Synthesis, characterization and anticonvulsant activity of new azobenzene-containing VV-hemorphin-5 bio photoswitch

A Tutorial Review on the Fluorescent Probes as a Molecular Logic Circuit-Digital Comparator

The rapid progress in the field of fluorescent probes and fluorescent sensing material extended this research area toward more complex molecular logic gates capable of carrying out a variety of sensing functions simultaneously. These molecules are able to calculate a composite result in which the analysis is not performed by a man but by the molecular device itself. Since the first report by de Silva of AND molecular logic gate, all possible logic gates have been achieved at the molecular level, and currently, utilization of more complicated molecular logic circuits is a major task in this field. Comparison between two digits is the simplest logic operation, which could be realized with the simplest logic circuit. That is why the right understanding of the applied principles during the implementation of molecular digital comparators could play a critical role in obtaining logic circuits that are more complicated. Herein, all possible ways for the construction of comparators on the molecular level were discussed, and recent achievements connected with these devices were presented.

A Novel Fluorescent Probe for Determination of pH and Viscosity Based on a Highly Water-Soluble 1,8-Naphthalimide Rotor

A novel highly water-soluble 1,8-naphthalimide with pH and viscosity-sensing fluorescence was synthesized and investigated. The synthesized compound was designed as a molecular device in which a molecular rotor and molecular “off-on” switcher were integrated. In order to obtain a TICT driven molecular motion at C-4 position of the 1,8-naphthalimide fluorophore, a 4-methylpiperazinyl fragment was introduced. The molecular motion was confirmed after photophysical investigation in solvents with different viscosity; furthermore, the fluorescence-sensing properties of the examined compound were investigated in 100% aqueous medium and it was found that it could be used as an efficient fluorescent probe for pH. Due to the non-emissive deexcitation nature of the TICT fluorophore, the novel system showed low yellow–green emission, which represented “power-on”/“rotor-on” state. The protonation of the methylpiperazine amine destabilized the TICT process, which was accompanied by fluorescence enhancement indicating a “power-on”/“rotor-off” state of the system. The results obtained clearly illustrated the great potential of the synthesized compound to serve as pH- and viscosity-sensing material in aqueous solution.

Study of Novel Peptides for Antimicrobial Protection in Solution and on Cotton Fabric

Some new N- and C-modified biomolecular peptide analogues of both VV-hemorphin-5 and VV-hemorphin-7 with varied amino acids (Cys, Glu, His), 1-adamantanecarboxylic acid, and niacin (nicotinic acid) were synthesized by solid-phase peptide synthesis-Fmoc (9-fluorenylmethoxy-carbonyl) chemistry and were characterized in water solutions with different pH using spectroscopic and electrochemical techniques. Basic physicochemical properties related to the elucidation of the peptide structure at physiological pH have been also studied. The results showed that the interaction of peptide compounds with light and electricity preserves the structural and conformational integrity of the compounds in the solutions. Moreover, textile cotton fibers were modified with the new compounds and the binding of the peptides to the surface of the material was proved by FTIR and SEM analysis. Washing the material with an alkaline soap solution did not show a violation of the modified structure of the cotton. Antiviral activity against the human respiratory syncytial virus (HRSV-S2) and human adenovirus serotype 5 (HAdV-5), the antimicrobial activity against B. cereus and P. aeruginosa used as model bacterial strains and cytotoxic effect of the peptide derivatives and modified cotton textile material has been evaluated. Antimicrobial tests showed promising activity of the newly synthesized compounds against the used Gram-positive and Gram-negative bacteria. The compounds C-V, H-V, AC-V, and AH-V were found slightly more active than NH7C and NCH7. The activity has been retained after the deposition of the compounds on cotton fibers.

