共查询到20条相似文献,搜索用时 31 毫秒
1.
Mozaffar Asadi Maryam Mohammadikish Pegah Mousavi Ramin Miri 《Inorganica chimica acta》2009,362(14):4906-1543
A series of new aluminum(III), gallium(III) and indium(III) complexes with some tridentate Schiff base, viz., N-{pyridine-2-ylmethyl}-2-hydroxy-5-methoxy-benzylideneamine [HL1], N-{pyridine-2-ylmethyl}-2-hydroxy-benzylideneamine [HL2], N-{pyridine-2-ylmethyl}-2-hydroxy-5-nitro-benzylideneamine [HL3], N-{pyridine-2-ylmethyl}-2-hydroxy-5-bromo-benzylideneamine [HL4], N-{pyridine-2-ylethyl}-2-hydroxy-5-methoxy-benzylideneamine [HL5], N-{pyridine-2-ylethyl}-2-hydroxy-benzylideneamine [HL6], N-{pyridine-2-ylethyl}-2-hydroxy-5-nitro-benzylideneamine [HL7], N-{pyridine-2-ylethyl}-2-hydroxy-5-bromo-benzylideneamine [HL8], with the general formula [ML2][Y] (M = Al3+, Ga3+, In3+; Y = NO3−, ClO4−) were synthesised and characterized by elemental analysis, 1H NMR, FT-IR, UV-Vis spectrophotometry and mass spectrometry. The thermodynamic formation constants of the complexes were determined spectrophotometrically at constant ionic strength (I = 0.10 M NaClO4) and at 25 °C in methanol. The trend of formation constants of the complexes are as follow:
Al<Ga<In 相似文献
2.
《International journal of radiation applications and instrumentation. Part B, Nuclear medicine and biology》1986,13(5):523-526
There is great interest in the application of positron labeled ligands to map the dopamine receptor in vivo. A series of fluorine-18-labeled N-alkyl and N-fluoroalkyl spiroperidol (SP) derivatives N-methyl[18F]SP; N-ethyl[18F]SP; N-(2-[18F]fluoroethyl)SP; N-propyl[18F]SP; N-(3-[18F]fluoropropyl)SP; N-(3-fluoropropyl) [18F]SP; N-(2-[18F]fluoropropyl)SP; N-(2-[18F]fluorobutyl)SP; N-(2-[18F]fluoropentyl)SP; and N-(2-[18F]fluorohexyl) SP were synthesized. The lipophilicity of these ligands (log octanol/water partition coefficient) varies from 2.67 to 5.56 and the initial brain uptake in rats, measured at 2 min, was greatest with the methyl, ethyl, propyl, fluoroethyl, and fluoropropyl derivatives. The highest striatum/cerebellum values 1 h after administration were obtained with the N-methyl, N-propyl, and N-3-fluoropropyl derivatives, while that of N-2-fluoroethyl showed the greatest uptake of total activity in the brain at this time. The uptake of all these ligands in the striatum could be blocked by cold SP showing the striatal uptake to be by the dopamine receptors. 相似文献
3.
Analysing the self-association behaviour of human erythrocyte spectrin is complicated by a large degree of nonideality. Adams and Fujita [1] proposed that, as a first order approximation, the logarithm of the activity coefficient of the protomer of a self-associating system can be considered to be linearly dependent on the total concentration of the protein, and that the same second virial coefficient could be considered to apply to all species. As a consequence of the Adams and Fujita approximation, the apparent equilibrium constant is equal to the thermodynamic equilibrium constant. The equilibrium concentrations at 30°C of each oligomer spectrin species up to the 14-mer were determined after electrophoresis at low temperature. An apparent equilibrium constant for forming tetramer (K2,4) of (1.2 ± 0.1) × 106 l/mol was obtained, a value of (9.4 ± 0.7) × 104 l/mol was obtained for K4,6 and for all reactions forming oligomers higher than the hexamer an average approximate value of (2.7 ± 0.4) × 105 l/mol was obtained. The apparent equilibrium constants for the formation of all oligomer species of spectrin up to the tetrakaidecamer (14-mer) remain relatively independent of total spectrin concentration, and indicate that within the precision of the measurements a single virial coefficient is sufficient to account for the nonideality of spectrin self-association over the range 2–42 g/l, thus further justifying the use of the Adams and Fujita approximation for this protein over this concentration range. 相似文献
4.
