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2016 Volume 74 Issue 9
2016, 74(9): 713-725
doi: 10.6023/A16030147
Abstract:
Antimicrobial is closely related to public life and efficient delivery of drug and gene is an indispensable means for the modern medicine. However, guanidinium-rich polymer has particular function in antimicrobial and delivery, such as the bactericidal mode of guanidinium-rich polymer is the non-specific interaction—electrostatic interaction, which is the driving force of the movement for the process of guanidinium-rich polymer getting close to the cell membrane of microbes, and from the perspective of biological evolution, which make bacterial hard to evolve resistance. On the other hand, the tight double-hydrogen bonded structure between guanidino and phosphate in the cell membrane phospholipids is the foundation for guanidinium-rich polymer exhibiting excellent performance on delivery, which will be an important grasp for the guanidinium-rich polymer and its carrying molecules entering the mammalian cell membrane. Moreover, relatively lower toxicity or nontoxicity of guanidinium-rich polymer for the mammalian cells remove the obstacle of applications. Therefore, this paper is based on available literature, sums up the fabrication methods of guanidinium-rich polymer, reviews the applications in microbial inhibition and delivery of drug or gene.
Antimicrobial is closely related to public life and efficient delivery of drug and gene is an indispensable means for the modern medicine. However, guanidinium-rich polymer has particular function in antimicrobial and delivery, such as the bactericidal mode of guanidinium-rich polymer is the non-specific interaction—electrostatic interaction, which is the driving force of the movement for the process of guanidinium-rich polymer getting close to the cell membrane of microbes, and from the perspective of biological evolution, which make bacterial hard to evolve resistance. On the other hand, the tight double-hydrogen bonded structure between guanidino and phosphate in the cell membrane phospholipids is the foundation for guanidinium-rich polymer exhibiting excellent performance on delivery, which will be an important grasp for the guanidinium-rich polymer and its carrying molecules entering the mammalian cell membrane. Moreover, relatively lower toxicity or nontoxicity of guanidinium-rich polymer for the mammalian cells remove the obstacle of applications. Therefore, this paper is based on available literature, sums up the fabrication methods of guanidinium-rich polymer, reviews the applications in microbial inhibition and delivery of drug or gene.
2016, 74(9): 726-733
doi: 10.6023/A16080384
Abstract:
A resistive memory operates as an electrical switch between high and low conductivity states (or multistates) in response to an external electric field. Due to the high capacity, high flexibility, good scalability, low cost, and low power consumption, resistive memory is promising for the next-generation high-density data storage. In addition to inorganic metal oxides, carbon nanomaterials, organic small molecular and polymeric semiconductor materials, transition-metal complexes have recently received much attention as active materials for resistive memory. In this contribution, the applications of transition-metal complexes in resistive memory reported to date are summarized and discussed, mainly including group VⅢ [Fe(Ⅱ), Ru(Ⅱ), Co(Ⅲ), Rh(Ⅲ), Ir(Ⅲ), and Pt(Ⅱ) complexes], group IB and ⅡB [Cu(Ⅱ), Au(Ⅲ), and Zn(Ⅱ) complexes], and lanthanide complexes [mainly Eu(Ⅲ) complexes]. The memory behavior and mechanism of these materials will be discussed. Transition-metal complexes often possess well-defined and reversible redox processes. The frontier energy levels and gaps can be easily modulated by changing the structures of ligands and metal species, which is beneficial for generating electrical bistates or multistates when they are used in resistive memory devices. These features make transition-metal complexes potentially useful as memory materials in practical applications.
A resistive memory operates as an electrical switch between high and low conductivity states (or multistates) in response to an external electric field. Due to the high capacity, high flexibility, good scalability, low cost, and low power consumption, resistive memory is promising for the next-generation high-density data storage. In addition to inorganic metal oxides, carbon nanomaterials, organic small molecular and polymeric semiconductor materials, transition-metal complexes have recently received much attention as active materials for resistive memory. In this contribution, the applications of transition-metal complexes in resistive memory reported to date are summarized and discussed, mainly including group VⅢ [Fe(Ⅱ), Ru(Ⅱ), Co(Ⅲ), Rh(Ⅲ), Ir(Ⅲ), and Pt(Ⅱ) complexes], group IB and ⅡB [Cu(Ⅱ), Au(Ⅲ), and Zn(Ⅱ) complexes], and lanthanide complexes [mainly Eu(Ⅲ) complexes]. The memory behavior and mechanism of these materials will be discussed. Transition-metal complexes often possess well-defined and reversible redox processes. The frontier energy levels and gaps can be easily modulated by changing the structures of ligands and metal species, which is beneficial for generating electrical bistates or multistates when they are used in resistive memory devices. These features make transition-metal complexes potentially useful as memory materials in practical applications.
