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排序方式: 共有102条查询结果,搜索用时 390 毫秒
21.
Jeffrey C. Pelletier Venkata VelvadapuMark E. McDonnell Jay E. WrobelAllen B. Reitz 《Tetrahedron letters》2014
We have found that α-amino acid amide derivatives of 2-aminobenzothiazoles undergo a time-dependent, thermal rearrangement in which the amine group attacks the 2-position carbon of the thiazole ring to form a 5,5-spiro ring system. This is followed by sulfur leaving and air oxidation to the corresponding symmetrical disulfide. The isolated yields of such products are quite high (>70%) if there is conformational bias to further promote the intramolecular reaction such as for the 2-aminobenzothiazole amides derived from proline or 4-aminopiperidine-4-carboxylic acid. This rearrangement has not been described previously for α-amino acid amide derivatives of 2-aminobenzothiazoles. However, a related reaction involving 2-semicarbazido benzothiazoles has been recently reported. 相似文献
22.
Mohamed H Russo AP Szarowski DH McDonnell E Lepak LA Spencer MG Martin DL Caggana M Turner JN 《Journal of chromatography. A》2006,1111(2):214-219
In lab-on-a-chip applications, filtration is currently performed prior to sample loading or through pre-cast membranes adhered to the substrate. These membranes cannot be patterned to micrometer resolution, and their adhesion may be incompatible with the fabrication process or may introduce contaminants. We have developed an on-chip separation process using a biocompatible polymer that can be patterned and has controllable molecular rejection properties. We spun cast cellulose acetate (CA) membranes directly onto silicon wafers. Characterization of the molecular flux across the membrane showed that molecular weight and charge are major factors contributing to the membranes' rejection characteristics. Altering casting conditions such as polymer concentration in the casting solution and the quenching-bath composition and/or temperature allowed control of the molecular weight cut-off (MWCO). Three MWCOs; 300, 350, and 700 Da have been achieved for non-linear molecules. Molecular shape is also very important as much higher molecular weight single-stranded DNA was electrophoresed across the membranes while heme with a similar negative charge density was rejected. This was due to DNA's small molecular cross section. This is an important result because heme inhibits polymerase chain reactions (PCR) reducing the detection and characterization of DNA from blood samples. 相似文献
23.
Maljaars CE Halkes KM de Oude WL Haseley SR Upton PJ McDonnell MB Kamerling JP 《Journal of combinatorial chemistry》2006,8(6):812-819
Two combinatorial glycopeptide libraries were synthesized on solid support via the "split-and-mix" method combined with the ladder synthesis strategy. The O-glycopeptide library contained Gal(beta1-O)Thr, whereas the S-,N-glycopeptide library contained both Gal(beta1-S)Cys and Gal(beta1-N)Asn. In this model study, the two libraries were screened against the fluorescently labeled lectin Ricinus communis agglutinin (RCA120). The screening results showed that both O- and S- or S-,N-glycopeptides were recognized by the lectin with similar amino acid recognition patterns. Surface plasmon resonance interaction studies demonstrated that both the selected S- or S-,N-glycopeptide hits and the O-glycopeptides bound to the lectin with a similar affinity. Structure 19, containing two glycosylated cysteine residues, bound to the receptor with the highest affinity (KA = 3.81 x 10(4) M(-1)), which is comparable to N-acetyllactosamine. Competition assays, in which some selected glycopeptides and methyl beta-d-galactopyranoside competed for the binding site of immobilized RCA120, showed that the glycopeptide-lectin interaction was carbohydrate-specific. Incubation of the O- and S-,N-glycopeptides with beta-galactosidase demonstrated the complete stability of S-,N-glycopeptides toward enzymatic degradation, whereas O-glycopeptides were not completely stable. 相似文献
24.
Liam A. McDonnell Alexandra van Remoortere Nico de Velde René J. M. van Zeijl André M. Deeldera 《Journal of the American Society for Mass Spectrometry》2010,21(12):1969-1978
Imaging MS now enables the parallel analysis of hundreds of biomolecules, spanning multiple molecular classes, which allows
tissues to be described by their molecular content and distribution. When combined with advanced data analysis routines, tissues
can be analyzed and classified based solely on their molecular content. Such molecular histology techniques have been used
to distinguish regions with differential molecular signatures that could not be distinguished using established histologic
tools. However, its potential to provide an independent, complementary analysis of clinical tissues has been limited by the
very large file sizes and large number of discrete variables associated with imaging MS experiments. Here we demonstrate data
reduction tools, based on automated feature identification and extraction, for peptide, protein, and lipid imaging MS, using
multiple imaging MS technologies, that reduce data loads and the number of variables by >100×, and that highlight highly-localized
features that can be missed using standard data analysis strategies. It is then demonstrated how these capabilities enable
multivariate analysis on large imaging MS datasets spanning multiple tissues. 相似文献
25.
