Double helix artificial muscles (Conference Presentation)

The so-called McKibben artificial muscle is one of the most efficient and currently one of the most widely used fluidic artificial muscles, due to the simplicity of its design, combining ease of implementation and analogous behaviour with skeletal muscles. Its working principle is very simple: The circumferential stress of a pressurized inner tube is transformed into an axial contraction force by means of a double-helix braided sheath whose geometry corresponds to a network of identical pantographs. However, behind this apparent simplicity lie two phenomena, which must be considered so as to fully understand how the McKibben muscle works. First, the non-linear relationship between stress and strain inside the inner tube elastomer, together with the complex relationship between physical artificial muscle parameters and its effective working pressure range. Second, the behaviour of the braided sheath which acts like a ‘flexible joint structure’ able to adapt itself during contraction to the increasing radius muscle in its middle portion, with the boundary constraint of rigid tips. By distinguishing an ideal model with a zero inner tube thickness from a real model with a non-zero inner tube thickness, we attempted to synthesize static models by including and excluding an elastic force component. However, we also highlight the possible need, in further modelling, to distinguish modelling thin-walled from thick-walled inner tube McKibben muscles. In our attempt to understand the hysteresis peculiar to the muscle, it seems, resulting from our review, that this hysteresis phenomenon is essentially due to strand-on-strand friction inside the weave. Nevertheless, although Hertz’s contact theory has shown its relevance in tackling this problem, friction modelling in a McKibben muscle is particularly hard due to the difficulties, first, to correctly determine the real contact surface strand-on-strand and, second, to estimate the friction coefficient and its possible dependence on pressure and velocity with the weaving peculiar to McKibben braided sheaths. We propose in a future approach to better integrate textile physics into this very complex modelling problem. Moreover, because we consider friction to be velocity-dependent, a distinction between static and dynamic modelling appears necessary to us and can help, in our view, towards a better understanding of the Hill-like character (or not) debate concerning artificial muscles.

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Dual high-stroke and high–work capacity artificial muscles inspired by DNA supercoiling

Science Robotics ◽

10.1126/scirobotics.abf4788 ◽

2021 ◽

Vol 6 (53) ◽

pp. eabf4788

Author(s):

Geoffrey M. Spinks ◽

Nicolas D. Martino ◽

Sina Naficy ◽

David J. Shepherd ◽

Javad Foroughi

Keyword(s):

Skeletal Muscle ◽

Double Helix ◽

Work Capacity ◽

Dna Supercoiling ◽

Artificial Muscles ◽

Alternative Mechanism ◽

Active System ◽

Miniature Robots ◽

Drive Systems ◽

High Work

Powering miniature robots using actuating materials that mimic skeletal muscle is attractive because conventional mechanical drive systems cannot be readily downsized. However, muscle is not the only mechanically active system in nature, and the thousandfold contraction of eukaryotic DNA into the cell nucleus suggests an alternative mechanism for high-stroke artificial muscles. Our analysis reveals that the compaction of DNA generates a mass-normalized mechanical work output exceeding that of skeletal muscle, and this result inspired the development of composite double-helix fibers that reversibly convert twist to DNA-like plectonemic or solenoidal supercoils by simple swelling and deswelling. Our modeling-optimized twisted fibers give contraction strokes as high as 90% with a maximum gravimetric work 36 times higher than skeletal muscle. We found that our supercoiling coiled fibers simultaneously provide high stroke and high work capacity, which is rare in other artificial muscles.

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Protamine-DNA interaction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081863 ◽

1978 ◽

Vol 36 (2) ◽

pp. 200-201

Author(s):

D.P. Bazett-Jones ◽

F.P. Ottensmeyer

Keyword(s):

Small Volume ◽

Double Helix ◽

Dna Interaction ◽

Dark Field ◽

Sperm Head ◽

Nuclear Proteins ◽

Field Electron Microscopy ◽

Dark Field Electron ◽

Dna Double Helix ◽

Positively Charged

Dark field electron microscopy has been used for the study of the structure of individual macromolecules with a resolution to at least the 5Å level. The use of this technique has been extended to the investigation of structure of interacting molecules, particularly the interaction between DNA and fish protamine, a class of basic nuclear proteins of molecular weight 4,000 daltons.Protamine, which is synthesized during spermatogenesis, binds to chromatin, displaces the somatic histones and wraps up the DNA to fit into the small volume of the sperm head. It has been proposed that protamine, existing as an extended polypeptide, winds around the minor groove of the DNA double helix, with protamine's positively-charged arginines lining up with the negatively-charged phosphates of DNA. However, viewing protamine as an extended protein is inconsistent with the results obtained in our laboratory.

