Vertebrate Muscle Research Articles

Nonspecific Amyloid Aggregation of Chicken Smooth-Muscle Titin: In Vitro Investigations.

A giant multidomain protein of striated and smooth vertebrate muscles, titin, consists of tandems of immunoglobulin (Ig)- and fibronectin type III (FnIII)-like domains representing β-sandwiches, as well as of disordered segments. Chicken smooth muscles express several titin isoforms of ~500-1500 kDa. Using various structural-analysis methods, we investigated in vitro nonspecific amyloid aggregation of the high-molecular-weight isoform of chicken smooth-muscle titin (SMTHMW, ~1500 kDa). As confirmed by X-ray diffraction analysis, under near-physiological conditions, the protein formed amorphous amyloid aggregates with a quaternary cross-β structure within a relatively short time (~60 min). As shown by circular dichroism and Fourier-transform infrared spectroscopy, the quaternary cross-β structure-unlike other amyloidogenic proteins-formed without changes in the SMTHMW secondary structure. SMTHMW aggregates partially disaggregated upon increasing the ionic strength above the physiological level. Based on the data obtained, it is not the complete protein but its particular domains/segments that are likely involved in the formation of intermolecular interactions during SMTHMW amyloid aggregation. The discovered properties of titin position this protein as an object of interest for studying amyloid aggregation in vitro and expanding our views of the fundamentals of amyloidogenesis.

Desmosomal connectomics of all somatic muscles in an annelid larva

Cells form networks in animal tissues through synaptic, chemical, and adhesive links. Invertebrate muscle cells often connect to other cells through desmosomes, adhesive junctions anchored by intermediate filaments. To study desmosomal networks, we skeletonised 853 muscle cells and their desmosomal partners in volume electron microscopy data covering an entire larva of the annelid Platynereis. Muscle cells adhere to each other, to epithelial, glial, ciliated, and bristle-producing cells and to the basal lamina, forming a desmosomal connectome of over 2000 cells. The aciculae - chitin rods that form an endoskeleton in the segmental appendages - are highly connected hubs in this network. This agrees with the many degrees of freedom of their movement, as revealed by video microscopy. Mapping motoneuron synapses to the desmosomal connectome allowed us to infer the extent of tissue influenced by motoneurons. Our work shows how cellular-level maps of synaptic and adherent force networks can elucidate body mechanics.

Generation of myostatin gene-edited blotched snakehead (Channa maculata) using CRISPR/Cas9 system

Blotched snakehead (Channa maculata) is one of the most important freshwater fish in China. Genome editing is of great potential in generating new snakehead strains with valuable economic traits without integration of exogenous genes. Myostatin (Mstn) inhibits the development and growth of skeletal muscle in vertebrates, including teleosts. Mstn mutations induced by genome editing can stimulate muscle growth and development, therefore Mstn is an appropriate candidate to breed the fast-growing snakehead strain. For this study, one orthologous Mstn gene was characterized in C. maculata, designated as CmMstn, which possessed the relatively conserved gene and protein structure. CmMstn had the highest expression level and sexual dimorphism in muscles. Two CRISPR/Cas9 target sites were designed to generate knockout mutants within the mature mRNA sequence of CmMstn located in Exon I and Exon II. 1 nL mixture solution of 200 pg gRNA and 300 pg Cas9 protein was directly microinjected into each snakehead embryonic yolk at 1⁓4 cell stage. Mstn was efficiently edited by CRISPR/Cas9 system in shakehead, and all designed gRNAs effectively worked at their target sites with high mutagenesis efficiencies, from 40.0% to 53.3%. The majority of mutations were frame-shift and resulted in premature termination of transcription and disruption of the molecular function of CmMstn protein. Furthermore, we obtained four founders (F0) of snakehead with the mutated Mstn gene in their primordial germ cells, and nineteen F1 offspring of the F0 mutants mated with wild-type individuals were displayed to carry Mstn null alleles. It is the first application of genome editing technology in blotched snakehead, and CRISPR/Cas9 system successfully edit the primordial germ cells. Our findings will accelerate our understanding of the role of Mstn gene in snakehead growth, and speed up the cultivation of the fast-growing snakehead strain.

