Current knowledge on the extraction,purification, identification,and validation of bioactive peptides from seaweed

Seaweed (macroalgae) is considered as a sustainable bioresource rich in high-quality nutrients such as protein. Seaweed protein can be used as an alternative to other protein sources. Furthermore, these proteins are natural reservoirs of bioactive peptides (BAPs) associated with various health benefits such as antioxidant, antihypertensive, and antidiabetic activities. However, seaweed-derived BAPs remain underexploited due to challenges that arise during protein extraction from algal biomass. Coupled with this, limited proteomic information exists regarding certain seaweed species. This review highlights the current state of the art of seaweed protein extraction techniques, e.g., liquid, ultrasound, microwave, pulsed electric field, and high hydrostatic pressure assisted extraction. The review also focuses on the enzymatic hydrolysis of seaweed proteins and characterization of the resultant hydrolysates/peptides using electrophoretic and chromatographic techniques. This includes reference to methods employed for separation, fractionation, and purification of seaweed BAPs, as well as the methodologies used for identification, e.g., analysis by mass spectrometry. Furthermore, a bioinformatics or in silico approach to aid discovery of seaweed BAPs is discussed herein. Based on the information available to date, it is suggested that further research is required in this area for the development of seaweed BAPs for nutraceutical applications.     

Fish and Shellfish-Derived Anti-Inflammatory Protein Products: Properties and Mechanisms

The interest in utilizing food-derived compounds therapeutically has been rising. With the growing prevalence of systematic chronic inflammation (SCI), efforts to find treatments that do not result in the side effects of current anti-inflammatory drugs are underway. Bioactive peptides (BAPs) are a particularly promising class of compounds for the treatment of SCI, and the abundance of high-quality seafood processing byproducts (SPB) makes it a favorable material to derive anti-inflammatory BAPs. Recent research into the structural properties of anti-inflammatory BAPs has found a few key tendencies including they tend to be short and of low molecular weight (LMW), have an overall positive charge, contain hydrophobic amino acids (AAs), and be rich in radical scavenging AAs. SPB-derived anti-inflammatory BAPs have been observed to work via inhibition of the NF-κB and MAPK pathways by disrupting the phosphorylation of IκBα and one or more kinases (ERK, JNK, and p38), respectively. Radical scavenging capacity has also been shown to play a significant role in the efficacy of SPB-derived anti-inflammatory BAPs. To determine if SPB-derived BAPs can serve as an effective treatment for SCI it will be important to understand their properties and mechanisms of action, and this review highlights such findings in recent research.     

Novel asymmetric 3,5‐bis(arylidene)piperidin‐4‐one derivatives: synthesis,crystal structures and cytotoxicity

3,5‐Bis(arylidene)piperidin‐4‐one derivatives (BAPs) display good antitumour activity because of their double α,β‐unsaturated ketone structural characteristics. Reported BAPs have generally been symmetric and asymmetric BAPs have been little documented. Three asymmetric BAPs, namely (5E)‐3‐(4‐tert‐butylbenzylidene)‐5‐(4‐fluorobenzylidene)‐1‐methylpiperidin‐4‐one, C₂₄H₂₆FNO, ( 5 ), (5E)‐3‐(4‐tert‐butylbenzylidene)‐5‐(3,5‐dimethoxybenzylidene)‐1‐methylpiperidin‐4‐one, C₂₆H₃₁NO₃, ( 6 ), and (5E)‐3‐{3‐[(E)‐(2,3‐dihydroxybenzylidene)amino]benzylidene}‐5‐(2‐fluorobenzylidene)‐1‐methylpiperidin‐4‐one, C₂₇H₂₃FN₂O₃, ( 12 ), were generated by Claisen–Schmidt condensation. They are characterized by NMR and FT–IR spectroscopies, and elemental analysis. Single‐crystal structure analysis reveals that the two arylidene rings on both sides of the BAP structures adopt an E stereochemistry of the olefinic double bonds and the compounds are E,E isomers. Molecules of ( 5 ) and ( 12 ) generate one‐dimensional chains through intermolecular hydrogen bonds, while compound ( 6 ) generates a two‐dimensional network through hydrogen bonds. Preliminary cytotoxicities toward human liver hepatocellular carcinoma cell line (HepG2), human acute mononuclear granulocyte leukaemia (THP‐1) and human normal hepatical cell line (LO2) were evaluated.     

