Silicon-Based Solid-State Batteries: Electrochemistry and Mechanics to Guide Design and Operation

Solid-state batteries (SSBs) are promising alternatives to the incumbent lithium-ion technology; however, they face a unique set of challenges that must be overcome to enable their widespread adoption. These challenges include solid-solid interfaces that are highly resistive, with slow kinetics, and a tendency to form interfacial voids causing diminished cycle life due to fracture and delamination. This modeling study probes the evolution of stresses at the solid electrolyte (SE) solid-solid interfaces, by linking the chemical and mechanical material properties to their electrochemical response, which can be used as a guide to optimize the design and manufacture of silicon (Si) based SSBs. A thin-film solid-state battery consisting of an amorphous Si negative electrode (NE) is studied, which exerts compressive stress on the SE, caused by the lithiation-induced expansion of the Si. By using a 2D chemo-mechanical model, continuum scale simulations are used to probe the effect of applied pressure and C-rate on the stress-strain response of the cell and their impacts on the overall cell capacity. A complex concentration gradient is generated within the Si electrode due to slow diffusion of Li through Si, which leads to localized strains. To reduce the interfacial stress and strain at 100% SOC, operation at moderate C-rates with low applied pressure is desirable. Alternatively, the mechanical properties of the SE could be tailored to optimize cell performance. To reduce Si stress, a SE with a moderate Young's modulus similar to that of lithium phosphorous oxynitride (∼77 GPa) with a low yield strength comparable to sulfides (∼0.67 GPa) should be selected. However, if the reduction in SE stress is of greater concern, then a compliant Young's modulus (∼29 GPa) with a moderate yield strength (1-3 GPa) should be targeted. This study emphasizes the need for SE material selection and the consideration of other cell components in order to optimize the performance of thin film solid-state batteries.

Mechanical behaviour of inorganic solid-state batteries: can we model the ionic mobility in the electrolyte with Nernst-Einstein's relation?

Inorganic solid-state lithium-metal batteries could be the next-generation batteries owing to their non-flammability and higher specific energy density. Many research efforts have been devoted to improving the ionic conductivity of inorganic solid electrolytes. For a wide range of electrolytes including liquid and solid polymer electrolytes, an independent measurement or calculation of both electrolyte conductivity and diffusion coefficient is often time-consuming and challenging. As a result, Nernst-Einstein's relation has been used to relate the ionic conductivity to ionic diffusivity after the determination of either parameter. Although Nernst-Einstein's relation has been used for different electrolytes, we demonstrate in this perspective that this relation is not directly transferable to describe the ionic mobility for many inorganic solid electrolytes. The fundamental physics of Nernst-Einstein's relation shows that the relationship between the diffusion coefficient and electrolyte conductivity is derived for ionic mobility in a viscous or a gaseous medium. This postulation contradicts state-of-the-art experimental studies measuring the mechanical behaviour of inorganic solid electrolytes, which show that inorganic solid electrolytes are usually brittle rather than viscoelastic at ambient room temperature. The measurement of loss tangent is required to justify the use of Nernst-Einstein's relation. The outcome of such measurement has two implications. First, if the loss tangent of inorganic solid electrolytes is less than unity in the range of batteries operating temperatures, the impacts of using Nernst-Einstein's relation in modelling the ionic mobility should be quantified. Secondly, if the measured loss tangent is comparable to that of solid polymers and lithium metal, inorganic solid electrolytes may behave in a viscoelastic manner as opposed to the brittle behaviour usually suggested.

Financial viability of electric vehicle lithium-ion battery recycling

Economically viable electric vehicle lithium-ion battery recycling is increasingly needed; however routes to profitability are still unclear. We present a comprehensive, holistic techno-economic model as a framework to directly compare recycling locations and processes, providing a key tool for recycling cost optimization in an international battery recycling economy. We show that recycling can be economically viable, with cost/profit ranging from (−21.43 - +21.91) $·kWh⁻¹ but strongly depends on transport distances, wages, pack design and recycling method. Comparing commercial battery packs, the Tesla Model S emerges as the most profitable, having low disassembly costs and high revenues for its cobalt. In-country recycling is suggested, to lower emissions and transportation costs and secure the materials supply chain. Our model thus enables identification of strategies for recycling profitability.

