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101.
A change of variables formula for mappings in is obtained, where the usual jacobian is replaced by the determinant of the approximate differential.
102.
Due to its potential as sample treatment for Analytical Chemistry, the Ultrasonic-Assisted Enzymatic Digestion (USAED) for total elemental determination and elemental speciation is described under the most recent achievements published in literature, focusing on the variables that critically affect the performance of this relatively new sample treatment, such as the type of enzymes or the type of ultrasonic system used for the acceleration of the solid-liquid extraction process. Moreover, analytical chemists are aware of common errors produced in data interpretation concerning USAED. In addition, a guide for the rapid application of this methodology is also provided along with detailed explanations. Finally, future trends regarding USAED are also given and commented. 相似文献
103.
Semi-empirical topological index: development of QSPR/QSRR and optimization for alkylbenzenes 总被引:1,自引:0,他引:1
The semi-empirical topological index, I(ET), was developed and optimized to describe the chromatographic retention of alkylbenzenes on the squalane stationary phase. The simple linear regression between the chromatographic retention and the proposed index, for 122 alkylbenzenes studied, is of good quality (determination coefficient, r(2)=0.9996, standard deviation, S.D.=5.5, and leave-one-out cross-validation correlation coefficient, r(CV)(2)=0.9996). The predictive ability of I(ET) was also verified for stationary phases with two different polarities (SE-30 and Carbowax 20 M), and good results were obtained, especially for the stationary phase with low polarity, showing that the specific molecular interactions occur on highly polar phases. The I(ET) was applied to construct quantitative structure-property relationship (QSPR) models for representative properties such as boiling point, Bp(degrees C), octanol/water partition coefficient, log P, van der Waals volume (V(W)) and molar refractivity (R(M)). Satisfactory quality QSPR models were obtained with Bp, V(W) and R(M) showing that the molecular size and dispersive forces are dominating factors with respect to the chromatographic retention. 相似文献
104.
Antônio Gomes dos Santos Neto Franciele de Matos Morawski Ana Caroline Ferreira Santos Cláudia Quintino da Rocha Roberto Batista de Lima Marília Oliveira Fonseca Goulart Clenilton Costa dos Santos Flávio Colmati Antônio Euzébio Goulart Santana Marco Aurélio Suller Garcia Auro Atsushi Tanaka 《Electroanalysis》2023,35(5):e202200390
Here, we report multiwalled carbon nanotubes (MWCNTs) functionalized with γ-cyclodextrins (γCD) as a novel electrochemical strategy for Rutin determination, showing superior performance than β-cyclodextrins (βCD) modified MWCNTs, suggesting an adequate environment for host-guest interactions. Under optimized conditions, the sensor showed a linear range of 39–975 nmol L−1 and a limit of detection of 7 nmol L−1. When tested with quercetin, catechin, and caffeine, the platform presented high selectivity with an interference response <10 %. The method was employed to quantify Rutin in spiked pharmaceutical and herbal extracts, providing recovery of 93–98.4 %. Also, HPLC-PDA confirmed the method‘s accuracy. 相似文献
105.
Light-Responsive Elastin-Like Peptide-Based Targeted Nanoparticles for Enhanced Spheroid Penetration
Dr. Duc H. T. Le Dr. Vusala Ibrahimova Sebastian A. H. van den Wildenberg Dr. Hanglong Wu Alba Fonseca Prof. Dr. Tomas Torres Dr. Elisabeth Garanger Dr. William P. J. Leenders Prof. Dr. Roland Brock Prof. Dr. Sébastien Lecommandoux Prof. Dr. Jan C. M. van Hest 《Angewandte Chemie (International ed. in English)》2023,62(24):e202300511
We describe here a near infrared light-responsive elastin-like peptide (ELP)-based targeted nanoparticle (NP) that can rapidly switch its size from 120 to 25 nm upon photo-irradiation. Interestingly, the targeting function, which is crucial for effective cargo delivery, is preserved after transformation. The NPs are assembled from (targeted) diblock ELP micelles encapsulating photosensitizer TT1-monoblock ELP conjugates. Methionine residues in this monoblock are photo-oxidized by singlet oxygen generated from TT1, turning the ELPs hydrophilic and thus trigger NP dissociation. Phenylalanine residues from the diblocks then interact with TT1 via π-π stacking, inducing the re-formation of smaller NPs. Due to their small size and targeting function, the NPs penetrate deeper in spheroids and kill cancer cells more efficiently compared to the larger ones. This work could contribute to the design of “smart” nanomedicines with deeper penetration capacity for effective anticancer therapies. 相似文献
106.
