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11.
3,4-Dimethylphosphorin is prepared in five steps from 2,3-dimethylbutadiene and 2-phenyl-4,5-dimethylphosphorin; this synthetic scheme is formally equivalent to a [4+2] cycloaddition between 2,3-dimethylbutadiene and HCP. 相似文献
12.
HOST CELL REACTIVATION BY FIBROBLASTS FROM PATIENTS WITH PIGMENTARY DEGENERATION OF THE RETINA 总被引:1,自引:0,他引:1
C. DavidLytle RobertE. Tarone†SusannaF. Barrett‡JonathanD. Wirtschafter§Jean-Marie Dupuy¶JayH. Robbins‡ 《Photochemistry and photobiology》1983,37(5):503-508
–Cockayne syndrome (CS) is an autosomal recessive disease characterized by numerous clinical abnormalities including acute sun sensitivity and primary pigmentary degeneration of the retina. Cultured fibroblasts from CS patients are hypersensitive to ultraviolet (UV) radiation. Since host cell reactivation of irradiated virus is a useful probe to evaluate repair in different host cells, we studied such host cell reactivation in CS and in other diseases with retinal degeneration. The survival of UV-irradiated Herpes simplex virus type 1 was determined in fibroblast lines from four normal donors. two patients with CS, one with both xeroderma pigmentosum (XP) and CS, and from several other patients with (Usher syndrome, olivopontocerebellar atrophy, retinitis pigmentosa) and without (XP, ataxia telangiectasia) primary pigmentary degeneration of the retina. The viral survival curves (log survival vs linear fluence) in all cell lines showed two components: a very sensitive initial component (not quantitated in this study) followed by an exponential, less sensitive component. The exponential component had greater sensitivity than normal in the case of the CS patients, the patient with both XP and CS. and the XP patient. We propose that patients with CS have defective repair of DNA which may be the cause of their retinal degeneration. 相似文献
13.
Ahunbay MG Perez-Pellitero J Contreras-Camacho RO Teuler JM Ungerer P Mackie AD Lachet V 《The journal of physical chemistry. B》2005,109(7):2970-2976
In this third article of the series, a new anisotropic united atoms (AUA) intermolecular potential parameter set has been proposed for the carbon force centers connecting the aromatic rings of polyaromatic hydrocarbons to predict thermodynamic properties using both the Gibbs ensemble and NPT Monte Carlo simulations. The model uses the same parameters as previous AUA models used for the aromatic CH force centers. The optimization procedure is based on the minimization of a dimensionless error criterion incorporating various thermodynamic data of naphthalene at 400 and 550 K. The new model has been evaluated on a series of polyaromatic and naphthenoaromatic hydrocarbons over a wide range of temperatures up to near-critical conditions. Vaporization enthalpy, liquid density, and normal boiling temperature are reproduced with good accuracy. The new potential parameters have also been tested successfully on toluene, 1,3,5-trimethylbenzene, styrene, m-xylene, n-hexylbenzene, and n-dodecylbenzene to demonstrate their transferability to alkylbenzenes. 相似文献
14.
The lithium and europium(III) cryptates of a macrobicyclic ligand 1 incorporating the 3,3′-biisoquinoline 2,2′-dioxide 2 have been prepared. The Eu(III) complex [Eu(2)2]Cl3 has also been obtained. These Eu(III) complexes present characteristic 1H-NMR spectra containing markedly shifted resonances. They are strongly luminescent; the emission spectra, quantum yields, and lifetimes have been determined. 相似文献
15.
Margaret M. Harding Ulrich Koert Jean-Marie Lehn Annie Marquis-Rigault Claude Piguet Jay Siegel 《Helvetica chimica acta》1991,74(3):594-610
A general strategy for the synthesis of oligobipyridine ligands 2 – 5 containing from two to five 2,2′-bipyridine subunits, for helical metal complexes is described (sec Scheme). Both the unsubstituted parent strands ( a series) as well as their derivatives bearing fester or amide functions in the 4,4′-positions of the bipyridine moieties ( b – d series) have been obtained. 相似文献
16.