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Comprehensive techno-economic cost model for electric vehicle battery recycling

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Net recycling profits for recycling in Asia, Europe, and the US are compared

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Reducing transportation and disassembly costs is crucial for a profitable process

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Economies of scale and battery materials are decisive for recycling profits

AB0058 ASSOCIATION BETWEEN HLA-DRB1*04:01, RHEUMATOID NODULES AND PARTICULAR EPITOPES OF CITRULLINATED FIBRIN IN PATIENTS WITH RHEUMATOID ARTHRITIS

Background:

Rheumatoid arthritis (RA) is associated with HLA-DRB1 genes encoding the shared epitope (SE), a 5 amino acid motive. RA is usually preceded by the emergence of anti-citrullinated protein antibodies (ACPAs) detected by anti-CCP2 tests. Citrullin is a neutral amino acid resulting from post translational modification of arginin by Peptidyl Arginyl Deiminases (PADs). ACPAs recognize epitopes from citrullinated human fibrinogen (Fib-cit) and can be specifically detected by the AhFibA assay. Five peptides derived from Fib-cit together represent almost all of the epitopes recognized by patients with ACPA-positive RA: β60–74cit, α36–50cit, α621–635cit, α501–515cit and α171–185cit. As RA is a pleiomorphic disease, whose evolution is difficult to predict, the use of antibody fine specificity as a marker of clinical phenotypes has become a major challenge.

Objectives:

Our objective was to study whether clinical characteristics and HLA-DRB1 genetic background were associated with a specific reactivity against these epitopes.

Methods:

184 ACPA positive RA patients fulfilling the 2010 ACR/EULAR criteria were studied. Patients characteristics, including HLA-DRB1 genotype, were collected from their medical files. Anti-CCP2, AhFibA, Rheumatoid Factors (RF), and antibodies against the five major Fib-cit peptides were analyzed using ELISA assays.

Results:

Anti-CCP2 and AhFibA titres were strongly correlated (rs: 0.7037; p = 5.69x10-29, Pearson’s). Anti-α505-515cit antibodies were associated with HLA-DRB1*04:01 (OR = 5.52 [2.00 – 13.64]; p = 0.0003). High level anti-α505-515cit antibodies were significantly associated with rheumatoid nodules (OR = 2.71 [1.00 – 7.16], p= 0.044). Anti α501–515cit antibodies were associated with RF (OR=2.31 [1.10 – 4.78], p= 0.026).

Conclusion:

Immune complexes containing anti-α501–515cit antibodies and rheumatoid factors might be involved in the development of rheumatoid nodules on the HLA-DRB1*04:01 background. These findings highlight the role played by the HLA-DRB1*04:01 molecule and its rapid intracellular route into the lysosomes, enabling original antigen processing. Finally, purifying these epitope specific antibodies might be a new therapeutic opportunity for rheumatoid nodules.

Disclosure of Interests:

None declared

Chest wall resection and reconstruction for Rosai-Dorfman disease masquerading as a chest wall sarcoma

Rosai-Dorfman disease (RDD) is a rare benign histiocytic proliferative disease that can present as a pseudotumour of soft tissue. We describe the first chest wall resection and reconstruction.

Modeling the voltage loss mechanisms in lithium–sulfur cells: the importance of electrolyte resistance and precipitation kinetics

We analyse the evolution of three major voltage-drop mechanisms in Li–S cells during discharge, with a particular emphasize on the importance of precipitation-induced variations in the electrolyte resistance and reaction potentials.