An improved procedure is described for the characterization of solute self-association by sedimentation equilibrium. Whereas previous statistical-mechanical approaches to allowance for the effects of thermodynamic nonideality have entailed tedious iteration because of their specification of activity coefficients in terms of the equilibrium concentrations of all species, such reliance upon knowledge of the solution composition is avoided by the adaptation of an alternative statistical-mechanical formulation [T. L. Hill and Y. D. Chen (1973) Biopolymers, Vol. 12, pp. 1285–1312] in which thermodynamic nonideality is expressed in terms of total solute concentration. The development of an analysis in terms of a relationship with total solute concentration as the experimental variable allows this attribute of the Adams-Fujita approach to be retained without sacrifice of statistical-mechanical rigor. Its use is illustrated by application to Rayleigh interferometric records of sedimentation equilibrium distributions reflecting α-chymotrypsin dimerization and lysozyme self-association. © 1996 John Wiley & Sons, Inc. 相似文献
5.
《Inorganica chimica acta》1988,142(2):291-299
In coordinating solvents, the complex 1, 4, 8, 11- tetramethyl-1, 4, 8, 11-tetraazacyclotetradecane nickel(II) bisperchlorate exists as an equilibrium mixture involving four coordinate R,S,R,S-[Ni(tmc)]2+ and five coordinate R,S,R,S-[Ni(tmc)(solvent)]2+ species. Spectrophotometric measurements of this equilibrium in a number of solvents have been conducted over a range of temperatures and pressures. The stability order for the five coordinate complex in the solvents investigated is CH3CN>DMF>DMSO>C6H5CN> H2O>ClCH2CN at 25 °C. Differences in stability are considered in terms of the measured thermodynamic parameters ΔH° and ΔS°. Both steric and electronic factors were found to influence solvent coordination with the macrocyclic complex.For the equilibrium in CH3CN, C6H5CN, DMF and H2O, reaction volumes, ΔV°, of −3.2±0.5, −4.2±0.5, −0.2±0.5 and −0.5±0.5 cm3 mol−1 respectively have been determined. Each is significantly smaller than the corresponding solvent molar volume. The ΔV° for the equilibrium in CH3CN is comparable with the previously determined activation volume for exchange of this solvent on R, S, R, S- [Ni(tmc)(CH3CN)]2+. The equilibrium and measured volume parameters are discussed in relation to the mechanism for solvent exchange. 相似文献
6.
Mingzhang Gao Min Wang Gary D. Hutchins Qi-Huang Zheng 《Bioorganic & medicinal chemistry letters》2010,20(8):2529-2532
[11C]Dimebon (2-[11C]methyl-8-methyl-5-(2-(6-methylpyridin-3-yl)ethyl)-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole), a new potential PET agent for imaging of Alzheimer’s disease and Huntington’s disease, was prepared by N-[11C]methylation of desmethyl-Domebon precursor with [11C]CH3OTf and purified with a semi-preparative HPLC method in 30–40% decay corrected radiochemical yield and 222–296 GBq/μmol specific activity at EOB. The measured lipophilicity coefficient (Log P) value of [11C]Dimebon was 2.53. 相似文献
7.
The mutual interaction of various amine bases with the (dibenzo[b,i][1,4,8,11] tetraazacyclotetradecinato)cobalt(II) (Co(II)-1) was investigated by measuring electronic spectra in methyl benzoate. The Co(II)-1 became the pentacoordinated complex by taking up an amine base in the axile site: Co(II)-1 + B ? BCo(II)-1. For the mutual interaction of substituted pyridines with the Co(II)-1, the general behavior of the equilibrium constants was explained on the basis of the amine basicity and the Hammett equation by reference to the corresponding behavior of the porphyrin, corrin and corrole complexes. Moreover, there exists a systematic correlation between log K and the chemical shift of the corresponding 4-position in the 13C-NMR spectra of substituted pyridines. The isoequilibrium temperature obtained from a plot of ΔH against ΔS was 260 K. The equilibrium is primarily controlled by entropy at the usual temperature. The weaker coordination tendency of some hindered pyridine such as 2-methyl- and 2,6-dimethylpyridine toward Co(II)-1 was attributed to the steric effect between the in-plane ligand of Co(II)-1 and the 2- and/or 6-methyl groups of substituted pyridines in the coordination process. 相似文献
8.