2016, 74(9): 734-737
doi: 10.6023/A16070352
Abstract:
Since the nanopore single-molecule technology has been proposed, it remains a big challenge to generate a sensitive and stable nano-scale pore. In order to achieve this goal, membrane proteins, solid-state nanopore and other materials such as DNA origami have been involved to fabricate a suitable nanopore. Compared to the solid-state nanopores, biological nanopores perform a higher resolution for single molecule analysis. Therefore, the investigation of finding new biological nanopores is very important to realize the discrimination of single oligonucleotide. Aerolysin biological nanopore has been applied for the study of oligosaccharides, peptides, protein unfolding and small organic molecules so far. Here, we report that Aerolysin could be utilized for oligonucleotide analysis. The data demonstrated that Aerolysin nanopore has a high resolution both for current and time compared with other most widely used wild-type biological nanopores, such as α-hemolysin and Mycobacterium smegmatis porin A (MspA). It may be because of its narrow diameter and positive charged amino acids in the lumen. One Aerolysin pore generates a 50 pA constant ion current in 1 mol/L KCl solution, as a three nucleotides length oligonucleotides (5'-AGG-3') traversing through nanopore could induce nearly 40% current blockage. In comparison, no current blockage signals were observed when 5'-AGG-3' driven from either cis or trans side of the α-hemolysin nanopore. Furthermore, the statistical analysis of duration time of single oligonucleotide through Aerolysin indicates a relationship scale with applied voltage, as the voltage increased from 80 to 160 mV, the duration gradually decreased. Although Aerolysin nanopore has been investigated for nearly 10 years, its ability to detect oligonucleotide was not highlighted. Our findings explored high sensing capabilities of Aerolysin nanopore in the analysis of single oligonucleotide, and extended its application to single-molecule nucleic acid analysis. Aerolysin is a promising candidate for the DNA sensing, DNA damage detection, microRNA analysis and other single molecule investigations.
Since the nanopore single-molecule technology has been proposed, it remains a big challenge to generate a sensitive and stable nano-scale pore. In order to achieve this goal, membrane proteins, solid-state nanopore and other materials such as DNA origami have been involved to fabricate a suitable nanopore. Compared to the solid-state nanopores, biological nanopores perform a higher resolution for single molecule analysis. Therefore, the investigation of finding new biological nanopores is very important to realize the discrimination of single oligonucleotide. Aerolysin biological nanopore has been applied for the study of oligosaccharides, peptides, protein unfolding and small organic molecules so far. Here, we report that Aerolysin could be utilized for oligonucleotide analysis. The data demonstrated that Aerolysin nanopore has a high resolution both for current and time compared with other most widely used wild-type biological nanopores, such as α-hemolysin and Mycobacterium smegmatis porin A (MspA). It may be because of its narrow diameter and positive charged amino acids in the lumen. One Aerolysin pore generates a 50 pA constant ion current in 1 mol/L KCl solution, as a three nucleotides length oligonucleotides (5'-AGG-3') traversing through nanopore could induce nearly 40% current blockage. In comparison, no current blockage signals were observed when 5'-AGG-3' driven from either cis or trans side of the α-hemolysin nanopore. Furthermore, the statistical analysis of duration time of single oligonucleotide through Aerolysin indicates a relationship scale with applied voltage, as the voltage increased from 80 to 160 mV, the duration gradually decreased. Although Aerolysin nanopore has been investigated for nearly 10 years, its ability to detect oligonucleotide was not highlighted. Our findings explored high sensing capabilities of Aerolysin nanopore in the analysis of single oligonucleotide, and extended its application to single-molecule nucleic acid analysis. Aerolysin is a promising candidate for the DNA sensing, DNA damage detection, microRNA analysis and other single molecule investigations.