Temperature and ligand dependence of conformation and helical order in myosin filaments

Mammalian myosin filaments are helically ordered only at higher temperatures (>20 degrees C) and become progressively more disordered as the temperature is decreased. It had previously been suggested that this was a consequence of the dependence of the hydrolytic step of myosin ATPase on temperature and the requirement that hydrolysis products (e.g., ADP.P(i)) be bound at the active site. An alternative hypothesis is that temperature directly affects the conformation of the myosin heads and that they need to be in a particular conformation for helical order in the filament. To discriminate between these two hypotheses, we have studied the effect of temperature on the helical order of myosin heads in rabbit psoas muscle in the presence of nonhydrolyzable ligands. The muscle fibers were overstretched to nonoverlap such that myosin affinity for nucleotides was not influenced by the interaction of myosin with the thin filament. We show that with bound ADP.vanadate, which mimics the transition state between ATP and hydrolysis products, or with the ATP analogues AMP-PNP or ADP.BeF(x)() the myosin filaments are substantially ordered at higher temperatures but are reversibly disordered by cooling. These results reinforce recent studies in solution showing that temperature as well as ligand influence the equilibrium between multiple myosin conformations [Málnási-Csizmadia, A., Pearson, D. S., Kovács, M., Woolley, R. J., Geeves, M. A., and Bagshaw, C. R. (2001) Biochemistry 40, 12727-12737; Málnási-Csizmadia, A., Woolley, R. J., and Bagshaw, C. R. (2000) Biochemistry 39, 16135-16146; Urbanke, C., and Wray, J. (2001) Biochem. J. 358, 165-173] and indicate that helical order requires the myosin heads to be in the closed conformation. Our results suggest that most of the heads in the closed conformation are ordered, and that order is not produced in a separate step. Hence, helical order can be used as a signature of the closed conformation in relaxed muscle. Analysis of the dependence on temperature of helical order and myosin conformation shows that in the presence of these analogues one ordered (closed) conformation and two disordered conformations with distinct thermodynamic properties coexist. Low temperatures favor one disordered conformation, while high temperatures favor the ordered (closed) conformation together with a second disordered conformation.

A new model for the surface arrangement of myosin molecules in tarantula thick filaments

Three-dimensional reconstructions of the negatively stained thick filaments of tarantula muscle with a resolution of 50 A have previously suggested that the helical tracks of myosin heads are zigzagged, short diagonal ridges being connected by nearly axial links. However, surface views of lower contour levels reveal an additional J-shaped feature approximately the size and shape of a myosin head. We have modelled the surface array of myosin heads on the filaments using as a building block a model of a two-headed regulated myosin molecule in which the regulatory light chains of the two heads together form a compact head-tail junction. Four parameters defining the radius, orientation and rotation of each myosin molecule were varied. In addition, the heads were allowed independently to bend in a plane perpendicular to the coiled-coil tail at three sites, and to tilt with respect to the tail and to twist at one of these sites. After low-pass filtering, models were aligned with the reconstruction, scored by cross-correlation and refined by simulated annealing. Comparison of the geometry of the reconstruction and the distance between domains in the myosin molecule narrowed the choice of models to two main classes. A good match to the reconstruction was obtained with a model in which each ridge is formed from the motor domain of a head pointing to the bare zone together with the head-tail junction of a neighbouring molecule. The heads pointing to the Z-disc intermittently occupy the J-position. Each motor domain interacts with the essential and regulatory light chains of the neighbouring heads. A near-radial spoke in the reconstruction connecting the backbone to one end of the ridge can be identified as the start of the coiled-coil tail.

The M.ADP.Pi state is required for helical order in the thick filaments of skeletal muscle