7α[3H]-25-Hydroxycholesterol and 7α-[3H]-Δ5,25(27)-cholestadien-3β-ol were administered to Convallaria majalis L. plants and the biosynthesized labeled convallamarogenin were isolated in both cases. The results are discussed in relation to the isomerization of the Δ24(25)-double bond of desmosterol to the Δ24(27)-double bond in convallamarogenin. 相似文献
9.
《Inorganica chimica acta》1988,154(2):209-214
The diastereoisomeric complex Δ-(+)-tris(cyclicO,O′, 1 (R), 2(R)(−)dimethylethylene dithiophosphato)chromium(III), was synthesized stereoselectively in tetrahydrofuran (THF) solution. The complex proves optically labile, [α]D=+106, in CHCl3, changing quickly to [α]D=+211. The CD spectra in THF enable us to characterize the complex and show a configuration inversion which gives the diastereoisomeric equilibrium Λ⇌Δ with an excess of the Λ-(R,R)(R,R)(R,R) diastereoisomeric form. The equilibrium constant K=0.86 at 25 °C is indicative of a different thermodynamic stability between the two diastereoisomers in THF solution, Λ-(R,R)> Δ-(R,R), δΔH°=1.5 kJ mol−1, δΔG°=0.3 kJ mol−1, δΔS°=4 J mol−1 K−1. The kinetic diastereoisomer Δ-(R,R)(R,R)(R,R) is stabilized in CHCl3, CH2Cl2, EtOH solvents where it is highly soluble and optically stable with a maximum negative chirality factor, g=−5×10−3, in CHCl3. 相似文献
10.
A series of flexible multidentate ligands containing N,P-donor, 2-[N-(diphenylphosphino)methyl]amino-pyridine (L1), 2-[N-bi-(diphenylphosphino) methyl]amino-pyridine (L2), 2-[N-(diphenylphosphino)methyl]amino-7-methyl-1,8-naphthyridine (L3) and 4-[(N-diphenylphosphino)methyl]amino-pyridine) (L4) have been synthesized. The mono- and dinuclear cyclometalated platinum(II) complexes [Pt(C^N^N)L1]ClO4 (HC^N^N = 6-phenyl-2,2′-bipyridine), [Pt2(C^N^N)2L1](ClO4)2, [Pt2(C^N^N)2L2](ClO4)2, [Pt(C^N^N)L3]ClO4 and [Pt2(C^N^N)2L4](ClO4)2 were prepared and their structures determined by X-ray crystal analysis. These complexes exhibit long-lived bright orange emissions ranging from 560 to 610 nm in the solid state at room temperature. In solution, dinuclear complexes have emissions with higher quantum yields than mononuclear complexes. This can be attributed to intramolecular interaction of free functional group with Pt(II) at axial position, resulting in the quenching of phosphorescence for platinum(II) complexes in the 3MLCT excited state. 相似文献
11.
Sun J An Y Zhang L Chen HY Han Y Wang YJ Mao ZW Ji LN 《Journal of inorganic biochemistry》2011,105(2):149-154
In this work, the interaction between the guanine-rich single-strand oligomer AG3(T2AG3)3 quadruplex and two Ru(II) complexes, [Ru(L1)(dppz)2](PF6)4 (1) and [Ru(L2)(dppz)2](PF6)4 (2) (L1 = 5,5′-di(1-(trimethylammonio)methyl)-2,2′-dipyridyl cation, L2 = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation, dppz = dipyrido[3,2-a:2′,3′-c] phenazine), has been studied by UV-Visible, fluorescence, DNA melting, and circular dichroism in K+ buffer. The two complexes after binding to G-quadruplex have shown different DNA stability and fluorescence enhancement. The results show that both complexes can induce the stabilization of quadruplex DNA. ΔTm values of complexes 1 and 2 at [Ru]/[DNA] ratio of 1:1 were 9.4 and 7.0, respectively. Binding stoichiometry along with the quadruplex was investigated through a luminescence-based Job plot. The major inflection points for complexes 1 and 2 were 0.49 and 0.46, respectively. The data were consistent with the binding mode at a [quadruplex]/[complex] ratio of 1:1. In addition, the conformation of G-quadruplex was not changed by the complexes at the high ionic strength of K+ buffer. 相似文献
12.
