稀土环己烷酸配合物合成及振动光谱研究

The solid state complexes of trivalent lanthanid, yttrium and scandium with cyclohexane carboxylic acid have been isolated and characterized by IR and Raman spectroscopy. It was found that there are only chelated carboxylate groups in the scandium complex and that there are the chelated, bridged and chelate-bridged carboxylate groups in other rare earth complexes. The former is a mononuclear complex and the latter is a polynuclear polymer. The RE—O coordinate bonds possess the characters of convalent ionic bond.     

Construction of a Novel Expression System in <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> and its Application for 1,3-Propanediol Production

A novel expression system of Klebsiella pneumoniae was developed in order to improve 1,3-propanediol (1,3-PD) production using a K. pneumoniae–Escherichia coli shuttle vector pET28a consisting of the kanamycin-resistance gene promoter Pkan. The recombinant plasmid pETPkan-cat carrying the chloramphenicol acetyltransferase gene cat as selectable marker was constructed to test the availability of the promoter Pkan in K. pneumoniae. The results showed that the chloramphenicol acetyltransferase was apparently expressed in K. pneumoniae, and the recombinant strain had a high-level resistance to chloramphenicol, suggesting that the promoter Pkan was efficient in K. pneumoniae. Then, the expression system was applied to the expression of 1,3-PD oxidoreductase in K. pneumoniae. The enzyme was over-expressed, and the recombinant K. pneumoniae showed a nearly 3.0-fold decrease in peak level of the intermediary metabolite 3-hydroxypropionaldehyde and an increase of 16.5% in yield of 1,3-PD with respect to the wild-type strain. From these results, the first reported expression system has paved the way for improvement of 1,3-PD production and will be available and efficient for other heterologous gene expression in K. pneumoniae.     

Ultrafast hydration dynamics in the lipidic cubic phase: Discrete water structures in nanochannels

We report here our studies of hydration dynamics of confined water in aqueous nanochannels (approximately 50 A) of the lipidic cubic phase. By systematically anchoring the hydrocarbon tails of a series of tryptophan-alkyl ester probes into the lipid bilayer, we mapped out with femtosecond resolution the profile of water motions across the nanochannel. Three distinct time scales were observed, revealing discrete channel water structures. The interfacial water at the lipid surface is well-ordered, and the relaxation dynamics occurs in approximately 100-150 ps. These dynamically rigid water molecules are crucial for global structural stability of lipid bilayers and for stabilization of anchored biomolecules in membranes. The adjacent water layers near the lipid interface are hydrogen-bonded networks and the dynamical relaxation takes 10-15 ps. This quasi-bound water motion, similar to the typical protein surface hydration relaxation, facilitates conformation flexibility for biological recognition and function. The water near the channel center is bulklike, and the dynamics is ultrafast in less than 1 ps. These water molecules freely transport biomolecules near the channel center. The corresponding orientational relaxation at these three typical locations is well correlated with the hydration dynamics and local dynamic rigidity. These results reveal unique water structures and dynamical motions in nanoconfinements, which is critical to the understanding of nanoscopic biological activities and nanomaterial properties.     

蛋氨酸稀土配合物构象的^13CNMR研究

本文测量了在7种不同稀土离子(La~(3 )、Pr~(3 )、Nd~(3 )、Dy~(3 )、Ho~(3 )、Er~(3 )和Tm~(3 ))的水溶液中蛋氨酸~(13)C稀土诱导位移。利用稀土诱导位移对蛋氨酸稀土配合物构象的模拟结果表明,蛋氨酸通过离子化的羧基与稀土离子配位,Ln~(3 )—O长度为2.7A在配合物中,蛋氨酸以伸展状态存在,C_0-C_α-C_β-C_γ和C_α-C_β-C_γ-S成反式构象,C_β-C_γ-S-C_δ成旁式构象。根据稀土诱导位移方法建立的构象模型符合~1H邻位质子偶合常数和~(13)C顺磁弛豫速率的结果。     