Early Divergence of the C-Terminal Variable Region of Troponin T Via a Pair of Mutually Exclusive Alternatively Spliced Exons Followed by a Selective Fixation in Vertebrate Heart.

Troponin T (TnT) is the thin filament anchoring subunit of troponin complex and plays an organizer role in the Ca2+-regulation of striated muscle contraction. From an ancestral gene emerged ~ 700 million years ago in Bilateria, three homologous genes have evolved in vertebrates to encode muscle type-specific isoforms of TnT. Alternative splicing variants of TnT are present in vertebrate and invertebrate muscles to add functional diversity. While the C-terminal region of TnT is largely conserved, it contains an alternatively spliced segment emerged early in C. elegans, which has evolved into a pair of mutually exclusive exons in arthropods (10A and 10B of Drosophila TpnT gene) and vertebrates (16 and 17 of fast skeletal muscle Tnnt3 gene). The C-terminal alternatively spliced segment of TnT interfaces with the other two subunits of troponin with functional significance. The vertebrate cardiac TnT gene that emerged from duplication of the fast TnT gene has eliminated this alternative splicing by the fixation of an exon 17-like constitutive exon, indicating a functional value in slower and rhythmic contractions. The vertebrate slow skeletal muscle TnT gene that emerged from duplication of the cardiac TnT gene has the exon 17-like structure conserved, indicating its further function in sustained and fatigue resistant contractions. This functionality-based evolution is consistent with the finding that exon 10B-encoded segment of Drosophila TnT homologous to the exon 17-encoded segment of vertebrate fast TnT is selectively expressed in insect heart and leg muscles. The evolution of the C-terminal variable region of TnT demonstrates a submolecular mechanism in modifying striated muscle contractility and for the treatment of muscle and heart diseases.

Creatine: A valuable supplement in aquafeeds?

AbstractCreatine is an amino acid derivate commonly found in vertebrate muscle tissue. Creatine facilitates the recycling of adenosine triphosphate and thus contributes to the energy supply of the muscles as well as the brain. Creatine is used as a supplement for several reasons and its effects in humans, particularly in sports medicine, have been studied excessively. Also, creatine supplementation has been studied for its functions and benefits in terrestrial farm animals. Up to date, little is known about the use of creatine as a supplement in fish nutrition. Yet, due to its many physiological functions, creatine may serve as a valuable supplement in aquafeeds of farmed aquaculture species. Indeed, creatine plays a pivotal role in the fish's muscle and may help to enhance performance of fish reared in aquaculture systems. With regard to swimming exercise, creatine may even amplify its metabolic effects. Upon supplementation, creatine stimulates muscle growth increasing body mass and it has the potential to improve feed utilisation particularly of plant‐based diets. Also, creatine plays a part in osmoregulation when fish adapt to changes in salinity. Furthermore, it may improve product quality upon slaughter. Here, we compile what is known about the many functions of creatine as well as its physiological effects in fish in comparison to mammals. We also highlight its potential beneficial effects as a supplement in aquaculture and infer why creatine can help increase the sustainability of fish feeds.

