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61.
According to the characterization of RNA secondary structures, the RNA secondary structures are transformed into elementary
sequences, namely characteristic sequences of RNA secondary structures, by representing A, U, G, C in A-U/ G-C pairs, as A′,
U′, G′, C′. Based on the representation, three recurrences for mapping RNA secondary structures into 1-D graph, 2-D graph
and 3-D graph are given, respectively. Furthermore, a frequency-based method for RNA secondary structures is given in terms
of 1-D graph. 相似文献
62.
Ke Jiang Li Juan Li Fan Shi Li Peng Gan Wei Sun Zhi Song Lu Zhuo Zou Chang Ming Li 《Electroanalysis》2023,35(10):e202300158
Dopamine (DA) plays an essential role in the central nervous, renal, hormonal and cardiovascular systems. Various modified carbon nanotubes (CNT)-based dopamine sensors have been reported, but inexpensive, highly sensitive plain CNT-based ones are seldom studied. In this work, a facile and inexpensive CNT-based DA sensor is made by rich-defect multi-walled carbon nanotubes (RD-CNT) via an ultrasound method. The defect and elemental states of the RD-CNT are systematically studied by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, X-ray powder diffraction (XRD) and X-ray-photoelectron spectroscopy (XPS). Results show that massive holes and cracks exist in RD-CNT. The level of defects increases from the additional exposed edges. The electrochemical characterizations indicate that the electrochemical sensor has the highest sensitivity of 438.4 μA/(μM ⋅ cm2) among all carbon materials-based DA sensors while well meeting the clinically required detection range and selectivity. The DA sensor was further used to detect live healthy human serum and live PC12 cells with satisfactory results, thus holding great promise for an inexpensive but sensitive DA sensor in practical applications of clinical diagnosis and biological research. 相似文献
63.
Xiaoyang Cheng Xiaotian Jiang Shuhu Yin Lifei Ji Yani Yan Guang Li Rui Huang Prof. Chongtai Wang Prof. Honggang Liao Prof. Yanxia Jiang Prof. Shigang Sun 《Angewandte Chemie (International ed. in English)》2023,62(34):e202306166
To achieve the Fe−N−C materials with both high activity and durability in proton exchange membrane fuel cells, the attack of free radicals on Fe−N4 sites must be overcome. Herein, we report a strategy to effectively eliminate radicals at the source to mitigate the degradation by anchoring CeO2 nanoparticles as radicals scavengers adjacent (Scaad-CeO2) to the Fe−N4 sites. Radicals such as ⋅OH and HO2⋅ that form at Fe−N4 sites can be instantaneously eliminated by adjacent CeO2, which shortens the survival time of radicals and the regional space of their damage. As a result, the CeO2 scavengers in Fe−NC/Scaad-CeO2 achieved ∼80 % elimination of the radicals generated at the Fe−N4 sites. A fuel cell prepared with the Fe−NC/Scaad-CeO2 showed a smaller peak power density decay after 30,000 cycles determined with US DOE PGM-relevant AST, increasing the decay of Fe−NCPhen from 69 % to 28 % decay. 相似文献
64.
Dr. Junning Kou Dr. Qi Wu Dr. Dongxu Cui Dr. Yun Geng Dr. Kunhao Zhang Prof. Dr. Min Zhang Prof. Dr. Hongying Zang Prof. Dr. Xinlong Wang Prof. Dr. Zhongmin Su Prof. Dr. Chunyi Sun 《Angewandte Chemie (International ed. in English)》2023,62(47):e202312733
Chiral induction has been an important topic in chemistry, not only for its relevance in understanding the mysterious phenomenon of spontaneous symmetry breaking in nature but also due to its critical implications in medicine and the chiral industry. The induced chirality of fullerenes by host–guest interactions has been rarely reported, mainly attributed to their chiral resistance from high symmetry and challenges in their accessibility. Herein, we report two new pairs of chiral porous aromatic cages (PAC), R- PAC-2 , S- PAC-2 (with Br substituents) and R- PAC-3 , S- PAC-3 (with CH3 substituents) enantiomers. PAC-2 , rather than PAC-3 , achieves fullerene encapsulation and selective binding of C70 over C60 in fullerene carbon soot. More significantly, the occurrence of chiral induction between R- PAC-2 , S- PAC-2 and fullerenes is confirmed by single-crystal X-ray diffraction and the intense CD signal within the absorption region of fullerenes. DFT calculations reveal the contribution of electrostatic effects originating from face-to-face arene-fullerene interactions dominate C70 selectivity and elucidate the substituent effect on fullerene encapsulation. The disturbance from the differential interactions between fullerene and surrounding chiral cages on the intrinsic highly symmetric electronic structure of fullerene could be the primary reason accounting for the induced chirality of fullerene. 相似文献
65.
