Raman spectroscopy has been successfully employed in order to investigate the formation of β-cyclodextrin host–guest inclusion molecular complexes with several different azo-dye structures. The Raman pattern of the carbohydrate framework results negligible when neared to the magnificent intensity of the highly polarisable guest systems and a complete and feasible comparison of the spectral features between the free and the complexed situation of the guest molecule is allowed. In general, with respect to the free guest state, it was found within the complex that a hampering of Raman intensity displays, accompanied by a levelling directed variation of the relative peak intensities, and peculiar Raman peak broadening with shifts occur, relatable to the host–guest settling of inclusive intermolecular interactions. Supportively to the other commonly established characterising methods, or in valid alternative, Raman technique has proved astoundingly useful under the perspective of the diagnostic evaluation of cyclodextrin host–guest molecular inclusion for azo-dyes and, more generally, for a highly polarisable guest structure. It features sample non-destructivity, handiness, fastness and sensitive reproducibility, occasionally providing useful suggestions about the complexation topology. 相似文献
CO2‐binding organic liquids (CO2BOLs) are mixtures of a base (typically an amidine or guanidine) and an alcohol, and have been shown to reversibly capture and release CO2 with low reaction energies and high gravimetric CO2 capacity. We now report the ability of such liquid blends to chemically bind and release other acid gases such as CS2, COS, and SO2 analogously to CO2. These systems bind with sulfur‐containing acid gases to form colored ionic liquids with new O‐alkylxanthate, O‐alkylthiocarbonyl, and O‐alkylsulfite anions. The capture and thermal stripping of each acid gas from these systems and their applicability towards flue gas desulfurization is discussed. 相似文献
The phthalocyanine photosensitizer Pc 4 has been shown to bind preferentially to mitochondrial and endoplasmic reticulum membranes. Upon photoirradiation of Pc 4-loaded cells, membrane components, especially Bcl-2, are photodamaged and apoptosis, as indicated by activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase, is triggered. A series of analogs of Pc 4 were synthesized, and the results demonstrate that Pcs with the aminopropylsiloxy ligand of Pc 4 or a similar one on one side of the Pc ring and a second large axial ligand on the other side of the ring have unexpected properties, including enhanced cell uptake, greater monomerization resulting in greater intracellular fluorescence and three-fold higher affinity constants for liposomes. The hydroxyl-bearing axial ligands tend to reduce aggregation of the Pc and direct it to lysosomes, resulting in four to six times more killing of cells, as defined by loss of clonogenicity, than with Pc 4. Whereas Pc 4-PDT photodamages Bcl-2 and Bcl-xL, Pc 181-PDT causes much less photodamage to Bcl-2 over the same dose–response range relative to cell killing, with earlier cleavage of Bid and slower caspase-3-dependent apoptosis. Therefore, within this series of photosensitizers, these hydroxyl-bearing axial ligands are less aggregated than is Pc 4, tend to localize to lysosomes and are more effective in overall cell killing than is Pc 4, but induce apoptosis more slowly and by a modified pathway. 相似文献
Assay of angiotensin I-converting enzyme (ACE) inhibitory activity always draws much attention because of diverse applications in the field of antihypertension and related pathogenesis. Recently, the use of a new synthetic substrate, 3-hydroxybutyrylglycyl-glycyl-glycine (3HB-GGG), for the assay of ACE inhibitory activity has been confirmed. To construct a rapid, economical, and automatic determination system of ACE inhibitory activity using 3HB-GGG, a flow injection analysis (FIA) system with enzymatic reactors was developed in this study. Enzyme reactors were composed of aminoacylase and 3-hydroxybutyrate dehydrogenase immobilized separately on CNBr-activated Sepharose 4B. The assay condition was optimized in terms of the conversion of 3HB-G into NADH by the enzymatic reactors when the reaction solution containing 3HB-G generated from 3HB-GGG (after the incubation with ACE) was repetitively injected into the FIA system. Under the optimized conditions, 3HB-G was converted to 3HB, and then 3HB was oxidized by NAD+ to form NADH. The developed system successfully detected practical ACE inhibitors with a great sensitivity, high sampling frequency (10 samples h−1) and a durable stability of the enzymatic reactors. 相似文献
A fluorogen named 1-decyl-1-methyl-2,5-bis{4-[(N,N-diethylamino)methyl]phenyl}-3,4-diphenylsilole (3) was synthesized. It emitted weakly as isolated molecule but strongly as
supramolecular aggregate, showing a characteristic behavior of aggregation-induced emission (AIE). The molecules of 3 formed
highly emissive nanoparticles in aqueous media, which quickly and selectively marked cytoplasm of HeLa cells and posed no
toxicity to the living cells. The fluorogen is thus a promising candidate material for cell imaging as a sensitive, selective
and cytocompatible biosensor.
