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PEO—PPO—PEO三嵌段共聚物自组装行为的耗散粒子动力学模拟 总被引：1，自引：0，他引：1
采用耗散粒子动力学方法（DPD）,模拟了聚氧乙烯-聚氧丙烯-聚氧乙烯（PEO—PPO—PEO）三嵌段共聚物在乙醇溶液中的自组装行为,考察了该共聚物的体积分数和聚氧乙烯（PEO）嵌段链长对介观形貌的影响。当F88（PEO104-PPO39-PEO104）体积分数为20％时,胶柬由初始的均衡分散态逐渐聚合,最终形成PPO为核、PEO为壳的平衡态柱状团聚体。改变共聚物的体积分数和PEO链的长度,会形成不同的介观结构,如：球状、柱状、立体网络、层状和穿孔状结构等。结果表明,DPD方法是研究三嵌段共聚物自组装行为和介观结构形成机理的有效工具,对合成具有特定结构性能的材料有一定的指导意义。 相似文献
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嵌段共聚物导向自组装作为一种自下而上的图案化工艺,受到工业界和学术界的广泛关注.然而,导向自组装中缺陷率与分子参数之间的关系研究尚不清晰.本文工作基于模块化合成策略,利用迭代指数增长法并结合巯基-双键的点击反应成功制备了高χ低N的单一分子量含氟聚酯嵌段共聚物(oLAn-FPOSS).单一分子量特征可以排除多分散性对自组装行为的影响.本体自组装研究表明聚酯嵌段和含氟嵌段具有强相分离驱动力,可以形成特征尺寸小于10 nm的六方柱状相结构(HEX).在薄膜自组装中,嵌段共聚物经过简单的热退火可以在硅片表面形成平行基底排布的柱状纳米图案.此外,通过对比研究不同链长单一分子量嵌段共聚物的薄膜组装行为,发现随着嵌段共聚物链长的增长薄膜组装图形缺陷率明显下降,初步揭示了薄膜自组装过程中缺陷形成对嵌段共聚物链长的依赖性. 相似文献
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《高等学校化学学报》2015,(11)
本文采用介观尺度上的耗散粒子动力学与基于ABEEM可极化力场的全原子分子动力学相结合的方式,从理论上探究了嵌段共聚物结构、对称性、分子组成及温度等对嵌段共聚物最终自组装结构形态的影响.模拟结果表明,这些因素均会对嵌段共聚物在选择性溶剂中的最终自组装结构产生一定影响.这一理论研究为实现可控操纵自组装结构,提供了有意义的参考. 相似文献
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应用实空间的自洽平均场理论研究了线性ABC三嵌段共聚物在均聚物C中的自组装. 模拟结果表明, 共聚物在均聚物中形成的分散相主要为核壳结构. 通过降低A与C之间的相互作用, 可以使核壳结构的成核嵌段发生从嵌段A向嵌段B的转变, 并且在转变过程中观察到了多种过渡结构, 包括带有凸起表面的盘状结构和柱状结构以及相互缠绕的柱状结构. 另外, 降低嵌段共聚物中A嵌段在共混体系中的含量有利于形成以B为核的核壳结构. 相似文献
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利用光气法,以三光气和苯丙氨酸为原料,合成了苯丙氨酸酸酐(b-Phe-NCA).用端氨基聚乙二醇单甲醚(MPEG-NH2)作大分子引发剂,引发b-Phe-NCA开环聚合,合成了不同分子量的聚乙二醇单甲醚-聚(L-苯丙氨酸)(MPEG44-b-Phe)AB型二嵌段共聚多肽.利用IR1、H-NMR、GPC对共聚物结构进行了表征.利用TEM研究了二嵌段共聚多肽MPEG44-b-Phe50及MPEG44-b-Phe7在水溶液中的自组装形态,结果表明合成出的两亲性二嵌段共聚物在水溶液中自组装形成胶束,随着嵌段共聚物中亲水嵌段含量的增高,共聚物溶水性增强,其在水溶液中的自组装形态更加均一. 相似文献
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Cody Loy Jana M. Holthoff Robert Weiss Stefan M. Huber Sergiy V. Rosokha 《Chemical science》2021,12(23):8246
Halogen-bonded (XB) complexes between halide anions and a cyclopropenylium-based anionic XB donor were characterized in solution for the first time. Spontaneous formation of such complexes confirms that halogen bonding is sufficiently strong to overcome electrostatic repulsion between two anions. The formation constants of such “anti-electrostatic” associations are comparable to those formed by halides with neutral halogenated electrophiles. However, while the latter usually show charge-transfer absorption bands, the UV-Vis spectra of the anion–anion complexes examined herein are determined by the electronic excitations within the XB donor. The identification of XB anion–anion complexes substantially extends the range of the feasible XB systems, and it provides vital information for the discussion of the nature of this interaction.Spontaneous formation of “anti-electrostatic” complexes in solution demonstrates that halogen bonding can be sufficiently strong to overcome anion–anion repulsion when the latter is attenuated by the polar medium.Halogen bonding (XB) is an attractive interaction between a Lewis base (LB) and a halogenated compound, exhibiting an electrophilic region on the halogen atom.1 It is most commonly related to electrostatic interaction between an electron-rich species (XB acceptor) and an area of positive electrostatic potential (σ-holes) on the surface of the halogen substituent in the electrophilic molecule (XB donor).2 Provided that mutual polarization of the interacting species is taken into account, the σ-hole model explains geometric features and the variation of stabilities of XB associations, especially in the series of relatively weak complexes.3 Based on the definition of halogen bonding and its electrostatic interpretation, this interaction is expected to involve either cationic or neutral XB donors. Electrostatic interaction of anionic halogenated species with electron-rich XB acceptors, however, seems to be repulsive, especially if the latter are also anionic. Yet, computational analyses predicted that halogen bonding between ions of like charges, called “anti-electrostatic” halogen bonding (AEXB),4 can possibly be formed5–12 and the first examples of AEXB