Mixed-ligand Ru(II) complexes with 2,2'-bipyridine and tetradentate Schiff bases auxiliary ligands: Synthesis, physico-chemical study, DFT analysis, electrochemical and Na+ binding properties

cis-Bis(2,2'-bipyridyl)dichlororuthenium(II)dihydrate complexed with Schiff bases salen (L1H2) and salophen (L2H2) provides complexes of compositions [Ru(L1)(bpy)2] 1 and [Ru(L2)(bpy)2] 2, respectively with cavity. The structure of these complexes characterized by spectroscopic studies were supported by their optimized geometries based on DFT calculations. Complexes 1 and 2 were then allowed to interact with methanolic solution of sodium perchlorate separately providing corresponding complexes 3 and 4 with the compositions 1.NaClO4 and 2.NaClO4, respectively. The formation constants were then evaluated by monitoring the changes in their UV-visible spectral features upon addition of different amount of sodium salts in the presence of a fixed concentration of the ruthenium complexes at a wavelength 294 nm. Emission (solution), luminescence microscopic and cyclic voltammetric studies of these complexes have also been made.     

Dynamics of p-terphenyl crystals at the phase transition temperature: a zero-field EPR study of the photoexcited triplet state of pentacene in p-terphenyl crystals

Pulsed zero-field electron paramagnetic resonance free induction decay (ZF EPR FID) techniques are employed to study the phase transition of p-terphenyl crystals (Tc = 193 K) by measuring selectively populated photoexcited triplet ZF transitions of dilute pentacene molecules in p-terphenyl single crystals. The sensitivity of ZF spectroscopy to small shifts in local magnetic fields enables the studies of guest-host configuration changes over a wide temperature range. Here we report the observation of guest pentacene (-h(14) and -d(14)) triplet ZF EPR FID spectra that disappear abruptly at Tc and of spectral broadening and shift below Tc. We interpret these spectral changes as evidence for guest couplings to host phenyl rings. Further, these data allow assignments of spectroscopic sites to crystallographic sites that occur in the phase transition.     

Principal component analysis of the absorption and resonance Raman spectra of the metallochromic indicator antipyrylazo III

Metallochromic indicators, whose spectral properties are changed in the presence of metal cations, are used mainly in biological studies to monitor Ca2+ and Mg2+ ions. Antipyrylazo III is such indicator, employed for mid-range Ca2+ concentrations (10-1000 microM). The stoichiometry of the interactions of antipyrylazo III with Ca2+, Mg2+, Ba2+, Sr2+ and Zn2+ ions and the relevant binding constants were studied by principal component analysis (PCA) of the absorption spectral changes. The resonance Raman spectra of the above systems were measured as well, and the resolved Raman spectra of the various species were calculated and assigned. The vibrational spectra are more featured, more characteristic of the binding ions and exhibit stronger relative spectral changes upon binding the cations. The basis sets of Raman spectra could thus be used as an analytical tool for these divalent metallic cations.     

C-H stretching vibrations of methyl, methylene and methine groups at the vapor/alcohol (N = 1-8) interfaces