Jean-Marie De Koninck 《Monatshefte für Mathematik》1993,116(1):13-37
Let
and, for each integern such that (n)k, denote byP
k
(n) itsk
th largest prime factor. Further, given a set of primesQ of positive density <1 satisfying a certain regularity condition, defineP(n, Q), as the largest prime divisor ofn belonging toQ, assuming thatP(n,Q)=+ if no such prime factor exists. We provide estimates of
, fork2, and of
. We also study the median value of the functionP(n,Q) and that of the functionP
k
(n) for eachk1. 相似文献
17.
A new speetrofluorimetric method for determination of ultratraces of lead is based on solvent extraction into chloroform of the ion-pair formed between the positively-charged cryptate of lead with cryptand 2.2.2 and the eosinate anion. The detection limit for lead is 1 ng ml , and the linear working range is from the detection limit to 250 ng ml . The relative standard deviation is 3.7% at the 100 ng ml level. The method is highly selective for the extraction and determination of lead in the presence of other cations, and has been tested for direct determination of lead contamination in soft drinks. Aggregation of the extracted ion-pair in the organic phase has been demonstrated in fundamental extraction studies. 相似文献
18.
Two efficient methods are described for the selective modification of all six primary hydroxyl groups of α-cyclodextrin (α-CD, 1 1 ). One, using an indirect strategy, involves protection of all 18 hydroxyl functions as benzoate esters, followed by selective deprotection of the six primary alcohol groups. The other, using a direct strategy, involves selective activation of the primary hydroxyl groups via a bulky triphenylphosphonium salt, which is then substituted by azide anion as the reaction proceeds. A number of modified α-cyclodextrin derivatives have been prepared and fully characterized, among which are: the useful intermediate α-cyclodextrin-dodeca (2, 3) benzoate ( 3 ); hexakis (6-amino-6-deoxy)-α-cyclodextrin hexahydrochloride ( 7 ); hexakis (6-amino-6-deoxy)-dodeca (2, 3)-O-methyl-α-cyclodextrin hexahydrochloride ( 9 ), hexa (6)-O-methyl-α-cyclodextrin ( 13 ). The direct substitution is shown to be even more efficient for β-cyclodextrin ( 16 ), giving the heptakis (6-azido-6-deoxy)-β-CD-tetradeca (2, 3)acetate ( 17 ), while the indirect strategy fails. The compounds are characterized by extensive use of 13C- and 1H-NMR. spectroscopy. The steric and statistical problems of selective polysubstitution reactions for the cyclodextrins are discussed, and possible reasons for the observed differences in reactivity between α- and β-cyclodextrins are examined. The dodecabenzoate 3 presents a very marked solvent effect on physical properties (IR. and NMR. spectra, optical rotation); the effects observed may be ascribed to an unusually strong intramolecular network of hydrogen bonds which severely distorts the α-cyclodextrin ring and lowers the symmetry from six-fold to three-fold. 相似文献
19.
Spherical Cryptates. Synthesis and Inclusion-Complexes of Spherical Macrotricyclic Ligands A general strategy for the synthesis of spherical macrotricyclic ligands has been developed. Four spherical cryptands, SC - 24 , SC - 25 , SC - 26 and SC - 27 have been obtained by this route. The synthesis and cation-complexing properties of these compounds are described in detail. Stability constants and cation exchange rates of the spherical cryptates obtained with alkali and alkaline-earth cations have been determined. Highly stable complexes are formed by SC - 24 ; the Rb+ and Cs+ cryptates of SC - 24 are the most stable complexes of these cations known to date. The size of the intramolecular cavity affects the complexation selectivity. The cation exchange rates are very slow, and the corresponding free energies of activation are even larger than, for macrobicyclic cryptates of similar stability. Both the high complex stabilities and the high activation energies required for cation exchange indicate a marked ‘spherical cryptate effect’ resulting from the highly connected nature of the molecular architecture of spherical macrotricyclic ligands. 相似文献
20.
Polyaza-polyoxa macrobicyclic ligands: its synthesis and metal complexes. The synthesis of the polyaza-polyoxa macrobicyclic ligands 1–4 is described. They form complexes with a variety of metal cations, transition metal cations as well as alkali and alkaline-earth cations. These complexes may be formulated as cation inclusion complexes, cryptates, in which the cation is contained in the intramolecular cavity. The properties of the complexes are described. An especially interesting feature is that these ligands, polymines of macrobicyclic topology, provide a means of trapping transition metal cations inside a molecular cavity; thus they impose coordination geometries and may modify the spectral and redox properties of the cations. 相似文献