complexes formed by different anions, i.e. halide anions and the anionic iodinated bis(dicyanomethylene)cyclopropanide derivatives 1 (see Scheme 1) or the anionic tetraiodo-p-benzoquinone radical, were characterized recently in the solid state.13,14 The identification of such complexes substantially extends the range of feasible XB systems, and it provides vital information for the discussion of the nature of this interaction. Computational results, however, significantly depend on the used methods and applied media (gas phase vs. polar environment and solvation models) and the solid state arrangements of the XB species might be affected by crystal forces and/or counterions. Unambiguous confirmation of the stability of the halogen-bonded anion–anion complexes and verification of their thermodynamic characteristics thus requires experimental characterization of the spontaneous formation of such associations in solution. Still, while the solution-phase complexes formed by hydrogen bonding between two anionic species were reported previously,15–17 there is currently no example of “anti-electrostatic” XB in solution.Open in a separate windowScheme 1Structures of the XB donor 1 and its hydrogen-substituted analogue 2.To examine halogen bonding between two anions in solution, we turn to the interaction between halides and 1,2-bis(dicyanomethylene)-3-iodo-cyclopropanide 1 (Scheme 1).‡ Even though this compound features a cationic cyclopropenylium core, it is overall anionic, and calculations have demonstrated that its electrostatic potential is universally negative across its entire surface.13 The solution of 1 (with tris(dimethylamino)cyclopropenium (TDA) as counterion) in acetonitrile is characterized by an absorption band at 288 nm with ε = 2.3 × 104 M−1 cm−1 (Fig. 1). As LB, we first applied iodide anions taken as a salt with n-tetrabutylammonium counter-ion, Bu4NI. This salt does not show absorption bands above 290 nm, but its addition to a solution of 1 led to a rise of absorption in the 290–350 nm range (Fig. 1). Subtraction of the absorption of the individual components from that of their mixture produced a differential spectrum which shows a maximum at about 301 nm (insert in Fig. 1). At constant concentration of the XB donor (1) and constant ionic strength, the intensity of the absorption in the range of 280–300 nm (and hence differential absorbance, ΔAbs) rises with increasing iodide concentration (Fig. S1 in the ESI†). This suggests that the interaction of iodide with 1 results in the formation of the [1, I−]-complex which shows a higher absorptivity in this spectral range (eqn (1)):1 + X− ⇌ [1, X−]1Open in a separate windowFig. 1Spectra of acetonitrile solutions with constant concentration of 1 (0.60 mM) and various concentrations of Bu4NI (6.0, 13, 32, 49, 75, 115 and 250 mM, solid lines from the bottom to the top). The dashed lines show spectra of the individual solutions 1 (c = 0.60 mM, red line) and Bu4NI (c = 250 mM, blue line). The ionic strength was maintained using Bu4NPF6. Insert: Differential spectra of the solutions obtained by subtraction of the absorption of the individual components from the spectra of their corresponding mixtures.To clarify the mode of interaction between 1 and iodide in the complex, we also performed analogous measurements with the hydrogen-substituted compound 2 (see Scheme 1). The addition of iodide to a solution of 2 in acetonitrile did not increase the absorption in the 280–300 nm spectral range. Instead, some decrease of the absorption band intensity of 2 with the increase of concentration of I− anions was observed (Fig. S2 in the ESI†). Such changes are related to a blue shift of this band resulting from the hydrogen bonding between 2 and iodide (formation of hydrogen-bonded [2, I−] complex is corroborated by the observation of the small shift of the NMR signal of the proton of 2 to the higher ppm values in the presence of I− anions, see Fig. S3 in the ESI†).