Supported by the Research Grants Council of Hong Kong (Grant Nos. 603008, 601608 and 602707), the National Natural Science
Foundation of China (Grant No. 20634020) and the CAO GuangBiao Foundation of Zhejiang University. 相似文献
In this work, we describe two different methods for generating protonated S-nitrosocysteine in the gas phase. The first method
involves a gas-phase reaction of protonated cysteine with t-butylnitrite, while the second method uses a solution-based transnitrosylation reaction of cysteine with S-nitrosoglutathione
followed by transfer of the resulting S-nitrosocysteine into the gas phase by electrospray ionization mass spectrometry (ESI-MS).
Independent of the way it was formed, protonated S-nitrosocysteine readily fragments via bond homolysis to form a long-lived
radical cation of cysteine (Cys•+), which fragments under collision-induced dissociation (CID) conditions via losses in the following relative abundance order:
•COOH ≫ CH2S > •CH2SH-H2S. Deuterium labeling experiments were performed to study the mechanisms leading to these pathways. DFT calculations were
also used to probe aspects of the fragmentation of protonated S-nitrosocysteine and the radical cation of cysteine. NO loss
is found to be the lowest energy channel for the former ion, while the initially formed distonic Cys•+ with a sulfur radical site undergoes proton and/or H atom transfer reactions that precede the losses of CH2S, •COOH, •CH2SH, and H2S. 相似文献
The physical properties of a fat are determined by its thermal history, processing conditions, chemical composition, polymorphism
and spatial distribution of mass. The mass fractal dimension of a fat crystal network can be determined from the slope of
the log–log plot of the storage modulus (G′) versus the solid fat content (SFC). Different SFCs were obtained by melting the fat, diluting it to different extents in
liquid oil, and crystallizing the blends under specific conditions. One of the major drawbacks of this method is the inability
of characterizing the native structure of an already crystallized fat. In the thermo-mechanical method developed in this study,
SFC is changed via temperature variations instead. At each temperature, the G′ and SFC were measured and the fractal dimension calculated as described above. The thermomechanical method proved to be
a simpler and more reliable estimator of the fractal dimension of a fat crystal network than the dilution method. 相似文献
In the swim : Colloidal nanoparticles coated with polylactide (PLA, red) and poly(ethylene glycol) brushes (PEG, black) can transfer from organic to aqueous phases across liquid/liquid or liquid/gel interfaces during degradation of the PLA coating (see picture: first step), which is driven selectively by the hydrogen bonding of the PEG coating with the aqueous phase (second step).
We have investigated how the non-zwitterionic and zwitterionic structures of aliphatic-only tripeptides affect the formation and dissociation of peptide radical cations in the gas phase. The non-zwitterionic forms of the aliphatic-only peptides in their metal complexes play an important role in determining whether the electron transfer pathway predominates. We extended this study by synthesizing permanent non-zwitterionic and zwitterionic forms of aliphatic-only peptide radical cations and exploring their reactivities in the gas phase. Collision-induced dissociation spectra demonstrated the feasibility of generating both non-zwitterionic and zwitterionic forms. Radical cations in zwitterionic forms may indeed mediate the beta and gamma carbon-carbon bond cleavages of leucine and isoleucine side chains from the GlyGlyXle radical peptides; this feature allows leucine and isoleucine residues to be distinguished unambiguously. 相似文献
Joule heating is inevitable when an electric field is applied across a conducting medium. It would impose limitations on the performance of electrokinetic microfluidic devices. This article presents a 3-D mathematical model for Joule heating and its effects on the EOF and electrophoretic transport of solutes in microfluidic channels. The governing equations were numerically solved using the finite-volume method. Experiments were carried out to investigate the Joule heating associated phenomena and to verify the numerical models. A rhodamine B-based thermometry technique was employed to measure the solution temperature distributions in microfluidic channels. The microparticle image velocimetry technique was used to measure the velocity profiles of EOF under the influence of Joule heating. The numerical solutions were compared with experimental results, and reasonable agreement was found. It is found that with the presence of Joule heating, the EOF velocity deviates from its normal "plug-like" profile. The numerical simulations show that Joule heating not only accelerates the sample transport but also distorts the shape of the sample band. 相似文献