In IR and Raman spectral studies, the congestion of the vibrational modes in the C-H stretching region between 2800 and 3000 cm(-1) has complicated spectral assignment, conformational analysis, and structural and dynamics studies, even with quite a few of the simplest molecules. To resolve these issues, polarized spectra measurement on a well aligned sample is generally required. Because the liquid interface is generally ordered and molecularly thin, and sum frequency generation vibrational spectroscopy (SFG-VS) is an intrinsically coherent polarization spectroscopy, SFG-VS can be used for discerning details in vibrational spectra of the interfacial molecules. Here we show that, from systematic molecular symmetry and SFG-VS polarization analysis, a set of polarization selection rules could be developed for explicit assignment of the SFG vibrational spectra of the C-H stretching modes. These polarization selection rules helped assignment of the SFG-VS spectra of vapor/alcohol (n = 1-8) interfaces with unprecedented details. Previous approach on assignment of these spectra relied on IR and Raman spectral assignment, and they were not able to give such detailed assignment of the SFG vibrational spectra. Sometimes inappropriate assignment was made, and consequently misleading conclusions on interfacial structure, conformation and even dynamics were reached. With these polarization rules in addition to knowledge from IR and Raman studies, new structural information and understanding of the molecular interactions at these interfaces were obtained, and some new spectral features for the C-H stretching modes were also identified. Generally speaking, these new features can be applied to IR and Raman spectroscopic studies in the condensed phase. Therefore, the advancement on vibrational spectra assignment may find broad applications in the related fields using IR and Raman as vibrational spectroscopic tools.     

Self-association of acetic acid in dilute deuterated chloroform. Wide-range spectral reconstructions and analysis using FTIR spectroscopy, BTEM, and DFT

The binary solution of acetic acid in CDCl(3) was studied at room pressure on the interval T = 293-313 K with a series of acetic acid concentrations up to 0.16 M. In-situ Fourier transform infrared (FTIR) spectroscopy measurements on the interval of 400-3800 cm(-1) were utilized as the analytical method to monitor the spectral changes due to self-association of acetic acid. The band-target entropy minimization (BTEM) algorithm was employed to reconstruct the underlying pure component spectra. Analysis successfully provided two major spectral estimates of acetic acid, namely, the monomer (primarily in the form of monomer-CDCl(3) complex) and the centrosymmetric cyclic dimer. In addition, analysis provided one minor spectral estimate containing signals from both noncyclic dimers and higher aggregates. Also, spectral estimates were obtained for phosgene and water which were present at trace levels even though considerable precaution was taken to conduct the experiments under anhydrous and anaerobic conditions. Density functional theory (DFT) calculation was performed to assign the acetic acid structures corresponding to the BTEM spectral estimates. Since the structure of dilute acetic acid has been the subject of numerous studies, the present investigation helps to resolve some issues concerning the speciation of acetic acid at low concentrations in low polarity solvents. In particular, the present study provides for the first time, wide-range spectral reconstructions of the species present.     

Metal(II) complexes of bioactive aminonaphthoquinone-based ligand: synthesis,characterization and BSA binding,DNA binding/cleavage,and cytotoxicity studies

An aminonaphthoquinone ligand, L, and its metal complexes of general formula [MLCl₂] {M = Co(II), Ni(II), Cu(II) and Zn(II)} have been synthesized and characterized by analytical and spectral techniques. Tetrahedral geometry has been assigned to Ni(II) and Zn(II) complexes and square planar geometry to Co(II) and Cu(II) complexes on the basis of electronic spectral and magnetic susceptibility data. The binding of complexes with bovine serum albumin (BSA) is relatively stronger than that of free ligand and alters the conformation of the protein molecule. Interaction of these complexes with CT-DNA has been investigated using UV-Vis and fluorescence quenching experiments, which show that the complexes bind strongly to DNA through intercalative mode of binding (K_app 10⁵ M^?1). Molecular docking studies reiterate the mode of binding of these compounds with DNA, proposed by spectral studies. The ligand and its complexes cleave plasmid DNA pUC18 to nicked (Form II) and linear (Form III) forms in the presence of H₂O₂ oxidant. The in vitro cytotoxicity screening shows that Cu(II) complex is more potent against MCF-7 cells and Zn(II) complex exhibits marked cytotoxicity against A-549 cells equal to that of cisplatin. Cell imaging studies suggested apoptosis mode of cell death in these two chosen cell lines.     

