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31.
Anjali Nirmala Indulekha Mukkatt Sreejith Shankar Ayyappanpillai Ajayaghosh 《Angewandte Chemie (International ed. in English)》2021,60(1):455-465
Temperature is often not considered as a precision stimulus for artificial chemical systems in contrast to the host–guest interactions related to many natural processes. Similarly, mimicking multi‐state volatile memory operations using a single molecular system with temperature as a precision stimulus is highly laborious. Here we demonstrate how a mixture of iron(II) chloride and bipyridine can be used as a reversible color‐to‐colorless thermochromic switch and logic operators. The generality of the approach was illustrated using CoII and NiII salts that resulted in color‐to‐color transitions. DMSO gels of these systems, exhibited reversible opaque‐transparency switching. More importantly, optically readable multi‐state volatile memory with temperature as a precision input has been demonstrated. The stored data is volatile and is lost instantaneously upon withdrawal or change of temperature. Simultaneous read‐out at multiple wavelengths results in single‐input/multi‐output sequential logic operations such as data accumulators (counters) leading to volatile memory states. The present system provides access to thermoresponsive materials wherein temperature can be used as a precision stimulus. 相似文献
32.
Sreejith RK Suresh CG Bhosale SH Bhavnani V Kumar A Gaikwad SM Pal JK 《Journal of fluorescence》2012,22(1):431-441
In mammalian cells, the heme-regulated inhibitor (HRI) plays a critical role in the regulation of protein synthesis at the
initiation step through phosphorylation of α-subunit of the eukaryotic initiation factor 2 (eIF2). In this study we have cloned
and performed biophysical characterization of the kinase catalytic domain (KD) of rabbit HRI. The KD described here comprises
kinase 1, the kinase insertion domain (KI) and kinase 2. We report here the existence of an active and stable monomer of HRI
(KD). The HRI (KD) containing three tryptophan residues was examined for its conformational transitions occurring under various
denaturing conditions using steady-state and time-resolved tryptophan fluorescence, circular dichroism (CD) and hydrophobic
dye binding. The parameter A and phase diagram analysis revealed multi-state unfolding and existence of three stable intermediates
during guanidine hydrochloride (Gdn-HCl) induced unfolding of HRI (KD). The protein treated with 6 M Gdn-HCl showed collisional
and static mechanism of acrylamide quenching and the constants (K
sv
= 3.08 M−1and K
s
= 5.62 M−1) were resolved using time resolved fluorescence titration. Based on pH, guanidine hydrochloride and temperature mediated
transitions, HRI (KD) appears to exemplify a rigid molten globule-like intermediate with compact secondary structure, altered
tertiary structure and exposed hydrophobic patches at pH 3.0. The results indicate the inherent structural stability of HRI
(KD), a member of the class of stress response proteins. 相似文献
33.
Sreejith Sudhakaran Jayabhavan Dipankar Ghosh Krishna K. Damodaran 《Molecules (Basel, Switzerland)》2021,26(21)
The structural modification of existing supramolecular architecture is an efficient strategy to design and synthesize supramolecular gels with tunable and predictable properties. In this work, we have modified bis(pyridyl urea) compounds with different linkers, namely hexylene and butylene, to their corresponding bis(pyridyl-N-oxide urea). The gelation properties of both the parent and the modified compounds were studied, and the results indicated that modification of the 3-pyridyl moieties to the corresponding 3-pyridyl-N-oxides induced hydrogelation. The stability of the parent and modified compounds were evaluated by sol-gel transition temperature (Tgel) and rheological measurements, and single-crystal X-ray diffraction was used to analyze the solid-state interactions of the gelators. The morphologies of the dried gels were analyzed by scanning electron microscopy (SEM), which revealed that the structural modification did not induce any prominent effect on the gel morphology. The stimuli-responsive behavior of these gels in the presence of salts in DMSO/water was evaluated by rheological experiments, which indicated that the modified compounds displayed enhanced gel strength in most cases. However, the gel network collapsed in the presence of the chloride salts of aluminum(III), zinc(II), copper(II), and cadmium(II). The mechanical strength of the parent gels decreased in the presence of salts, indicating that the structural modification resulted in robust gels in most cases. The modified compounds formed gels below minimum gel concentration in the presence of various salts, indicating salt-induced gelation. These results show the making and breaking ability of the gel network in the presence of external stimuli (salts), which explains the potential of using LMWGs based on N-oxide moieties as stimuli-responsive materials. 相似文献
34.