McDonnell G 《Journal of AOAC International》2003,86(2):407-411
Dacron suture loops were demonstrated to be inert, consistent carriers in the presence of peracetic acid-based sterilants, whereas black silk sutures had a variable preparation process and interacted with peracetic acid. In addition, Dacron suture loops provided comparable spore loading to black silk suture loops and an HCI resistance of > or = 2 min. These results indicate that black silk suture loops are not appropriate carriers for assessing peracetic acid-based sterilants, and Dacron loops are an acceptable alternative. This finding is consistent with the Office of Science and Technology Laboratory (Center for Devices and Radiological Health) study which determined that "polyester suture material is a viable alternative to silk for the AOAC sporicidal test for liquid disinfectants." 相似文献
26.
Solute diffusion coefficients (D) can indicate a dependence upon actual solute concentrations. Here a single compartment has been utilized, in which effective HCl diffusion to a membrane-mounted glass pH electrode can be measured across the pH spectrum. The study has investigated HCl diffusion through both mucus and water layers as a function of HCl concentration. The observed dynamic responses of a liquid-film and mucus-coated electrodes over a range of HCl concentrations suggest that the speed at which equilibrium is attained is pH dependent; equilibrium was reached rapidly under more acidic and alkaline conditions. Estimated values of DHCl also indicate a strong pH dependence for both liquid film and mucus. In both instances, a greater than 10-fold reduction in DHCl at pH 7.5 as compared with that at pH 3.5 has been demonstrated. Furthermore, estimated values of DHCl are approximately 4-fold smaller through the mucus gel, as compared with a water layer. The findings indicate that the most powerful influence on diffusional resistance is pH itself, whereby a marked drop in H+ diffusion is likely to occur towards neutral pH irrespective of the composition of the gel barrier. Possible implications of the findings are discussed in relation to mucosal protection from acid. 相似文献
27.
28.
Francesco Greco Federica Anastasi Luca Fidia Pardini Marialaura Dilillo Eleonora Vannini Laura Baroncelli Matteo Caleo Liam A. McDonnell 《Molecules (Basel, Switzerland)》2021,26(19)
Glioblastoma Multiforme (GBM) is a brain tumor with a poor prognosis and low survival rates. GBM is diagnosed at an advanced stage, so little information is available on the early stage of the disease and few improvements have been made for earlier diagnosis. Longitudinal murine models are a promising platform for biomarker discovery as they allow access to the early stages of the disease. Nevertheless, their use in proteomics has been limited owing to the low sample amount that can be collected at each longitudinal time point. Here we used optimized microproteomics workflows to investigate longitudinal changes in the protein profile of serum, serum small extracellular vesicles (sEVs), and cerebrospinal fluid (CSF) in a GBM murine model. Baseline, pre-symptomatic, and symptomatic tumor stages were determined using non-invasive motor tests. Forty-four proteins displayed significant differences in signal intensities during GBM progression. Dysregulated proteins are involved in cell motility, cell growth, and angiogenesis. Most of the dysregulated proteins already exhibited a difference from baseline at the pre-symptomatic stage of the disease, suggesting that early effects of GBM might be detectable before symptom onset. 相似文献
29.
Recently, Clarke, Mason and Tescari have proposed a modified Patterson function for deriving surface structures from LEED intensity data. The technique is analysed in this paper by applying it to “averaged” experimental data and to data from kinematical calculations. It is found that truncation errors (associated particularly with the inner potential) prevent the technique from being generally useful, and their absence in the work of Clarke et al. was due to their use of an unrealistic inner potential. In addition, the complex form of scattering factors applicable to LEED provide a fundamental barrier to the use of Patterson functions for the analysis of LEED data in the most interesting case of adsorbate structures on surfaces. 相似文献
30.
Michael McDonnell 《Optics Communications》1978,25(3):320-322
The necessity of translating a scaled input function in the logarithmic coordinates necessary to perform an optical Mellin transform is demonstrated. The implications of this requirement in the processing of two dimensional inputs for pattern recognition are discussed. 相似文献