Trans-Cis Kinetic Study of Azobenzene-4,4'-dicarboxylic Acid and Aluminium and Zirconium Based Azobenzene-4,4'-dicarboxylate MOFs

Metal organic frameworks (MOFs) are porous hybrid crystalline materials that consist of organic linkers coordinated to metal centres. The trans–cis isomerisation kinetics of the azobenzene-4,4′-dicarboxylic acid (AZB(COOH)₂) precursor, as well as the Al³⁺ (Al-AZB)- and Zr⁴⁺ (Zr-AZB)-based MOFs with azobenzene-4,4′-dicarboxylate linkers, are presented. The photo-isomerization in the MOFs originates from singly bound azobenzene moieties on the surface of the MOF. The type of solvent used had a slight effect on the rate of isomerization and half-life, while the band gap energies were not significantly affected by the solvents. Photo-responsive MOFs can be classified as smart materials with possible applications in sensing, drug delivery, magnetism, and molecular recognition. In this study, the MOFs were applied in the dye adsorption of congo red (CR) in contaminated water. For both MOFs, the UV-irradiated cis isomer exhibited a slightly higher CR uptake than the ambient-light exposed trans isomer. Al-AZB displayed a dye adsorption capacity of over 95% for both the UV-irradiated and ambient light samples. The ambient light exposed Zr-AZB, and the UV irradiated Zr-AZB had 39.1% and 44.6% dye removal, respectively.

Synthesis and characterization of new 5,5′-dimethyl- and 5,5′-diphenylhydantoin-conjugated hemorphin derivatives designed as potential anticonvulsant agents

Herein, the synthesis and characterization of some novel N-modified hybrid analogues of hemorphins containing a C-5 substituted hydantoin residue as potential anticonvulsants and for the blockade of sodium channels are presented.

Synthesis of New Modified with Rhodamine B Peptides for Antiviral Protection of Textile Materials

Here we report on the synthesis and characterization of three new N-modified analogues of hemorphin-4 with rhodamine B. Modified with chloroacetyl, chloride cotton fabric has been dyed and color coordinates of the obtained textile materials were determined. Antiviral and virucidal activities of both the peptide-rhodamine B compounds and the dyed textile material were studied. Basic physicochemical properties (acid-base behavior, solvent influence, kinetics) related to the elucidation of structural activity of the new modified peptides based on their steric open/closed ring effect were studied. The obtained results lead to the conclusion that in protic solvent with change in pH of the environment, direct control over the dyeing of textiles can be achieved. Both the new hybrid peptide compounds and the modification of functionalized textile materials with these bioactive hemorphins showed virucidal activity against the human respiratory syncytial virus (HRSV-S2) and human adenovirus serotype 5 (HAdV-5) for different time intervals (30 and 60 min) and the most active compound was Rh-3.

Hemorphins-From Discovery to Functions and Pharmacology

During the last three decades, a variety of different studies on bioactive peptides that are opioid receptor ligands, have been carried out, with regard to their isolation and identification, as well as their molecular functions in living organisms. Thus, in this review, we would like to summarize the present state-of-the art concerning hemorphins, methodological aspects of their identification, and their potential role as therapeutic agents. We have collected and discussed articles describing hemorphins, from their discovery up until now, thus presenting a very wide spectrum of their characteristic and applications. One of the major assets of the present paper is a combination of analytical and pharmacological aspects of peptides described by a team who participated in the initial research on hemorphins. This review is, in part, focused on the analysis of endogenous opioid peptides in biological samples using advanced techniques, description of the identification of synthetic/endogenous hemorphins, their involvement in pharmacology, learning, pain and other function. Finally, the part regarding hemorphin analogues and their synthesis, has been added.

Structure-activity relationship study on new hemorphin-4 analogues containing steric restricted amino acids moiety for evaluation of their anticonvulsant activity