Reaction of the five-coordinate trigonal-bipyramidal platinum(II) complex, [Pt(pt)(pp3)](BF4) (pt = 1-propanethiolate, pp3 = tris[2-(diphenylphosphino)ethyl]phosphine), with I− in chloroform gave the five-coordinate square-pyramidal complex with a dissociated terminal phosphino group and an apically coordinated iodide ion in equilibrium. The thermodynamic parameters for the equilibrium between the trigonal-bipyramidal and square-pyramidal geometries, [Pt(pt)(pp3)]+ + I− ? [PtI(pt) (pp3)], and the kinetic parameters for the chemical exchange were obtained as follows: , ΔH0 = − 10 ± 2.4 kJ mol−1, ΔS0 = − 36 ± 10 J K−1 mol−1, , ΔH‡ = 34 ± 4.7 kJ mol−1, ΔS‡ = − 50 ± 21 J K−1 mol−1. The square-planar trinuclear platinum(II) complex was formed by bridging reaction of one of the terminal phosphino groups of trigonal-bipyramidal [PtCl(pp3)]Cl with trans-[PtCl2(NCC6H5)2] in chloroform. From these facts, ligand substitution reactions of [PtX(pp3)]+ (X = monodentate anion) are expected to proceed via an intermediate with a dissociated phosphino group. The rate constants for the chloro-ligand substitution reactions of [PtCl(pp3)]+ with Br− and I− in chloroform approached the respective limiting values as concentrations of the entering halide ions are increased. These kinetic results confirmed the preassociation mechanism in which the square pyramidal intermediate with a dissociated phosphino group and an apically coordinated halide ion is present in the rapid pre-equilibrium. 相似文献
13.
The sterols of Zea mays shoots were isolated and characterized by TLC, HPLC, GC/MS and 1H NMR techniques. In all, 22 4-demethyl sterols were identified and they included trace amounts of the Δ23-, Δ24- and Δ25-sterols, 24-methylcholesta-5,E-23-dien-3β-ol, 24-methylcholesta-5,Z-23-dien-3β-ol, 24-methylcholesta-5,25-dien-3β-ol, 24-ethylcholesta-5,25-dien-3β-ol and 24-ethylcholesta-5,24-dien-3β-ol. In the 4,4-dimethyl sterol fraction, cycloartenol and 24-methylenecycloartanol were the major sterol components but small amounts of the Δ23-compound, cyclosadol, and the Δ25-compound, cyclolaudenol, were recognized. These various Δ23- and Δ25-sterols may have some importance in alternative biosynthetic routes to the major sterols, particularly the 24β-methylcholest-5-en-3β-ol component of the C28-sterols. Radioactivity from both [2-14C]MVA and [methyl-14C]methionine was incorporated by Z. mays shoots into the sterol mixture. Although 24-methylene and 24-ethylidene sterols were relatively highly labelled, the various Δ23- and Δ25-sterols contained much lower levels of radioactivity, which is possibly indicative of their participation in alternative sterol biosynthetic routes. (24R)-24-Ethylcholest-5-en-3β-ol (sitosterol) had a significantly higher specific activity than the 24-methylcholest-5-en-3β-ol indicating that the former is synthesized at a faster rate. 相似文献
14.
Scolaro C Hartinger CG Allardyce CS Keppler BK Dyson PJ 《Journal of inorganic biochemistry》2008,102(9):1743-1748
The hydrolysis of [Ru(η6-p-cymene)Cl2(PTA)] (PTA = 1,3,5-triaza-7-phosphatricyclo-[3.3.1.1]decanephosphine; RAPTA-C) was studied using UV-visible (UV-vis) spectrophotometry and NMR spectroscopy. In analogy to in silico studies, [Ru(η6-p-cymene)Cl(H2O)(PTA)]+ was found to be the most abundant hydrolysis product, although the dihydrolysed species [Ru(η6-p-cymene)(OH)(H2O)(PTA)]+ and the dichloro compound are present. Rate constants for the different aquation and anation steps and the equilibrium constants were determined. Hydrolysis is suppressed at high chloride concentrations. These results have important implications on the mode of action of the RAPTA drug candidates. 相似文献
15.
