[material] polymer can also have protein structure: preparation of multi-stage structure polymer

Protein is the basic substance of life All the important metabolism in the body needs the participation of protein, so there are countless kinds of protein But from the chemical point of view, protein is essentially a kind of polymer formed by amino acid condensation In theory, simple amino acid arrangement can not give protein such rich functions Through the study of protein, people found that protein not only has the first-order structure (the sequence of amino acid residues), but also has more complex and diverse second-order, third-order and even fourth-order structures It is these unique multistage structures that make protein have a variety of functions In the past decade, the research on polymers has been no longer limited to polymers with only one-stage structure, but also devoted to the development of polymers with multi-stage structure similar to proteins, such as single chain nanoparticles (scnp) In recent years, scientists have been able to construct multi-level scnps through noncovalent interaction and covalent bond Compared with the thermally driven synthesis method, the optically driven reaction can provide more precise control in space and time However, high-energy ultraviolet light will not only cause light damage, but also reduce the bioorthogonality of materials In addition, in the process of scnp formation, in order to avoid the interaction of polymer chain molecules, the concentration is generally below 0.1 mg / ml, which is lower than the detection limit of many analytical methods, so there are few reports on real-time analysis of scnp formation process Fig 1 Structure and scnp formation of styrene pyrene based polymer (photo source: J am Chem SOC.) recently, Professor Christopher Barner kowollik from Queensland University of science and technology, Australia and Karlsruhe Institute of technology, Germany, reported a polymer based on styrene pyrene, in which the styrene pyrene structural unit can Scnp is formed by dimerization in sunlight (Fig 1) Moreover, the introduction of the polymer will greatly improve the efficiency of the dimerization of styrene pyrene, and the polymerization can be carried out at a concentration of up to 15 mg / ml This achievement was published in the Journal of the American Chemical Society (DOI: 10.1021 / JACS 8b04531) under the title of "photography in found environments for single chain nano particle design" Fig 2 A) sec of P1 under 430nm light; b) UV spectrum of P1 under 430nm light; c) UV spectrum of polymer content changing with photon number based on UV data (photo source: J am Chem SOC.) the synthesis of polymer single chain is relatively simple The author combines methacrylate containing styrene pyrene and methyl methacrylate by reversible addition -The polymers with different styrene pyrene contents (P1: 28 mol%; P2: 10 mol%; P3: 3 mol%) were obtained by reverse addition fragmentation chain transfer (RAFT) polymerization After these polymers were obtained, the effect of styrene pyrene addition on polymer folding was studied It can be seen from the molecular exclusion chromatography (SEC) (Fig 2a), with the increase of irradiation time, the size of the polymer is gradually decreasing, while the UV also shows a similar change (Fig 2b) By calculating the change of molar extinction coefficient at 383 nm in UV spectrum, the dimerization of styrene pyrene in different polymers was quantitatively studied (Fig 2C) It was found that the higher the content of styrene pyrene, the higher the degree of dimerization However, even if only 3 mol% of P3 is contained, the degree of dimerization is 75% Compared with P1 and P2, most of the styrene pyrene in P3 is encapsulated by polymer, which shows that the encapsulation of polymer does not hinder the photodegradation of styrene pyrene In addition to studying the effect of styryl pyrene on polymer folding, the author also studied the effect of polymer on the dimerization of styryl pyrene The results showed that under the same conditions, styryl pyrene without polymer can only undergo the transformation of configuration, but not dimerization (Fig 2C) Fig 3 The influence of concentration (left) and wavelength (right) on polymerization (photo source: J am Chem SOC.) after understanding the basic properties of polymers, the author studied two major problems in the formation of scnp First, the effect of concentration on the polymerization was studied It has been mentioned that the intermolecular polymerization will take place at high concentration (left in Figure 3), which will greatly reduce the efficiency of scnp formation Therefore, the author took P2 as an example to test the concentration gradient of the polymer The results show that P2 can effectively carry out intramolecular polymerization even at a concentration of up to 15 mg / ml Secondly, the light source is studied Although strong UV can improve the reaction efficiency, the negative effect is more serious It is found that scnp can be effectively formed by polymer P1 even when sunlight is used as light source In addition, the photodegradation of such polymers does not require special treatment of solvents (such as deaeration), which further increases the scope of application of such polymers Finally, the author said that the previous studies on scnp need to separate the products for detailed analysis, but the scnp prepared by this method of styrene pyrene has high reaction concentration and no other compounds are introduced, so it is not only unnecessary to separate, but also can monitor the reaction process in real time This study introduces a simple and efficient method for the preparation of multi-stage structural materials The new method not only overcomes the limitation of substrate concentration on multi-stage materials, but also has mild reaction conditions, so it is expected to be widely used in the preparation of single chain nanoparticles The full text is written by Hendrik Frisch, Jan P Menzel, Fabian R BL ö Dier, David marschner, Kai mundsinger, and Christopher Barner kowollik