FRACTALS OF HYBRID ORBITALS AND THEIR APPLICATIONS IN THE ENZYME MODELS

An enzyme is a kind of protein with catalytic activity and long chain,and its structure and shape are determined by the hybridized state of atomic orbital.The fractal dimension(D_f)is closely related to the hybridization,e.g.D_f=2ln2/ln[2(1+α/(1-α))]for the spa type, where a denotes the fraction of the s orbital in the hybridized molecular orbital.This relationship and the five fractal theorems introduced by the present paper play an important role in the investigations of the model of imitative enzyme.

Study of enzyme models and imitation of enzyme action

This paper deals With some of the mh activities in our group in recent years in the areas of artificial enzyme models with porphyrin, steroids and calixarenes as building units. Wherein two kinds of novel enzym models of steroids-metalloporphyrin and calixarene-metalloporphyrin have been synthesized and employed as cytochrome P450 modeling. These biomimetic systems exhibited high catalytic selectivity and efficiency in oxidation of olefins (styrene, cyclohexene) and hydrocarbonds (isopropylbenzene) as well as phenol (p-benzenediol). The excellent catalytic property stems mainly from hydrophobic effect and multiple recognition sites that lead to cooperative catalysis.

STEROID-BISPORPHYRIN. A NOVEL PORPHYRIN DIMER AS ENZYME MODEL

In the present communcation a novel steroid-bisporphyrin model compound has been synthesized. The configuration of which is also presented.

ConformationsofCytochromeP─450Modelsby1Dand2DNMR

Conformations of organic compounds in solution relate to their physical and chemical properties and biological activities. Two calix arene porphyrin derivatives were synthesized as models of cytochrome p 450 monooxygenase. The conformations of the models were determined using DQFCOSY (double quantum filter correlation spectroscopy), NOESY (nuclear overhauser effect spectroscopy), etc. The calix arene part showed cone conformation in the compound 1 and showed mainly partial cone conformation in the compound 2. The calix arene and the porphyrin were situated side by side in the compound 1, and above and below each other in the compound 2.

Mechanistic Investigations into the Catalytic Mode of a Dehydratase Complex Involved in the Biosynthesis of Lantibiotic Cacaoidin

Dehydration of serine/threonine residues necessitates the activity of a dehydratase enzyme(domain)during the biosynthesis of RiPP.Recently,it was reported that dehydration in the thioviridamide pathway relies on a distinct dehydratase complex that showcases the activities of a phosphotransferase TvaC for serine/threonine phosphorylation and a lyase TvaD for subsequent phosphate elimination.Herein,we report that dehydration reactions in the pathway of lantibiotic cacaoidin involves a similar dehydratase complex,CaoK/CaoY.Remarkably,this dehydratase complex exhibits flexible enzymatic activity and tolerates significant variations in its substrate peptide sequence.By binding with the leader peptide(LP)sequence of precursor peptide CaoA,the dehydration reactions proceed in a directional manner from the C-terminus of the core peptide(CP)to the N-terminus,and C-terminally truncated variants of CP are acceptable.We show that fusing CaoK to CaoY in a 1:1 molar ratio enables the resulting enzyme CaoYK to exert enhanced dehydration activity.CaoK binds with the LP to improve its own solubility and to ensure the phosphate transfer activity,while CaoY functions in a manner independently of LP.This work advances our understanding of the dehydration process during cacaoidin formation,and provides useful enzymes and methods for the studies of the rapidly emerging RiPPs.

Steroid-bismetalloporphyrin as enzyme model of cytochrome P-450 monooxygenase

The model compounds of androgenic steroid-bismetalloporphyrins 3a—3d and androgenic monometalloporphyrins 2a—2d have been synthesized. Catalytic study in two-phase condition on epoxidation of styrene under the catalysis of model catalysts shows that the catalytic performances of steroid-bismetalloporphyrin is superior to steroid-metalloporphyrin and the corresponding simple metalloporphyrin. The excellent catalytic property of steriod-bismetalloporphyrin can be rationalized as the hydrophobic action of steroid framework and the cooperative action of two metalloporphyrins in catalysis.

A novel manganese(Ⅲ)-peroxo complex bearing a proline-derived pentadentate aminobenzimidazole ligand

Manganese(Ⅲ)-peroxo complexes are invoked as key intermediates in the enzymatic cycles of Mncontaining enzymes, and the synthesis of reactive manganese(Ⅲ)-peroxo complexes with rationally designed ligand has been of great interest in the communities of bioinorganic and biomimetic chemistry.Herein, we designed a novel pentadentate aminobenzimidazole ligand and obtained its manganese(Ⅱ)complex, which was successfully applied in the synthesis of a reactive manganese(Ⅲ)-peroxo complex by treatment with hydrogen peroxide in the presence of triethylamine. The manganese(Ⅲ)-peroxo complex was well characterized with various spectroscopic techniques, including ultraviolet-visible(UV-vis)spectrophotometry, coldspray ionization time-of-flight mass spectrometry(CSI-TOF MS), and continuous wave electron paramagnetic resonance(CW-EPR) spectroscopy. Besides, its reactivity in aldehyde deformylation was investigated, demonstrating second-order kinetics in the reaction with 2-phenylpropionaldehyde and affording acetophenone as the sole product.