人红细胞摄入Cd2+离子的动力学和机理

不同Cd²⁺离子浓度引起的人红细胞相对溶血率及临界溶血浓度CH⁰已经测定,CH⁰=2.5×10^-4mol·L^-1。Cd²⁺跨膜进入人红细胞遵从一级动力学过程,其一级速率常数为1.2×10^-2h^-1。阴离子通道抑制剂DIDS及K⁺,Na⁺-ATPase抑制剂均可部分抑制人红细胞摄入Cd相似文献   

Analysis of tryptophan at nmoll(-1) level based on the fluorescence enhancement of terbium-gadolinium-tryptophan-sodium dodecyl benzene sulfonate system

It is found that Tb³⁺ can react with tryptophan (Trp) and sodium dodecyl benzene sulfonate (SDBS), and emits the intrinsic fluoresence of Tb³⁺. The fluorescence intensity can be enhanced by La³⁺, Gd³⁺, Lu³⁺, Sc³⁺ and Y³⁺, among which Gd³⁺ has the greatest enhancement. This is a new co-luminescence system. The studies indicate that in the Tb-Gd-Trp-SDBS system, there is both Tb-Trp-SDBS and Gd-Trp-SDBS complexes, and they aggregate together and form a large congeries. The fluorescence enhancement of the Tb-Gd-Trp-SDBS system is considered to originate from intramolecular and intermolecular energy transfers, and the energy-insulating sheath effect of Gd-Trp-SDBS complex.Under the optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of Trp in the range from 4×10⁻⁸ to 4×10⁻⁵ mol l⁻¹. The detection limit is 10⁻⁹ mol l⁻¹. The proposed method is one of the most sensitive fluoremetries of Trp.     

CI study of rovibrational dependence of nuclear quadrupole coupling constants of all isotopic variants of OH+ in the X3Σ− state

The ¹⁷O and ²H quadrupole coupling constants of rovibrational levels of ¹⁷O¹H⁺, ¹⁷O²H⁺, and ¹⁶O²H⁺ in their X³Σ⁻ state have been calculated from molecular wave functions that explicitly describe nuclear motion. The ¹⁷O quadrupole coupling is predicted to be strong and its vibrational dependence differs from that known for other nuclei A in the first-row hydrides AH or AH⁺. The deuterium coupling in ¹⁷O²H⁺ and ¹⁶O²H⁺ is found to be weak and its behavior is similar to that of other first-row hydrides. The change with rotational excitation is unimportant. The quadrupole hyperfine patterns of ¹⁷O²H⁺ in its ground state are dominated by the strong oxygen coupling. © 1996 John Wiley & Sons, Inc.     

Use of Ag(II) as a removable template in porphyrin chemistry: diol cleavage products of [meso-tetraphenyl-2,3-cis-diolchlorinato]silver(II)

The use of Ag^II as a removable template in synthetic porphyrin chemistry is described. Mild procedures for the insertion of Ag^II into chlorins and the demetallation of the [chlorinato]Ag^II complexes are delineated. The UV-vis spectra of the novel [chlorinato]Ag^II complexes are discussed. The diol cleavage products of [meso-tetraphenyl-2,3-diolchlorinato]silver(II) under a number of conditions are characterized and compared to those resulting from the cleavage of the corresponding free base diol chlorin or its Ni^II complex, highlighting the unique templating effect of Ag^II. The scopes and limits of electrospray ionization mass spectrometry (ESI-MS) for the analysis of Ag^II chlorins is described. The use of Ag^II as a templating metal is superior over Ni^II or Zn^II for the preparation of free base pyrrole-modified porphyrins along metal templated pathways.     

Electrochemical behavior and determination of epinephrine at a mercaptoacetic acid self-assembled gold electrode

The electrochemical behavior of epinephrine (EP) at a mercaptoacetic acid (MAA) self-assembled monolayer modified gold electrode was studied. The MAA/Au electrode is demonstrated to promote the electrochemical response of epinephrine by cyclic voltammetry. The possible reaction mechanism is also discussed. The diffusion coefficient D of EP is 6.85 × 10⁻⁶ cm² s⁻¹. In 0.1 mol L⁻¹ phosphate buffer (pH 7.20), a sensitive oxidation peak was observed at 0.177 V, and the peak current is proportional to the concentration of EP in the range of 1.0 × 10⁻⁵–2.0 × 10⁻⁴ mol L⁻¹ and 1.0 × 10⁻⁷–1.0 × 10⁻⁶ mol L⁻¹. The detection limit is 5 × 10⁻⁸ mol L⁻¹. The modified electrode is highly stable and can be applied to the determination of EP in practical injection samples. The method is simple, quick, sensitive and accurate.     