Evaluation of some cardiac markers in relation to COVID-19 mRNA vaccine

Background: Acute myocardial infarction (AMI) is a dangerous cardiovascular illness that has a significant impact on people's health. Several biomarkers, including Myoglobin and troponin I (cTnI) were utilized to diagnose AMI in recent decades. The Troponin I (cTnI) was designated as the "gold standard" cardiac biomarker for the prediction of cardiomyopathy. It's a heart muscle regulating protein found on normal myocyte actin filaments. When cardiac muscles are injured, cTnI, one of the main subunits of the cardiac troponin complex, is released into the circulation (e.g., myocardial infarction). Myoglobin denoted by (symbols Mb and MB) seems to be an iron- and o2-binding protein present in the vertebrate heart and skeletal muscle tissues and, more specifically, nearly all mammals. In humans, MB is only present in the bloodstream following muscle damage. Its primary function is to supply myocytes with oxygen. Also essential to nitric oxide hemostasis was myoglobin. Additionally, it facilitates the detoxification of response oxygen molecules from the body. MB is accountable for most vertebrate muscles' red hue.The aim: To assess the difference in the level of (MYOGLOBIN and TROPONIN_I) between patients with and without mRNA Vaccination. Methods: This study included 125 patients (65 male and 60 female) with vaccinated and non-vaccinated covid-19 with an age range of 20–69 years. These patients are divided into two main groups: 1. vaccinated (vaccinated with COVID-19 infection, vaccinated without COVID-19 disease, vaccinated recovered from the CoV-19 virus),2. unvaccinated (infected with the CoV-19 virus and non-vaccinated, recovered from covid-19 and unvaccinated). The outcome is measured using the Enzyme-linked immunosorbent assay (ELISA) technique. This study was conducted during the period from November 2021 to May 2022 at the Martyr Dr. Fairouz General Hospital, Wasit governorate, Iraq. Results: Estimation of serum Troponin I and Myoglobin concentration showed that concentrations of Troponin I and Myoglobin were significantly higher (P<0.0001) in individuals infected with CoV-19 virus and unvaccinated higher than vaccinated with CoV-19 disease indicating the impact of the vaccine on the increment of both markers. However, the level of each marker was substantially higher (P<0.0001) in vaccinated with CoV-19 infection more than vaccinated without or recovered from COVID-19 illness. Conclusions: The use of mRNA CoV-19 vaccination significantly modulate the increment of Troponin I and Myoglobin and improves the cardiac symptomatology in patients with CoV-19 infection.

A new continuous cell line from the pest insect, Anomala cuprea (Coleoptera; Scarabaeidae): emergence of contractile cells.

Insect contractile cells frequently appear at an early phase of cell culture, but in most cases, they disappear before a continuous cell line is established, so the cell line ceases to contract. Continuous contractile insect cell lines are currently available from only one species each of Hymenoptera and Diptera. Here, we obtained a new cell line that contracted long after being established as a continuous cell line. The cell line contracted for a short period at an early phase of insect cell culture before a continuous cell line was established, but then did not contract again for several years. After this cell line entered the continuous growth phase, it produced spontaneously contractile tissues for about 4 mo but stopped contracting again. This is the first instance of a cell line that contracted after its establishment as a non-contractile continuous cell line. It is unclear whether the contractile cells survive or die after contraction ceases at an early phase of cell culture, and our results indicate that potential contractile cells survive for years after they stop to contract. The cells of this line sometimes produced complex contractilestructures, such as sheet-like tissues. Only a few continuous cell lines have been derived from scarabaeid beetles. The new continuous cell line was derived from the culture of the fat bodies of the scarab beetle Anomala cuprea, which is a pest in the agriculture and forestry of Japan. The population doubling time of the new cell line was 2.5 d and thus it grows very rapidly among coleopteran continuous cell lines. Our new cell line will facilitate research on the physiology and pathology of Coleoptera, including scarab beetles, and may also contribute to research on invertebrate muscles.

Superfast excitation-contraction coupling in adult zebrafish skeletal muscle fibers.

The zebrafish has emerged as a very relevant animal model for probing the pathophysiology of human skeletal muscle disorders. This vertebrate animal model displays a startle response characterized by high-frequency swimming activity powered by contraction of fast skeletal muscle fibers excited at extremely high frequencies, critical for escaping predators and capturing prey. Such intense muscle performance requires extremely fast properties of the contractile machinery but also of excitation-contraction coupling, the process by which an action potential spreading along the sarcolemma induces a change in configuration of the dihydropyridine receptors, resulting in intramembrane charge movements, which in turn triggers the release of Ca2+ from the sarcoplasmic reticulum. However, thus far, the fastest Ca2+ transients evoked by vertebrate muscle fibers has been described in muscles used to produce sounds, such as those in the toadfish swim bladder, but not in muscles used for locomotion. By performing intracellular Ca2+ measurements under voltage control in isolated fast skeletal muscle fibers from adult zebrafish and mouse, we demonstrate that fish fast muscle fibers display superfast kinetics of action potentials, intramembrane charge movements, and action potential-evoked Ca2+ transient, allowing fusion and fused sustained Ca2+ transients at frequencies of excitation much higher than in mouse fast skeletal muscle fibers and comparable to those recorded in muscles producing sounds. The present study is the first demonstration of superfast kinetics of excitation-contraction coupling in skeletal muscle allowing superfast locomotor behaviors in a vertebrate.