§ Furthermore, since H-compound 2 should be at least as suitable as XB donor 1 to form anion–π complexes with the halide, this finding (as well as solid-state and computational data¶) rules out that any increase in absorption in this region observed with the I-compound 1 may be due to this alternative interaction.Likewise, the addition of NBu4I to a solution of TDA cations taken as a salt with Cl− anions did not result in an increase in the relevant region. Hence, we could also rule out anion–π interactions with the TDA counter-ions as source of the observed changes, which is in line with previous reports on the electron-rich nature of TDA.18All these observations (supported by the computational analysis, vide infra) indicate that the [1, I−] complex (eqn (1)) is formed via halogen bonding of I− with iodine substituents in 1. The changes in the intensities of the differential absorption ΔAbs as a function of the iodide concentration (with constant concentration of XB donor (1) as well as constant ionic strength) are well-modelled by the 1 : 1 binding isotherm (Fig. S1 in the ESI†). The fit of the absorption data produced a formation constant of K = 15 M−1 for the [1, I−] complex (Table 1).|| The overlap with the absorption of the individual XB donor hindered the accurate evaluation of the position and intensity of the absorption band of the corresponding complex which is formed upon LB-addition to 1. As such, the values of Δλmax shown in Table 1 represent a wavelength of the largest difference in the absorptivity of the [1, I−] complex and individual anion 1, and Δε reflects the difference of their absorptivity at this point (see the ESI† for the details of calculations).Equilibrium constants and spectral characteristics of the complexes of 1 with halide anions X−
Open in a separate windowaAll measurements performed in CH3CN at 22 °C, unless stated otherwise.bIn CH2Cl2.cWavelength of the maximum of the differential spectra.dDifferences in extinction coefficients of XB [1, I−] complex and individual 1 at Δλmax.Since earlier computational studies demonstrated substantial dependence of formation of the AEXB complexes on polarity of the medium,6–12 interaction between 1 and I− anions was also examined in dichloromethane. The spectral changes in this moderately-polar solvent were analogous to that in acetonitrile (Fig. S4 in the ESI†). * The values for the formation constants of the [1, I−] complex and Δε (obtained from the fitting of the ΔAbs vs. [I−] dependence) in CH2Cl2 are lower than those in acetonitrile (Table 1). This finding is in line with the computational studies,6–12 predicting stronger binding in more polar solvents.The addition of bromide or chloride salts to an acetonitrile solution of 1 caused changes in the UV-Vis range which were generally similar to that observed upon addition of iodide. The variations of the magnitude of the differential absorption intensities with the increase in the bromide or chloride concentrations are less pronounced than that observed upon addition of iodide (in agreement with the results of the DFT computations of the UV-Vis spectra of the complexes, vide infra). Yet, they could also be fitted using 1 : 1 binding isotherms (see Fig. S5 and S6 in the ESI†). The formation constants of the corresponding [1, Br−] and [1, Cl−] complexes resulted from the fitting of these dependencies are listed in Table 1. The values of K (which correspond to the free energy changes of complex formation in a range of −6 to −8 kJ mol−1) are comparable to those reported for complexes of neutral monodentate bromo- or iodosubstituted aliphatic or aromatic electrophiles with halides.19–22 Thus, despite the “anti-electrostatic” nature of XB complexes between two anions, the stabilities of such associations are similar to that observed with the most common neutral XB donors.In contrast to the similarity in thermodynamic characteristics, the UV-Vis spectral properties of the complexes of the anionic XB donor 1 with halides are substantially different from that reported for the analogous associations with the neutral XB donors. Specifically, a number of earlier