2016, 74(9): 738-743
doi: 10.6023/A16070343
Abstract:
A translucent flow-controllable actuator based on the superaligned carbon nanotube films and polymers has been designed and fabricated. The actuator serves as a valve and shows an inspiring concept of controlling the fluid flow without heavy mechanical transmission devices. The flow can be precisely controlled or even shut off by the heating power (or applied voltage), and the process can be clearly observed through the translucent actuator wall. Owing to the advantages of low driving voltage ( < 6 V), good biocompatibility, great flexibility and long service life (>5000 cycles), the actuator will have great potential applications in the biomimetic field.
A translucent flow-controllable actuator based on the superaligned carbon nanotube films and polymers has been designed and fabricated. The actuator serves as a valve and shows an inspiring concept of controlling the fluid flow without heavy mechanical transmission devices. The flow can be precisely controlled or even shut off by the heating power (or applied voltage), and the process can be clearly observed through the translucent actuator wall. Owing to the advantages of low driving voltage ( < 6 V), good biocompatibility, great flexibility and long service life (>5000 cycles), the actuator will have great potential applications in the biomimetic field.
2016, 74(9): 752-757
doi: 10.6023/A16060281
Abstract:
In this paper, an amphiphilic copolymer poly(2, 2'-(1, 10-diaza-[18]crown-6-1, 10-diyl)diethyl 5-((adenin-9-yl)-methyl)isophthalate) (PDCAI) was designed and synthesized by simulating the chemical structure of DNA. We observed its self-organized morphology in the aqueous solution and in potassium solution with scanning electron microscopy (SEM), amphiphilic copolymer PDCAI spontaneously aggregated into strip aggregates in aqueous solution, and which could change into a rod, nanotube or helical rod aggregates in KNO3 solution. In addition, the molecular recognition between copolymer PDCAI and thymine substrate has been studied via FT-IR, and it is found that C2=O of thymine had recognized with PDCAI through complementary nucleobases in aqueous solution, the C2=O stretching band of thymine at 1737 cm-1 shifted to 1710 cm-1 after recognition, however, the band of the C4=O of thymine did not change at 1677 cm-1. Meanwhile we attempted to regulate the molecular recognition of copolymer PDCAI with thymine substrate with K+, we surprisingly found that hydrogen bonding occurs on C4=O of thymine when it recognized with PDCAI in KNO3 solution, the C4=O stretching band of thymine at 1677 cm-1 shifted to 1671 cm-1, however, the band of the C2=O of thymine did not change at 1737 cm-1 after recognition. It proves that the recognizing conformation of thymine re-organized during identification process due to the transition of aggregation form of PDCAI. And we further confirmed and studied the hydrogen bond formation and fracture process by variable temperature FT-IR, which formed at room temperature gradually broke while temperature rising from 25℃ up to 115℃, when temperature was above 115℃, hydrogen bonds broke completely, thymine and PDCAI return to their pre-recognition state. The formations of hydrogen bonds between adenine in the polymer and thymine substrate in nanospheres could enhance their interaction and loading capacity. The results have reference value for research of molecular characteristics of polymer which spontaneously formed spiral, preparation of helical polymer, and nucleic acid imitation drug carriers and its function regulation.
In this paper, an amphiphilic copolymer poly(2, 2'-(1, 10-diaza-[18]crown-6-1, 10-diyl)diethyl 5-((adenin-9-yl)-methyl)isophthalate) (PDCAI) was designed and synthesized by simulating the chemical structure of DNA. We observed its self-organized morphology in the aqueous solution and in potassium solution with scanning electron microscopy (SEM), amphiphilic copolymer PDCAI spontaneously aggregated into strip aggregates in aqueous solution, and which could change into a rod, nanotube or helical rod aggregates in KNO3 solution. In addition, the molecular recognition between copolymer PDCAI and thymine substrate has been studied via FT-IR, and it is found that C2=O of thymine had recognized with PDCAI through complementary nucleobases in aqueous solution, the C2=O stretching band of thymine at 1737 cm-1 shifted to 1710 cm-1 after recognition, however, the band of the C4=O of thymine did not change at 1677 cm-1. Meanwhile we attempted to regulate the molecular recognition of copolymer PDCAI with thymine substrate with K+, we surprisingly found that hydrogen bonding occurs on C4=O of thymine when it recognized with PDCAI in KNO3 solution, the C4=O stretching band of thymine at 1677 cm-1 shifted to 1671 cm-1, however, the band of the C2=O of thymine did not change at 1737 cm-1 after recognition. It proves that the recognizing conformation of thymine re-organized during identification process due to the transition of aggregation form of PDCAI. And we further confirmed and studied the hydrogen bond formation and fracture process by variable temperature FT-IR, which formed at room temperature gradually broke while temperature rising from 25℃ up to 115℃, when temperature was above 115℃, hydrogen bonds broke completely, thymine and PDCAI return to their pre-recognition state. The formations of hydrogen bonds between adenine in the polymer and thymine substrate in nanospheres could enhance their interaction and loading capacity. The results have reference value for research of molecular characteristics of polymer which spontaneously formed spiral, preparation of helical polymer, and nucleic acid imitation drug carriers and its function regulation.