Ca2+ as a coordinator of skeletal muscle differentiation, fusion and contraction.

Muscle regeneration is essential for vertebrate muscle homeostasis and recovery after injury. During regeneration, muscle stem cells differentiate into myocytes, which then fuse with pre-existing muscle fibres. Hence, differentiation, fusion and contraction must be tightly regulated during regeneration to avoid the disastrous consequences of premature fusion of myocytes to actively contracting fibres. Cytosolic calcium (Ca2+ ), which is coupled to both induction of myogenic differentiation and contraction, has more recently been implicated in the regulation of myocyte-to-myotube fusion. In this viewpoint, we propose that Ca2+ -mediated coordination of differentiation, fusion and contraction is a feature selected in the amniotes to facilitate muscle regeneration.

Atrogin-1 knockdown inhibits the autophagy-lysosome system in mammalian and avian myotubes

Atrogin-1 plays an important role in ubiquitin-proteasome proteolysis in vertebrate skeletal muscles. Recently, atrogin-1 has been shown to be involved in the autophagy-lysosome system, another proteolytic system, in the murine and fish hearts and skeletal muscles. With the aim to elucidate the effect of atrogin-1 on the autophagy-lysosome system in mammalian and avian skeletal muscles, this study has examined the effects of atrogin-1 knockdown on autophagy-lysosome-related proteins in C2C12 and chicken embryonic myotubes. Using the levels of microtubule-associated protein light chain 3 (LC3)-II protein, it was confirmed that atrogin-1 knockdown blocked the autophagic flux in both the myotubes. In addition, atrogin-1 knockdown in C2C12 myotubes significantly decreased the level of autophagy-related gene (ATG)12-ATG5 conjugate, which is supposedly necessary for the fusion of autophagosomes and lysosomes. Atrogin-1 knockdown also resulted in downregulation of forkhead box O3, a transcription factor for ATG12. These data suggest that atrogin-1 is essential for the normal autophagy-lysosome system in the striated muscles of vertebrates.

Fine‐regulation of myosin relaxed states in vertebrate muscle

Vertebrate muscle myosin, the motor protein, has evolved over long periods of time. In the present study, we specifically aimed at identifying how this evolution has fine‐tuned myosin conformational states to the specific needs of organisms with different body masses. As myosin has two different relaxed states (super‐relaxed and disordered‐relaxed), we initially hypothesized that a linear positive correlation would exist between the amount of myosin molecules in the super‐relaxed conformation and the body weight of the organisms in which they are expressed. To verify this hypothesis, we extracted muscle fibres from multiple vertebrate species with body weights ranging from grams to tons. By using a loaded Mant‐ATP chase protocol, we observed that vertebrate species with body weights above 1000 kilograms have significantly higher proportions of super‐relaxed myosin proteins in their muscle fibres. As myosin heads in the super‐relaxed conformation consume five times less ATP than the ones in the disordered‐relaxed state, our finding suggest that heavy vertebrate animals have adapted their motor protein conformations to potentially avoid inappropriate and large energy consumption in their metabolically demanding muscles.

Carnosine synthase deficiency in mice affects protein metabolism in skeletal muscle