A simple ratiometric fluorescence probe based on vinylpyrrole end-capped bipyridine for the visual sensing of Zn2+ under aqueous physiological pH (6.8-7.4) is described. The fluorophores 3a-c showed strong emission around 537 nm in acetonitrile with a quantum yield of 0.4. In buffered (HEPES, pH 7.2) acetonitrile-water mixture (9:1 v/v), titration of transition metal salts to 3c showed strong quenching of the emission at 547 nm except in the case of Zn2+, which resulted in a red-shifted emission at 637 nm. Alkali and alkaline earth metal salts could not induce any considerable changes to the emission behavior of 3a-c. The binding of Zn2+ was highly selective in the presence of a variety of other metal ions. Though Cu2+ quenches the emission of 3c, in the presence of Zn2+, a red emission prevails, indicating the preference of 3c toward Zn2+. Job plot and Benesi-Hildebrand analysis revealed a 1:1 complexation between the probe and the metal ion. The selective visual sensing of Zn2+ with a red emission is ideally suited for the imaging of biological specimens. 相似文献
35.
A pyrrole end-capped bipyridyl ligand incorporating a chiral handle exhibited high solid-state emission when compared to the achiral analogue 1b and to the racemic molecule 1c which allowed the design of a reusable fluorescent probe for the selective detection of Zn2+ under aqueous conditions. 相似文献
36.
37.
Natural product analogue generation is important, providing tools for chemical biology, enabling structure activity relationship determination and insight into the way in which natural products interact with their target biomolecules. The generation of analogues is also often necessary in order to improve bioavailability and to fine tune compounds' activity. This review provides an overview of the catalogue of approaches available for accessing series of analogues. Over the last few years there have been major advances in genome sequencing and the development of tools for biosynthetic pathway engineering; it is therefore becoming increasingly easy to combine molecular biology and synthetic organic chemistry in order to enable expeditious access to series of natural products. This review outlines the various ways of combining biology and chemistry that have been applied to analogue generation, drawing upon a series of examples to illustrate each approach. 相似文献
38.
Bhupinder Singh Sumedha Ahuja Renu Pandey RK Singhal 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(3):1315-1320
Root release of organic compounds and rate of the vascular sap flow are important for understanding the nutrient and the source-sink dynamics in plants, however, their determination is procedurally cumbersome and time consuming. We report here a simple method involving 14C labeling for rapid and reliable measurement of root exudates and vascular sap flow rate in a variable groundnut population developed through seed gamma irradiation using a cobalt source (60Co). An experimental hypothesis that a higher 14C level in the vascular sap would indicate a higher root release of carbon by the roots into the rhizosphere was verified. 相似文献
39.
Kizhmuri P. Divya Sivaramapanicker Sreejith Dr. Cherumuttathu H. Suresh Divya S. Philips Dr. Ayyappanpillai Ajayaghosh 《化学:亚洲杂志》2013,8(7):1579-1586
An unprecedented, positional effect of the isomeric repeat unit on chain folding in donor–acceptor‐linked oligomers, which contain alternating bipyridine and carbazole moieties that are connected through an acetylinic linkage, is reported. 4,4′‐Linked oligomer 1 adopts an intrachain helical conformation (CD‐active) in CHCl3/MeCN (20:80 v/v), whereas oligomer 2 , which contains an isomeric 6,6′‐linkage, forms interchain randomly coiled aggregates (CD‐inactive). The substitution position plays a significant role in controlling the variations in electronic effects and dipole moments around the bipyridyl moiety, which are responsible for this observed phenomenon. Two model compounds of oligomers 1 and 2 ( 3 and 4 , respectively) were prepared and their properties were compared. A systematic investigation of the photophysical and CD properties of these structures, as well as theoretical studies, support our conclusions. 相似文献
40.
Three new 2-component unsubstituted ( 4P ), diiodo- ( 5P ), and dibromo- ( 6P ) distyryl-BODIPY-bridged cyclotriphosphazene dimers were designed and synthesized. The newly synthesized BODIPY-cyclotriphosphazene systems were characterized by 1 H, 13 C, and 31 P NMR spectroscopy. The photophysical properties of the distryl-BODIPYs (4–6) and BODIPY-cyclotriphosphazene dyads ( 4P – 6P ) were studied by UV-Vis absorption and fluorescence emission spectroscopy. In these derivatives, the bino-type cyclotriphosphazene derivative bearing unsubstituted BODIPY unit 4P exhibited high fluorescence and no singlet oxygen generation due to the lack of spin converter. The attachment of heavy atoms (iodine and bromine) enabled the production of singlet oxygen. The bino-type BODIPY-cyclotriphosphazenes ( 5P and 6P ) were also used as triplet photosensitizers in the photooxidation of 1,3-diphenylisobenzofuran to endoperoxide via generation of the singlet oxygen in dichloromethane. The singlet oxygen production of these compounds was also investigated via a direct method and produced a singlet oxygen phosphorescence peak at 1270 nm. 相似文献