维生素B6的合成工艺改进

＂噁唑法＂是目前工业上合成维生素B6的通用方法,本文对其关键步骤—芳构化进行改进,以2-正丙基-4,7-二氢-1,3-二氧七环、4-甲基-5-乙氧基噁唑为原料,经Diels-Alder、芳构化和水解三步反应制得维生素B6,总收率达81.6%。该工艺操作简单、能耗低,缩短了生产周期,适于工业化应用。     

The HP1a disordered C terminus and chromo shadow domain cooperate to select target peptide partners

Drosophila melanogaster heterochromatin protein 1a (HP1a) is essential for compacted heterochromatin structure and the associated gene silencing. Its chromo shadow domain (CSD) is well known for binding to peptides that contain a PXVXL motif. Heterochromatin protein 2 (HP2) is a non-histone chromosomal protein that associates with HP1a in the pericentric heterochromatin, telomeres, and the fourth chromosome. Using NMR spectroscopy, fluorescence polarization, and site-directed mutagenesis, we identified an LCVKI motif in HP2 that binds to the HP1a CSD. The binding affinity of the HP2 fragment is approximately two orders of magnitude higher than that of peptides from PIWI (with a PRVKV motif), AF10 (with a PLVVL motif), or CG15356 (with LYPLL and LSIVA motifs). To delineate differential interactions of the HP1a CSD, we characterized its structure, backbone dynamics, and dimerization constant. We found that the dimerization constant is bracketed by the affinities of HP2 and PIWI, which dock to the same HP1a homodimer surface. This suggests that HP2, but not PIWI, interaction can drive the homodimerization of HP1a. Interestingly, the integrity of the disordered C-terminal extension (CTE) of HP1a is essential for discriminatory binding, whereas swapping the PXVXL motifs does not confer specificity. Serine phosphorylation at the peptide binding surface of the CSD is thought to regulate heterochromatin assembly. Glutamic acid substitution at these sites destabilizes HP1a dimers, but improves the interaction with both binding partners. Our studies underscore the importance of CSD dimerization and cooperation with the CTE in forming distinct complexes of HP1a.     

Spacer effects on in vivo properties of DOTA-conjugated dimeric [Tyr3]octreotate peptides synthesized by a "Cu(I)-click" and "sulfo-click" ligation method

We report on the SSTR2-binding properties of a series of four dimeric [Tyr3]octreotate analogues with different spacer lengths (nine, 19, 41, and 57 atoms) between the peptides. Two analogues (9 and 57 atoms) were selected as precursors for the design, synthesis, and biological evaluation of DOTA-conjugated dimeric [Tyr3]octreotate analogues for tumor targeting. These compounds were synthesized by using a two-stage click ligation procedure: a Cu(I) -catalyzed 1,3-dipolar cycloaddition ("copper-click" reaction) and a thio acid/sulfonyl azide amidation ("sulfo-click" reaction). The IC(50) values of these DOTA-conjugated [Tyr3]octreotate analogues were comparable, and internalization studies showed that the nine-atom (111) In-DOTA-labeled [Tyr3]octreotate dimer had rapid and high receptor binding. Biodistribution studies with BALB/c nude mice bearing subcutaneous AR42J tumors showed that the (111) In-labeled [Tyr3]octreotate dimer (nine atoms) had a high tumor uptake at 1 h p.i. (38.8 ± 8.3 % ID g(-1) ), and excellent tumor retention at 4 h p.i. (40.9 ± 2.5 % ID g(-1) ). However, the introduction of the extended hydrophilic 57 atoms spacer led to rapid clearance from the circulation; this limited tumor accumulation of the radiotracer (21.4 ± 4.9 % ID g(-1) at 1 h p.i.). These findings provide important insight on dimerization and spacer effects on the in vivo properties of DOTA-conjugated [Tyr3]octreotate dimers.     

Simulation of the C5 Aliphatic Petroleum Resins Production Process

Abstract

Petroleum resins are used widely in many industries. They are solvable in most of aromatic and aliphatic solvents. There are different grades of petroleum resins from dark and viscose liquids to bright and hard ones. They are used mostly in the adherent industry as binder. In this article the production process of aliphatic petroleum resin is simulated based on the process described in Stanford Research Institute International. Regarding the lack of kinetic information about the dimerization process of cylcopentadiene as well as the polymerization process, suitable kinetic rate equations are derived from experimental tests done by Shakeri (2002) Shakeri, M. 2002. Experimental and theoretical study of the effective parameters on petroleum resins cationic polymerization kinetics Tehran: Amirkabir University of Technology. Stanford Research Institute. M.Sc. Thesis [Google Scholar] and used in the simulation. Simulation outputs are in good accordance with the given data in SRI.     

