the field. In contrast, no appreciable change was observed in hemoglobin in sodium-chloride water solution after exposure.Conclusion:This protective effect of sodium-chloride can be explained by the orientation of water molecules due to the strong electric field around each ion that reduces the possibility of rotation of the protein in response to an applied electromagnetic field.

A carbon dots based fluorescent probe for selective and sensitive detection of hemoglobin

In this work, we presented a rapid, selective and highly sensitive probe for hemoglobin (HGB) based on the quenched fluorescence of carbon dots (CDs). The CDs were synthesized by microwave irradiation technique in one pot according to our previous report. The fluorescence of CDs was effectively quenched by HGB due to the ground state complex formation between CDs and HGB. A number of key factors including the amount of CDs, pH value of phosphate buffer solution, the concentration of salt solution, and the reaction time those influenced the analytical performance of CDs in HGB determination were investigated thoroughly. Under the experimental conditions, the fluorescence intensity of CDs was inversely proportional to the concentration of HGB ranging from 1 to 4000nM with a correlation coefficient of 0.9987. The limit of detection for HGB was as low as 0.12nM. Some common substances, including other heme proteins, did not affect HGB determination significantly. The method was utilized to detect HGB in human urine and human blood samples with satisfactory results. The static quenching mechanism of this system was further investigated by UV–vis absorption spectrometry and time-resolved fluorescence spectrometry. The α-helix content of HGB decreased and the secondary structure of HGB was rearranged after the interaction with CDs.

Fourier Self-Deconvolution Analysis of β-Sheet Contents in the Amide I Region of Hemoglobin Aqueous Solutions under Exposure to 900 MHz Microwaves and Bioprotective Effectiveness of Sugar and Salt Solutions

Spectroscopic Fourier self-deconvolution analysis was used to investigate β-sheet features in the secondary structure of hemoglobin under mobile phone microwaves at 900 MHz. To this end, four samples of hemoglobin in bidistilled water, sucrose, trehalose, and sodium chloride aqueous solutions were exposed for up to 4 hr to 900 MHz microwaves at an average H-field intensity of 42 mA/m. Quantitative spectral analyses highlighted significant increases in β-sheet contents in the Amide I region of hemoglobin samples in bidistilled water solution, but no appreciable change was observed in hemoglobin samples in sucrose, trehalose, and sodium chloride solutions. These results led us to conclude that mobile phone microwaves can denaturate hemoglobin in bidistilled water solution whereas sucrose, trehalose, and sodium chloride solutions produce a protective effect against microwaves, preserving the protein from unfolding.

Comparative studies of interactions of hemoglobin with single-chain and with gemini surfactants

The interactions of hemoglobin with glutamic acid-based gemini surfactants (L 2G 2C n ) and with n-dodecylammonium α-glutamate (GDA) have been studied with isothermal titration microcalorimetry, fluorescence spectroscopy, UV–vis spectroscopy, and circular dichroism. The results indicate that GDA monomer can make the hemoglobin denatured, and that when the concentration of GDA is higher than cmc, heme monomer is released from the hydrophobic cavity of hemoglobin. On the other hand, L 2G 2C n surfactants can also interact with hemoglobin. Compared with GDA, L 2G 2C n have a much smaller binding ability with hemoglobin, and the circular dichroism spectra results show that the secondary structure of hemoglobin is possibly stabilized by a small amount of L 2G 2C n , which may generate hydrophobic linkages between the nonpolar residues of hemoglobin. However, with further addition of L 2G 2C n , the secondary structure of hemoglobin is unfolded, and the percentage of α helix in hemoglobin molecule is decreased. In addition, the L 2G 2C n surfactant with a longer spacer can reduce the denaturing degree of hemoglobin.

Preservation of Trehalose-Loaded Red Blood Cells by Lyophilization

A method for freeze-drying red blood cells (RBCs) while maintaining high viability has important implications in blood transfusion and clinical medicine. RBCs loaded with the disaccharide trehalose can be freeze-dried in a formulation of hydroxyethyl starch, human serum albumin, and trehalose to residual water contents between 2% and 4%. Rehydration of the freeze-dried erythrocytes resulted in about 55% survival, based on the percent hemolysis. The surviving cells can synthesize ATP and 2,3-DPG, have preserved morphology, and have low levels of methemoglobin. Biochemical analyses showed that the activities of superoxide dismutase and catalase in freezedried RBCs are very similar to those of fresh RBCs. Secondary structure of hemoglobin was similar to that of fresh hemoglobin. Trehalose loading is required to achieve the stabilization of hemoglobin. These data provide an important step towards a stable erythrocyte product, which can prove invaluable for transfusion and clinical applications.

Infrared spectroscopic identification of beta-thalassemia.

The aim of this study was to investigate the potential of infrared (IR) spectroscopy as a fast and reagent-free adjunct tool in the diagnosis and screening of beta-thalassemia. Blood was obtained from 56 patients with beta-thalassemia major, 1 patient with hemoglobin H disease, and 35 age-matched controls. Hemolysates of blood samples were centrifuged to remove stroma. IR absorption spectra were recorded for duplicate films dried from 5 microL of hemolysate. Differentiation between the two groups of hemoglobin spectra was by two statistical methods: an unsupervised cluster analysis and a supervised linear discriminant analysis (LDA). The IR spectra revealed changes in the secondary structure of hemoglobin from beta-thalassemia patients compared with that from controls, in particular, a decreased alpha-helix content, an increased content of parallel and antiparallel beta-sheets, and changes in the tyrosine ring absorption band. The hemoglobin from beta-thalassemia patients also showed an increase in the intensity of the IR bands from the cysteine -SH groups. The unsupervised cluster analysis, statistically separating spectra into different groups according to subtle IR spectral differences, allowed separation of control hemoglobin from beta-thalassemia hemoglobin spectra, based mainly on differences in protein secondary structure. The supervised LDA method provided 100% classification accuracy for the training set and 98% accuracy for the validation set in partitioning control and beta-thalassemia samples. IR spectroscopy holds promise in the clinical diagnosis and screening of beta-thalassemia.

A physico-chemical study of the interaction between human hemoglobin and benzene

The interaction between human hemoglobin and benzene produced difference spectra (in the visible region) changing with time. In addition to these changes we studied the dependence of the interaction on temperature and on concentration of the two components. The interaction of hemoglobin and benzene was also followed by means of CD spectra. These spectra in the region 200-260 nm demonstrate that the secondary structure of hemoglobin was not affected by the interaction. By contrast, in the region 270-300 nm the CD spectra show a change in the quaternary structure of hemoglobin, which goes from the R state to the T state, and after a period it returns to the original state.