studies revealed that intermolecular (XB or anion–π) complexes of halide anions are characterized by distinct absorption bands, which could be clearly segregated from the absorption of the interacting species.21–23 If the same neutral XB donor was used, the absorption bands of the corresponding complexes with chloride were blue shifted, and absorption bands of the complexes with iodide as LB were red shifted as compared to the bands of complexes with bromide. For example, XB complexes of CFBr3 with Cl−, Br− or I− show absorption band maxima at 247 nm, 269 nm and 312 nm, respectively (individual CFBr3 is characterized by an absorption band at 233 nm).21 Within a framework of the Mulliken charge-transfer theory of molecular complexes,24 such an order is related to a rise in the energy of the corresponding HOMO (and electron-donor strength) from Cl− to Br− and to I− anions. In the complexes with the same electron acceptor, this is accompanied by a decrease of the HOMO–LUMO gap, and thus, a red shift of the absorption band. The data in Table 1 shows, however, that the maxima of differential absorption spectra for these systems are observed at roughly the same wavelength. To clarify the reason for this observation, we carried out computational analysis of the associations between 1 and halide anions.The DFT optimization†† at M06-2X/def2-tzvpp level with acetonitrile as a medium (using PCM solvation model)25 produced thermodynamically stable XB complexes between 1 and I−, Br− or Cl− anions (they were similar to the complexes which were obtained earlier via M06-2X/def2-tzvp computations with SMD solvation model13). The calculated structure of the [1, I−] complex is shown in Fig. 2 and similar structures for the [1, Br−] and [1, Cl−] are shown in Fig. S7 in the ESI.†Open in a separate windowFig. 2Optimized geometries of the [1, I−] complex with (3, −1) bond critical points (yellow spheres) and the bond path (green line) from the QTAIM analysis. The blue–green disc indicates intermolecular attractive interactions resulting from the NCI treatments (s = 0.4 a.u. isosurfaces, color scale: −0.035 (blue) < ρ < 0.02 (red) a.u.).QTAIM analysis26 of these structures revealed the presence of the bond paths (shown as the green line) and (3, −1) bond critical points (BCPs) indicating bonding interaction between iodine substituent of 1 and halide anions. Characteristics of these BCPs (electron density of about 0.015 a.u., Laplacians of electron density of about 0.05 a.u. and energy density of about 0.0004 a.u., see Table S1 in the ESI†) are typical for the moderately strong supramolecular halogen bonds.27 The Non-Covalent Interaction (NCI) Indexes treatment28 produced characteristic green–blue discs at the critical points'' positions, confirming bonding interaction in all these complexes.Binding energies, ΔE, for the [1, X−] complexes are listed in Table 2. They are negative and their variations are consistent with the changes in experimental formation constants measured with three halide anions in Table 1. The ΔE value for [1, I−] calculated in dichloromethane is also negative. Its magnitude is lower than that in acetonitrile, in agreement with the smaller formation constant of [1, I−] in less polar dichloromethane.Calculated characteristics of the [1, X−] complexesa
Open in a separate windowaIn CH3CN, if not noted otherwise.bIn CH2Cl2.cExtinction coefficient for the lowest-energy absorption band of the complex.dPosition and extinction coefficient of the differential absorption (see Fig. 3).The TD DFT calculations of the individual XB donor 1 and its complexes with halides (which were carried at the same level as the optimizations) produced strong absorption bands in the UV range (Fig. 3). The calculated spectrum of the individual anion 1 (λmax = 252 nm and ε = 4.27 × 104 M−1 cm−1) is characterized by somewhat higher energy and intensity of the absorption band than the experimental one, but the differences of about 0.6 eV in energy and about 0.3 in log ε are common for the TD DFT calculations.Open in a separate windowFig. 