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311.
Smith JT Tomfohr JK Wells MC Beebe TP Kepler TB Reichert WM 《Langmuir : the ACS journal of surfaces and colloids》2004,20(19):8279-8286
A novel technique for the quantitative observation of cell migration along linear gradient substrates functionalized with adhesive proteins is presented. Gradients of the cell adhesion molecule fibronectin are generated by the cross diffusion of functionalizable alkanethiols on gold and characterized by X-ray photoelectron spectroscopy and surface plasmon resonance. Two distinct migration assays are described that characterize the movement of either sparsely populated noncontacting cells or a confluent monolayer of cells into free space. The drift speed of bovine aortic endothelial cells is measured and shown to increase along a fibronectin gradient when compared to a uniform control substrate using both assays. The results of these experiments establish reproducible conditions for studies of cell migration on gradients of surface-bound ligands. 相似文献
312.
Akoumianaki-Ioannidou A Georgakopoulos JH Fasseas C Argyroudi-Akoyunoglou JH 《Journal of photochemistry and photobiology. B, Biology》2004,73(3):149-158
We studied photoacclimation in Spathiphyllum grown at an irradiance of 40 or 420 micromol/m2 s (LL or HL, respectively). All parameters studied responded to acclimation. Leaves at LL, in contrast to HL, were thinner and oriented perpendicular to the incident light, had more chlorophyll per g f w, fewer stomata on the upper leaf surface and a reduced layer of mesophyll cells. Their chloroplasts at HL had wider grana with less thylakoids per granum, and better organized photosystems than at LL. PSI and PSII activities per mg chlorophyll ( Vmax ), and PSI and PSII content (total activity per g f w), were lower at LL than at HL and so was the light requirement for saturation of the PSI or PSII partial photoreactions, suggesting that fewer photosystems with larger antenna size prevail at LL, but many more with smaller antenna size at HL. Analysis of chlorophyll distribution among the thylakoid pigment-protein complexes showed less antenna chlorophyll serving PSII (CPa+LHCP1+LHCP3) than that serving PSI (CPIa+CPI+LHCP2) at LL as compared to HL, and thus a lower PSII/PSI ratio at LL, in agreement with the general finding that LL plants, with larger PSII antenna size, have lower PSII/PSI ratio. The increase in PSI antenna size at LL was correlated with the increase in the distribution of chlorophyll in pigment-protein complexes serving PSI, and a very large chlorophyll/protein molar ratio in the isolated CPI complex. On the other hand, the PSII antenna chlorophyll (CPa+LHCP1+LHCP3) on a g f w basis, and the chlorophyll a/b ratio remained more or less constant at LL or HL. This may reflect our finding that Spathiphyllum contains mainly the 27 kDa inner LHCII antenna protein, the size of which remains unaffected by photoacclimation. The increase in the distribution of chlorophyll in pigment-protein complexes serving PSII at HL, therefore, reflects the higher population of PSII at HL. Very high PSI activity was found at HL, which we attribute to the highly organized small in size PSI. 相似文献
313.
Harding WW Tidgewell K Schmidt M Shah K Dersch CM Snyder J Parrish D Deschamps JR Rothman RB Prisinzano TE 《Organic letters》2005,7(14):3017-3020
[reaction: see text] Two new neoclerodane diterpenes, salvinicins A (4) and B (5), were isolated from the dried leaves of Salvia divinorum. The structures of these compounds were elucidated by spectroscopic techniques, including (1)H and (13)C NMR, NOESY, HMQC, and HMBC. The absolute stereochemistry of these compounds was assigned on the basis of single-crystal X-ray crystallographic analysis of salvinicin A (4) and a 3,4-dichlorobenzoate derivative of salvinorin B. 相似文献
314.
John F. Callan A. P. De Silva R. C. Mulrooney B. Mc Caughan 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):257-262
Summary This review highlights recent advances in the use of quantum dots (QD’s) as luminescent sensors. The bulk of the study concentrates
on systems that possess organic ligands bound to the surface of QD’s. These ligands vary from low molecular weight thiols
to larger molecules such as maltose binding protein. All have one thing in common: when a target analyte binds to the ligand/receptor,
a perturbation of the system occurs, that registers itself as a change in the luminescence intensity of the QD. Two main mechanisms
are prevalent in controlling the luminescent intensity in such systems. The first is Photoinduced Electron Transfer (PET)
and the second energy transfer. This review looks at current sensors that operate by using these mechanisms. Two component
systems are also investigated where a quencher is first added to a solution of the QD, followed by addition of the target
analyte that interacts with the quencher to influence the luminescence intensity. 相似文献
315.
