Topic Review
Biomechanics of Table Tennis
Table tennis is a popular recreational and competitive sports at all levels. Recent research on table tennis maneuvers identified the differences between playing levels and between maneuvers using parameters which included ball and racket speed, joint kinematics and kinetics, electromyography, and plantar pressure distribution. Different maneuvers underlined changes on body posture and lines of movement which were accommodated particularly by the racket face angle, trunk rotation, knee and elbow joint movements, and thus different contributions of muscles. Higher-level players produced ball and strike at higher accuracy and repeatability but not necessarily lead to higher speed. In addition, higher-level players utilize superior whole-body coordination and footwork to compromise between agility and stability for a quality strike. Strengthening shoulder and wrist muscles could enhance the speed of the strike while personalized training shall be considered since motor coordination and adaptation vary among individuals.
  • 2856
  • 29 Oct 2020
Topic Review
Protein dynamics
Protein dynamics is a highly complex phenomenon comprising numerous contributions from motions with different mechanisms of action and happening with diverse timescales and amplitudes that highly depend on the system and the local environment.
  • 2232
  • 01 Nov 2020
Topic Review
Impedance Based Cellular Assays
The development of organ on a chip technology utilising human cells, has the advantages of replacing animal experimentation and providing data more applicable to study of human cell biochemistry and disease. However, measurement of metabolites often requires cell lysis permitting only a single end-point measurement. Development of non-destructive methods for monitoring cell cultures in real-time is desirable in helping to inform pathways of disease and define targets for pharmacological intervention. Impedance-based cellular assays, representing one such technique, are designed to monitor cellular impedance, a property of the insulating nature of cell membranes, resulting from changes in cell shape caused by signalling events inside and between cells. This relies on culturing primary cells or cell lines in vitro directly on microelectrodes or using electrodes in culture media and then monitoring changes in impedance over time in response to external treatments compared to untreated controls. Impedance measurements are recorded in real-time at one or several frequencies and can be sampled several times a second for as long as desired. This is beneficial in pinpointing changes with time in culture and can be useful in determining the starting point of a toxic effect or a therapeutic window. A further advantage of impedance-based cellular assays lie in their ability to monitor the cell culture without using specific cell or protein labels, which might otherwise influence the target being studied. Depending on the system used, changes in impedance can be correlated with alterations in basolateral adhesion, membrane integrity, tight junctions and barrier function.
  • 829
  • 30 Oct 2020
Topic Review
Plasmonic biosensing schemes for virus
The uncertain proportions of pandemic outbreaks have triggered the need of reliable and cost-effective protocols easily adaptable to the changing virulence of virus strains. In recent years, plasmonic biosensors are being increasingly applied for clinical diagnosis of viral and other infectious diseases. Typical plasmonic biosensing strategies rely on the versatility of SPR and LSPR as label-free detection systems capable of monitoring binding interactions in a short period of time. Nevertheless, the incorporation of technological advancements has precipitated the development of nanomaterial-based applications for improving the sensitivity and specificity of classical configurations. The unique optical properties of plasmonic nanostructures has been exploited in combination with SERS colorimetric, fluorescence or luminescence enhancement for viral diagnosis. Likewise, the development of plasmonic virus sensing approaches has also benefitted from the variety of virus biomarkers. Thus, a high number of virus plasmonic biosensors have prompted the advance of novel functionalization strategies to achieve the effective coverage of the biological receptor while ensuring the affinity and specificity towards the target viral nucleic acids, proteins or whole virus. The huge potential for single virus detection along with the effectiveness and simplicity of current plasmonic configurations will impact on the routine surveillance of virus in clinical settings during this decade.
  • 590
  • 27 Oct 2020
Topic Review
Iron oxide nanoparticles are frequently used in various biomedical applications, in particular as magnetic resonance imaging contrast agents in liver imaging. Indeed, number of iron oxide nanoparticles have been withdrawn due to their poor clinical performance and/or toxicity issues. In the literature it has been criticized that failure of clinical applications is to a large extent due to poor understanding of the sub-cellular molecular targets of nanoparticles. Nanoparticles were found to change the activity of autophagic flux via lysosome-dependent signalling. However, precise underlying mechanisms of such modulation remain poorly understood.