The methyl C-H blueshift in N,N-dimethylformamide-water mixtures probed by two-dimensional Fourier-transform infrared spectroscopy

Two-dimensional correlation spectroscopy was used to study the composition-dependent spectral variations of the CH-stretching bands of N,N-dimethylformamide (DMF)-water mixtures with X(DMF) ranging from 0.98 to 0.60. By a detailed correlation analysis of the spectral changes of the CH- and OH-stretching bands, it is found that the intensities of the CH and OH bands change in different ways when the water content is increased. It is also found that two different regions of the water content can be distinguished, in which the intensity changes have different signatures. A tentative explanation for how these phenomena might be related to structural changes in the mixture is proposed. The structural change of DMF induced by the water hydrogen bonded on the carbonyl group is supposed to be the possible origin of the methyl C-H blueshift instead of the direct C-H...O interactions before the hydrophobic hydration takes place.     

Effects of pulse strength, width, and sample spinning speed on the spectral spin diffusion of multiquantum coherences of spin-3/2 quadrupolar nuclei

The effects of radio-frequency pulse strength, width, and sample spinning speed on the spin-diffusion spectrum of half-integer quadrupolar spins in solids have been studied by theoretical, numerical, and experimental investigations. It is revealed that the line shape of the cross peaks changes nonmonotonically with respect to the change of pulse strength, pulse width, or sample spinning speed. It is also found that the sample spinning speed has much more pronounced influence on the spin diffusion spectral line shape. In many cases of practical importance, the effect of sample spinning must be included in spectral analysis, in contrast to the practice of previous studies. Moreover, this effect can be exploited to further improve the precision in the determination of relative orientation of the electric-field gradient tensors of the exchange partners.     

Structural transitions in polyriboadenylic acid induced by the changes in pH and temperature: vibrational circular dichroism study in solution and film states

A correlation of the changes in vibrational absorption and vibrational circular dichroism (VCD) spectral features with the structural changes of polyriboadenylic acid (polyA) as a function of pH is reported. Analysis of the solution spectral data as a function of pH led us to establishing the importance of a previously unrecognized absorption band at approximately 1665 cm(-1). The present studies indicate that this absorption band and associated VCD originate from the double-helical structure of polyA. The observed changes in solution-state VCD features are indicative of the pH-dependent transitions among the three acidic forms of polyA (A, B, and "frozen" form). In addition to the solution-state spectral data, pH-dependent absorption and VCD spectra for films of polyA, derived from dilute H2O solutions, are also presented. The pH-dependent changes in the absorption and VCD spectra of films are also correlated to the polyA structural changes.     

Characterization of fresh and aged natural ingredients used in historical ointments by molecular spectroscopic techniques: IR,Raman and fluorescence

Natural organic materials used to prepare pharmaceutical mixtures including ointments and balsams have been characterized by a combined non-destructive spectroscopic analytical approach. Three classes of materials which include vegetable oils (olive, almond and palm tree), gums (Arabic and Tragacanth) and beeswax are considered in this study according to their widespread use reported in ancient recipes. Micro-FTIR, micro-Raman and fluorescence spectroscopies have been applied to fresh and mildly thermally aged samples. Vibrational characterization of these organic compounds is reported together with tabulated frequencies, highlighting all spectral features and changes in spectra which occur following artificial aging. Synchronous fluorescence spectroscopy has been shown to be particularly useful for the assessment of changes in oils after aging; spectral difference between Tragacanth and Arabic gum could be due to variations in origin and processing of raw materials. Analysis of these materials using non-destructive spectroscopic techniques provided important analytical information which could be used to guide further study.     

Micellar modification of the spectral, intensity and lifetime characteristics of the fluorescence of fluorescein-labelled phenobarbital

The effects of association with micelles on the fluorescence properties of fluorescein-labelled phenobarbital were studied as a function of pH (in the range 5.8-7.8) and micelle concentration. The largest changes were observed at pH 5.8, including red-shifts of 10 nm in the emission and excitation maxima, spectral intensity enhancements as great as 500%, and 0.5-nsec increases in fluorescence lifetime. Micelles induced much greater changes than cyclodextrins, which were also studied. These studies indicate the potential usefulness of micelles and cyclodextrins as auxiliary binding reagents for both heterogeneous and homogeneous fluoroimmunoassay techniques.     

