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排序方式: 共有104条查询结果,搜索用时 15 毫秒
1.
The possibility of obtaining immobilized horseradish peroxidase (HRP) materials with K'(m) values close to that of the native enzyme, but with good thermal stability, was investigated. The photochemical reaction was used as the immobilization methodology. Temperature and catalyst concentration were found to be the main parameters able to control the immobilization reaction mechanism more than type of functional monomer, polymer-matrix, and enzyme-polymer ratios. By carrying out the immobilization reaction at 35 degrees C and using either bisacryloylpiperazine (BAP) or hexhydro-1,3,5-triacryloyl-s-triazine (HTsT) as the functional monomer, materials with a good thermal stabilization (the retained activity after 240 min at 60 degrees C was between 65-25%) as well as kinetic constants (0.6-0.8 x 10(-4)M) similar to that of the free enzyme (0.57 x 10(-4)M) were obtained. Since low K'(m) values were obtained also using a high polymer content (pBAP copolymers, 25%; pHTsT copolymers, 30%) and neither limitation to substrate diffusion nor a reduction of the enzyme mobility was found, the enzyme should be linked to the matrix during the last steps of monomer polymerization, and it should have an external disposition with respect to the support. 相似文献
2.
G Carrea F Colombi G Mazzola P Cremonesi E Antonini 《Biotechnology and bioengineering》1979,21(1):39-48
The hydroxysteroid dehydrogenases: beta-HSDH, 20 beta-HSDH, and 3 alpha-HSDH, were immobilized on CNBr-activated Sepharose. The effect of various immobilization conditions on the activity recovery and stability were examined. The presence of cofactor during the immobilization reaction increased the activity recovery (40--60% of the total) and also led to materials highly stable in the presence of organic solvents. For example, beta-HSDH maintained 60% of its original activity two months after continuous use in the water--ethyl-acetate system. Kinetic experiments showed that the increase of the apparent Km values is poor and demonstrated that the organic solvent behaves as a weak inhibitor (ki greater than 0.2M) for the substrate. The immobilized enzymes lyophilized in the presence of sucrose had full activity restored even after several months storage at room temperature. Immobilized hydroxysteroid dehydrogenases were shown to be suitable for preparative transformation of steroids in water--organic solvent systems. 相似文献
3.
Aline Sampaio Cremonesi Lilia I. De la Torre Maximillia Frazão de Souza Gabriel S. Vignoli Muniz M. Teresa Lamy Cristiano Luis Pinto Oliveira Andrea Balan 《Biochemistry and Biophysics Reports》2021
ATP-Binding Cassette transporters (ABC transporters) are protein complexes involved in the import and export of different molecules, including ions, sugars, peptides, drugs, and others. Due to the diversity of substrates, they have large relevance in physiological processes such as virulence, pathogenesis, and antimicrobial resistance. In Xanthomonas citri subsp. citri, the phytopathogen responsible for the citrus canker disease, 20% of ABC transporters components are expressed under infection conditions, including the putative putrescine/polyamine ABC transporter, PotFGHI. Polyamines are ubiquitous molecules that mediate cell growth and proliferation and play important role in bacterial infections. In this work, we characterized the X. citri periplasmic-binding protein PotF (XAC2476) using bioinformatics, biophysical and structural methods. PotF is highly conserved in Xanthomonas sp. genus, and we showed it is part of a set of proteins related to the import and assimilation of polyamines in X. citri. The interaction of PotF with putrescine and spermidine was direct and indirectly shown through fluorescence spectroscopy analyses, and experiments of circular dichroism (CD) and small-angle X-ray scattering (SAXS), respectively. The protein showed higher affinity for spermidine than putrescine, but both ligands induced structural changes that coincided with the closing of the domains and increasing of thermal stability. 相似文献
4.
Mario Ramírez Gabriel Guillén Sara I. Fuentes Luis P. Íñiguez Rosaura Aparicio‐Fabre David Zamorano‐Sánchez Sergio Encarnación‐Guevara Dario Panzeri Bianca Castiglioni Paola Cremonesi Francesco Strozzi Alessandra Stella Lourdes Girard Francesca Sparvoli Georgina Hernández 《Physiologia plantarum》2013,149(3):389-407
5.
Qiaomei Fu Alissa Mittnik Philip L.F. Johnson Kirsten Bos Martina Lari Ruth Bollongino Chengkai Sun Liane Giemsch Ralf Schmitz Joachim Burger Anna Maria Ronchitelli Fabio Martini Renata G. Cremonesi Jiří Svoboda Peter Bauer David Caramelli Sergi Castellano David Reich Johannes Krause 《Current biology : CB》2013,23(7):553-559
6.
7.
This paper is a response to Gray MM, Sutter NB, Ostrander EA, Wayne RK: The IGF1 small dog haplotype is derived from Middle Eastern grey wolves. BMC Biology 2010, 8:16. 相似文献
8.
