The interaction of 7 kinds of cephalosporin-medicine with HSA and BSA was studied and compared using fluorescence enhancement and fluorescence quenching method, then deeply analyzed. The binding characteristics of medicine with albumin and usual characteristic constants such as dissociation constant, quenching constant, quenching efficiency, energy-transfer efficiency and the distance between donor and accepter were also deeply analyzed.
Although lithium possesses neuropro- tective functions, the molecular mechanism underly- ing its actions has not been fully elucidated. In the present paper, the effects of lithium chloride on volt- age-dependent potassium currents in the CA1 py- ramidal neurons acutely isolated from rat hippocam- pus were studied using the whole-cell patch-clamp technique. Depolarizing test pulses activated two components of outward potassium currents: a rapidly activating and inactivating component, IA and a de- layed component, IK. Results showed that lithium chloride increased the amplitude of IA in a concentra- tion-dependent manner. Half enhancement concen- tration (EC50) was 22.80±5.45 μmol?L?1. Lithium chloride of 25 μmol?L?1 shifted the steady-state acti- vation curve and inactivation curve of IA to more negative potentials, but mainly affected the activation kinetics. The amplitude and the activation processes of IK were not affected by lithium chloride. The effects of lithium chloride on potassium channel appear to possess neuroprotective properties by Ca2+-lowing effects modulate neuronal excitability by activating IA in rat hippocampal neurons.
Using the whole cell patch clamp technique, the effect of Cu^2＋on transient outward K^＋current （/to） and delayed rectifier K^＋ current （Idr） was studied in acutely isolated rat hippocampal neurons.Ito and Idr were increased when the concentration of Cu^2＋ was lower than 2 × 10^-5 and 10^-5 tool/L, respectively, and increased ratio was decreased with increasing Cu^2＋concentration in the bath solutions. When the concentration continued to increase to 5× 10^-5 and 2 × 10^- 5 mol/L, the currents were hardly changed, while the concentration was more than 10^-4 and 5 × 10^-5 mol/L, the currents were inhibited remarkably. Cu^2＋ （10^-5 mol/L） did not affect the activation and inactivation process of Ito. The activation curve of Idr was shifted toward positive potential, but 10^-5 mol/L Cu^2＋did not affect slope factor. According to these results, it was considered that Cu^2＋at low concentration in the bath solution could promote Ito and Idr while at high concentration could inhibit them, and change of amplitude was different with different membrane voltage. Conclusion was drawn： Cu^2＋may be involved in the pathophysiologic mechanism of diseases with neuropathological components.
In this work, the recognition of DNA including G：T mismatched pairs by the two different structures of [Ru（phen）2hpip]^2＋ was firstly studied with molecular modeling respectively. The results revealed that all of the four chiral isomers of the two structures could recognize the mismatched DNA from the minor groove orientation especially and the interaction was enantioselective and sitespecific. The two left isomers were more preferential than the right ones. Especially, the structure Ⅱ which had much lower energy after interacting with DNA was the advantaged structure. Detailed energy analysis indicated that the steric interaction in the process of the complex inserting base stack determined the recognition results and the electrostatic interaction made an effect to some extent.
The [2] pseudorotaxane of cucurbit[6]uril(CB[6]) with guest molecule 1,6-bis(imidazol-1-yl)hexane dihydrochloride(BIMH-Cl) made pBR322 DNA hydrolyzed efficiently in physiological environment. The cleavage mechanism was proposed that was a cooperation process of the CB[6] molecule and the guest BIMH molecule. In this mechanism, the protonated imidazole might bind DNA via the electrostatic interactions and the CB[6] glycoluril carbonyl oxygen atoms activated a water molecule to attack the phosphorus atom.