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Electron microscopic assays of restriction endonuclease cutting, exonuclease digestion, and hybridization

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113317 ◽

1984 ◽

Vol 42 ◽

pp. 686-687

Author(s):

Mark Hannibal ◽

Jacob Varkey ◽

Michael Beer

Keyword(s):

Electron Microscope ◽

Low Temperature ◽

Restriction Endonuclease ◽

Double Helix ◽

Test Material ◽

Electron Microscopic ◽

Exonuclease Iii ◽

Dna Molecule ◽

Linear Molecules ◽

Exonuclease Digestion

Workman and Langmore have recently proposed a procedure for isolating particular chromatin fragments. The method requires restriction endonuclease cutting of the chromatin and a probe, their digestion with two exonucleases which leave complimentary single strand termini and low temperature hybridization of these. We here report simple electron microscopic monitoring of the four reactions involved.Our test material was ϕX-174 RF DNA which is cut once by restriction endonuclease Xho I. The conversion of circles to linear molecules was followed in Kleinschmidt spreads. Plate I shows a circular and a linear DNA molecule. The rate of cutting is shown in Figure 1.After completion of the endonuclease cutting, one portion of the DNA was treated with exonuclease III, an enzyme known to digest the 3' terminals of double helical DNA. Aliquots when examined in the electron microscope reveal a decreasing length of double helix and increasing bushes at the ends.

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MEASUREMENT OF THE UNWINDING FORCE OF A DNA DOUBLE HELIX

Журнал структурной химии ◽

10.15372/jsc20170213 ◽

2017 ◽

Keyword(s):

Double Helix ◽

Dna Double Helix

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DNA Inspirited Rational Construction of Nonconventional Luminophores with Efficient and Color-Tunable Afterglow

10.26434/chemrxiv.11786448 ◽

2020 ◽

Author(s):

Yunzhong Wang ◽

Saixing Tang ◽

Yating Wen ◽

Shuyuan Zheng ◽

Bing Yang ◽

...

Keyword(s):

Rational Design ◽

Room Temperature ◽

Double Helix ◽

Mechanical Grinding ◽

Room Temperature Phosphorescence ◽

Color Tunable ◽

Potential Applications ◽

Rational Construction ◽

Double Helix Structure ◽

Made In

<div>Persistent room-temperature phosphorescence (p-RTP) from pure organics is attractive </div><div>due to its fundamental importance and potential applications in molecular imaging, </div><div>sensing, encryption, anticounterfeiting, etc.1-4 Recently, efforts have been also made in </div><div>obtaining color-tunable p-RTP in aromatic phosphors5 and nonconjugated polymers6,7. </div><div>The origin of color-tunable p-RTP and the rational design of such luminogens, </div><div>particularly those with explicit structure and molecular packing, remain challenging. </div><div>Noteworthily, nonconventional luminophores without significant conjugations generally </div><div>possess excitation-dependent photoluminescence (PL) because of the coexistence of </div><div>diverse clustered chromophores6,8, which strongly implicates the possibility to achieve </div><div>color-tunable p-RTP from their molecular crystals assisted by effective intermolecular </div><div>interactions. Here, inspirited by the highly stable double-helix structure and multiple </div><div>hydrogen bonds in DNA, we reported a series of nonconventional luminophores based on </div><div>hydantoin (HA), which demonstrate excitation-dependent PL and color-tunable p-RTP </div><div>from sky-blue to yellowish-green, accompanying unprecedentedly high PL and p-RTP </div><div>efficiencies of up to 87.5% and 21.8%, respectively. Meanwhile, the p-RTP emissions are </div><div>resistant to vigorous mechanical grinding, with lifetimes of up to 1.74 s. Such robust, </div><div>color-tunable and highly efficient p-RTP render the luminophores promising for varying </div><div>applications. These findings provide mechanism insights into the origin of color-tunable </div><div>p-RTP, and surely advance the exploitation of efficient nonconventional luminophores.</div>

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