The thick filaments of mammalian and avian skeletal muscle fibers are disordered at low temperature, but become increasingly ordered into an helical structure as the temperature is raised. Wray and colleagues (Schlichting, I., and J. Wray. 1986. J. Muscle Res. Cell Motil. 7:79; Wray, J., R. S. Goody, and K. Holmes. 1986. Adv. Exp. Med. Biol. 226:49-59) interpreted the transition as reflecting a coupling between nucleotide state and global conformation with M.ATP (disordered) being favored at 0 degrees C and M.ADP.P(i) (ordered) at 20 degrees C. However, hitherto this has been limited to a qualitative correlation and the biochemical state of the myosin heads required to obtain the helical array has not been unequivocally identified. In the present study we have critically tested whether the helical arrangement of the myosin heads requires the M.ADP.P(i) state. X-ray diffraction patterns were recorded from skinned rabbit psoas muscle fiber bundles stretched to non-overlap to avoid complications due to interaction with actin. The effect of temperature on the intensities of the myosin-based layer lines and on the phosphate burst of myosin hydrolyzing ATP in solution were examined under closely matched conditions. The results showed that the fraction of myosin mass in the helix closely followed that of the fraction of myosin in the M.ADP.P(i) state. Similar results were found by using a series of nucleoside triphosphates, including CTP and GTP. In addition, fibers treated by N-phenylmaleimide (Barnett, V. A., A. Ehrlich, and M. Schoenberg. 1992. Biophys. J. 61:358-367) so that the myosin was exclusively in the M.ATP state revealed no helical order. Diffraction patterns from muscle fibers in nucleotide-free and in ADP-containing solutions did not show helical structure. All these confirmed that in the presence of nucleotides, the M.NDP.P(i) state is required for helical order. We also found that the spacing of the third meridional reflection of the thick filament is linked to the helical order. The spacing in the ordered M.NDP.P(i) state is 143.4 A, but in the disordered state, it is 144. 2 A. This may be explained by the different interference functions for the myosin heads and the thick filament backbone.

The structure of the head-tail junction of the myosin molecule

An atomic model of the junction between the two heads and tail of a myosin molecule has been created by attaching a scallop regulatory domain to the end of each of the two alpha-helical strands of a model of the scallop alpha-helical coiled coil. The C-terminal alpha-helix of the heavy chain of each regulatory domain was superposed over the corresponding sequence in the coiled coil. In the structure created, the two heads lie alongside one another with their bases in contact but remarkably without steric clash. The principal interactions between the two heads are between the regulatory light chains and there are also head-tail interactions between each regulatory light chain and its heavy chain partner in the coiled coil. The invariant proline residues cause the heavy chains to flare to form the fork. The direction of the turn at the WQW sequence within the regulatory domain causes the long alpha-helix of the heavy chains within the head to continue the sense of the supercoil. With the bases of heads interacting, motion of the heads could still occur by a flexing of the coiled coil close to the heads and by a flexing and twisting of the long alpha-helices in the head. The model accounts for some of the conserved sequence features in myosins from different sources and provides a structural basis for understanding the head-head interactions in regulated myosin. Using the C alpha atoms of subfragment 1 we have also constructed a model with two complete heads. The clockwise curvature of the heads when the model is viewed end-on towards the tail accounts for the most common appearance of myosin molecules in electron micrographs. These models are predicated on the assumption that the entire heptad sequence of the heavy chains forms a coiled coil. Previous evidence from electron micrographs of myosin molecules that this was not the case can be explained by the foreshortening of the tail close to the heads.

Computer modelling of the alpha-helical coiled coil: packing of side-chains in the inner core

In order to predict the structure of alpha-helical coiled-coil proteins from their sequences, it is necessary to know how the side-chains pack in the interface between the alpha-helical strands. Since in alpha-fibrous proteins leucine is the most common residue at both the a and d positions of the heptad repeat, which form the inner core of the interface, we determined the lowest-energy conformation for a two-stranded coiled-coil with the sequence (LAALAAA)5. Coiled-coils were constructed using the Crick equations with a range of pitches, major helical radii and relative rotations of the two strands, and with different starting side-chain conformations. On energy minimisation, convergence occurred to a small number of structures. The lowest-energy coiled-coil had 2-fold rotational symmetry, an average pitch of 131 A and an average radius of 4.52 A; the leucine side-chain conformations were tt and g+t at the a and d positions. This coiled-coil was used as a former to determine the lowest-energy side-chain conformations for the 63 combinations of a and d residues that occur in the repeating heptad sequence of rat skeletal myosin. The leucine residues at the a and d positions of the central heptad were replaced by the a-d pair of interest and molecular dynamics simulations performed to allow the side-chains of these residues to explore conformational space. The lowest-energy side-chain conformation of a residue at an a or d position depends on the nature of the partnering residue, consistent with the fact that these side-chains pack against one another. In most cases the lowest-energy structure was symmetric but in a few cases the side-chains were asymmetrically disposed in the two strands. The local pitch is very sensitive to the nature of the residues in the inner core and varies over a twofold range. In contrast, the radius and relative rotation of the two strands were relatively insensitive to sequence.

