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11.
H.-K. Kim E. Tuite B. Nordén B.W. Ninham 《The European physical journal. E, Soft matter》2001,4(4):411-417
The source of the activation energy that allows cutting of DNA by restriction enzymes is unclear. A systematic study of the
cutting efficiency of the type-II restriction endonuclease EcoRI, with varying background electrolyte ion pair and buffer reported here, shows only a modest dependence of efficiency on
cation type. Surprisingly, efficiency does depend strongly on the presumed indifferent anion of the background salt. What
emerges is that competition between the background salt anion and the buffer anion for the enzyme and DNA surfaces is crucial.
The results are unexpected and counterintuitive from the point of view of conventional electrolyte theory. However, taken
together with recent developments in surface chemistry, the results do fall into place and could also suggest a novel mechanism
for enzyme activity as an alternative to metal-activated hydrolysis: microscopic cavitation in a hydrophobic pocket might
be the source of activation energy.
Received 19 June 2000 and Received in final form 17 October 2000 相似文献
12.
13.
Josef Schurz 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):471-478
After a discussion of the different levels of macromolecules, the phenomenon of life is regarded as a complex polymer system. The thermodynamic basis of general system theory is explained as well as the character of system laws. The important notion of emergent system properties is stressed, and life is explained as a system property of a sufficiently complex system. The general applicability of the systemic approach is pointed out, and some examples are provided. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 471–478, 2004 相似文献
14.
Yongbing Song Run Jiang Zheng Wang Lang Wang Yuhua Yin Baohui Li An‐Chang Shi 《Macromolecular theory and simulations》2016,25(6):559-570
The self‐assembled morphologies of cyclic amphiphiles, which are composed of a long hydrophobic block and a short hydrophilic block, in selective solutions are studied by using a simulated annealing method. The morphological dependence of the aggregates on solvent quality is investigated. The topology effects are studied by comparing results from linear counterparts of the amphiphiles. It is observed that, in addition to spherical micelles, cylindrical micelles, disklike micelles, vesicles, and large compound micelles, muticompartment vesicles with several fluidic cores can be formed by the cyclic systems. The morphologies are regulated by the interaction parameter εAS between the hydrophobic block and solvents. Furthermore, it is revealed that the differences of characteristics of the self‐assembled aggregates originate from the difference in architectural constraint. The wide region of forming multicompartment vesicles suggests that cyclic amphiphilic macromolecules could be a suitable candidate for applications to deliver multiple functional components by compartmentalizing different components in different confined space of vesicles. 相似文献
15.
Prof. Dr. Francesc Teixidor Dr. Ariadna Pepiol Prof. Dr. Clara Viñas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10650-10653
A new class of globular polybranched macromolecules that contain multiple anionic metallacarborane clusters at the o‐carborane periphery is reported. The water soluble high boron rich containing molecules could be of interest for boron neutron capture therapy (BNCT) as well as for drug delivery. The reinforced electrostatic noncovalent interactions between anionic polyethylene glycol cobaltabisdicarbollide (PEG‐COSAN) branches and the ammonium cation have been shown using ESI‐MS. 相似文献
16.
The shape of the steady-state three-dimensional flow velocity profile established in carrier liquid flowing inside the rectangular cross-sectional channel for field-flow fractionation should be taken into account to optimize the separation. The central parts of this profile in the planes parallel to the main channel walls are flat with almost identical flow velocities which drop down to zero at the side walls. The separated species transported by the flow in the close-to-side walls regions move with lower average velocities compared to the species transported in the central part of the channel and are undesirably broadened. The hydrodynamic splitting of the carrier liquid at the entry of the channel where the sample is injected only into the central part of the channel eliminates the excessive zone broadening. The aspect ratio of the breadth to the thickness of the channel ratio can thus be reduced. The effect of various aspect ratios on the shape of the flow velocity profile is calculated and the results are used to optimize the aspect ratio of microfluidic channels. The experiments carried out by microthermal field-flow fractionation confirmed that the aspect ratio cannot be reduced to a value of 1, proposed by other authors. 相似文献
17.