José Luis Fonseca María José Sosa Gabriela Petroselli Rosa Erra-Balsells Matías I. Quindt Sergio M. Bonesi Alexander Greer Edyta M. Greer Andrés H. Thomas Mariana Vignoni 《Photochemistry and photobiology》2023,99(2):593-604
Here, we provide mechanistic insight to the photocleavage of a compound in the folate family, namely pteroic acid. A bis-decyl chain derivative of pteroic acid was synthesized, structurally characterized and photochemically investigated. We showed that, like folic acid, pteroic acid and the decylated derivative undergo a photocleavage reaction in the presence of H2O, while no reaction was observed in methanol solution. Furthermore, density functional theory calculations were carried out to predict relative stabilities of hypothetical mono-, bis- and tris-decylated pteroic acid derivatives to help rationalize the regioselectivity of the bis-decyl pteroic acid product. Additionally, the lipophilicity of the bis-decyl pteroic acid appears to confer a hydrophobic property enabling an interaction with biomembranes. 相似文献
107.
Pereira EM Sierakowski MR Jó TA Moreira RA Monteiro-Moreira AC França RF Fonseca BA Petri DF 《Colloids and surfaces. B, Biointerfaces》2008,66(1):45-52
Formation of stable thin films of mixed xyloglucan (XG) and alginate (ALG) onto Si/SiO(2) wafers was achieved under pH 11.6, 50mM CaCl(2), and at 70 degrees C. XG-ALG films presented mean thickness of (16+/-2)nm and globules rich surface, as evidenced by means of ellipsometry and atomic force microscopy (AFM), respectively. The adsorption of two glucose/mannose-binding seed (Canavalia ensiformis and Dioclea altissima) lectins, coded here as ConA and DAlt, onto XG-ALG surfaces took place under pH 5. Under this condition both lectins present positive net charge. ConA and DAlt adsorbed irreversibly onto XG-ALG forming homogenous monolayers approximately (4+/-1)nm thick. Lectins adsorption was mainly driven by electrostatic interaction between lectins positively charged residues and carboxylated (negatively charged) ALG groups. Adhesion of four serotypes of dengue virus, DENV (1-4), particles to XG-ALG surfaces were observed by ellipsometry and AFM. The attachment of dengue particles onto XG-ALG films might be mediated by (i) H bonding between E protein (located at virus particle surface) polar residues and hydroxyl groups present on XG-ALG surfaces and (ii) electrostatic interaction between E protein positively charged residues and ALG carboxylic groups. DENV-4 serotype presented the weakest adsorption onto XG-ALG surfaces, indicating that E protein on DENV-4 surface presents net charge (amino acid sequence) different from E proteins of other serotypes. All four DENV particles serotypes adsorbed similarly onto lectin films adsorbed. Nevertheless, the addition of 0.005mol/L of mannose prevented dengue particles from adsorbing onto lectin films. XG-ALG and lectin layers serve as potential materials for the development of diagnostic methods for dengue. 相似文献
108.
Pierrefixe SC Fonseca Guerra C Bickelhaupt FM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(3):819-828
Why is silicon hypervalent and carbon not? Or why is [Cl? CH3? Cl]? labile with a tendency to localize one of its axial C? Cl bonds and to largely break the other one, while the isostructural and isoelectronic [Cl? SiH3? Cl]? forms a stable pentavalent species with a delocalized structure featuring two equivalent Si? Cl bonds? Various hypotheses have been developed over the years focusing on electronic and steric factors. Here, we present the so‐called ball‐in‐a‐box model, which tackles hypervalence from a new perspective. This model reveals the key role of steric factors and provides a simple way of understanding the above phenomena in terms of different atom sizes. Our bonding analyses are supported by computation experiments in which we probe, among other things, the shape of the SN2 potential‐energy surface of Cl? attacking a carbon atom in the series of substrates CH3Cl, .CH2Cl, ..CHCl, and ...CCl. Our findings for ClCH3Cl? and ClSiH3Cl? are generalized to other Group 14 central atoms (Ge, Sn, and Pb) and axial substituents (F). 相似文献
109.
110.