Atomic force microscopy of the myosin molecule

Atomic force microscopy (AFM) has been used to study the structure of rabbit skeletal muscle myosin deposited onto a mica substrate from glycerol solution. Images of the myosin molecule have been obtained using contact mode AFM with the sample immersed in propanol. The molecules have two heads at one end of a long tail and have an appearance similar to those prepared by glycerol deposition techniques for electron microscopy, except that the separation of the two heads is not so well defined. The average length of the tail (155 +/- 5 nm) agrees well with previous studies. Bends in the myosin tail have been observed at locations similar to those observed in the electron microscope. By raising the applied force, it has been possible locally to separate the two strands of the alpha-helical coiled-coil tail. We conclude that the glycerol-mica technique is a useful tool for the preparation of fibrous proteins for examination by scanning probe microscopy.

Skip residues correlate with bends in the myosin tail

Sharp bends have previously been observed in the tail of the skeletal myosin molecule at well-defined positions 44, 75 and 135 nm from the head-tail junction, and in vertebrate smooth myosin at two positions about 45 and 96 nm from this junction. The amino acid sequence of the heavy chain does not straightforwardly account for such bending on the original model of the tail in which an invariant proline residue is present at the head-tail junction and the repeating seven amino acid pattern of hydrophobic residues lies entirely in the tail. Recently, a revised model has been proposed by Rimm et al. in which the first seven to eight heptads lie in the heads. It is shown here that with this model the observed bends in the tail of skeletal myosin coincide with three of the four additional (skip) residues that interrupt the heptad repeat. It is concluded that the skip residues, by causing localized instability of the coiled-coil, are responsible for the bends. Smooth myosin lacks the second of these skip residues explaining the absence of a bend at 75 nm.

The ultrastructural location of C-protein, X-protein and H-protein in rabbit muscle

Purified antibodies to the thick filament accessory proteins, C-protein, X-protein and H-protein, have been used to label fibres of three rabbit muscles, psoas (containing mainly fast white fibres), soleus (containing mainly slow red fibres) and plantaris (a muscle of mixed fibre type) and their location has been examined by electron microscopy. These accessory proteins are present on one or more of a set of eleven transverse stripes about 43 nm apart that have been observed previously in each half A-band. Each protein has a limited set of characteristic distributions. H-protein is present on stripe 3 (counting from the M-line) in the majority of psoas fibres but is absent in soleus and plantaris muscle. C-protein can occur on stripes 4-11 (the commonest pattern seen in psoas); on stripes 5-11 (in psoas and plantaris); on stripes 3 together with stripes 5-11 (in plantaris); or on none (in red fibres of all three muscles). X-protein can occur on stripes 3-11 in the red fibres of all three muscles; on stripe 4 only (in psoas and plantaris); on stripes 3 and 4 (in psoas and plantaris) or on none. Stripes labelled with anti-X are wider than those labelled with anti-C and consist of a doublet with an internal spacing of 16 nm. The patterns for the three accessory proteins, while overlapping, are in no case identical; this suggests the proteins do not simply substitute for one another. The precise axial positions of the anti-C labelled stripes differ from those of the anti-X stripes; the anti-X stripes lie about 8-9 nm further from the M-line than the corresponding anti-C stripes. This implies that the inner member of an X-protein doublet lies in a very similar position to a C-protein stripe. The anti-H labelled stripe seen in most psoas fibres lies 14 nm nearer the M-line than stripe 3 of the anti-X labelled array in psoas red fibres and is staggered from a continuation of the C-protein array by about 4 nm. The labelling patterns were constant within a fibre and suggest a very precise assembly mechanism. The number of classes of fibre, as defined by the accessory proteins present and their arrangement, exceeds the number of fibre types presently recognized.