Oxidative demetalation of cyclohexadienyl ruthenium(II) complexes: a net Ru-mediated dearomatization
[reaction: see text] An experimentally simple method for the demetalation of spirocyclic cyclohexadienylruthenium(II) complexes has been developed. Treatment of an alkoxy-substituted cyclohexadienyl complex with CuCl(2) affords either azaspiro[4.5]decane derivatives or heavily functionalized tetrahydroisoquinolines. The former reaction manifold completes a net Ru-mediated dearomatization as the organometallic starting materials are prepared from (eta(6)-arene)Ru(II) precursors. Both of these heterocyclic products are well suited for further synthetic elaboration. 相似文献
316.
Single p-toluic acid pendant groups were attached to 1,4,7,10,13-pentaazacyclopentadecane (15aneN5) and 1,4,8,11-tetraazacyclotetradecane (cyclam) to prepare bifunctional reagents for radiolabeling monoclonal antibodies with (64,67)Cu. The ligands are 1,4,7,10,13-pentaazacyclopentadecane-1-(alpha-1,4-toluic acid) (PCBA) and 1,4,8,11-tetraazacyclotetradecane-1-(alpha-1,4-toluic acid) (CPTA). For the parent macrocycles and their pendant arm derivatives, the 1:1 Cu(2+) complexes dissociate only below pH 2. At pH 0.0 and 25 degrees C the CPTA-Cu complex has a half-life toward complete dissociation of 24 days. A new approach was developed for the estimation of the Cu(2+) stability constant for the kinetically robust CPTA. All other formation constants were determined at 25.0 degrees C with batch spectrophotometric techniques. Potentiometric titrations were used to determine the protonation constants of the macrocyclic ligands as well as of the metal chelates. The protonation constants, stability constants, and pM's are discussed in terms of both molecular mechanics calculations and the ligands' potential applicability as copper(II) radiopharmaceuticals. 相似文献
317.
Jean-Claude Muller Henri Rarouz John Daly Peter Schönholzer 《Helvetica chimica acta》1982,65(5):1454-1466
The structure of new 2-oxo-2,8-dihydro-[l,2,4]oxadiazolo-[2,3-a]pyrimidine-carbamates 1 was established by correlating the IR. and NMR. data with these of analogous compounds. A X-ray crystallographic analysis of 1c gave an unequivocal proof of structural assignment. 相似文献
318.
The colorless Cs4ZrO4 is obtained from the reaction of stoichiometric proportions of Cs, CsO2, and finely divided ZrO2 in a sealed Ag container at 400–650°C for several days. Regrinding and re-reaction provide a single phase sample. The compound is monoclinic (P21/c, Z = 4, a = 7.172 (1) Å, b = 19.907 (1) Å, c = 7.157 (1) Å, β = 113.1 (1)Å, R = 0.032) and isostructural with Cs4PbO4, with isolated ZrO44? tetrahedra (d(Zr–O) = 1.97 Å). The compound decomposes to Cs2ZrO3 (a) in the presence of excess oxygen or CsO2, (b) in high vacuum near 275°C, or (c) in a sealed container at about 730 ± 10°C. 相似文献
319.
Byrne SJ Corr SA Gun'ko YK Kelly JM Brougham DF Ghosh S 《Chemical communications (Cambridge, England)》2004,(22):2560-2561
Denatured (substantially single-stranded) herring sperm DNA acts as a template for the preparation of magnetic nanowires, forming stable aqueous suspensions, which exhibit unprecedentedly high relaxivity at low field, suggesting that the material may be a potentially useful reagent for MRI. 相似文献
320.
Geng J Ducati C Shephard DS Chhowalla M Johnson BF Robertson J 《Chemical communications (Cambridge, England)》2002,(10):1112-1113
A nanoscale ruthenium/gold bimetallic cluster of clusters has been used as a molecular precursor to produce pure ruthenium nanoparticles (seeds) as catalysts for the growth of carbon nanohorns (CNHs). 相似文献