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541.
Patrice Soumillion Laurent Jespers Mich’ele Bouchet Jacqueline Marchand-Brynaert Pascale Sartiaux Jacques Fastrez 《Applied biochemistry and biotechnology》1994,47(2-3):175-190
Despite recent progress, our understanding of enzymes remains limited: the prediction of the changes that should be introduced
to alter their properties or catalytic activities in an expected direction remains difficult. An alternative to rational design
is selection of mutants endowed with the anticipated properties from a large collection of possible solutions generated by
random mutagenesis. We describe here a new technique of in vitro selection of genes on the basis of the catalytic activity
of the encoded enzymes.
The gene coding for the enzyme to be engineered is cloned into the genome of a filamentous phage, whereas the enzyme itself
is displayed on its surface, creating a phage enzyme. A bifunctional organic label containing a suicide inhibitor of the enzyme
and a ligand with high affinity for an immobilized receptor are constructed. On incubation of a mixture of phage enzymes,
those phages showing an activity on the inhibitor under the conditions of the experiment are labeled. These phages can be
recovered by affinity chromatography.
The design of the label and the factors controlling the selectivity of the selection are analyzed. The advantages of the technique
and its scope in terms of the enzymes that can be engineered are discussed. 相似文献
542.
MALDI-TOF MS analysis of soluble PEG based multi-step synthetic reaction mixtures with automated detection of reaction failure 总被引:1,自引:0,他引:1
Enjalbal C Ribière P Lamaty F Yadav-Bhatnagar N Martinez J Aubagnac JL 《Journal of the American Society for Mass Spectrometry》2005,16(5):670-678
Macromolecules of tunable solubility, used to mimic inert insoluble materials while maintaining solution conditions, allowed the performance of efficient supported organic chemistry and facilitated in situ reaction monitoring. To satisfy the high throughput requirements of automated synthetic processes, organic syntheses carried out on bifunctional polyethylene glycol polymers (PEG(3400)-OH) were monitored step-by-step by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). A protocol was designed to control the ionization mechanism of such polymers exhibiting high affinity for alkali metal cations. Automated, rapid, and reliable data interpretation was performed by an in-house developed visual basic application relying on the sodiated ion accurate monoisotopic mass measurement. The methodology was illustrated through the monitoring of a six-step synthetic scheme. 相似文献
543.
544.
Immobilised artificial membrane (IAM) chromatography was utilised to study the interactions of usual membrane probes with grafted phosphatidylcholine silica support, in relation to the presence of calcium ions introduced in the mobile phase as they are present in nutritional mixtures. IAM acts as a mimetic membrane of lipid emulsion globules, a major component of nutritional mixtures. The tested probes were 1,6-diphenyl-1,3,5-hexatriene (DPH), 9-diethylamino-5H-benzo[alpha]phenoxazine-5-one or nile red (NR) and 2-(p-toluidinyl)naphtalene-6-sulfonate (TNS). For each probe, partition coefficients and thermodynamic parameters of transfer from the mobile phase to the IAM stationary phase have been measured. Our results suggested that the interactions of neutral probes (i.e. DPH and NR) with phosphatidylcholine are driven by hydrophobic forces. Addition of calcium chloride to the mobile phase slightly decreased the retention of these neutral probes and dramatically increased that of anionic TNS. Moreover, an enthalpy-entropy compensation study revealed that the mechanism of interaction between TNS and IAM is independent of the calcium concentration. Results argued for the existence of electrostatic repulsion forces exerted by IAM phase towards anionic TNS. Addition of calcium ions into the mobile phase led to the establishment of an ionic double layer at the zwitterionic stationary phase surface weakening the electrostatic barrier and increasing TNS retention. Consequently, it was demonstrated that IAM appears as a suitable model to get a better insight on the lipid-calcium interactions taking place in nutritional mixtures. 相似文献
545.
Patrice Rubini Andrea LakatosDelphine Champmartin Tamas Kiss 《Coordination chemistry reviews》2002,228(2):137-152
Complexes formed with low molecular mass biomolecules are the ‘dynamic or mobile units’ of Al(III), which may be involved in the absorption and transport processes of this toxic element in organisms. This paper reviews the interactions of Al(III), from speciation and structural aspects, with biologically relevant endogenous and exogenous small biomolecules such as inorganic ligands (hydroxide, fluoride, (oligo)phosphates and silicic acid), amino acids, phosphorylated amino acids, oligopeptides, biophosphates including nucleotides, phosphonates, hydroxamates, and aromatic and aliphatic hydroxycarboxylates. The importance of time in biospeciation is demonstrated on the examples of binary and ternary systems involving Al(III) and citric acid. Examples are also given for the implications of the speciation of Al(III) with such small biomolecules in biology. 相似文献
546.