Binding of organophosphate insecticides with serum albumin: multispectroscopic and molecular modelling investigations

The interaction between two organophosphate insecticides (monocrotophos and phosphamidon) and bovine serum albumin (BSA) under physiological conditions is investigated by UV-Vis, fluorescence (steady state, synchronous and three-dimensional) and circular dichroism spectroscopy. The UV-Vis and fluorescence spectral studies indicate the formation of complex between BSA and the insecticides. The complex formation is a spontaneous process as evidenced by negative free energy changes. The positive values of entropy changes reveal that hydrophobic forces played the major role in the interaction process, which is well supported by the molecular docking studies. Synchronous and three-dimensional fluorescence investigations suggest that there is no significant change in the conformation of BSA upon binding with the insecticides, which is strongly supported by the results of circular dichroism spectral studies.     

Synthesis,spectroscopic, and antimicrobial studies of the bivalent cobalt,nickel, and copper complexes of thioacetamide

A series of metal complexes of cobalt(II), nickel(II), and copper(II) having the general composition [M(L)₂X₂] with thioacetamide have been prepared and characterized by elemental chemical analysis, molar conductance, magnetic susceptibility measurements, mass, IR, EPR, and electronic spectral studies. The IR spectral data suggests the involvement of sulfur and amino nitrogen in coordination to central metal ion. On the basis of spectral studies, an octahedral geometry has been assigned for the cobalt(II) and nickel(II) complexes whereas tetragonal geometry for copper(II) complexes. Thioacetamide and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties.     

Hydrogen bonding properties of Coumarin 151, 500, and 35: the effect of substitution at the 7-amino position

The steady-state spectral properties (absorption and emission) of three structurally similar Coumarin dyes, C151, C500, and C35 were investigated in 13 different solvents. A Kamlet-Taft (KT) analysis of the spectral peak frequencies reveals that, in addition to polarity, hydrogen bonding between the carbonyl oxygen and a protic solvent in the excited state imparts maximum stabilization for C151 and minimum for C35, while that for C500 lies in between. The spectral properties of the three dyes in two solvents, chloroform and THF, which have similar polarity in the KT scale but have only hydrogen-bond donor (chloroform) and hydrogen-bond acceptor (THF) properties, are seen to be sensitive to the substitution pattern at the 7-amino position. In addition, a slow emission spectral relaxation is observed for C151 and C500 having a time constant of approximately 500 ps in chloroform. For C35 this was too fast to be detected by the time resolution of our setup. The exact reason for this slow spectral relaxation in chloroform is unclear at present, and further studies are needed to understand clearly the structural effects on the hydrogen bonding dynamics of these dyes.     

Preparation, structure and spasmolytic activities of some derivatives of harmine series of alkaloids

Keeping in view the interesting chemistry and pharmacological importance of harmine series of bases -- the beta-carboline alkaloids, a number of new derivatives of tetrahydroharmine and harmalol have been prepared and characterized through spectral studies. Some of these derivatives showed spasmolytic activity. It was observed that all the N-acyl tetrahydroharmine derivatives are stable, not labile and no ring opening occurs in these compounds, as reported recently.     

Free-jet studies of the visible spectroscopy of some perhalonitrosomethanes

Recent work on the electronic spectroscopy of halogen substituted nitrosomethanes in the visible spectral region is reviewed with particular reference to laser-induced fluorescence and photofragment yield spectra in supersonic free-jet expansions. The A(n, π*)-X electronic spectra in the 650–720 nm region are dominated by progressions in low frequency torsional modes, that reflect eclipsed to staggered dihedral conformational changes upon electronic excitation. The observed torsional progressions can be understood well on the basis of spectral simulations that utilize a simple one-dimensional Hamiltonian for the hindered internal rotation. The relevance of these laser spectroscopic studies for current work on the state-selected photophysics and photodissociation dynamics of the title compounds is highlighted.     

N，N-二甲酰基二硫代氨基甲酸根金属配合物的研究

本文首次报道了一系列N，N-二甲酰基二硫代氨基甲酸根为配体的过渡金属配合物，对它们进行了化学分析、光谱表征和磁性质研究。研究结果表明，在配合物中，配体二硫代氨基甲酸根一般为较弱的双齿配位。