The structure of C-protein and X-protein molecules and a polymer of X-protein

C-protein and X-protein are components of the thick filaments in vertebrate skeletal muscles and occupy similar locations in different fibre types. We find that the molecules are both rods about 30 to 40 A wide, but they differ significantly in their lengths, the X-protein molecule being about 350 A long and the C-protein molecule about 280 A. This suggests they are not isoforms. The short length of the C-protein molecule implies that it cannot act in the thick filament as a length-determining agent by a simple vernier mechanism. X-protein associates at low ionic strength (KCl concentration less than 0.07 M) but, unlike C-protein, forms long ordered polymers. These have been examined by electron microscopy to gain information on the molecular shape and on how the molecules interact. The polymers are helically twisted ribbons with a repeat distance along the axis of 660 A. The cross-section of the ribbon is approximately elliptical with major and minor axes of 405 A and 166 A, respectively. From an analysis of the micrographs by optical diffraction, we deduce that the molecules run across the face of the ribbon at an angle of about 15 degrees to the diameter and lie on a two-stranded helix. Models for the polymer are discussed in which the molecules are slightly bowed outwards and bind to each other only at their ends. We suggest that interactions similar to those in the polymer might occur in the thick filaments of muscle, and propose that at each axial position where X-protein attaches along the myosin filament, three X-protein molecules might form an approximately triangular ring around the filament backbone. The appearance of the X-protein polymers is similar to that of the twisted structures called paired helical filaments that make up the neurofibrillary tangles associated with dementia of the Alzheimer type.

Location of C-protein, H-protein and X-protein in rabbit skeletal muscle fibre types

The locations of C-protein, H-protein and X-protein in rabbit psoas, plantaris and soleus muscles have been investigated with fluorescently tagged specific antibodies. Two systems have been examined: isolated myofibrils allowed the locations of these proteins within the sarcomere to be determined, while cryosections allowed a comparison of the amounts of these proteins between different types of fibre in the three muscles. Using antibody-labelled cryosections, we find that the amounts of each of these proteins depends closely on the fibre type. In all the muscles studied, C-protein is present in the largest amounts in fast white and fast intermediate fibres and is absent from slow red fibres, while X-protein is absent from fast white fibres and is present in the largest amounts in fast and slow red fibres. In psoas muscle, H-protein is present in the largest amounts in fast white fibres and is absent in fast and slow red fibres. In plantaris muscle, however, H-protein is absent from fast white fibres but occurs in some slow red fibres. All psoas myofibrils label with anti-C and anti-H and a minority label with anti-X. In each case the pattern of labelling is a zone in each half of the A-band. Measured across the middle of the A-band, the zones for H-protein are much closer together than for C-protein; the centre-to-centre spacings are 0.35 micron for anti-H and 0.64 micron for anti-C. The fluorescent zones for X-protein are slightly but significantly closer (0.52 micron) than those for C-protein. All soleus myofibrils label with anti-X but the centre-to-centre spacing was greater (0.67 micron). With plantaris myofibrils, where labelling occurs with anti-C or anti-H, the spacings resemble those in psoas myofibrils, but with anti-X the spacing resembles that in soleus myofibrils. The spacing of the fluorescent zones in an A-band, whether produced by anti-C, anti-X or anti-H does not vary with sarcomere length. We conclude that X-protein and H-protein, like C-protein, are thick filament components. With both fibres and myofibrils, there is no simple relationship between the amount of X-protein and the amount of C-protein. Many fast intermediate fibres in psoas and plantaris muscle label as strongly with anti-C as do fast white fibres but also label as strongly with anti-X as do fast and slow red fibres.(ABSTRACT TRUNCATED AT 400 WORDS)

[Needle aspiration cytology in the diagnosis of thyroid nodules]

Routine cytological fine needle aspiration was introduced in cases where scintigraphy and echography revealed cold, solid thyroid nodules. The cytological patterns of goitre, thyroiditis and neoplasias are briefly described. Needle aspiration cytology appears to provide substantial diagnostic accuracy with a low incidence of false positives or negatives. This examination is essentially risk-free, and easy to perform, providing fast, accurate diagnosis and making surgery superfluous.