3Calculated spectra of 1 and its complexes (as indicated). The dashed lines show differential absorption obtained by subtraction of absorption of 1 from the absorption of the corresponding complex.The TD DFT calculations of the XB complexes with all three anions produced absorption bands at essentially the same wavelength as that of the individual XB donor 1, but their intensities were higher (in contrast, the hydrogen-bonded complex of 2 with iodide showed absorption band with slightly lower intensity than that of individual 2). The differential spectra obtained by subtraction of the spectra of individual anion 1 from the spectra of the complexes are shown in Fig. 3, and their characteristics are listed in Table 2. Similarly to the experimental data in Table 1, the calculated values of Δλmax are very close in complexes with different halides, and values of Δε are increasing in the order 1·Cl− < 1·Br− < 1·I−.An analysis of the calculated spectra of the complexes revealed that the distinction in spectral characteristics of the XB complexes of anionic and neutral XB donors with halides are related to the differences in the molecular orbital energies of the interacting species. Specifically, the energy of the highest occupied molecular orbital (HOMO) of the anionic XB donor 1 is higher than the energies of the HOMOs of I−, Br− and Cl−, and the energy of the lowest unoccupied molecular orbital (LUMO) of 1 is lower than those of the halides (Table S2 in the ESI†). As such, the lowest-energy electron excitations (with the substantial oscillator strength) in the AEXB complexes involve molecular orbitals localized mostly on the XB donor (see Fig. S8 in the ESI†). Accordingly, the energy of the absorption bands is essentially independent on the halide. Still, due to the molecular orbital interactions between the halides and 1, the small segments of the HOMOs of the complexes are localized on the halides, which affected the intensity of the transitions.‡‡ In contrast, in the XB complexes with the neutral halogenated electrophiles, the energies of the HOMOs and LUMOs of the halides are higher than the energies of the corresponding orbitals of the XB donors. As such, the HOMO of such complexes (as well as the other common molecular complexes) is localized mostly on the XB acceptors (electron donor), and the LUMO on the XB donor (electron acceptor). Accordingly, their lowest energy absorption bands represent in essence charge-transfer transition, and its energy vary with the energies of the HOMO of halides (the TD DFT calculations suggest that similar charge-transfer transitions in complexes of halides with 1 occur at higher energies, and they are overshadowed by the absorption of components).In summary, combined experimental (UV-Vis spectral) and computational studies of the interaction between halides and 1 demonstrated spontaneous formation of the anion–anion XB complexes in moderately-polar and polar solvents (which attenuate the electrostatic anion–anion repulsion and facilitate close approach of the interacting species§§). To the best of our knowledge, this constitutes the first experimental observation of AEXBs in solution. Stabilities of such “anti-electrostatic” associations are comparable to that formed by halide anions with the common neutral bromo- and iodo-substituted aliphatic or aromatic XB donors. These findings confirm that halogen bonding between our anionic XB donor 1 and halides is sufficiently strong to overcome electrostatic repulsion between two anions. It also supports earlier conclusions29 that besides electrostatics, molecular-orbital (weakly-covalent interaction) play an important role in the formation of XB complexes. Since the HOMO of 1 is higher in energy than those of the halides, the lowest-energy absorption bands in the anion–anion complexes is related mostly to the transition between the XB-donor localized MOs (in contrast to the charge transfer transition in the analogous complexes with neutral XB donors). Therefore, the energies of these transitions are similar in all complexes and the interaction with halides only slightly increase their intensities. 相似文献
