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As a result of their natural capacity to recover harmonic current and reactive power from alternating current sources, power electronic devices utilized in conjunction with nonlinear loads have the potential to generate significant harmonic problems within the power system when employed in this way. When this occurs, voltage instability occurs, which must be avoided in order to maintain the consistency and dependability of the power system's power flow. With this approach, the series controller has been replaced by a multilevel modular controller in order to improve power handling capability and achieve higher modular levels with minimal distortions. The shunt compensator is the most effective way to achieve an extremely protected energy system as well as righteous steadiness in electric potential difference under a variety of load constraints. The DQ thesis is employed in this proposed converter to separate the harmonic components by establishing reference frame current, which is accomplished by machine learning techniques. As part of the constant mode operation, the PI controller contributes to maintaining the direct current-potential difference, which is given to the PWM generator. Optimization of the values of K p and K i is accomplished by the use of particle swarm optimization (PSO). The construction of this power system simulation model has been made feasible by the use of time-fluctuating characteristics modeling and the MATLAB programming environment. The new (unified power flow controller) UPFC research that has been made available is persuasive in its capacity to reduce distortions and watt-less power components while simultaneously enhancing efficiency and reducing costs., Competing Interests: The authors of this manuscript declare that they do not have any conflicts of interest., (Copyright © 2022 Shoaib Kamal et al.)

Short peptides composed of phenylalanine and sequences derived from amyloidogenic peptides have the ability to self-assemble to form nanostructures including hydrogels. The self-assembly of peptides composed of only hydrophobic amino acids and aliphatic protecting groups have not been investigated in detail. We have examined various aspects of nanostructures formed by N-terminal t-butyloxycarbonyl-protected aliphatic dipeptide methyl esters dissolved in various solvents. Scanning electron microscopic images indicate that depending on the sequence, position of the amino acid and solvent of dissolution, the peptides self-assemble into superstructures such as nanotubes and needles particularly from aqueous mixtures of organic solvents. Crystallization was not required for self-assembly into nanostructures. Circular dichroism and attenuated total internal reflection fourier transform infrared spectroscopy studies indicate that the peptides adopt β-conformation in the superstructures both in solution and solid state. The nanostructures composed of entirely aliphatic moieties have the ability to bind to aromatic dyes such as Rhodamine 6G, Nile red and Congo red. They also bind to Thioflavin T although the structures do not resemble amyloid fibrils. The powder X-ray diffraction patterns suggest distinctive packing of the monomers. These structures are stabilized by intermolecular hydrogen bonds and hydrophobic interactions resulting in superstructures containing long distance order and were devoid of hemolytic activity., (© 2017 Wiley Periodicals, Inc.)

Background: Amyloid fibrils, which are implicated in several diseases, are highly ordered structures formed by aggregation of proteins. Intriguingly, several short peptides, some of which are unrelated to the disease-causing proteins, also aggregate to form amyloid fibrils in vitro. The aggregation behavior of these short peptides can be modulated so that they form nanostructures that are not in any way related to amyloid fibrils. These observations have led to extensive research aimed at getting insights into how peptides aggregate to form amyloids as well as non-amyloidogenic structures., Methods: This review examines the aggregation behavior of peptides that form highly polymorphic structures including fibrils, nanotubes, nanospheres and hydrogels. The review also describes how short peptides composed of only two and three hydrophobic and aromatic amino acids can selfassemble to form nanotubes and nanospheres., Results: Peptides with widely varying amino acid composition and lengths aggregate to form indistinguishable fibrils and nanostructures. The potential application of these aggregated structures in the design of novel biomaterials is reviewed and highlighted., Conclusion: It is evident that highly polymorphic aggregated structures of peptides can be obtained by varying conditions such as solvent of dissolution, temperatures, pH and even surfaces of deposition., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)

The morphology of structures formed by the self-assembly of short N-terminal t-butyloxycarbonyl (Boc) and C-terminal methyl ester (OMe) protected and Boc-deprotected hydrophobic peptide esters was investigated. We have observed that Boc-protected peptide esters composed of either only aliphatic hydrophobic amino acids or aliphatic hydrophobic amino acids in combination with aromatic amino acids, formed highly organized structures, when dried from methanol solutions. Transmission and scanning electron microscopic images of the peptides Boc-Ile-Ile-OMe, Boc-Phe-Phe-Phe-Ile-Ile-OMe and Boc-Trp-Ile-Ile-OMe showed nanotubular structures. Removal of the Boc group resulted in disruption of the ability to form tubular structures though spherical aggregates were formed. Both Boc-Leu-Ile-Ile-OMe and H-Leu-Ile-Ile-OMe formed only spherical nanostructures. Dynamic light scattering studies showed that aggregates of varying dimensions were present in solution suggesting that self-assembly into ordered structures is facilitated by aggregation in solution. Fourier transform infrared spectroscopy and circular dichroism spectroscopy data show that although all four of the protected peptides adopt well-defined tertiary structures, upon removal of the Boc group, only H-Phe-Phe-Phe-Ile-Ile-OMe had the ability to adopt β-structure. Our results indicate that hydrophobic interaction is a very important determinant for self-assembly and presence of charged and aromatic amino acids in a peptide is not necessary for self-assembly., (Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.)