H-protein and X-protein. Two new components of the thick filaments of vertebrate skeletal muscle

With a view to obtaining a more complete view of the composition and structure of the thick filaments of vertebrate skeletal muscle, we have isolated and characterized two new myofibrillar components, H-protein and X-protein. These were purified by hydroxyapatite column chromatography of an impure C-protein preparation itself made from impure myosin extracted from rabbit back and leg muscles. H-protein is the protein responsible for band H on sodium dodecyl sulphate/polyacrylamide gel electrophoresis of crude myosin. X-protein, although present in such preparations in significant quantities, was not detected previously since it is difficult to resolve from C-protein by sodium dodecyl sulphate/polyacrylamide gel electrophoresis. Physical-chemical parameters have been determined for the new proteins and compared with those of C-protein. The apparent chain weight of H-protein estimated by sodium dodecyl sulphate/polyacrylamide gel electrophoresis is 69,000, whereas that of X-protein (152,000) is only slightly greater than that of C-protein (140,000). The molecular weights of H- and X-proteins determined by sedimentation equilibrium centrifugation show that the molecules contain only a single polypeptide chain. The circular dichroism spectra indicate that the proteins have low alpha-helical contents. Both proteins, particularly H-protein, have a high proline content. Although X-protein is of similar chain weight to C-protein, the two show distinct differences in other properties. The sedimentation coefficient of X-protein is markedly lower than that of C-protein, suggesting X-protein is a more asymmetrical molecule. The amino acid compositions, although broadly similar, also show clear differences. Antibodies to H-protein, X-protein and C-protein have been raised in goats and shown not to cross-react.

Structure of filamin and the F-actin-heavy merofilamin complex

Rotary-shadowed filamin molecules appear as long, highly flexible rods curved into a variety of configurations. The particles observed were 2.7 nm wide but had contour lengths of either 98 nm or 193 nm. The longer particles are probably end-to-end dimers of the shorter but it is not clear how many polypeptide chains these particles contain. Heavy merofilamin, obtained by digestion of filamin with a calcium-activated protease from muscle, has been used to investigate where filamin binds on the actin filaments. Negatively stained filaments of actin plus heavy merofilamin resemble those of pure actin; occasionally rod-shaped material sticking out from the filament is observed suggesting that the elongated shape of filamin is maintained after digestion. Optical diffraction patterns of electron micrographs of paracrystals of actin plus heavy merofilamin indicate that the helical symmetry of the actin filament is unchanged, but the observed interfilament spacing is larger than in F-actin paracrystals. Increased intensity of the second layer-line reflection is observed, suggesting that additional material is lying along the grooves of the actin helix. The elongated shape of filamin and its ability to bind to F-actin in a way similar to tropomyosin suggest a possible role for this protein in regulating the organization and aggregation of actin filaments.

Investigation, by cross-linking, of conformational changes in F-actin during its interactions with myosin

The hypothesis that the subunits of F-actin rotate during interactin with myosin and ATP has been tested by using the specific cross-linking reagent p-phenylene-N,N'-bis(maleimide) (PM). The insertion of cross-links between F-actin subunits does not change the ability of the F-actin to activate the ATPase of either myosin subfragment-1 (S-1) or heavy meormyosin, and its ability to superprecipitate with myosin is unimpaired. We conclude that large-scale rotations of actin subunits are not required for activity. The cross-linking of F-actin by PM is, however, inhibited in a noncooperative fashion by S-1 binding, suggesting that a small local change in actin structure may accompany the binding of S-1 or that S-1 sterically blocks the cross-linking by binding near the contact region between actin subunits.

p-NN'-phenylenebismaleimide, a specific cross-linking agent for F-actin

Covalent cross-links can be inserted between the subunits of F-actin by using p-NN'-phenylenebismaleimide. Cross-linking reaches its maximum value when one molecule of reagent has reacted with each actin subunit. p-NN'-Phenylenebismaleimide reacts initially with a cysteine residue on one subunit, the slower cross-linking reaction involving a lysine residue on a neighbouring subunit. Hydrolysis of the actin-bound reagent limits the extent of cross-linking. Quantitative analysis of the amounts of cross-linked oligomers seen on polyacrylamide gels containing sodium dodecyl sulphate suggests that neither the binding of the reagent to actin nor the formation of cross-links introduces strain into the structure. The cross-links do not join together different F-actin filaments, and evidence is presented that suggests that the cross-links join subunits of the same long-pitched helix.