Carnosine and anserine are abundant peptides found in the skeletal muscle and nervous system in many vertebrates. Several in vitro and in vivo studies have demonstrate that exogenously administered carnosine improves exercise performance. Furthermore, carnosine is an antioxidant and antifatigue supplement. However, the physiological functions of endogenous carnosine and its related histidine-containing dipeptides in a living organism remain unclear. We aimed to clarify the physiological roles of endogenous carnosine by investigating the characteristics of carnosine synthase gene-deficient mice and the effects of carnosine on skeletal muscle protein metabolism. We discovered that carnosine and anserine were undetectable in the skeletal muscle of carnosine synthase knockout mice. We also quantified protein gene expression and enzyme levels in muscle protein metabolism. Gene and protein levels of the muscle protein synthesizer insulin-like growth factor-1 (IGF-1) and the degrading enzyme cathepsin B were markedly lower in carnosine synthase gene-deficient mice than those in wild-type mice. The amount of 3-methylhistidine (a marker for muscle proteolysis) in forced exercise and the weight of the gastrocnemius muscle were considerably lower in carnosine synthase gene-deficient mice than in wild-type mice. Consequently, we showed that carnosine deficiency affects weight maintenance and protein metabolism in skeletal muscle, suggesting that carnosine regulates skeletal muscle protein metabolism.

Functional Adaptation of Vocalization Revealed by Morphological and Histochemical Characteristics of Sonic Muscles in Blackmouth Croaker (Atrobucca nibe).

Simple SummarySound production is common in numerous fish species. Some species can emit calls through the contraction of specialized muscles called sonic or drumming muscles. The sonic muscles of fish are among the fastest muscles in vertebrates. Although numerous studies have investigated the mechanism underlying sound production in fish, only the distinct features of the sonic muscles of a few species have been investigated. We demonstrated that the sonic muscles have functionally adapted for fast twitching and fatigue resistance, which support vocalization in the blackmouth croaker (Atrobucca nibe).Sound production in the blackmouth croaker (Atrobucca nibe) was characterized using acoustic, morphological, and histochemical methods. Their calls consisted of a train of two to seven pulses; the frequency ranged from 180 to 3000 Hz, with a dominant frequency of 326 ± 40 Hz. The duration of each call ranged from 80 to 360 ms. Male A. nibe possess a pair of bilaterally symmetric sonic muscles attached to the body wall adjacent to the swim bladder. The average diameter of the sonic muscle fibers was significantly shorter than that of the abdominal muscle fibers. Semithin sections of the sonic muscle fibers revealed a core-like structure (central core) and the radial arrangement of the sarcoplasmic reticulum and myofibrils. Numerous mitochondria were distributed within the central core and around the periphery of the fibers. Most of the fibers were identified as Type IIa on the basis of their myosin adenosine triphosphatase activities, but a few were identified as Type IIc fibers. All sonic muscle fibers exhibited strong oxidative enzyme activity and oxidative and anaerobic capabilities. The features suggest that the sonic muscles of A. nibe are morphologically and physiologically adapted for fast twitching and fatigue resistance, which support fish vocalization.

A model for self-organization of sensorimotor function: the spinal monosynaptic loop.

Recent spinal cord literature abounds with descriptions of genetic preprogramming and the molecular control of circuit formation. In this paper, we explore to what extent circuit formation based on learning rather than preprogramming could explain the selective formation of the monosynaptic projections between muscle spindle primary afferents and homonymous motoneurons. We adjusted the initially randomized gains in the neural network according to a Hebbian plasticity rule while exercising the model system with spontaneous muscle activity patterns similar to those observed during early fetal development. Normal connectivity patterns developed only when we modeled β motoneurons, which are known to innervate both intrafusal and extrafusal muscle fibers in vertebrate muscles but were not considered in previous literature regarding selective formation of these synapses in animals with paralyzed muscles. It was also helpful to correctly model the greatly reduced contractility of extrafusal muscle fibers during early development. Stronger and more coordinated muscle activity patterns such as observed later during neonatal locomotion impaired projection selectivity. These findings imply a generic functionality of a musculoskeletal system to imprint important aspects of its mechanical dynamics onto a neural network, without specific preprogramming other than setting a critical period for the formation and maturation of this general pattern of connectivity. Such functionality would facilitate the successful evolution of new species with altered musculoskeletal anatomy, and it may help to explain patterns of connectivity and associated reflexes that appear during abnormal development.NEW & NOTEWORTHY A novel model of self-organization of early spinal circuitry based on a biologically realistic plant, sensors, and neuronal plasticity in conjunction with empirical observations of fetal development. Without explicit need for guiding genetic rules, connection matrices emerge that support functional self-organization of the mature pattern of Ia to motoneuron connectivity in the spinal circuitry.