| Complexa | K [M−1] | Δλmaxc [nm] | 10−3Δεd [M−1 cm−1] |
|---|---|---|---|
| 1·I− | 15 ± 2 | 302 | 9.0 |
| 1·I−b | 8 ± 2 | 303 | 8.0 |
| 1·Br− | 17 ± 2 | 302 | 3.7 |
| 1·Cl− | 40 ± 8 | 302 | 3.0 |
| Complex | ΔE, kJ mol−1 | λ max,c nm | 10−4ε,c M−1 cm−1 | Δλmax,d M−1 cm−1 | 10−3Δε,d M−1 cm−1 |
|---|---|---|---|---|---|
| 1·I− | −14.2 | 252 | 5.70 | 255 | 14 |
| 1·I−b | −4.7 | 253 | 6.07 | — | — |
| 1·Br− | −14.8 | 252 | 5.02 | 253 | 7.4 |
| 1·Cl− | −16.2 | 251 | 4.78 | 249 | 5.3 |
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Zi-Shu Yang Yuhang Yao Adam C. Sedgwick Cuicui Li Ye Xia Yan Wang Lei Kang Hongmei Su Bing-Wu Wang Song Gao Jonathan L. Sessler Jun-Long Zhang 《Chemical science》2020,11(31):8204
We report here porphodilactol derivatives and their corresponding metal complexes. These systems show promise as “all-in-one” phototheranostics and are predicated on a design strategy that involves controlling the relationship between intersystem crossing (ISC) and photothermal conversion efficiency following photoexcitation. The requisite balance was achieved by tuning the aromaticity of these porphyrinoid derivatives and forming complexes with one of two lanthanide cations, namely Gd3+ and Lu3+. The net result led to a metalloporphodilactol system, Gd-trans-2, with seemingly optimal ISC efficiency, photothermal conversion efficiency and fluorescence properties, as well as good chemical stability. Encapsulation of Gd-trans-2 within mesoporous silica nanoparticles (MSN) allowed its evaluation for tumour diagnosis and therapy. It was found to be effective as an “all-in-one” phototheranostic that allowed for NIR fluorescence/photoacoustic dual-modal imaging while providing an excellent combined PTT/PDT therapeutic efficacy in vitro and in vivo in 4T1-tumour-bearing mice.We report here porphodilactol derivatives and their corresponding metal complexes as “all-in-one” phototheranostics by controlling the relationship between intersystem crossing (ISC) and photothermal conversion efficiency following photoexcitation. 相似文献
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Multi-drug resistant pathogens are a rising danger for the future of mankind. Iodine (I2) is a centuries-old microbicide, but leads to skin discoloration, irritation, and uncontrolled iodine release. Plants rich in phytochemicals have a long history in basic health care. Aloe Vera Barbadensis Miller (AV) and Salvia officinalis L. (Sage) are effectively utilized against different ailments. Previously, we investigated the antimicrobial activities of smart triiodides and iodinated AV hybrids. In this work, we combined iodine with Sage extracts and pure AV gel with polyvinylpyrrolidone (PVP) as an encapsulating and stabilizing agent. Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), Surface-Enhanced Raman Spectroscopy (SERS), microstructural analysis by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-Ray-Diffraction (XRD) analysis verified the composition of AV-PVP-Sage-I2. Antimicrobial properties were investigated by disc diffusion method against 10 reference microbial strains in comparison to gentamicin and nystatin. We impregnated surgical sutures with our biohybrid and tested their inhibitory effects. AV-PVP-Sage-I2 showed excellent to intermediate antimicrobial activity in discs and sutures. The iodine within the polymeric biomaterial AV-PVP-Sage-I2 and the synergistic action of the two plant extracts enhanced the microbial inhibition. Our compound has potential for use as an antifungal agent, disinfectant and coating material on sutures to prevent surgical site infections. 相似文献
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Kazuo Umemura Ryo Hamano Hiroaki Komatsu Takashi Ikuno Eko Siswoyo 《Molecules (Basel, Switzerland)》2021,26(10)