Spectra and structure of small ring compounds. LIX

The Raman (3200 to 10 cm^–1) and far infrared (380 to 60 cm^–1) spectra of gaseous fluorocyclobutane,c-C₄H₇F, have been recorded. A series of Q-branches observed in both of these spectra beginning at 166 cm^–1 with successive transitions falling to lower frequencies have been assigned to the ring puckering vibrations of both the low energy equatorial and high energy axial conformers. These data have been fit to an asymmetric potential function of the form:V (cm^–1)=(1.76±0.05)10³X+(4.88±0.28)10⁴X²+(2.12 ±0.16)10³ exp(–5.66±0.41)10X² with a reduced mass function ofg ₄₄= 0.00386–0.00295X+0.03485X²+0.1228X³ +0.3459X⁴, whereX is the ring puckering coordinate. Utilizing this potential, the difference between the puckering angles for the two conformers was calculated to be 4° with the equatorial conformer having the larger value of 28°. This potential function is consistent with an energy difference between the equatorial and axial forms of 447 cm^–1 (1.28 kcal/mol) and a barrier to ring inversion from the equatorial to the axial conformation of 713 cm^–1 (2.04 kcal/mol). Experimental values for the enthalpy difference between the two conformers have been determined for both the liquid (400±30 c^–1) and gas (413±43 cm^–1) from investigations of the Raman spectra at variable temperatures. The conformational stability, enthalpy difference, structural parameters, and fundamental vibrational frequencies, which have been determined experimentally, are compared to those obtained from ab initio Hartree-Fock calculations employing the 3-21G, 6-31 G^*, and 6-31 G^** basis sets.For part LVIII, seeStruct. Chem. 1991,2, 195.Taken in part from the thesis of M. J. Lee, which has been submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree, May 1991.     

几种医用卟啉的核磁共振谱

通常对于带侧链羧基的卟啉,是以其酯的形式在CDCl₃溶液中测量核磁共振谱的。与之相反,本文直接提供血卟啉、原卟啉和卟啉C在酸性溶液中的质子谱和碳-13谱。这种途径有利于这些医用卟啉的结构鉴定和生产监控。     

水溶液中L-半胱氨酸与稀土离子作用的NMR研究

本文测定了在八种不同稀土离子存在下(La、Pr、Nd、Eu、Dy、Ho、Er和Tm)L-半胱氨酸的¹H和¹³C稀土诱导位移。络合物生成位移和诱导位移的pH依赖关系说明L-半胱氨酸通过离子化的羧基与稀土离子配位,络合物稳定常数说明巯基的存在有利于氨基酸的配位作用。对偶极位移模拟结果表明,在半胱氨酸稀土络合物中,羧基和巯基成旁式,羧基以单齿形式与稀土离子配位。     

时间分辨荧光(TRF)测量及其应用

荧光寿命和时间分辨荧光光谱是荧光光谱学的两个重要参量,随着探测技术的发展而得到更多的应用.本文简述TRF测量技术及其在化学、物理、生化和医学方面的应用,以期促进TRF在国内的广泛利用.     

The Nonlinear Enhancement Effect of Sputered Ag-atoms With FeCl+ Bombardment

Measurements of the angular distributions and yields of atoms sputtered from Ag target by bombardment with FeCl⁺,⁵⁶Fe⁺ and ³⁵Cl⁺ are reported.Large enhancement occurs in the measured Ag atom yield for FeCl⁺ projectile in comparison with the sum of the sputtering yields for ⁵⁶Fe⁺ and ³⁵Cl⁺ bombardment at same impact velocities.The enhanecment can be explained by a model of the thermal spike-evaporation plus surface topography effect.     

铀原子多色三光子共振电离谱研究

利用Ｎｄ：ＹＡＧ二倍频激光同步泵浦的脉冲染料激光系统、原子束装置、飞行时间质谱和Ｂｏｘｃａｒ技术测量了＾２３８Ｕ的多色三光子共振电离谱。研究了电场对铀原子第一激发态的影响。解决了如何确定三角三光子共振电离谱图中所含的单色,双色和三色共振电离峰的问题。