Comparison of excitation–contraction coupling between Drosophila and vertebrate muscle

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Amphioxus muscle transcriptomes reveal vertebrate-like myoblast fusion genes and a highly conserved role of insulin signalling in the metabolism of muscle

BackgroundThe formation and functioning of muscles are fundamental aspects of animal biology, and the evolution of ‘muscle genes’ is central to our understanding of this tissue. Feeding-fasting-refeeding experiments have been widely used to assess muscle cellular and metabolic responses to nutrition. Though these studies have focused on vertebrate models and only a few invertebrate systems, they have found similar processes are involved in muscle degradation and maintenance. Motivation for these studies stems from interest in diseases whose pathologies involve muscle atrophy, a symptom also triggered by fasting, as well as commercial interest in the muscle mass of animals kept for consumption. Experimentally modelling atrophy by manipulating nutritional state causes muscle mass to be depleted during starvation and replenished with refeeding so that the genetic mechanisms controlling muscle growth and degradation can be understood.ResultsUsing amphioxus, the earliest branching chordate lineage, we address the gap in previous work stemming from comparisons between distantly related vertebrate and invertebrate models. Our amphioxus feeding-fasting-refeeding muscle transcriptomes reveal a highly conserved myogenic program and that the pro-orthologues of many vertebrate myoblast fusion genes were present in the ancestral chordate, despite these invertebrate chordates having unfused mononucleate myocytes. We found that genes differentially expressed between fed and fasted amphioxus were orthologous to the genes that respond to nutritional state in vertebrates. This response is driven in a large part by the highly conserved IGF/Akt/FOXO pathway, where depleted nutrient levels result in activation of FOXO, a transcription factor with many autophagy-related gene targets.ConclusionReconstruction of these gene networks and pathways in amphioxus muscle provides a key point of comparison between the distantly related groups assessed thus far, significantly refining the reconstruction of the ancestral state for chordate myoblast fusion genes and identifying the extensive role of duplicated genes in the IGF/Akt/FOXO pathway across animals. Our study elucidates the evolutionary trajectory of muscle genes as they relate to the increased complexity of vertebrate muscles and muscle development.

A Roadmap to Reconstructing Muscle Architecture from CT Data.

Skeletal muscle is responsible for voluntary force generation across animals, and muscle architecture largely determines the parameters of mechanical output. The ability to analyze muscle performance through muscle architecture is thus a key step towards better understanding the ecology and evolution of movements and morphologies. In pennate skeletal muscle, volume, fiber lengths, and attachment angles to force transmitting structures comprise the most relevant parameters of muscle architecture. Measuring these features through tomographic techniques offers an alternative to tedious and destructive dissections, particularly as the availability of tomographic data is rapidly increasing. However, there is a need for streamlined computational methods to access this information efficiently. Here, we establish and compare workflows using partially automated image analysis for fast and accurate estimation of animal muscle architecture. After isolating a target muscle through segmentation, we evaluate freely available and proprietary fiber tracing algorithms to reconstruct muscle fibers. We then present a script using the Blender Python API to estimate attachment angles, fiber lengths, muscle volume, and physiological cross-sectional area. We apply these methods to insect and vertebrate muscle and provide guided workflows. Results from fiber tracing are consistent compared to manual measurements but much less time-consuming. Lastly, we emphasize the capabilities of the open-source three-dimensional software Blender as both a tool for visualization and a scriptable analytic tool to process digitized anatomical data. Across organisms, it is feasible to extract, analyze, and visualize muscle architecture from tomography data by exploiting the spatial features of scans and the geometric properties of muscle fibers. As digital libraries of anatomies continue to grow, the workflows and approach presented here can be part of the open-source future of digital comparative analysis.