In the present study, several new analogues of hemorphin-4, modified with unnatural conformationally restricted amino acids followed the structure Aaa-Tyr-Xxx-Trp-Thr-NH₂, where Aaa is the low-molecular-weight lipophilic adamantyl building block, and Xxx is Ac5c (1-aminocyclopentanecarboxylic acid) or Ac6c (1-aminocyclohexane carboxylic acid) was synthesized, characterized and investigated for anticonvulsant activity in three seizure tests, the maximal electroshock test (MES), 6-Hz psychomotor seizure test and timed intravenous pentylenetetrazole infusion (ivPTZ) test. The acute neurological toxicity was determined using the rota-rod test. The new synthetic neuropeptide analogues were prepared by solid-phase peptide synthesis-Fmoc chemistry and were evaluated in three doses of 1, 3 and 5 µg, respectively, administered intracerebroventricularly in male ICR mice. The physicochemical properties of these peptide analogues were evaluated as pKa and pI values were calculated using potentiometry. The IR spectrum of the compounds was recorded and the characteristic lines of both adamantane moiety and the peptide backbone were registered in the wavelength range from 4000 to 400 cm^-1. The hexapeptide Ang IV was used as a positive control. From the six synthesized peptide analogues, the P4-5 was the most active at doses of 1 and 3 µg in the three seizure tests. The order of potency of other peptides was as follows: P4 > P4-3 = P4-4 > P4-2 > Ang IV in MES, P4-4 ≥ P4-1 > P4-3 > P4-2 > P4 > Ang IV in 6-Hz test and P4-4 = P4-3 > P4-2 = P4 > Ang IV in ivPTZ test. None of the peptides displayed neurotoxicity in the rota-rod test. Docking study results suggest that direct H-bonding and ionic interactions between our synthetic ligands and residues, responsible for coordination of Zn²⁺ along with hydrophobic interactions between our ligands and IRAP active site are the most important for the ligand binding. The results propose that incorporation of adamantane and cycloalkane building blocks in the peptide chain of the hemorphin-4 scaffold is important for the potential high biological activity.

Molecular basis of the therapeutic properties of hemorphins

Hemorphins are endogenous peptides, 4-10 amino acids long, belonging to the family of atypical opioid peptides released during the sequential cleavage of hemoglobin protein. Hemorphins have been shown to exhibit diverse therapeutic effects in both human and animal models. However, the precise cellular and molecular mechanisms involved in such effects remain elusive. In this review, we summarize and propose potential mechanisms based on studies that investigated the biological activity of hemorphins of different lengths on multiple therapeutic targets. Special emphasis is given to molecular events related to renin-angiotensin system (RAS), opioid receptors and insulin-regulated aminopeptidase receptor (IRAP). This review provides a comprehensive coverage of the molecular mechanisms that underpin the therapeutic potential of hemorphins. Furthermore, it highlights the role of various hemorphin residues in pathological conditions, which could be explored further for therapeutic purposes.

Potential anticonvulsant activity of novel VV-hemorphin-7 analogues containing unnatural amino acids: synthesis and characterization

Herein, some new analogues of VV-hemorphin-7, modified at position 4 and 7 by the unnatural amino acids followed the structure Val-Val-Tyr-Xxx-Trp-Thr-Yyy-Arg-Phe-NH₂, where Xxx is Ac5c (1-aminocyclopentanecarboxylic acid) or Ac6c (1-aminocyclohexane carboxylic acid) and Yyy is Dap (diaminopropanoic acid) or Dab (diaminobutanoic acid), were synthesized, characterized and investigated for anticonvulsant activity. The new synthetic peptide analogues were prepared by standard solid-phase peptide synthesis-Fmoc chemistry. A single intracerebroventricular (i.c.v.) injection at doses of 5, 10, and 20 µg/10 µl, respectively, was given before evaluation with timed intravenous pentylenetetrazole (ivPTZ) infusion test and 6-Hz psychomotor seizure test in mice. The acute neurological toxicity was determined using the rotarod test. To explain the structure-active properties of the modified peptides, some physicochemical characteristic was obtained. The FT-IR spectra and their second derivatives of the amide I, II, and III bands of the peptides show ß-sheet structure conformation. The calculation of isoelectric points, by potentiometric determination of dissociated constants, is in the range from 9.79 to 10.84. This study, for the first time, also reported on the reduction-oxidative potentials of the guanidine at Arg-moiety on such kind of peptides containing arginine and tyrosine residues in different medium and electrode surface. The VV-hemorphin-7 analogues 4 and 5 were the most active against the ivPTZ test, with the effect comparable to that of peptide 1 used as a positive control. Except compound 8, all other tested peptide analogues were ineffective to raise the threshold for the clonic seizures. The peptide analogue 5 showed 100% protection in the 6-Hz test, while the other seven VV-hemorphin-7 analogues have dose-dependent activity against psychomotor seizures comparable to 1. The novel peptides did not show neurotoxicity in the rotarod test.