《Inorganica chimica acta》1986,119(2):131-139
In an effort to quantitatively estimate steric contributions to the aquation rates of a series of structurally related cobalt(III) tetraamine complexes, strain energy minimization calculations have been performed on the reactant and some plausible transition state structures. Free energies of activation ΔG*obs, are factored as: ΔG*obs, = ΔG*bb + ΔG*strain + ΔG*CF + ΔG*solvation + … where ΔG*bb is the free energy change associated with bond breaking, ΔG*solvation is the solvation free energy difference between the reactant and a proposed transition stare, ΔG*CF is the difference in crystal field stabilization between the reactant and a proposed transition state, and ΔG*strain is the strain energy difference between the reactant complex and a proposed transition state. The activation energy for the aquation of a hypothetical ‘strain free’ complex is defined as ΔG*int and reflects the energy required for the bond breaking step with all other terms. For the cations trans-(RR,SS)-dichloro-1,8- diamino-3,6-diazaoctanecobalt(III)(trans [Co(2,2,2- tet)Cl2]+), trans-(RR,SS)- or trans-(RS)-dichloro-1.9- diamino-3,7-diazanonanecobalt(III)(trans [Co(2,3,2- tet)Cl2]+ and trans-(RS)-dichloro-1,10-diamino-4,7- diazadecanecobalt(III)(trans[Co(3,2,3-tet)Cl2]+) ΔG*int is found to be a constant 123 kJ/mol. For the trans-dichlorocobalt(III) complexes with the ligands 1,4,7,10-tetraazacyclotridecane([13]-ane-N4), 1,4,8, 11-tetraazacyclotetradecane([14]-ane-N4), 1,4,8,12- tetraazacyclopentadecane([15]-ane-N4) and 1,5,9,13- tetraazacyclohexadecane([16]-ane-N4), ΔG*int lies in the range 133–139 kJ/mol. 相似文献
16.
Myint Myint Khine Norbert Arnold Katrin Franke Andrea Porzel Jürgen Schmidt Ludger Wessjohann 《Biochemical Systematics and Ecology》2007
A new cardenolide, 17β-H-periplogenin-3-O-β-d-digitoxoside (1), and a new pregnane glycoside, Δ5-pregnene-3β,16α-diol-d-O-[2,4-O-diacetyl-β-digitalopyranosyl-(1 → 4)-β-d-cymaropyranoside]-16-O-[β-d-glucopyranoside] (2) were isolated from the roots of Streptocaulon tomentosum (Asclepiadaceae) together with a series of known compounds. Their chemotaxonomic significance for the separation of S. tomentosum from Streptocaulon juventas is discussed, suggesting a rather clear distinction of these species. 相似文献
17.
To characterize driving forces and driven processes in formation of a large-interface, wrapped protein-DNA complex analogous to the nucleosome, we have investigated the thermodynamics of binding the 34-base pair (bp) H′ DNA sequence to the Escherichia coli DNA-remodeling protein integration host factor (IHF). Isothermal titration calorimetry and fluorescence resonance energy transfer are applied to determine effects of salt concentration [KCl, KF, K glutamate (KGlu)] and of the excluded solute glycine betaine (GB) on the binding thermodynamics at 20 °C. Both the binding constant Kobs and enthalpy ΔH°obs depend strongly on [salt] and anion identity. Formation of the wrapped complex is enthalpy driven, especially at low [salt] (e.g., ΔHoobs = − 20.2 kcal·mol− 1 in 0.04 M KCl). ΔH°obs increases linearly with [salt] with a slope (dΔH°obs/d[salt]), which is much larger in KCl (38 ± 3 kcal·mol− 1 M− 1) than in KF or KGlu (11 ± 2 kcal·mol− 1 M− 1). At 0.33 M [salt], Kobs is approximately 30-fold larger in KGlu or KF than in KCl, and the [salt] derivative SKobs = dlnKobs/dln[salt] is almost twice as large in magnitude in KCl (− 8.8 ± 0.7) as in KF or KGlu (− 4.7 ± 0.6).A novel analysis of the large effects of anion identity on Kobs, SKobs and on ΔH°obs dissects coulombic, Hofmeister, and osmotic contributions to these quantities. This analysis attributes anion-specific differences in Kobs, SKobs, and ΔH°obs to (i) displacement of a large number of water molecules of hydration [estimated to be 1.0(± 0.2) × 103] from the 5340 Å2 of IHF and H′ DNA surface buried in complex formation, and (ii) significant local exclusion of F− and Glu− from this hydration water, relative to the situation with Cl−, which we propose is randomly distributed. To quantify net water release from anionic surface (22% of the surface buried in complexation, mostly from DNA phosphates), we determined the stabilizing effect of GB on Kobs: dlnKobs/d[GB] = 2.7 ± 0.4 at constant KCl activity, indicating the net release of ca. 150 H2O molecules from anionic surface. 相似文献
18.