Specific density as parameter for separating feed ingredients

Description of the subject. Specific densities of 13 samples of eight vegetable feed ingredients and of blood meal have been established. Objectives. The aim of the study was to use the parameter specific density for classification of a selection of feed materials. The range of specific densities for each of the tested materials could support the identification of ingredients in a compound feed. Ingredients in mixtures could be separated when different specific densities apply to these ingredients. Method. The share of the flotate and of the sediment of each of the tested materials has been established in duplicate along a range of increased specific density of the solvent mixture, from 1.22 g·cm-3 up to 1.52 g·cm-3, initially in four steps. Intermediate densities have been used where appropriate for collecting more detailed ranges. The specific densities which resulted in approximately 100% sediment and in approximately 100% flotate are used as indicators for the range of the specific density of that material. Results. The materials used appeared to show three different ranges of specific density: corn gluten and blood meal (1.12 – 1.32 g·cm-3), corn distillers’ grain, rapeseed kernel meal, soya kernel meal and wheat middlings (1.25 – 1.42 g·cm-3), and palm kernel meal, citrus pulp and beet pulp (1.35 – 1.55 g·cm-3). The specific densities range from those found for vertebrate muscles and insect fragments (below 1.3 g·cm-3) up to the specific density of bone fragments (exceeding 1.62 g·cm-3). Four mixed samples, each existing of two different ingredients at a ratio of 1:1 (w/w) were tested with solutions at different specific densities. The ingredients of each mixed sample appeared to separate in the expected fractions, predominantly in either the flotate or in the sediment. Conclusions. The experiments show that separation based on specific density can assist in the identification of feed ingredients in one or more combinations of sediment and flotate fractions.

Geometric frustration in the myosin superlattice of vertebrate muscle.

Geometric frustration results from an incompatibility between minimum energy arrangements and the geometry of a system, and gives rise to interesting and novel phenomena. Here, we report geometric frustration in a native biological macromolecular system---vertebrate muscle. We analyse the disorder in the myosin filament rotations in the myofibrils of vertebrate striated (skeletal and cardiac) muscle, as seen in thin-section electron micrographs, and show that the distribution of rotations corresponds to an archetypical geometrically frustrated system---the triangular Ising antiferromagnet. Spatial correlations are evident out to at least six lattice spacings. The results demonstrate that geometric frustration can drive the development of structure in complex biological systems, and may have implications for the nature of the actin--myosin interactions involved in muscle contraction. Identification of the distribution of myosin filament rotations with an Ising model allows the extensive results on the latter to be applied to this system. It shows how local interactions (between adjacent myosin filaments) can determine long-range order and, conversely, how observations of long-range order (such as patterns seen in electron micrographs) can be used to estimate the energetics of these local interactions. Furthermore, since diffraction by a disordered system is a function of the second-order statistics, the derived correlations allow more accurate diffraction calculations, which can aid in interpretation of X-ray diffraction data from muscle specimens for structural analysis.

Structural insights into the binding behavior of NiO with myoglobin

Valuable and useful information on the biotechnological and medical applications of nanoparticles can be achieved through the interactions of proteins with nanoparticles and the structural changes exerted by nanoparticles on these biomolecules. Nickel oxide (NiO) nanoparticles have widespread industrial and therapeutic applications in the medical and biological sciences. Therefore, structural changes and stability exerted by NiO nanoparticles on myoglobin as a globular protein sample were examined at a pH of 7.4 using UV–Vis spectroscopy and fluorescence emission techniques. Myoglobin is a monomeric protein that functions as oxygen storage in the skeletal muscle of vertebrates. Theoretical molecular docking technique was also applied to predict the interactions between myoglobin and NiO nanoparticle complex. Results showed that binding of NiO nanoparticles to myoglobin quenched its emission signals through a static quenching mechanism. Also, electrostatic interaction was predominating in the complex formation relative to other non-covalent interactions. Besides, the spontaneous bonding of NiO nanoparticles was confirmed by negative Gibbs free energy (ΔG°). Measurements performed by protein thermal stability assay showed that thermal stability of myoglobin increased with rising concentrations of NiO nanoparticles. CD spectroscopic studies showed that in the presence of NiO nanoparticles, the content of α-helix protein increased and the content of other secondary structures decreased. Accordingly, it is clearly evident that the structure and stability of myoglobin are altered based on the experimental and theoretical data obtained under the influence of NiO nanoparticles.