Improved methods of obtaining Nim-trityl-substituted histidine derivatives

Two variants are proposed for the synthesis of N^α-Boc-N^im-tritylhistidiine. The first variant starts from N^α,N^im-di-Boc-histidine, from which the N^im-Boc group is removed with hydrazine hydrate. The N^α-Boc-histidine formed is esterified with chlorotrimethylsilane, tritylated in the imidazole group, and, after the elimination of the trimethylsilyl protection from the carboxyl group, N^α-Boc-N^im-tritylglycine is obtained with a yield of 80%. The second variant starts from N^α,N^im-ditritylhistidine, which, by treatment with hydrochloric acid in acetone and then with dilute ammonia, is converted into N^im-tritylhistidine. From this, by acylation with di-tert-butyl pyrocarbonate, N^α-Boc-N^im-tritylhistidine is obtained with a yield of 91%. The acylation of N^im-tritylhistidine with other alkoxycarbonylating reagents leads to N^α-tert-amyl-, N^α-benzyl-, and N^α-4-methoxybenzyloxycarbonyl derivatives of N^im-tritylhistidine.     

A DFT Study of Tungsten–Methylidene Formation on a W/ZSM‐5 Zeolite: The Metathesis Active Site

Tungsten–methylidene formation from ethene on either the W^IV, W^V, or W^VI active sites of a W/ZSM‐5 zeolite is investigated by using the M06‐L functional. The reaction is assumed to proceed in two steps; the first step is the [2+2] cycloaddition between ethene and the W?O active site to form an oxametallacycle intermediate. The intermediate is then decomposed to produce the W–methylidene active site from the metathesis reaction. The overall activation barrier of the reaction on W^VI (27.3 kcal mol^?1) is considerably lower than the ones for W^IV and W^V (69.4 and 37.1 kcal mol^?1, respectively). Moreover, the reaction involving the W^VI site also stabilizes intermediates and products to a larger extent than the ones on the W^IV and W^V sites. As a result, we have demonstrated that the reaction of the W–methylidene metathesis active site is both kinetically and thermodynamically favored to occur on the W^VI active site of the zeolite.     

CS+(B2Σ+ → A 2Πi) fluorescence from penning excitation of CS

The energy transfer reation of He(2³S) + CS was studied spectroscopically in a flowing afterglow apparatus. The CS⁺(B²Σ⁺ → A ²Π_i) transition is identified via three members of the Δν = 0 sequence (406–415 nm). The spin-orbit splitting of the (0, 0) band of CS⁺(A ²Π_i) is 301 ± 5 cm^?1. A weak emitting system (280–340 nm) is tentatively identified as CS⁺(B²Σ⁺→ X²Σ⁺).     

Spectrophotometric and solvent extraction study of o-hydroxybenzaldehyde isonicotinoyl hydrazone complexes with gallium and indium

Complex formation of o-hydroxybenzaldehyde isonicotinoyl hydrazone with Ga^III, In^III and Tl^III has been studied. The thallium complex is unstable. The composition and the instability constants of gallium and indium complexes were determined. Molar absorptivity of gallium complex at 390 nm is 3.40 × 10⁴ and that of indium at 380 nm is 3.20 × 10⁴ l mole^?1 cm^?1. Both complexes were found to be rapidly and quantitatively transfered into 1-pentanol. The corresponding aluminum complex is not extracted. Possible analytical application for separation and spectrophotometric determination of these elements is also examined.     

The photoassociation and photodissociation in laser‐assisted collision reaction H + Cl+

The collision reaction H + Cl⁺ assisted by the ultra‐short laser pulse is investigated using the time‐dependent quantum wave packet method. The probability of dissociation depends on the yield ratio of association product HCl⁺. The greater the laser frequency is, the lower the vibrational level of HCl⁺ is. With lowering laser frequency, the probabilities of photoassociation and photodissociation increase, and the ratio of products H⁺ + Cl(²P⁰) to H(²S) + Cl⁺(¹D) also increases. The kinetic energy spectra of the dissociated fragments at low frequency are wider than those at high frequency. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008