2016, 74(9): 758-763
doi: 10.6023/A16050230
Abstract:
In this paper, the global minimum search and structural optimization for the B-Al binary clusters [BxAl13-x]- (x=0～13) are performed using the genetic algorithm (GA) method coupled with density functional theory (DFT). The effects of composition on the atomic structures, electronic properties including the energy gaps and vertical detachment energies of B-Al binary clusters are discussed. The results distinctly reveal a three dimensional (3D) to (quasi-)planar (2D) structural transition as a function of x upon increasing the number of boron atoms. When x is in the range of 0 to 7, the clusters are Al-rich and the B-Al binary systems maintain the 3D structure. Whereas, the binary system trends to be quasi-planar structure, and the critical B:Al ratios for the 2D-3D transition are between x=7 and 8. To study the stability of the [BxAl13-x]- clusters, we defined the relative energy (Erel=E([BxAl13-x]-)-xE(B13-)/13–yE(Al13-)/13), where the cluster with a more negative Erel is more stable. At x=1, Erel is the most negative, indicating the highest stability. In order to further understand the stability of clusters, the vertical detachment energies (VDE) and the HOMO-LUMO energy gaps (EH-L) of [BxAl13-x]- (x=0～13) clusters are also calculated. The results show that the energy decreases with the increasing number of B atoms, indicating a lower stability. The largest EH-L of BAl12- cluster indicates that it is the most stable among all the series of this clusters. Molecular orbitals (MO) of BAl12- cluster are analyzed and the result shows that the electronic shells of 1s2 and 1p6 are virtually unchanged when the central Al atom is replaced by the B atom. It also indicates that the electron shell closing model could be regarded as a simple but valid tool for explaining the structures and stabilities of metal clusters. Chemical bonding analysis by Adaptive Natural Density Partitioning (AdNDP) method for the B13- cluster reveals that it is a π-antiaromatic system with 8 delocalized π-electrons.
In this paper, the global minimum search and structural optimization for the B-Al binary clusters [BxAl13-x]- (x=0～13) are performed using the genetic algorithm (GA) method coupled with density functional theory (DFT). The effects of composition on the atomic structures, electronic properties including the energy gaps and vertical detachment energies of B-Al binary clusters are discussed. The results distinctly reveal a three dimensional (3D) to (quasi-)planar (2D) structural transition as a function of x upon increasing the number of boron atoms. When x is in the range of 0 to 7, the clusters are Al-rich and the B-Al binary systems maintain the 3D structure. Whereas, the binary system trends to be quasi-planar structure, and the critical B:Al ratios for the 2D-3D transition are between x=7 and 8. To study the stability of the [BxAl13-x]- clusters, we defined the relative energy (Erel=E([BxAl13-x]-)-xE(B13-)/13–yE(Al13-)/13), where the cluster with a more negative Erel is more stable. At x=1, Erel is the most negative, indicating the highest stability. In order to further understand the stability of clusters, the vertical detachment energies (VDE) and the HOMO-LUMO energy gaps (EH-L) of [BxAl13-x]- (x=0～13) clusters are also calculated. The results show that the energy decreases with the increasing number of B atoms, indicating a lower stability. The largest EH-L of BAl12- cluster indicates that it is the most stable among all the series of this clusters. Molecular orbitals (MO) of BAl12- cluster are analyzed and the result shows that the electronic shells of 1s2 and 1p6 are virtually unchanged when the central Al atom is replaced by the B atom. It also indicates that the electron shell closing model could be regarded as a simple but valid tool for explaining the structures and stabilities of metal clusters. Chemical bonding analysis by Adaptive Natural Density Partitioning (AdNDP) method for the B13- cluster reveals that it is a π-antiaromatic system with 8 delocalized π-electrons.