Maria A. Simonova Elvira V. Tarasova Marina M. Dudkina Andrey V. Tenkovtsev Alexander P. Filippov 《International Journal of Polymer Analysis and Characterization》2019,24(1):87-95
Properties of individual molecules of star-like polystyrene with calix[8]arene core in dilute chloroform solutions were studied using methods of static light scattering, translation diffusion, and viscometry. The solution behavior of the polymer investigated significantly differs from the properties of linear polymers. Star-like polystyrene macromolecules in solutions are characterized by compact structure—the hydrodynamic radius is not higher than 5.5?nm at M?=?125,000?g?mol?1. The shape of star-like polystyrene macromolecules differs slightly from spherical. 相似文献
18.
Waldemar Konrad Christian Fengler Sarrah Putwa Christopher Barner‐Kowollik 《Angewandte Chemie (International ed. in English)》2019,58(21):7133-7137
An advanced light‐induced avenue to monodisperse sequence‐defined linear macromolecules via a unique photochemical protocol is presented that does not require any protection‐group chemistry. Starting from a symmetrical core unit, precision macromolecules with molecular weights up to 6257.10 g mol?1 are obtained via a two‐monomer system: a monomer unit carrying a pyrene functionalized visible light responsive tetrazole and a photo‐caged UV responsive diene, enabling an iterative approach for chain growth; and a monomer unit equipped with a carboxylic acid and a fumarate. Both light‐induced chain growth reactions are carried out in a λ‐orthogonal fashion, exciting the respective photosensitive group selectively and thus avoiding protecting chemistry. Characterization of each sequence‐defined chain (size‐exclusion chromatography (SEC), high‐resolution electrospray ionization mass spectrometry (ESI‐MS), and NMR spectroscopy), confirms the precision nature of the macromolecules. 相似文献
19.
{Nb288O768(OH)48(CO3)12}: A Macromolecular Polyoxometalate with Close to 300 Niobium Atoms 下载免费PDF全文
Yan‐Lan Wu Dr. Xin‐Xiong Li Yan‐Jie Qi Hao Yu Lu Jin Prof. Dr. Shou‐Tian Zheng 《Angewandte Chemie (International ed. in English)》2018,57(28):8572-8576
A protein‐sized (ca. 4.2×4.2×3.6 nm3) non‐biologically derived molecule {Nb288O768(OH)48(CO3)12} ( Nb288 ) containing up to 288 niobium atoms has been obtained, which is by far the largest and the highest nuclearity polyoxoniobate (PONb). Particularly, in terms of metal nuclearity number, Nb288 is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb288 can be described as a giant windmill‐like cluster aggregate of six nanoscale high‐nuclearity PONb units {Nb47O128(OH)6(CO3)2} ( Nb47 ) joined together by six additional Nb ions. Interestingly, the 47‐nuclearity Nb47 units generated in situ can be isolated and bridged by copper complexes to form an inorganic–organic hybrid three‐dimensional PONb framework, which exhibits effective catalytic activity for hydrolyzing nerve agent simulant of dimethyl methylphosphonate. The unique Nb47 cluster also provides a new type of topology to very limited family of Nb‐O clusters. 相似文献
20.
Thermal, photophysical and magnetic properties of some novel fullerenol–silane adducts are described. Excellent improvement of thermal stability and high char yield due to the presence of silicon is the key feature of these adducts. Highest luminescence quenching due to maximum π–π electronic interactions between phenyl ring and fullerene are observed in the aromatic-silane adducts and the quenching ability of the aromatic ring reduces with further delocalization of the π-electrons as in naphthyl silane. The alkyl vinyl silane, on the other hand, records better fluorescence intensity owing to increase population of the electron density (+I effect) and non-effective charge transfer complex formation between isolated vinylic double bond and fullerene. Emission peak positions of these adducts are comparable to fullerenol because of control derivatization of fullerene ring causing less perturbation of the symmetric π-electronic system. These adducts are paramagnetic in nature with peaks around 3515 G and higher g-values (2.005–2.009) compared to fullerenol (1.985). The fullerenol–silane adducts are synthesized using fullerenol as substrate and different chloro and alkoxy silanes as silylating agents adopting simple nucleophilic displacement and transesterification reactions. All the fullerenol–silane adducts are characterized spectroscopically. 相似文献