  • 503
  • 03 Feb 2021
Topic Review
Heart Failure
Heart failure (HF) is marked by dampened cardiac contractility. A mild therapeutic target that improves contractile function without desensitizing the β-Adregenric system during HF may improve cardiac contractility and potentially survival. Inhibiting PKCα activity may fit the criteria of the therapeutic target with milder systemic effects that still boosts contractility in HF patients. PKCα activity has been observed to increase during HF. This increase in PKCα activity is perplexing because it is also accompanied by the up-regulation of a molecular braking mechanism. Here, I aim to explore how PKCα activity can be increased and maintained during HF despite the presence of a molecular braking mechanism? Using, a computational approach, I show that the local DAG signaling is regulated through a two-compartment signaling system in cardiomyocytes. These results imply that after massive myocardial infarction (MI), local homeostasis of DAG signaling is disrupted. The loss of this balance leads to prolonged activation of PKCα, a key molecular target linked to LV remodeling and dysfunctional filling and ejection in the mammalian heart. This study also proposes an explanation for how DAG homeostasis is regulated during the normal systolic and diastolic cardiac function. A novel two-compartment computational model is proposed for regulating DAG homeostasis during Ang II-induced heart failure. This model provides a promising tool with which to study mechanisms of DAG signaling regulation during heart failure. The model can also aid in the identification of novel therapeutic targets with the aim of improving the quality of life for heart failure patients.
  • 494
  • 05 Nov 2020
Topic Review
Lipids of Sulfolobus spp.
Archaea, and thereby, Sulfolobus spp. exhibit a unique lipid composition of ether lipids, which are altered in regard to the ratio of diether to tetraether lipids, number of cyclopentane rings and type of head groups, as a coping mechanism against environmental changes. Sulfolobales mainly consist of C40-40 tetraether lipids (caldarchaeol) and partly of C20-20 diether lipids (archaeol). A variant of caldarchaeol called glycerol dialkylnonitol tetraether (GDNT) has only been found in Sulfolobus and other members of the Creanarchaeota phylum so far. Altering the numbers of incorporated cyclopentane rings or the the diether to tetraether ratio results in more tightly packed membranes or vice versa.
  • 467
  • 26 Oct 2020
Topic Review
α-Lactalbumin (α-LA) is a small (Mr 14,200), acidic (pI 4-5), Ca2+-binding protein. α-LA is a regulatory component of lactose synthase enzyme system. α-LA is very important in infant nutrition since it constitutes a large part of the whey and total protein in human milk. The protein possesses a single strong Ca2+-binding site, which can also bind Mg2+, Mn2+, Na+, K+, and some other metal cations. It contains several distinct Zn2+-binding sites. Physical properties of α-LA strongly depend on the occupation of its metal binding sites by metal ions. In the absence of bound metal ions α-LA is in the molten globule-like state. The binding of metal ions, and especially of Ca2+, increases stability of α-LA against action of heat, various denaturing agents, and proteases, while the binding of Zn2+ to the Ca2+-loaded protein decreases its stability and causes its aggregation. The thermal unfolding of apo-α-LA takes place in the temperature region from 10 to 30 °C. The binding of Ca2+ under the conditions of low ionic strength shifts the thermal transition to higher temperatures by more than 40 °C. The binding of Mg2+, Na+, and K+ increases protein stability as well. The stronger an ion binds to the protein, the more pronounced the thermal transition shift. All four classes of surfactants (anionic, cationic, non-ionic, and zwitterionic) denature α-LA and the denaturation involves at least one intermediate. The position of any denaturation transition in α-LA (half-transition temperature, half-transition pressure, half-transition denaturant concentration) depends upon metal ion concentration in solution (especially if this metal ion is Ca2+). Therefore, values of denaturation temperature or urea or guanidine hydrochloride denaturing concentration are relatively meaningless for α-LA without specifying the metal ion content(s) and their solution concentration(s). At a neutral or slightly acidic pH at a physiological temperature, α-LA can associate with membranes. The conformations of the membrane-bound protein range from native-like to molten globule-like states. At a low pH, α-LA penetrates the interior of the negatively charged membranes and exhibits a molten globule conformation. Depending on external conditions, α-LA can form amyloid fibrils, amorphous aggregates, nanoparticles, and nanotubes. At pH 2, α-LA in the classical molten globule conformation can form amyloid fibrils. Some of these aggregated states of α-LA (nanoparticles, nanotubes) can be used in practical applications such as drug delivery to tissues and organs. The structure and self-assembly behavior of α-LA are governed by a subtle balance between hydrophobic and polar interactions and this balance can be finely tuned through the addition of selected substances. Small size nanoparticles of α-LA (100 to 200 nm) can be obtained with the use of various desolvating agents. Partially hydrolyzed α-LA can form nanotubes. α-LA and some of its fragments possess bactericidal and antiviral activities. Complexes of partially unfolded α-LA with oleic acid showed significant cytotoxicity to various tumor and bacterial cells. α-LA in such complexes plays a role of a delivery carrier of cytotoxic fatty acid molecules into tumor cells across the cell membrane. Cytotoxic protein–oleic acid complexes possess a common core-shell structure, where an oily core is made of a micellar oleic acid, whereas a proteinaceous shell, which stabilizes the oleic acid micelle, is formed from the flexible, partially unfolded proteins. These complexes called liprotides (lipids and partially denatured proteins), which are potential novel anti-tumorous drugs, can be considered as molten globular containers filled with the toxic oil.