2016, 74(9): 764-772
doi: 10.6023/A16060308
Abstract:
The phosphorescent photophysical properties for three Ir(Ⅲ) complexes 1～3 containing dimesitylboryl moiety were investigated by DFT. The electronic structure of the ground and excited state, absorption and emission spectra, the spin-orbital coupling matrix < T1α|HSOC|Sn >, the radiative and non-radiative transition process for complexes 1～3 were calculated by DFT/TD-DFT approach. The effect of dimesitylboryl substitution at different site of Ir(Ⅲ) complex with phenylpyridine and acetylacetone ligand on the phosphorescent radiative and non-radiative process was discussed. The results reveal that the introduction of B(Mes)2 group to the pyridine ring of the phenylpyridine (ppy) ligand can strengthen the interactions between the metal and the acetylacetone (acac) ligand, reduce the structure relaxation of the molecule from the ground state to the excited triplet state, and maintain the structures of octahedral field, which is conducive to restricted non-radiative transition. Moreover the singlet-triplet energy splitting ΔE(S1-T1) is decreased, the intersystem crossing rate and radiative transition rate are increased. In addition, compared with the substitution at the pyridinyl in complex 1, modifying phenyl group with B(Mes)2 group in complex 2 and 3 could induce larger structural changes from S0 to T1 state and enhance the < S0|HSOC|T1 > value, the spin orbit coupling matrix element between S0 and T1 state of 2 and 3 are greater than that of 1, which will induce a larger non-radiative transition rate for 2 and 3. The variety of substitution position of B(Mes)2 group leads to different d-splitting, different spin-orbital coupling effect in the x, y or z direction, induces the changes of zero field splitting energy and the inequality of radiative transition rates in the three substates (namely, krx, kry, and krz), and the largest radiative rates of 1～3 are all located in z substates with values of 2.32×105, 1.20×105, and 5.50×105 s-1, respectively. Therefore, we explained the reason that complex 1 has higher phosphorescence quantum efficiency through modifying the pyridine ring of the ppy ligand rather than the benzene ring.
The phosphorescent photophysical properties for three Ir(Ⅲ) complexes 1～3 containing dimesitylboryl moiety were investigated by DFT. The electronic structure of the ground and excited state, absorption and emission spectra, the spin-orbital coupling matrix < T1α|HSOC|Sn >, the radiative and non-radiative transition process for complexes 1～3 were calculated by DFT/TD-DFT approach. The effect of dimesitylboryl substitution at different site of Ir(Ⅲ) complex with phenylpyridine and acetylacetone ligand on the phosphorescent radiative and non-radiative process was discussed. The results reveal that the introduction of B(Mes)2 group to the pyridine ring of the phenylpyridine (ppy) ligand can strengthen the interactions between the metal and the acetylacetone (acac) ligand, reduce the structure relaxation of the molecule from the ground state to the excited triplet state, and maintain the structures of octahedral field, which is conducive to restricted non-radiative transition. Moreover the singlet-triplet energy splitting ΔE(S1-T1) is decreased, the intersystem crossing rate and radiative transition rate are increased. In addition, compared with the substitution at the pyridinyl in complex 1, modifying phenyl group with B(Mes)2 group in complex 2 and 3 could induce larger structural changes from S0 to T1 state and enhance the < S0|HSOC|T1 > value, the spin orbit coupling matrix element between S0 and T1 state of 2 and 3 are greater than that of 1, which will induce a larger non-radiative transition rate for 2 and 3. The variety of substitution position of B(Mes)2 group leads to different d-splitting, different spin-orbital coupling effect in the x, y or z direction, induces the changes of zero field splitting energy and the inequality of radiative transition rates in the three substates (namely, krx, kry, and krz), and the largest radiative rates of 1～3 are all located in z substates with values of 2.32×105, 1.20×105, and 5.50×105 s-1, respectively. Therefore, we explained the reason that complex 1 has higher phosphorescence quantum efficiency through modifying the pyridine ring of the ppy ligand rather than the benzene ring.
