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Topic Review
β-Amyloid Vaccination
β-amyloid (Aβ) is a peptide, 38 to 43 amino acids long, that derives from the proteolytic processing of amyloid precursor protein (APP) by the γ-secretase; Aβ40 and Aβ42 are the most studied Aβ peptide species.
  • 761
  • 20 Apr 2021
Topic Review
α-Lactalbumin
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.
  • 1.5K
  • 31 Aug 2020
Topic Review
Yeast Heterologous Expression Systems Study Plant Membrane Proteins
Researchers are often interested in proteins that are present in cells in small ratios compared to the total amount of proteins. These proteins include transcription factors, hormones and specific membrane proteins. However, sufficient amounts of well-purified protein preparations are required for functional and structural studies of these proteins, including the creation of artificial proteoliposomes and the growth of protein 2D and 3D crystals. This aim can be achieved by the expression of the target protein in a heterologous system. The most popular for heterologous protein expression are the two species, baker’s yeast S. cerevisiae and methylotrophic yeast P. pastoris, expression in which is a well-established and widely used technique. 
  • 156
  • 26 Jul 2023
Topic Review
Water between Membrane and Colloidal Theories for Cells
To incorporate water as a structural and thermodynamic component of biomembranes, the consideration of the membrane interphase as a bidimensional hydrated polar head group solution, coupled to the hydrocarbon region allows for the reconciliation of two theories on cells in dispute today: one considering the membrane as an essential part in terms of compartmentalization, and another in which lipid membranes are not necessary and cells can be treated as a colloidal system. The criterium followed is to describe the membrane state as an open, non-autonomous and responsive system using the approach of Thermodynamic of Irreversible Processes. The concept of an open/non-autonomous membrane system allows for the visualization of the interrelationship between metabolic events and membrane polymorphic changes. Therefore, the Association Induction Hypothesis (AIH) and lipid properties interplay should consider hydration in terms of free energy modulated by water activity and surface (lateral) pressure.
  • 461
  • 25 Aug 2022
Topic Review
Vibrational Imaging Techniques and Hard Dental Tissues
Raman Microspectroscopy (RMS) represents an innovative tool to in vitro situation hard dental tissues. In fact, this vibrational technique has the advantage of providing, at the same time and on the same sample, a morpho-chemical correlation between the microscopic information from the visual analysis of the sample and its chemical and macromolecular composition. Moreover, thanks to the light scattering, it is possible to simultaneously perform the imaging analysis of both the inorganic and organic components of teeth, at a high spatial resolution level and in a confocal mode. The identification of specific Raman markers representative of sound and pathological hard dental tissues is crucial to improve the diagnosis of several dental pathologies and to detect dental lesions at an early stage when they are not visually detectable .
  • 599
  • 25 Apr 2022
Topic Review
Uses of Magnetic Fields for Health Applications
Early life on Earth evolved in the contexts of temperature, available elements, and molecules (including water), as well as the biophysical boundary conditions of the planet. The latter include gravity (1 g), exogenous and endogenous radiation from particles from beyond Earth and radioactive elements on Earth, and magnetic fields due to the planet’s magnetic field and local concentrations of molecules such as iron. Humans and other animals, plants, and microorganisms have been exposed to a variety of magnetic fields other than the geomagnetic field of Earth and deposits of ferro materials. Magnetic fields, static or electromagnetic, have been used in attempts to improve outcomes for the repair of a variety of tissues.
  • 71
  • 24 Jan 2024
Topic Review
Two phytochrome A Types in Plants
The phytochrome (phy) system of plants with the main phyA and phyB controls their development beginning from seed germination to fruiting and senescence. The regulation reactions are categorized into three modes—the very low and low fluence responses (VLFR and LFR) and the high irradiance responses (HIR). The phyA is unique among the other phytochromes; it is major in etiolated seedlings and light-labile, and mediates all the three photoresponse modes. The phyB is light-stable, dominates in deetiolated plants, and performs the LFR. The phyA is itself heterogeneous which may explain its functional complexity. It comprises two native types, phyA′ and phyA″, the products of post-translational modification of the molecule at the N-terminus, possibly, via serine phosphorylation. This alters chromophore-apoprotein interactions resulting in the different photochemical, phenomenological, and functional properties of the two phyA pools. The phyA′ is major, water-soluble, and light-labile; the phyA″ is minor, amphiphilic, and relatively light-stable. The phyA′ mediates the VLFR whereas the water-soluble fraction of phyA″ is responsible for the HIR and LFR, the processes taking place in the nucleus. The membrane- (protein-) associated fraction of phyA” is likely to participate in the cytoplasmic photoregulation processes. The phyA pools' functions—their mode, intensity and sign—depend on plant's species, genotype and organ/tissue. The evidence of the existence of the two distinct phyA types in a plant, and their physicochemical properties and their role in the phyA functioning are discussed.
  • 417
  • 17 May 2023
Topic Review
Tumor Microenvironment in Osteosarcoma Cells
Osteosarcoma (OS) is a malignancy that is becoming increasingly common in adolescents. OS stem cells (OSCs) form a dynamic subset of OS cells that are responsible for malignant progression and chemoradiotherapy resistance. The unique properties of OSCs, including self-renewal, multilineage differentiation and metastatic potential, 149 depend closely on their tumor microenvironment.
  • 451
  • 30 Dec 2022
Topic Review
TPC1 in plants
TPC1 in plants is localized in the vacuolar membrane. Its activity is strictly regulated by several factors emphasizing its complex structure and function. The physiological role of TPC1 is under debate. The TPC1 hyperactive version fou2 (carring D454N mutation) is characterized by an overproduction of jasmonate acid (JA), however the tpc1-2 knockout mutant has no pronounced phenotype. The intriguing concept of Ca2+-induced Ca2+ release was assigned to Vicia faba TPC1 in 1994 by Ward and Schroeder, however it has still not been confirmed for the model plant Arabidopsis thaliana.
  • 906
  • 27 Oct 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.
  • 2.3K
  • 04 Feb 2021
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