Deposition of insoluble fibrillar aggregates of β-amyloid (Aβ) peptides in the brain is a hallmark of Alzheimer's disease. Apart from forming fibrils, these peptides also exist as soluble aggregates. Fibrillar and a variety of nonfibrillar aggregates of Aβ have also been obtained in vitro. Hexafluoroisopropanol (HFIP) has been widely used to dissolve Aβ and other amyloidogenic peptides. In this study, we show that the dissolution of Aβ40, 42, and 43 in HFIP followed by drying results in highly ordered aggregates. Although α-helical conformation is observed, it is not stable for prolonged periods. Drying after prolonged incubation of Aβ40, 42, and 43 peptides in HFIP leads to structural transition from α-helical to β-conformation. The peptides form short fibrous aggregates that further assemble giving rise to highly ordered ring-like structures. Aβ16-22, a highly amyloidogenic peptide stretch from Aβ, also formed very similar rings when dissolved in HFIP and dried. HFIP could not induce α-helical conformation in Aβ16-22, and rings were obtained from freshly dissolved peptide. The rings formed by Aβ40, 42, 43, and Aβ16-22 are composed of the peptides in β-conformation and cause enhancement in thioflavin T fluorescence, suggesting that the molecular architecture of these structures is amyloid-like. Our results clearly indicate that dissolution of Aβ40, 42 and 43 and the amyloidogenic fragment Aβ16-22 in HFIP results in the formation of annular amyloid-like structures., (Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.)

Indolicidin, ILPWKWPWWPWRR-NH(2), a short 13-residue antimicrobial and cytolytic peptide characterized from bovine neutrophils, has the calmodulin-recognition 1-5-10 hydrophobic pattern (indicated by amino acids in bold), is cationic, and thereby fulfills the requirements to interact with calmodulin. Hence, we have investigated the calmodulin-binding properties of indolicidin. Indolicidin interacted with calmodulin with fairly high affinity in a Ca(2+)-dependent manner. However, when bound, the peptide did not adopt helical conformation. Indolicidin also inhibited calmodulin-stimulated phosphodiesterase activity with IC(50) values in the nanomolar range. Replacement of either the proline residues of indolicidin with alanines or tryptophan residues with phenylalanines did not affect binding to calmodulin. However, these replacements had distinctive effects on the conformations of the bound peptides. While the alanine analog of indolicidin adopted predominantly alpha-helical conformation, the phenylalanine analog remained largely unordered. Differences in the ability of these analogs to inhibit the calmodulin-stimulated phosphodiesterase activity were observed. While the alanine analog was capable of inhibiting the activity with IC(50) values comparable to that of indolicidin, the phenylalanine analog did not inhibit the activity. Our results indicate that ability to adopt amphiphilic alpha-helical structure is not a prerequisite for binding to calmodulin and also binding does not necessarily result in inhibition of calmodulin-stimulated enzyme activities.

The major carotenoid pigments of an Antarctic psychrotolerant bacterium, Sphingobacterium antarcticus, and a mesophilic bacterium, Sphingobacterium multivorum, were identified as zeaxanthin, beta-cryptoxanthin, and beta-carotene. Analysis was based on ultraviolet-visible spectroscopy, mass spectroscopy, and reversed-phase HPLC. Photoacoustic spectroscopy of intact bacterial cells revealed that the bulk of the pigments in S. antarcticus and S. multivorum was associated with the cell membrane. In vitro studies with synthetic membranes of phosphatidylcholine demonstrated that the major pigment was bound to the membranes and decreased their fluidity. The relative amounts of polar pigments were higher in cells grown at 5 degrees C than in cells grown at 25 degrees C. In the mesophilic strain, the synthesis of polar carotenoids was quantitatively less than that of the psychrotolerant strain.

Seminalplasmin (SPLN) is a 47-residue protein isolated from bovine seminal plasma having potent antimicrobial activity against a broad spectrum of microorganisms. SPLN, also known as caltrin, acts as a calcium transport regulator in bovine sperms. Analysis of the sequence of SPLN reveals a 27-residue stretch with the sequence SLSRYAKLANRLANPKLLETFLSKWIG more hydrophobic than the rest of the protein. It is demonstrated that a synthetic peptide corresponding to this 27-residue segment has antimicrobial activity comparable to that of SPLN. It does not exhibit hemolytic activity at concentrations where antibacterial activity is observed. Since P27 can be conveniently obtained in large amounts by chemical synthesis, it could serve not only as a starting compound to obtain peptides with improved antibacterial activity but also to understand the role of SPLN in reproductive physiology.

Several analogs of the 13-residue antimicrobial and hemolytic peptide PKLLETFLSKWIG (SPF), which is the most hydrophobic region of the 47-residue antimicrobial protein seminalplasmin [Sitaram, N. & Nagaraj, R. (1990) J. Biol. Chem. 265, 10438-10442] have been synthesized. The antimicrobial and hemolytic properties of the peptides were investigated with a view to gain a insight into the structural and charge requirements for these activities of SPF. Peptides in which E was replaced by K exhibited considerably improved antimicrobial activity with no concomitant increase in hemolytic activity. A peptide in which the aromatic amino acids were replaced by leucine exhibited antimicrobial activity like those of the peptides which had aromatic amino acids. Interchange in the positions of E and K and total replacement of K by E resulted in complete loss of activity. The peptides having antimicrobial activity like those of the peptides which had aromatic amino acids. Interchange in the positions of E and K and total replacement of K by E resulted in complete loss activity. The peptides having antimicrobial activities showed appreciable helical content in a hydrophobic environment, whereas inactive peptides did not. Thus, by suitable 'engineering' the biological activity of a short 13-residue peptide can be altered by yield peptides specifically having only antimicrobial activity with increased potency.