Solubilization of carbon nanotubes (CNTs) is a fundamental technique for the use of CNTs and their conjugates as nanodevices and nanobiodevices. In this work, we demonstrate the preparation of CNT suspensions with “green” detergents made from coconuts and bamboo as fundamental research in CNT nanotechnology. Single-walled CNTs (SWNTs) with a few carboxylic acid groups (3–5%) and pristine multi-walled CNTs (MWNTs) were mixed in each detergent solution and sonicated with a bath-type sonicator. The prepared suspensions were characterized using absorbance spectroscopy, scanning electron microscopy, and Raman spectroscopy. Among the eight combinations of CNTs and detergents (two types of CNTs and four detergents, including sodium dodecyl sulfate (SDS) as the standard), SWNTs/MWNTs were well dispersed in all combinations except the combination of the MWNTs and the bamboo detergent. The stability of the suspensions prepared with coconut detergents was better than that prepared with SDS. Because the efficiency of the bamboo detergents against the MWNTs differed significantly from that against the SWNTs, the natural detergent might be useful for separating CNTs. Our results revealed that the use of the “green” detergents had the advantage of dispersing CNTs as well as SDS. 相似文献
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This review provides information on available methods for engineering glycan-binding proteins (GBP). Glycans are involved in a variety of physiological functions and are found in all domains of life and viruses. Due to their wide range of functions, GBPs have been developed with diagnostic, therapeutic, and biotechnological applications. The development of GBPs has traditionally been hindered by a lack of available glycan targets and sensitive and selective protein scaffolds; however, recent advances in glycobiology have largely overcome these challenges. Here we provide information on how to approach the design of novel “designer” GBPs, starting from the protein scaffold to the mutagenesis methods, selection, and characterization of the GBPs. 相似文献
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Severyn Salis Nadia Spano Marco Ciulu Ignazio Floris Maria I. Pilo Gavino Sanna 《Molecules (Basel, Switzerland)》2021,26(14)
5-(hydroxymethyl)furan-2-carbaldehyde, better known as hydroxymethylfurfural (HMF), is a well-known freshness parameter of honey: although mostly absent in fresh samples, its concentration tends to increase naturally with aging. However, high quantities of HMF are also found in fresh but adulterated samples or honey subjected to thermal or photochemical stresses. In addition, HMF deserves further consideration due to its potential toxic effects on human health. The processes at the origin of HMF formation in honey and in other foods, containing saccharides and proteins—mainly non-enzymatic browning reactions—can also produce other furanic compounds. Among others, 2-furaldehyde (2F) and 2-furoic acid (2FA) are the most abundant in honey, but also their isomers (i.e., 3-furaldehyde, 3F, and 3-furoic acid, 3FA) have been found in it, although in small quantities. A preliminary characterization of HMF, 2F, 2FA, 3F, and 3FA by cyclic voltammetry (CV) led to hypothesizing the possibility of a comprehensive quantitative determination of all these compounds using a simple and accurate square wave voltammetry (SWV) method. Therefore, a new parameter able to provide indications on quality of honey, named “Furanic Index” (FI), was proposed in this contribution, which is based on the simultaneous reduction of all analytes on an Hg electrode to ca. −1.50 V vs. Saturated Calomel Electrode (SCE). The proposed method, validated, and tested on 10 samples of honeys of different botanical origin and age, is fast and accurate, and, in the case of strawberry tree honey (Arbutus unedo), it highlighted the contribution to the FI of the homogentisic acid (HA), i.e., the chemical marker of the floral origin of this honey, which was quantitatively reduced in the working conditions. Excellent agreement between the SWV and Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC) data was observed in all samples considered. 相似文献