Flex activation

Larsen MB, Boydston AJ (2013) Flex-activated mechanophores using polymer mechanochemistry to direct bond bending activation. J Am Chem Soc 135 8189... 

A mechanophore (blue in Fig. 2a) is a strategically designed chemical entity which responds to mechanical force in a predictable and useful manner (Fig. 2d-f). The polymer strand here acts as an actuator to transmit macroscopic force to the target. For a fully extended polymer chain, the maximum tension force is at the middle point of the chain contour. So the mechanophore should be incorporated into the middle of the chain with its active bond along the chain contotu (Fig. 2a) [15, 29, 32]. Examples of mechanochemical reactions include homolytic scission of weak bonds (diazo [33]), electrocyclic ring-opening (benzocyclobutenes [29], spiropyrans [32, 34 5], gem-dichlorocyclopropanes [46-49], ge/n-difluorocyclo-propanes [30, 50], and epoxide [51]), cycloreversion reactions (cyclobutane derivatives [52-56], Diels-Alder adducts [57, 58], 1,3-dipolar adducts [59, 60], and 1,2-dioxetanes [61]), dative bond scission [62-64], and flex-activated reactions [34, 65, 66], as recently reviewed by Bielawski [67]. 

Keywords Catalysis Chemiluminescence Chromism Cycloreversion Dioxetane Flex activation Mechanochemistiy Polymers Self-healing... 

Later on12, Koshland proposed the induced fit model of the active site action that considers that during the formation of the enzyme-substrate complex, the enzyme can change its conformation so as to wrap the substrate like it happens when a hand (substrate) fits in a globe (enzyme). This flexing puts the active site and bonds in the substrate under strain, which weakens the bonds and helps to lower the activation energy for the catalyzed reaction. 

Dihydroquinoline derivatives offer moderate antioxidant and flex cracking activity with excellent metal poison protection. 

Diaryl-phenylenediamines have very good antioxidant activity with good to moderate antiozonant characteristics, with low volatility but will possibly bloom to the rubber surface. They give very good flex cracking resistance. 

The 12-MR pores in the CIT-1 structure [International Zeolite Association (IZA) structure code, CON] are 6.8 x 6.4 A in diameter while the intersecting 10-MR pores are5.1x5.lA.B oth pore dimensions might be regarded as small for the ring size but interestingly molecular simulation of the pores between 0 and 200 K indicate the 10-MR pores can flex by >1 A (25). The potential catalytic activity of... 

Usually, the corrosion-fatigue limit of a metal in sea water is lower than in fresh water. Repeated flexing allows the corrosion to proceed at the breaks in the protective film where active metal is exposed. 

Polgar T., Keseril G.M., Ensemble docking into flexible active sites. Critical evaluation of FlexE against JNK-3 and (3-secretase. J. Chem. Inf. Model. 2006, 46, 1795-1805. 

Dinuclear and trinuclear platinum complexes represent a new class of anticancer agents, distinct in DNA-binding and profile of antitumor activity from their mononuclear counterparts. The dinuclear motif was first reported in 1988 and consisted of two m-PtCl2(NH3) units linked by a flex-... 

The data from such EXAFS studies show that in all cases the metal clusters remained intact and are catalytically active. However, as shown, for example, in Figure 41, the clusters did remain bonded to the oxide support, but underwent slight rearrangements to accommodate the reaction intermediates. For example, it was shown that as the concentration of adsorbed reaction intermediates (e.g., n-bonded alkenes, alkyl species) on the clusters increased, the cluster frames expanded, and the clusters flexed away from the support. 

The resultant fabrics are unique in that they have many functional property improvements thermal adaptability due to the phase change nature of the bound polyol, durable press or resiliency, soil release, reduction of static charge, antimicrobial activity, enhanced hydrophilicity and improved flex life, and resistance to pilling. Because of the different molecular weights of polyols, resins, acid catalysts, and fabric constructions, there are numerous modified fabrics that can be produced with sets of improved attributes. Each fabric must be carefully evaluated for optimum curing conditions and formulations to produce the desired product. Several licenses have been granted for this process. Various types of apparel, healthcare items, and industrial fabrics are currently evaluated for commercial production [381,382]. 

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