The interaction of C-protein with heavy meromyosin and subfragment-2

C-protein has previously been shown to bind to the light-meromyosin region of the myosin tail. Examination of mixtures of C-protein with heavy meromyosin or subfragment-2 or subfragment-1 in the analytical ultracentrifuge shows that there is also a binding site for C-protein in the subfragment-2 region of the tail.

Can a myosin molecule bind to two actin filaments?

It is suggested that in striated muscles the two heads of one myosin molecule are able to interact with different actin filaments. This would provide a simple explanation for the appearance and arrangement of cross-bridges in insect flight muscle in rigor.

[Hashimoto's thyroiditis. Clinical contribution]

--After a brief account of anatomical and clinical findings of Hashimoto's thyroiditis, 8 cases, personally observed, are presented. The various aspects of this disease and in particular the most recent diagnostic methods are examined and therapeutical possibilities, from the medical and surgical standpoint, are discussed.

Electron microscopy of myosin molecules from muscle and non-muscle sources

Myosin molecules from adult and embryonic vertebrate skeletal muscle, vertebrate cardiac muscle, vertebrate smooth muscle, invertebrate muscle, blood platelets and brain have been examined by a modification of Hall’s mica-replication technique in which droplets of myosin in ammonium formate and glycerol solution are sprayed on a mica substrate at low temperature and then dried in vacuum prior to uni-directional shadowing with platinum. Myosin molecules from all these sources are morphologically indistinguishable and have two globular heads joined to a tail whose length does not differ by more than 10 nm from species to species. The absolute value of the tail length is 150 ± 20 nm (a larger error is given because of the difficulty in defining the point where the tail divides to give the two heads).

The location of C-protein in rabbit skeletal muscle

Antibodies to C-protein have been used to label fibres of glycerinated rabbit psoas muscle. The labelling patterns observed in the electron microscope show that C-protein is located on 7 stripes, spaced about 43 nm apart in each half of the A-band. Between two and four C-protein molecules per filament are present at each stripe. The labelling patterns also reveal the existence of two previously unrecognized components of the thick filament present in two further stripes in each half of the A-band. The location of C-protein and these other components accounts for many of the stripes seen in sections of the A-band and in negatively stained A-segments and provides new information on the packing of myosin molecules in the thick filament.

The antigenicity of myosin and C-protein

Rabbit myosin prepared in the conventional manner by repeated precipitation at low ionic strength was recently shown to contain substantial amounts of impurities; the principal impurity is a component of the myofibril called C-protein. Because antiserum to such conventionally prepared myosin has been used in the past for labelling studies of muscle, it was necessary to study the immunological characteristics of myosin and C-protein and in particular to test the specificity of this antiserum. Antisera to both rabbit myosin and C-protein have been successfully elicited in goats. These antisera have been analysed by immunodiffusion and by precipitin reactions in solution. The analysis has been helped by the examination of immunoprecipitates by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate. It is concluded that: ( a ) C-protein and myosin are antigenically distinct and therefore that C-protein is not derived from myosin. ( b ) Purified myosin can behave as a classically simple antigen giving a single precipitin line when diffused against its homologous antiserum. ( c ) C-protein is a powerful immunogen; the amount present as an impurity in myosin prepared in the conventional way by repeated precipitation at low ionic strength is capable of eliciting a large amount of antibody. Consequently the pattern obtained by labelling myofibrils with antiserum to conventionally prepared myosin would contain information about the location of C-protein superimposed on information about the location of myosin.