| Hemoglobin (Hb) is a physiologically important globular protein. It has a molecular weight of64.5kDa. The Hb molecule contains four globin chains, of which two are α-chains and two are β-chains. Hb is a kind of respiratory protein of vertebrate erythrocytes. It’s important in oxygen transport, H2O2dispersion and electron transfer to all organs and parts of the body. Moreover, Hb is often selected as a model protein for the understanding of its structure because the structure of protein relates to its biological function nearly. The surfactant contained in the detergents in modern life may permeate into body by food chain and skin, which would interact with protein, change the structure of protein and induce the sickness, or disturb the drug absorption of the body. Recently, more and more attentions are paid to the effects of surfactant on the health of people. Surfactant-protein interactions are very common in the fields of medicine, chemistry, biology, and so on. Surfactant aggregates, such as micelles, microemulsions, and lyotropic liquid crystals, have a great deal of application in the field, such as chemistry, material, biology, bionics, and so on. And what should be especially noted is that microemulsions and lamellar liquid crystals can be used to simulate some biological systems, and hence, the research on the surfactant-protein interaction carried out in microemulsions and lamellar liquid crystals can offer useful information on life and medicine.In this paper, we have studied the interaction of Hb with different kinds of surfactants by UV-vis absorption spectra, fluorescence spectra, CD spectra, electrical conductivity, negative staining-TEM, freeze-fractured-TEM, ITC and1HNMR methods. We try to expatiate upon the influence of surfactant molecular organized assemblies on the above interaction, and discuss the influence of UV-irradiation. The paper includes the following three parts: 1. The Interaction of Hemoglobin with Hexadecyltrimethylammonium BromideSurfactant is widely used in life science and biotechnology as anti-pathogenic microorganism medicine due to its ability to permeate into biomembrane. Hb can be transformed from oxyhemoglobin (oxyHb) to methemoglobin (metHb) and hemichrome, while hemichrome accumulation in red cells is typical of some blood diseases and aging of the erythrocyte. Thus, the interrelated study of the conversion between metHb and hemichrome will be worthful not only in theory but also in practice. In this chapter, the change of CTAB cmc with or without Hb was studied by electrical conductivity method, the structure of Hb in different CTAB concentration was studied by UV-vis spectra, and micrographs were obtained with a transmission electronic microscope by freeze-fractured technique, and then the interaction in different pH value were discussed. The results show that, Hb can increase the cmc of CTAB, decrease the diffusion coefficient (D) of CTAB. NMR studies show that the line width of CTAB proton signals is increased obviously and the chemical shifts (8) of all the protons in CTAB molecules are upfield shift with the addition of Hb; on the other hand, CTAB monomer can convert methemoglobin (metHb) to hemichrome, and CTAB molecular assemblies, such as micelle, microemulsion and lamellar liquid crystal, can induce heme monomer to leave the hydrophobic cavity of Hb; with the increase of CTAB concentration, the concentration of metHb decreases in water and in the buffer solution with pH value being8, while it increases in the buffer solution with pH value being4. As it can be seen, the addition of Hb can change the aggregation of CTAB, and the CTAB and pH value of solution can control the transform the Hb structure.2. The Interaction between Hemoglobin with SDS and DTABThe interactions between two surfactants with a same hydrophobic tail and a different charged head group in structure with hemoglobin are investigated by UV-vis absorption spectra, fluorescence spectra methods, and discuss the interaction in different pH values, which should be helpful to expatiate upon the influence of Hb on different types of surfactant aggregations, and understand the change of the structure of Hb by surfactant more thoroughly. The results show that Hb can increase the cmc of SDS and DTAB. NMR studies show that the line width of SDS proton signals is increased obviously and the chemical shifts (8) of all the protons in SDS molecules are upfield shift with the addition of Hb. ITC studies show that the observed enthalpies (△Hobs) of SDS decrease gradually and even to a negative value, while the△Hobs of DTAB increase slowly first and then decrease gradually; on the other hand, SDS and DTAB can convert metHb to hemichrome, and then induce heme monomer to leave the hydrophobic cavity of Hb. When change the pH values of solution, Hb is positively charged in acidic medium (pH=5.8), which can make the interaction between SDS and Hb stronger because of the electrostatic interaction, while when pH=7.0and8.0, the positive charges on Hb surface are decreased and more negative charges appear. Thus, the interaction between SDS and Hb is weakened. On the contrary, the opposite interaction between DTAB and Hb can be derived. As it can be shown, the interaction mechanism between surfactants with different charged head group and Hb is differently, and the control of pH value can adjust the interaction.3. The photostabilization of Hb in surfactant micelle and microemulsionThe study of Hb is mostly performed in homogeneous system in recent year, while the homogeneous system is different from biology environment. Thus, the study can not reflect the biochemistry and biophysics character of Hb. Micelles and microemulsions can be regarded as the ideal model biomembranes to study as bionic model. Furthermore, with the pollution of environment, the earth aerosphere becomes thinner and the ultraviolet radiation of sun hurt the people more obviously. The damnification mechanism of ultraviolet to protein of body brings the attention of people. This chapter studies the photophysics and photochemistry of Hb using the micelle and microemulsion as a model of biological systems. The results show that UV-irradiation can convert metHb to hemichrome, and then induce heme monomer to leave the hydrophobic cavity of Hb. The UV-irradiation make the absorption intensity of Soret band of Hb decrease, while the addition of surfactant can reduce the decrease speed of absorption intensity, which shows that surfactant can protect Hb in UV-irradiation. If comparing the protection function of different surfactants to Hb, the effect can be seen in the order:cationic surfactant CTAB> anionic surfactant SDS> Triton X-100, and the formation of micelle may benefit to the photo-stability of Hb, while the different structure of microemulsion have a different effect on the photo-stability of Hb. According to the study of the photo-stability of heme, it can be seen that the essence of protection function of surfactant to Hb is the protection function of heme. In conclusion, these studies whould be helpful to expatiate upon the influence of ultraviolet radiation to the protein of body, and be worthy in accelerating the development of life science.4. Interaction between small biological molecule and Hb modulated by surfactantsThe interactions of proteins with drugs have received a great deal of interest for many years due to their application in a great variety of industrial, biological, and cosmetic systems. Their surprising capacity to reversibly bind a large variety of drugs results in their prevailing role in drug pharmacokinetics and pharmacodynamics. Hence, it is important to characterize the binding sites of protein by studying its interaction with drugs. To the best of our knowledge, few investigations have been conducted to study the interaction between morin and chrysin with Hb, such as the binding mechanism, binding site, binding distance and so on. However, these parameters are very important in the interaction of morin and chrysin to Hb, when morin and chrysin are used as a drug. Hence, investigating the interaction between morin and chrysin with Hb will help in understanding the drug’s toxicity and its distribution in the organism. And then the influences of surfactants to the interaction have been study. |
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