Studies On The Interactions Between Monofunctional Platinum Complexes And Zinc Fluorescence Chemosensor With Proteins

Proteins are the most important biomoleculars that play an important part in life hierarchy. The interactions between small drug molecular and proteins are important for molecular biology investigation. Human serum albumin (HSA) is the most abundant protein constituent of blood plasma and serves as a storage component protein. Human hemoglobin (Hb) is an oxygen-carrying protein.γ-Globin (γ-Gb), one of the most important immunoGlobin in organism, can also bind with drugs and antigen reversibly. In order to reduce the cellular resistance and systemic toxicity of cisplatin, some new platinum complexes have been designed and represented a new class of anticancer agents with distinctive cytotoxic activities and different mechanism of action. However, those new platinum complexes behavior towards proteins are totally unknown. Therefore, studies on the molecular details of such interactions could promote the understanding of platinum drugs in vivo and benefit the design of new platinum antitumor complexes.In this paper, on the basis of the previous research about the interactions of small molecular with proteins, the interactions between a monofunctional Pt (Ⅱ) complex(8-QA-Pt), a naphthalimide platinum complex (PEN-Pt), a dinuclear monofunctional Pt(Ⅱ) complex (Pt2-L) and a trinuclear monfunctional platinum(Ⅱ) complex (Pt3-L) and HSA, Hb and y-Gb were investigated by ultraviolet-visible(UV-Vis), Fourier transform infrared (FT-IR), circular dichroism (CD), and fluorescence spectroscopy, MALDI-TOF and molecular modeling methods. The results showed that the interaction mode of 8-QA-Pt, PEN-Pt, Pt2-L and Pt3-L with proteins were different from that of cisplatin. The associations between HSA (or Hb andγ-Gb) and 8-QA-Pt, PEN-Pt, and Pt3-L are most likely maintained through noncovalent interactions. However, the association between Pt2-L and HSA is most likely maintained through covalent interactions, the associations between Hb (andγ-Gb) are most likely noncovalent interactions. The binding constants, binding sites, and acting forces between 8-QA-Pt, PEN-Pt, Pt2-L and Pt3-L and proteins were discussed on the basis of fluorescence spectroscopic data. Chemical-induced protein denaturation and ligand competition experiments were performed to further identify the HSA primary binding site for 8-QA-Pt, PEN-Pt, Pt2-L and Pt3-L. The results show that 8-QA-Pt enters into the Subdomain IB, PEN-Pt, Pt2-L and Pt3-L partly enter subdomainⅡA. The binding regions and binding modes of the four platinum complexes on Hb andγ-Gb were obtained from the molecular modeling results. The effects of platinum complexes on the conformation of proteins were analyzed using UV-Vis, CD, FT-IR, synchronous fluorescence and three-dimensional fluorescence spectra. Noncovalent interactions with proteins are favorable for the availability of platinum drugs to tumor cells because they do not compromise the DNA binding ability of the drugs during delivery. In this case, proteins may function as an "unselfish" drug carrier and the protein-platinum complex system may serve as a drug reservoir for the therapeutic purpose. These results are beneficial to understanding the antitumor activity and toxicity of the monofunctional platinum (Ⅱ) complexes.Protein selective quantification is of fundamental importance in biochemical, biomedical research and disease treatment. As far as we know, few direct methods of detecting alcohol dehydrogenase (ADH) from Lactobacillus kefir quantity by fluorescence probes have been reported. In the paper, we used NBD-TPEA fluorescence probe to fluorescence detect ADH. The effects of human serum albumin, bovine serum albumin, lysozyme, trypsin,γ-Globin, carbonic anhydrase, glutamic dehydrogenase on the fluorescence of NBD-TPEA (of NBD-TPEA-Zn) were also studied. The results show that ADH enhances the fluorescence emission intensity of NBD-TPEA (of NBD-TPEA-Zn). The spectroscopic and thermodynamic data show that the interaction is a spontaneous process and the hydrogen bond, hydrophobic and ionic interactions are the primary contributors to the interaction between ADH and NBD-TPEA (or NBD-TPEA-Zn). The number of Trp in proteins is not the major reason of enhancing the fluorescence intensity of NBD-TPEA (or NBD-TPEA-Zn). The binding regions and binding modes of the NBD-TPEA (or NBD-TPEA-Zn) on proteins were also obtained from the molecular modeling method. The results show that the hydrogen bond between Tyr155 and NBD is mainly the reason of the fluorescence enhancing of NBD-TPEA (or NBD-TPEA-Zn). The remarkable fluorescence properties of NBD-TPEA help to extend the development of fluorescence probes for investigating enzymes in a biological context.