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Intrinsic enzymatic properties modulate the self-propulsion of micromotors.

ABSTRACT: Bio-catalytic micro- and nanomotors self-propel by the enzymatic conversion of substrates into products. Despite the advances in the field, the fundamental aspects underlying enzyme-powered self-propulsion have rarely been studied. In this work, we select four enzymes (urease, acetylcholinesterase, glucose oxidase, and aldolase) to be attached on silica microcapsules and study how their turnover number and conformational dynamics affect the self-propulsion, combining both an experimental and molecular dynamics simulations approach. Urease and acetylcholinesterase, the enzymes with higher catalytic rates, are the only enzymes capable of producing active motion. Molecular dynamics simulations reveal that urease and acetylcholinesterase display the highest degree of flexibility near the active site, which could play a role on the catalytic process. We experimentally assess this hypothesis for urease micromotors through competitive inhibition (acetohydroxamic acid) and increasing enzyme rigidity (?-mercaptoethanol). We conclude that the conformational changes are a precondition of urease catalysis, which is essential to generate self-propulsion.

SUBMITTER: Arque X

PROVIDER: S-EPMC6597730 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Intrinsic enzymatic properties modulate the self-propulsion of micromotors.

Arqué Xavier X Romero-Rivera Adrian A Feixas Ferran F Patiño Tania T Osuna Sílvia S Sánchez Samuel S

Nature communications 20190627 1

Bio-catalytic micro- and nanomotors self-propel by the enzymatic conversion of substrates into products. Despite the advances in the field, the fundamental aspects underlying enzyme-powered self-propulsion have rarely been studied. In this work, we select four enzymes (urease, acetylcholinesterase, glucose oxidase, and aldolase) to be attached on silica microcapsules and study how their turnover number and conformational dynamics affect the self-propulsion, combining both an experimental and mol ...[more]

PMID: 31249381

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Project description:Highlights • Metatarsalphalangeal joint quasi-stiffness during jumping was reduced by the application of a selective tibial nerve block, which removed the active contributions of the intrinsic foot muscles• When jumping under the nerve block, ankle leverage and torque were reduced when compared to normal conditions• Fascicle and muscle–tendon unit velocity were not different during jumping propulsion between normal and nerve block conditions• Although impulse was similar between conditions, jump height was reduced under the nerve block condition due to a lower take-off position of the center of mass Background During human locomotion, a sufficiently stiff foot allows the ankle plantar flexors to generate large propulsive powers. Increasing foot stiffness (e.g., via a carbon plate) increases the ankle's external moment arm in relation to the internal moment arm (i.e., increasing gear ratio), reduces plantar flexor muscles’ shortening velocity, and enhances muscle force production. In contrast, when activation of the foot's intrinsic muscles is impaired, there is a reduction in foot and ankle work and metatarsophalangeal joint stiffness. We speculated that the reduced capacity to actively control metatarsophalangeal joint stiffness may impair the gearing function of the foot at the ankle. Methods We used a tibial nerve block to examine the direct effects of the intrinsic foot muscles on ankle joint kinetics, in vivo medial gastrocnemius’ musculotendinous dynamics, and ankle gear ratio on 14 participants during maximal vertical jumping. Results Under the nerve block, the internal ankle plantar flexion moment decreased (p = 0.004) alongside a reduction in external moment arm length (p = 0.021) and ankle joint gear ratio (p = 0.049) when compared to the non-blocked condition. Although medial gastrocnemius muscle–tendon unit and fascicle velocity were not different between conditions, the Achilles tendon was shorter during propulsion in the nerve block condition (p < 0.001). Conclusion In addition to their known role of regulating the energetic function of the foot, our data indicate that the intrinsic foot muscles also act to optimize ankle joint torque production and leverage during the propulsion phase of vertical jumping. Graphical Abstract Image, graphical abstract

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Intrinsic enzymatic properties modulate the self-propulsion of micromotors.

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Intrinsic enzymatic properties modulate the self-propulsion of micromotors.

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