This paper considers a dividend strategy with investment in
Omega model. If at a potential dividend-payment time the surplus is above, part
of the excess are paid as dividends directly, the other part are used as dynamic
investment capital, at a particular time, the sum of profits and investment capital
will be paid as another dividend. Under this dividend policy, we get the optimal
dividend strategy and the optimal portfolio policy. 相似文献
66.
《Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)》1998,44(2):295-300
Artesunate is an important new antimalarial drug. The interaction of artesunate with hemin was investigated by electrochemical methods and UV spectroelectrochemistry (UV-SEC). Artesunate underwent an entirely irreversible reduction at ca. −1.27 V (vs. Ag/AgCl) on the glassy carbon electrode. Hemin can catalyze the decomposition of artesunate. In the presence of concentration of hemin as low as 2×10−8 M, the cathodic overpotential of artesunate was reduced ca. 680 mV (Epc=−0.59 V vs. Ag/AgCl). UV-SEC experiments further confirm this process. UV spectra show that the decomposed products of artesunate have absorption behavior similar to artesunate. These results indicated that artesunate might undergo the identical antimalarial mechanism as its parent compound Qinghaosu, and hemin plays a catalyst role in the process of action of Qinghaosu-type antimalarial drugs. 相似文献
67.
《Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)》1998,44(2):261-269
AC-electric fields of low strength and low frequency were applied to roots of garden cress (Lepidium sativum L.) growing in aqueous medium. These fields strongly affected the growth, shape and statocyte structure of the roots. A maximum growth-promoting effect was observed with a field frequency of 10 Hz and field strengths of 10−3 to 10−1 V cm−1. Growth rates of roots were similar to controls, i.e., roots growing without AC fields, at field strengths of 10−4 and 1 V cm−1. Ultrastructural analyses of root cap cells showed that an AC-electric field of 10 Hz caused a significant increase in abundance of endoplasmic reticulum (ER) in the statocytes. Both phenomena, growth promotion and ER volume increase, are most likely effected by stimulation of the plasma membrane H+-ATPase of the root cells. 相似文献
68.
《Polyhedron》1999,18(23):3035-3039
New tetradentate Schiff base–oxovanadium(IV) complexes which have electron donating or withdrawing groups at the 5-position of the salicylaldehyde moieties, [VO{Xsal-(R,R)-2,4-ptn}] (H2{Xsal-(R,R)-2,4-ptn}: N,N′-di-Xsalicylidene-(R,R)-2,4-pentanediamine; X=5-MeO (methoxy), 5-Br, and 5-NO2) were prepared. The structures and redox potentials for the V(V)/V(IV) couple of the complexes were compared with those of other [VO{Xsal-(R,R)-2,4-ptn}] (X=3-EtO (ethoxy), 3-MeO, and H). The 5-MeO substituted complex which has electron donating groups at the 5-position of the salicylaldehyde moieties forms a monomeric structure in the solid state. The 3-EtO substituted complex has both monomeric and polymeric structures. On the other hand, the other [VO{Xsal-(R,R)-2,4-ptn}] (X=H, 3-MeO, 5-Br, 5-NO2) complexes have only polymeric structures. X-ray crystal structure analysis of [VO{5-MeOsal-(R,R)-2,4-ptn}]⋅CH3OH (1) was carried out. Complex 1 has a monomeric five-coordinate square–pyramidal structure. The six-membered N–N chelate ring forms a distorted flattened boat form with two methyl groups in the axial positions. 相似文献
69.
Chemical sensors based on optical signal detection are of increasing importance. Optical sensors of bulk optodes have the advantage of being robust and showing a highly reversible response explainable by means of the chemical equilibria involved. Therefore, a great number of new ion-selective bulk optodes have reported within a few years. Several sensors for detecting toxicologically revalant ions,such as Pb2+,Ag+,Hg2+ and UO22+ have been developed recently and exhibit the low detection limit required. Although a number of ionophores have been used in optodes and ISEs,the sensors described so far are inadequate for monitoring Ag+ in water, especially in drinking water because of their limited selectivity and/or insufficient sensitivity. More recently Pretsch et al designed and synthesized an improved optical sensor, methylene bis(2-thiobenzothiazole),which was Ag+-selective. Here we report synthesis of another ionophore,1,2-bis(2-thiobenzothiazole) ethane, and its IR, ESI-MS, 1HNMR and UV-Vis. 相似文献
70.
Recently, much attention has been paid to Ru(II) complexes because of their excellent properties of photochemistry, phtophysis. Bis(2,2'-bipyridine)[4-methyl-4'-(6-bromohexyl)-2,2'-bipyridine] ruthenium(II) perchlorate has been used as an active material for electrochemiluminescent (ECL) sensor for selective detection of oxalic acid.It is known that ECL efficiency of Ru(phen)32+ is much higher than that of Ru(bpy)32+. In order to make out more efficient ECL sensor, we have designed and synthesized a new Ru(II) complex, Ru(phen)2[phen-NHCO(CH2)4Br](PF6)2. 相似文献