Solid-phase extraction of iron(III) with an ion-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique

A new Fe(III)-imprinted amino-functionalized silica gel sorbent was prepared by a surface imprinting technique for selective solid-phase extraction (SPE) of Fe(III) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Compared with non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had higher selectivity and adsorption capacity for Fe(III). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Fe(III) was 25.21 and 5.10 mg g⁻¹, respectively. The largest selectivity coefficient of the Fe(III)-imprinted sorbent for Fe(III) in the presence of Cr(III) was over 450. The relatively selective factor (α_r) values of Fe(III)/Cr(III) were 49.9 and 42.4, which were greater than 1. The distribution ratio (D) values of Fe(III)-imprinted polymers for Fe(III) were greatly larger than that for Cr(III). The detection limit (3σ) was 0.34 μg L⁻¹. The relative standard deviation of the method was 1.50% for eight replicate determinations. The method was validated by analyzing two certified reference materials (GBW 08301 and GBW 08303), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace iron in plants and water samples with satisfactory results.     

酶的分子仿生研究进展

回顾了近几十年来印迹高分子和有机团簇对酶的仿生发展历程，总结了目前的 研究现状，探讨了电子效应和空间效应（柔性空间效应）对仿对酶在催化过程中实 现类似酶的识别和诱导契合的影响，并展望了酶的仿生发展趋势。     

Unraveling the mystery of efficacy in Chinese medicine formula: New approaches and technologies for research on pharmacodynamic substances

Traditional Chinese medicine (TCM) is the key to unlock treasures of Chinese civilization. TCM and its compound play a beneficial role in medical activities to cure diseases, especially in major public health events such as novel coronavirus epidemics across the globe. The chemical composition in Chinese medicine formula is complex and diverse, but their effective substances resemble “mystery boxes”. Revealing their active ingredients and their mechanisms of action has become focal point and difficulty of research for herbalists. Although the existing research methods are numerous and constantly updated iteratively, there is remain a lack of prospective reviews. Hence, this paper provides a comprehensive account of existing new approaches and technologies based on previous studies with an in vitro to in vivo perspective. In addition, the bottlenecks of studies on Chinese medicine formula effective substances are also revealed. Especially, we look ahead to new perspectives, technologies and applications for its future development. This work reviews based on new perspectives to open horizons for the future research. Consequently, herbal compounding pharmaceutical substances study should carry on the essence of TCM while pursuing innovations in the field.     

Selectivity features of molecularly imprinted polymers recognising the carbamate group

The molecular recognition properties of molecular imprinted polymers which bind the carbamate function were studied. Functional monomers potentially able to form non-covalent interactions with the model molecule N,O-dibenzylcarbamate were selected on the basis of a computational approach describing possible interactions between the template and a small library of vinylic monomers. These results were in accordance with N,O-dibenzylcarbamate batch-rebinding measurements performed on several miniMIPs prepared with the same library. From these preliminary results, four polymers were prepared by thermoinduced radical polymerization, using ethylene dimethacrylate as a cross-linker, chloroform (MIP1, MIP3) or acetonitrile (MIP2, MIP4) as porogens and methacrylic acid (MIP1, MIP2) or acrylamide (MIP3, MIP4) as functional monomers. Molecular recognition features of these materials were studied by high-performance liquid chromatography. In this manner selectivity was evaluated by considering the column retention of a library of sixteen structural analogues of dibenzylcarbamate, characterized by the transformation of the carbamate into a related function, or by the alteration of the molecular structure.The experimental results show that methacrylic acid is more efficient than acrylamide as a functional monomer (imprinting factors: MIP1 = 24.1, MIP2 = 25.6, MIP3 = 13.3, MIP4 = 2.44), and that chloroform enhances polymer selectivity. As regards structural motifs which conditionate the selectivity, the carbamate function strictly controls the presence/absence of molecular recognition, while shape and dimension of the substituents modulate the recognition itself. In particular, a marked recognition for analogs which were slightly bigger than the template was observed (N-benzyl-O-phenethylcarbamate: MIP1 α = 1.13, MIP2 α = 1.41, MIP3 α = 0.97; N-phenethyl-N-benzylcarbamate: MIP1 α = 1.61, MIP2 α = 1.17, MIP3 α = 0.81; N,O-diphenethylcarbamate: MIP1 α = 0.89, MIP2 α = 1.20, MIP3 α = 0.55).     

Optimization of the process parameters of synthesis of vinblastine imprinted polymer

Molecularly imprinted polymers (MIPs) are tailor-made polymers with high selectivity for the template molecule. This selectivity arises from the synthetic procedure followed to prepare the MIP. In this work, the influence of process parameters on the preparation of vinblastine (VLB) imprinted polymers was presented. In the procedure of polymerization, VLB (0.1 mmol) was used as the template molecule and a commonly used initiator, azobisisobutyronitrile (AIBN), was employed to initiate the reaction at 60 °C. The influence of the following parameters was investigated: the moles of functional monomer (MAA, 0.3-1.0 mmol), the moles of cross-linker (EDMA, 1.5-5.0 mmol) and the porogenic solvent (toluene or acetonitrile). A mathematical method of uniform design was applied to optimize these selected parameters in order to increase the selectivity of MIP for template molecule. The experimental data were analyzed to obtain the regression model and the optimal conditions were achieved by optimization with uniform design software. The MIP was synthesized under the optimal conditions that 1.0 mmol of MAA and 5.0 mmol of EDMA copolymerized in toluene in the presence of 0.1 mmol of VLB. After removal of the template molecule, the obtained MIP was then employed as the sorbents of solid-phase extraction (SPE) to separate VLB from Catharanthus roseus extract. The results showed that the polymer exhibited high affinity to the template molecule and could separate and enrich VLB from C. roseus extract effectively. The recovery of VLB on the optimal MIP was 89.00%, which agreed closely with the predicted recovery. Therefore it is possible to further improve the nature of the polymer by optimizing the polymerization parameters with the method of uniform design.     