Paulo FP Pimenta Alessandra S Orfano Ana C Bahia Ana PM Duarte Claudia M Ríos-Velásquez Fabrício F Melo Felipe AC Pessoa Giselle A Oliveira Keillen MM Campos Luis Martínez Villegas Nilton Barnabé Rodrigues Rafael Nacif-Pimenta Rejane C Sim?es Wuelton M Monteiro Rogerio Amino Yara M Traub-Cseko José BP Lima Maria GV Barbosa Marcus VG Lacerda Wanderli P Tadei Nágila FC Secundino 《Memórias do Instituto Oswaldo Cruz》2015,110(1):23-47
In the Americas, areas with a high risk of malaria transmission are mainly located in
the Amazon Forest, which extends across nine countries. One keystone step to
understanding the Plasmodium life cycle in Anopheles species from the Amazon Region
is to obtain experimentally infected mosquito vectors. Several attempts to colonise
Ano- pheles species have been conducted, but with only short-lived success or no
success at all. In this review, we review the literature on malaria transmission from
the perspective of its Amazon vectors. Currently, it is possible to develop
experimental Plasmodium vivax infection of the colonised and field-captured vectors
in laboratories located close to Amazonian endemic areas. We are also reviewing
studies related to the immune response to P. vivax infection of Anopheles aquasalis,
a coastal mosquito species. Finally, we discuss the importance of the modulation of
Plasmodium infection by the vector microbiota and also consider the anopheline
genomes. The establishment of experimental mosquito infections with Plasmodium
falciparum, Plasmodium yoelii and Plasmodium berghei parasites that could provide
interesting models for studying malaria in the Amazonian scenario is important.
Understanding the molecular mechanisms involved in the development of the parasites
in New World vectors is crucial in order to better determine the interaction process
and vectorial competence. 相似文献
9.
Corradetti B Lange-Consiglio A Barucca M Cremonesi F Bizzaro D 《Cell proliferation》2011,44(4):330-342
Objectives: Umbilical cord matrix (UCM) has been recently proposed as an alternative source of mesenchymal stem cells (MSCs). The aim of this study was to isolate and characterize presumptive stem cells from intervascular and perivascular equine UCM and to obtain homogeneous subpopulations from both sites. Materials and methods: Umbilical cords were processed for retrieval of MSCs. Unsieved cells from intervascular and perivascular portions were evaluated for cell cycle analysis and for immunophenotyping by flow cytometry. Cells from each site were separated into larger and smaller sieved populations using multi‐dishes with 8‐μm pore transwell inserts. Each cell population was characterized in terms of renewal capability, specific marker expression and differentiation potential. Cryopreservation was performed on sieved cells only. Results: Cells from both areas expressed MSC and pluripotential specific markers and were able to differentiate into mesodermic and ectodermic lineages. The sieving procedure yielded two relatively homogeneous subpopulations with comparable characteristics. Surprisingly, after sieving, large intervascular and small perivascular cells were the most rapidly replicating cells [20.53 and 19.49 cell population doublings (PD) after 31 days respectively] and also showed higher fibroblast colony forming unit frequency. Unsieved cell populations were used as controls, and showed PD of 9.42(intervascular cells) and 8.54 (perivascular cells) after 31 days. Conclusions: Here, cells from UCM represented an intermediate stage between pluripotent embryonic and adult stem cells. Size‐sieving can be used to isolate more rapidly proliferating cell populations. 相似文献
10.
Fetal DNA detection in maternal plasma throughout gestation 总被引:12,自引:0,他引:12
Galbiati S Smid M Gambini D Ferrari A Restagno G Viora E Campogrande M Bastonero S Pagliano M Calza S Ferrari M Cremonesi L 《Human genetics》2005,117(2-3):243-248
The presence of fetal DNA in maternal plasma may represent a source of genetic material which can be obtained noninvasively. We wanted to assess whether fetal DNA is detectable in all pregnant women, to define the range and distribution of fetal DNA concentration at different gestational ages, to identify the optimal period to obtain a maternal blood sample yielding an adequate amount of fetal DNA for prenatal diagnosis, and to evaluate accuracy and predictive values of this approach. This information is crucial to develop safe and reliable non-invasive genetic testing in early pregnancy and monitoring of pregnancy complications in late gestation. Fetal DNA quantification in maternal plasma was carried out by real-time PCR on the SRY gene in male-bearing pregnancies to distinguish between maternal and fetal DNA. A cohort of 1,837 pregnant women was investigated. Fetal DNA could be detected from the sixth week and could be retrieved at any gestational week. No false-positive results were obtained in 163 women with previous embryo loss or previous male babies. Fetal DNA analysis performed blindly on a subset of 464 women displayed 99.4, 97.8 and 100% accuracy in fetal gender determination during the first, second, and third trimester of pregnancy, respectively. No SRY amplification was obtained in seven out of the 246 (2.8%) male-bearing pregnancies. Fetal DNA from maternal plasma seems to be an adequate and reliable source of genetic material for a noninvasive prenatal diagnostic approach. 相似文献