  • 466
  • 31 Aug 2020
Topic Review
Thermodynamic Dissipation Theory of Life
The Thermodynamic Dissipation Theory of the Origin and Evolution of Life argues that the escence of the origin of life was the microscopic dissipative structuring under UVC light of organic pigments (now known as the fundamental molecules of life - those common to all three domains) and their proliferation over the entire Earth surface, driven by the thermodynamic imperative of dissipating this part of the Archean solar spectrum into heat. With time, dissipative structuring led to ever more complex biosynthetic pathways for creating pigments and their support structures (and processes) which could dissipate not only the UVC region but also other UV regions and the visible wavelengths, until today reaching the "red edge" (at approximately 700 nm). The heat of dissipation of photons absorbed on organic pigments in water then catalyzes a host of coupled secondary dissipative processes such as; the water cycle, ocean and wind currents, hurricanes, etc. pushing the limit for dissipation of the incident light even further towards the infrared. The thermodynamic dissipation theory thus assgins an explicit thermodynamic function to life; the dissipative structuring, proliferation, and evolution of molecular pigments and their complexes from common precursor carbon based molecules under the impressed short wavelength solar photon potential to perform the explicit thermodynamic function of dissipating this light into long wavelength infrared light (heat). In a general sense, the origin of life is no different than the origin of other dissipative structuring processes like hurricanes and the water cycle, except that these latter processes deal with structuring involving hydrogen bonding while life deals with structuring involving covalent bonding. The external photon potential supplied continuously by the environment (our Sun), and its dissipation into heat by the assembly of dissipative structures, are, therefore, both integral components necessary for understanding life. Difficult problems related to the origin of life, such as enzyme-less replication of RNA and DNA, homochirality of the fundamental molecules, and the origin of amino acid -codon assignments (information encoding in RNA and DNA), also find simple explanations within this same dissipative thermodynamic framework once the existence of a relation between primordial RNA and DNA replication and UV-C photon dissipation is established.
  • 443
  • 04 Feb 2021
Topic Review
Calcium Phosphate Nanocluster Complexes
Calcium phosphate nanocluster complexes comprise a core of amorphous calcium phosphate and a sequestering shell of intrinsically disordered phosphopeptides or phosphoproteins. Solutions containing the nanocluster complexes can be thermodynamically stable or metastable due to a tendency to form a precipitate enriched in calcium phosphate. Theoretical and biophysical studies with native and recombinant phosphopeptides have shown how the radius of the core and the stability of the solution depend on the concentration of the sequestering peptide, its affinity for the calcium phosphate and its concentration in relation to the concentration of the calcium phosphate. The thickness of the sequestering shell depends on the conformation of the peptide on the core surface. A sequestering peptide is a flexible sequence including one or more short linear motifs, each of which usually contains several phosphorylated and other acidic residues.  These are the main binding sites to the core so that a peptide with several binding motifs can forms loops and trains on the core surface. Calcium phosphate nanocluster complexes were first identified as substructures of casein micelles in milk and have been prepared as individual particles from peptides derived from caseins and osteopontin. Stable biofluids containing nanocluster complexes cannot cause soft tissues to become mineralized whereas stable or metastable biofluids containing nanocluster complexes can help to mineralize hard tissues.
  • 416
  • 09 Nov 2020
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