Andrzej Bierzyński Hanna Kozz.xl;lowska Zbigniew Proba K.L. Wierzchowski 《Biophysical chemistry》1977,6(3):231-237
General equations relating fluorescence quantum yield and lifetime of a compound with its intramolecular stacking equilibrium and kinetics were derived. Intramolecular stacking association of 9,9'-[1,3-propylene]-bis-2-aminopurine in aqueous solution was examined within the range of temperatures from 0 to 90°C. A two-state thermodynamic model of the association was verified. The stacking enthalpy and entropy can be taken, with a good approximation, as temperature-independent (δH = ?2.0 , ΔS = ?3.25 e.u.) although the function ΔG = ?0.00886 T2 + 8.847 T ?2876 describes more precisely the observed changes of stacking free enthalpy with temperature. The association rate constants were determined. Activation energy of the reaction (2 ) is the same as in the case of association between free 2-aminopurine molecules. It confirms a two-step mechanism of the process. The advantages and shortcomings of the fluorescence quenching method are discussed. 相似文献
19.
Jin Ha Park Hyun Suk Lee Myung Duk Jang Sung Wook Han 《Journal of biomolecular structure & dynamics》2018,36(8):1948-1957
The interaction of Δ- and Λ-[Ru(phen)2DPPZ]2+ (DPPZ = dipyrido[3,2-a:2′, 3′-c]phenazine, phen = phenanthroline) with a G-quadruplex formed from 5′-G2T2G2TGTG2T2G2–3′(15-mer) was investigated. The well-known enhancement of luminescence intensity (the ‘light-switch’ effect) was observed for the [Ru(phen)2DPPZ]2+ complexes upon formation of an adduct with the G-quadruplex. The emission intensity of the G-quadruplex-bound Λ-isomer was 3-fold larger than that of the Δ-isomer when bound to the G-quadruplex, which is opposite of the result observed in the case of double stranded DNA (dsDNA); the light switch effect is larger for the dsDNA-bound Δ-isomer. In the job plot of the G-quadruplex with Δ- and Λ-[Ru(phen)2DPPZ]2+, a major inflection point for the two isomers was observed at x ≈ .65, which suggests a binding stoichiometry of 2:1 for both enantiomers. When the G base at the 8th position was replaced with 6-methyl isoxanthopterin (6MI), a fluorescent guanine analog, the excited energy of 6-MI transferred to bound Δ- or Λ-[Ru(phen)2DPPZ]2+, which suggests that at least a part of both Ru(II) enantiomers is close to or in contact with the diagonal loop of the G-quadruplex. A luminescence quenching experiment using [Fe(CN)6]4- for the G-quadruplex-bound Ru(II) complex revealed downward bending curves for both enantiomers in the Stern–Volmer plot, which suggests the presence of Ru(II) complexes that are both accessible and inaccessible to the quencher and may be related to the 2:1 binding stoichiometry. 相似文献
20.
The low-affinity fluorescent Ca2+ indicators OGB-5N, Fluo-5N, fura-5N, Rhod-5N, and Mag-fluo-4 were evaluated for their ability to accurately track the kinetics of the spatially averaged free Ca2+ transient (Δ[Ca2+]) in skeletal muscle. Frog single fibers were injected with one of the above indicators and, usually, furaptra (previously shown to rapidly track Δ[Ca2+]). In response to an action potential, the full duration at half-maximum of the indicator's fluorescence change (ΔF) was found to be larger with OGB-5N, Fluo-5N, fura-5N, and Rhod-5N than with furaptra; thus, these indicators do not track Δ[Ca2+] with kinetic fidelity. In contrast, the ΔF time course of Mag-fluo-4 was identical to furaptra's; thus, Mag-fluo-4 also yields reliable kinetic information about Δ[Ca2+]. Mag-fluo-4's ΔF has a larger signal/noise ratio than furaptra's (for similar indicator concentrations), and should thus be more useful for tracking Δ[Ca2+] in small cell volumes. However, because the resting fluorescence of Mag-fluo-4 probably arises largely from indicator that is bound with Mg2+, the amplitude of the Mag-fluo-4 signal, and its calibration in Δ[Ca2+] units, is likely to be more sensitive to variations in [Mg2+] than furaptra's. 相似文献