Anthony D'Aléo Dr. Guillaume Pompidor Bénédicte Elena Dr. Jean Vicat Prof. Patrice L. Baldeck Dr. Loïc Toupet Dr. Richard Kahn Dr. Chantal Andraud Dr. Olivier Maury Dr. 《Chemphyschem》2007,8(14):2125-2132
The linear and non-linear photophysical properties of tris-dipicolinate europium and terbium complexes (absorption, emission, lifetime, luminescence induced by two-photon absorption) are studied in the crystalline state as well as in protein derivative crystals and compared to those in solution. Upon laser irradiation at 532 nm, luminescence of terbium is induced by a two-photon antenna effect, whereas luminescence of europium results from one-photon absorption in forbidden f-f transitions. Finally, linear and two-photon microscopy imaging experiments on biological and bio-inspired crystals are performed. These first proof-of-concept experiments open the way for the development of time-resolved non-linear microscopy that should combine the advantages of lanthanide luminescence (long lifetime, sharp emission bands, insensitivity to oxygen) with those of confocal biphotonic excitation (near-IR excitation, 3D resolution and reduced photodamage). 相似文献
547.
T Patrice M T Foultier S Yactayo M C Douet F Maloisel L Le Bodic 《Journal of photochemistry and photobiology. B, Biology》1990,6(1-2):157-165
Endoscopic photodynamic therapy (PDT) with haematoporphyrin derivative was used in the primary treatment of 69 patients with inoperable gastrointestinal neoplasms. Patients were divided into three groups: 31 with oesophageal squamous cell carcinoma, 17 with adenocarcinoma of the stomach or lower third of the oesophagus and 21 with rectosigmoid adenocarcinoma. After infusion of 2.5-5.0 mg haematoporphyrin derivative per kilogram of body weight, lesions were irradiated using an argon dye laser (632 nm). During a follow-up period averaging 20 months (27.9 months for 35 surviving patients), complete local tumour destruction and negative histology were observed in 32 out of 69 cases. Flow-cytometric analysis of DNA content before and after PDT suggests that a clonal selection occurs in some cases of treatment failure. The results of this open pilot study suggest the potential efficacy of PDT as a curative treatment for selected cases of inoperable gastrointestinal cancers. 相似文献
548.
Misa V. Jovanovic Edward R. Biehl Patrice De Meester Shirley S. C. Chu 《Journal of heterocyclic chemistry》1986,23(3):801-807
Nitration of 2-chloro-10-methylphenothiazine, 1 , yields two mono-nitro compounds identified as sulfoxide 2 and sulfone 3 . The nmr analyses of the 13C spectra of 2 and 3 establish unequivocally that in both compounds substitution has occurred at the seven position. This is supported by the X-ray crystal structure of one of the compounds 2-chloro-7-nitro-10-methylphenothiazine 5-oxide, 2 , which also shows that the sulfoxide group is in the “pseudo-axial” configuration. Crystals of 2 are monoclinic, space group P21/n, a = 11.606(4), b = 13.970(4)Å, c = 9.837(2), β = 127.49(2)° and Z = 4. The structure has been refined by full-matrix least-squares to R = 0.033 and Rw = 0.035, using 1704 observed reflections. 相似文献
549.
Suman K. Chopra Shirley S.C. Chu Patrice De Meester Darren E. Geyer Michael Lattman Scott A. Morse 《Journal of organometallic chemistry》1985,294(3):347-355
Cat2PMn(CO)5 (1, cat = ) is found to undergo carbonyl substitution reactions with phosphorus donors to give the isolable products cat2PMn(CO)4L, where L = cis-PPh3 (2); trans-PPh3 (3); cis-P(OMe)3 (4); and cis-P(OPh)3 (5). No evidence for CO insertion into the pentacoordinate PMn bond is observed. The X-ray crystal structure of 5 shows that the crystals are monoclinic, space group P21/n. The unit cell parameters are: a 10.523(2), b 25.765(5), c 13.344(2) Å, β 99.11(2)°, and Z = 4. Full matrix least squares refinement reached R= 0.054 for 3099 observed reflections. The pentacoordinate phosphorus adopts a distorted trigonal bipyramid geometry with the Mn in an equatorial position. Noteworthy is the small equatorial OPO angle of 110.1(2)°. 相似文献
550.
Robert Nouguier Michel Crozet Patrice Vanelle José Maldonado 《Tetrahedron letters》1985,26(45):5523-5524
Heterogeneous reaction of TRIS 1 with nitro-aldehydes leads to oxazolidines in good yield. New products are obtained as monocyclic or bicyclic compounds, and are of potential medicinal value. 相似文献