A new enzyme model for enantioselective esterases based on molecularly imprinted polymers

An efficient enzyme model exhibiting enantioselective esterase activity was prepared by using molecular imprinting techniques. The enantiomerically pure phosphonic monoesters 4 L and 5 L were synthesized as stable transition-state analogues. They were used as templates connected by stoichiometric noncovalent interactions to two equivalents of the amidinium binding site monomer 1. After polymerization and removal of the template, the polymers were efficient catalysts for the hydrolysis of certain nonactivated amino acid phenylesters (2 L, 2 D, 3 L, 3 D) depending on the template used. Imprinted catalyst IP4 (imprinted with 4 L) enhanced the hydrolysis of the corresponding substrate 2 L by a factor of 325 relative to that of a buffered solution. Relative to a control polymer containing the same functionalities, prepared without template 4 L, the enhancement was still about 80-fold, showing the highest imprinting effect up to now. In cross-selectivity experiments a strong substrate selectivity of higher than three was found despite small differences in the structure of the substrate and template. Plots of initial velocities of the hydrolysis versus substrate concentration showed typical Michaelis-Menten kinetics with saturation behavior. From these curves, the Michaelis constant K(M) and the catalytic constant k(cat) can be calculated. The enantioselectivity shown in these values is most interesting. The ratio of the catalytic efficiency k(cat)/K(M), between the hydrolysis of 2 L- and 2 D-substrate with IP4, is 1.65. This enantioselectivity derives from both selective binding of the substrate (K(M)L/K(M)D=0.82), and from selective formation of the transition state (k(cat)L/k(cat)D=1.36). Thus, these catalysts give good catalysis as well as high imprinting and substrate selectivity. Strong competitive inhibition is caused by the template used in imprinting. This behavior is also quite similar to the behavior of natural enzymes, for which these catalysts are good models.     

Biocatalysis and biorecognition in nonaqueous media. Some perspectives in analytical biochemistry

Biocatalysis and, to a lesser extent, biorecognition in non-aqueous media (including organic solvents as well as supercritical fluids and gases) constitute at present an exciting research area which has already demonstrated its biotechnological potential in numerous, varied applications. Less attention, however, has been paid to its analytical possibilities, even though many advantages have been postulated and a wide range of poorly water-soluble analytes are present in samples (or waste materials) from food and drink, petrochemical, pharmaceutical, military and other industries. The main approaches, developed in recent years to exploit the use of enzymes, antibodies or antibody mimics in water-restricted environments for analytical purposes, as well as possible future directions are briefly discussed.     

三甲氧基苄啶分子印迹整体柱的制备及色谱性能

选择甲基丙烯酸为功能单体\, 甲基丙烯酸乙二醇双酯为交联剂, 制备了三甲氧基苄啶分子印迹整体柱, 对整体柱材料的形貌进行了表征, 并且研究了TMP和5种磺胺类药物在分子印迹整体柱上的色谱行为.     

Synthesis and Molecular Recognition of Molecularly Imprinted Polymer with Ibuprofen as Template

Ibuprofen and ketoprofen are chemically similar non‐steroidal anti‐inflammatory drugs widely used in the treatment of arthritis. Using a molecular imprinting technique, a simple and rapid method was developed for the simultaneous separation and determination of ibuprofen and ketoprofen. Molecular imprinting introduces artificial binding sites into a synthetic polymer matrix, allowing it to exhibit selective rebinding of template molecules. Imprinted polymers can be regarded as an HPLC stationary phase, important for pharmaceutical analysis. Most molecularly imprinted polymers (MIPs) are synthesized by free radical polymerization of functional monomers, resulting in an excess of crosslinking monomers. In this study, MIPs have been prepared with a ibuprofen template, which can form intramolecular hydrogen bonds. Methacrylic acid (MAA) and ethyleneglycol dimethacrylate (EGDMA) were used as the functional monomer and cross‐linker, respectively. Bulk polymerization was carried out at 4 °C under UV radiation. The resulting MIP was ground into 25?44 μm particles, which were slurry‐packed into analytical columns. Template molecules were removed by methanol‐acetic acid (9:1, v/v). We evaluated the template binding performance of the MIP using HPLC, with ultraviolet (UV) detection at 234 nm. Chromatographic resolution of ibuprofen and ketoprofen on the MIPs were appraised using buffer/acetonitrile (45/55, v/v) as the mobile phase. Results show that the MIPs prepared using ibuprofen as the template had a significant molecular imprinting effect. The method was successfully applied to the separation and analysis of ibuprofen and ketoprofen in pharmaceuticals.     

分子印迹技术制备石油有机硫组分固相萃取剂的研究

用分子印迹技术合成了对石油有机硫组分二苯并噻吩(Dibenzothiophene，DBT)具有高效选择性的分子模板聚合物(Molecularly Imprinted Polymer，MIP)，通过静态吸附的方法研究了不同功能单体和致孔剂及其用量对模板聚合物特异性识别能力的影响．实验表明，以4-乙烯基吡啶(4-VP)为功能单体，在甲苯溶剂中聚合得到的固相萃取剂对DBT具有较大的吸附富集能力和识别特性．其饱和吸附容量达到48．3mg／g．