(R/S)‐BINOL‐α‐Phosphoryloxy Enecarbamate‐Mediated and (R/S)‐Titanium(IV) BINOLates‐Catalyzed Enantioselective Intramolecular Heck/Aza‐Diels–Alder Cycloaddition (IHADA): An Expedient Methodology

An (R/S)‐titanium(IV) BINOLate‐catalyzed highly enantioselective intramolecular Heck/aza‐Diels–Alder cycloaddition (IHADA) cascade was developed to prepare tetrahydropyridoindoles (tHPs) and octahydropyrazinopyridoindoles (oHPPs) from in situ generated (R/S)‐BINOL α‐phosphoryloxy carbamate ( αPPC2 ) in one pot. Chiral cooperativity between (R/S)‐αPPC2 and (R/S)‐titanium(IV) BINOLate was observed and successfully utilized for the construction of various tHPs (7 examples) and oHPPs (17 examples).

     

MTBE装置反应精馏塔工艺操作条件的探讨及优化

从反应精馏的工艺操作入手 ,针对操作过程中出现的反应精馏塔内二聚反应的发生及控制、反应精馏塔进料中甲醇含量的探讨及优化、反应精馏塔进料温度的调节及优化、反应精馏塔釜所带碳四及控制、反应精馏塔内二甲醚副反应的发生及控制等问题 ,进行探讨、分析并进行优化     

The Hydrophilic Loop of Arabidopsis PIN1 Auxin Efflux Carrier Harbors Hallmarks of an Intrinsically Disordered Protein

Much of plant development depends on cell-to-cell redistribution of the plant hormone auxin, which is facilitated by the plasma membrane (PM) localized PIN FORMED (PIN) proteins. Auxin export activity, developmental roles, subcellular trafficking, and polarity of PINs have been well studied, but their structure remains elusive besides a rough outline that they contain two groups of 5 alpha-helices connected by a large hydrophilic loop (HL). Here, we focus on the PIN1 HL as we could produce it in sufficient quantities for biochemical investigations to provide insights into its secondary structure. Circular dichroism (CD) studies revealed its nature as an intrinsically disordered protein (IDP), manifested by the increase of structure content upon thermal melting. Consistent with IDPs serving as interaction platforms, PIN1 loops homodimerize. PIN1 HL cytoplasmic overexpression in Arabidopsis disrupts early endocytic trafficking of PIN1 and PIN2 and causes defects in the cotyledon vasculature formation. In summary, we demonstrate that PIN1 HL has an intrinsically disordered nature, which must be considered to gain further structural insights. Some secondary structures may form transiently during pairing with known and yet-to-be-discovered interactors.     

化学反应和气相色谱法联合测定含烯汽油中共轭二烯烃含量

建立了利用共轭二烯烃与马来酸酐的Ｄｉｅｌｓ－Ａｌｄｅｒ特性反应和１ｍ×１．７ｍｍ（ｉｄ）非极性固定液ＳＥ－３０填充柱气相色谱法联合分析含烯汽油中的共轭二烯烃含量的方法。该柱能用低碳数的正构烷烃如正十一烷作内标物，内标物与油样组份分离很好，色谱分析一次４ｍｉｎ，油样的相对标准偏差为１．７％。在一定的化学反应条件下，用Ｉ２和ＡｌＣｌ３作催化剂，当Ｉ２、ＡｌＣｌ３与共轭二烯烃的物质的量比分别为０．８×１０－５和（１～２）×１０－３时，异戊二烯有最高的转化率分别为６８．５１％和９８．１８％，回流反应装置的挥发损失率为０．２８％。     

Regulation of Immune Activation by Optical Control of TLR1/2 Heterodimerization

The activation of toll-like receptors (TLRs) plays important roles in the immune response. The ability to control the activities of TLRs could be usable as a switch for immune response. Here we have rationally designed and synthesized a photoswitchable Pam₃CSK₄ derivative— P10 —to control the activation of TLR1/2. The ground-state trans- P10 was able to stimulate and activate antigen-presenting cells (APCs) by promoting TLR1/2 heterodimerization. However, cis- P10 , derived from UV irradiation of trans- P10 , reduced the activities of APCs by impeding the TLR1/2 heterodimerization. In the absence of UV radiation, the cis- P10 slowly returned to its ground trans state, restoring the activities of the APCs stimulation. Our results indicated that optical control of TLR1/2 heterodimerization mediated by the photoswitchable P10 offers the potential to regulate immune activation and inflammation.     

Pressure-Induced Dimerization of Metmyoglobin

Pressure treatment at 7.5 kbar of solutions of metmyoglobin led, as shown by electrophoresis and chromatographic analysis, to the formation of spectrally similar monomeric and dimeric forms. The dimer was formed in the pH range 6–10, though maximum formation was around the isoelectric point (pH 6.9). At acid pH no dimer or higher oligomers formed. In sodium chloride (0.5 to 2M), at neutral pH lower concentrations of dimer formed than in its absence. The dimer was stabilized by SDS-labile linkages and had a slightly lower thermal denaturation temperature than the monomer. If similar changes occur with other proteins, then food quality may be modified by pressure treatments.