Values Of Dihedral Angles Research Articles

Sulfide Melt Wetting Properties in Earth's Mantle: New Constraints From Combined 2D and 3D Imaging

AbstractBase‐metal sulfur liquids (mattes) play a crucial role as metasomatic agents and carriers of highly siderophile elements (HSE) within the Earth's mantle. Prior research has predominantly focused on sulfur‐poor metallic liquids involved in core formation scenarios. We conducted high‐pressure experiments using a multi‐anvil apparatus to investigate the effects of pressure, non‐ferrous compounds in mattes, and the mineral composition of the silicate host on matte wetting properties. Specifically, we explored conditions representing both the lithospheric (6 and 7 GPa) and sub‐lithospheric Earth's mantle (13 GPa). We characterized the experiments using the distribution of the dihedral angle in backscattered‐electron sections and the sphericity and network topology of the mattes in tomography scans. Our findings reveal distinct behaviors: while the matte in olivine‐dominated samples exhibited behaviors consistent with previous studies, such as high dihedral angle values (94° and 100°), the majorite‐bearing sample run at 13 GPa formed a disseminated network with a mean dihedral angle of 43°, below the connectivity threshold of 60°. Furthermore, in an experiment involving a garnet‐bearing silicate host, we observed a decrease in the matte's dihedral angle to 72°. Our results suggest that pressure within mafic hosts contributes to increased matte mobility in the sub‐lithospheric Earth's mantle, especially inasmuch as the stability of garnet phases is concerned. Consequently, mattes within subducted oceanic crusts may efficiently transport HSE into surrounding lithologies, while mattes within depleted, more harzburgitic lithologies and the ambient mantle may remain trapped within the silicate host at low melt fractions.

Structural Equilibrium Configuration of Benzene and Aniline: A First-Principles Study

The present work describes the equilibrium configuration of aromatic compounds like benzene and aniline molecules using the first principle (ab initio) calculation method implemented by the Gaussian 98 programs. The ground state energy for benzene and aniline molecules obtained using the DFT (B3LYP) calculation is lower than that obtained with the HF+MP2 method which, in turn, is lower than that obtained with the HF calculation. The calculated values of bond length, bond angle, and dihedral angle for these molecules with HF, HF+MP2, and DFT (B3LYP) levels of calculation agree with each other within 2%. The calculated C-C and C-H bond lengths of the benzene molecule are 1.394 Å and 1.084 Å at DFT (B3LYP) calculation and these values agree well with the experimental value of 1.395 Å and 1.084 Å for C-C and C-H bond. Also, the calculated value of bond angles and dihedral angles for benzene molecule are 120° and 180° respectively. For aniline molecule, the C-N and N-H bond lengths are found 1.378 Å and 1.003 Å respectively at DFT (B3LYP) calculation, which agrees with the experimental value of C-N and N-H bond lengths with values of 1.475 Å and 1.008 Å within 7% respectively. For the benzene molecule, there is a symmetrical charge distribution. The total dipole moment of the benzene molecule is zero, indicating that the centers of positive and negative charge coincide with each other such that the benzene molecule is non-polar whereas aniline is a polar molecule with a dipole moment of 1.9828 Debye

Synthesis, Crystal Structure and Spectroscopic Study of (E)-2-methoxy-4-((1-phenylethylimino)methyl)phenol

A new unsymmetrical ligand (E)-2-methoxy-4-((1-phenylethylimino)methyl)phenol C16N17NO2 (I), was synthetized by one-step condensation reaction. The structure of this new compound was confirmed by elemental analysis, FT-IR, UV-Visible and 1H and 13C NMR spectroscopy techniques. The compound (I) crystallizes in the orthorhombic space group P212121 with the following unit cell parameters a = 11.7570 (6) Å, b = 10.0711 (6) Å, c = 23.4478(13) Å, V = 2776.4(3) Å3, Z = 4, R1 = 0.045 and wR2 = 0.125. The title compound crystallizes with two enanti­omers (A and B) in the asymmetric unit which are both in E-stereoisomers. In the crystal structure of the racemic compound, the most noticeable difference between these two mol­ecules is the dihedral angle values between the phenyl rings: 61.61 (1)° and 60.96(1)°.

Synthesis and Characterization of Co(II), Ni(II), Cu(II) and Zn(II) Complexes with N'-( phenyl ( pyridin-2-yl)methylene)Nicotinohydrazide

The Schiff base (HL), derived from 2-benzoylpyridine and nicotinic hydrazide, and its complexes with some metal transition (Co, Ni, Cu, Zn) have been synthesized. These compounds have been characterized by means of elemental analysis, 1H and 13C NMR (for HL), FTIR spectroscopy, UV–Vis spectroscopy, molar conductance and room temperature magnetic measurements. The compounds are found isostructural and are formulated as {[Co(L)2].2H2O} (1), {[Ni(L)2].2H2O} (2). {[Cu(L)2].3H2O} (3). {[Zn(L)2].H2O} (4). The two ligand molecules act in their monodeprotonated forms through one azomethine nitrogen atom, one pyridine nitrogen atom and one iminolate oxygen atom yielding six coordinate metal center. The complex 4 crystallizes in the monoclinic space group P21 with cell parameters of a = 9.3429(8) A, b = 10.3034(9) A, c = 16.6349(14) A, β = 101.109(4)°, V = 1571.3(2) A3, Z = 2, R1 = 0.027, wR2 = 0.074. The zinc atom is six-coordinated, and the coordination polyhedron is best described as a distorted octahedral geometry. The aromatic rings of the ligand molecules are twisted each other with dihedral angle values in the range 10.168(2)°–74.430(1)°.

Chiral and Achiral Crystal Structures of Au25 (PET)18 0 Reveal Effects of Ligand Rotational Isomerization on Optoelectronic Properties.

The crystal structures of 4 ligand-rotational isomers of Au25 (PET)18 are presented. Two new ligand-rotational isomers are revealed, and two higher-quality structures (allowing complete solution of the ligand shell) of previously solved Au25 (PET)18 clusters are also presented. One of the structures lacks an inversion center, making it the first chiral Au25 (SR)18 structure solved. These structures combined with previously published Au25 (SR)18 structures enable an analysis of the empirical ligand conformation landscape for Au25 (SR)18 clusters. This analysis shows that the dihedral angles within the PET ligand are restricted to certain observable values, and also that the dihedral angle values are interdependent, in a manner reminiscent of biomolecule dihedral angles such as those in proteins and DNA. The influence of ligand conformational isomerism on optical and electronic properties was calculated, revealing that the ligand conformations affect the nanocluster absorption spectrum, which potentially provides a way to distinguish between isomers at low temperature.

Insights into synthesis, structural, energetic, vibrational, anticancer activity and molecular characteristics of 2-((2-aminopyridin-3-yl)methylene)-N-phenylhydrazinecarbothioamide as evaluated using spectroscopic and DFT investigations

Synthesis of 2-((2-aminopyridin-3-yl)methylene)-N-phenylhydrazinecarbothioamide (APHB) was attempted. Elemental analysis and NMR spectra were used to ascertain its formation. Torsional potential energy scans, for all the rotating bonds were made to get approximate initial values of dihedral angles. FT-IR, FT Raman, and UV–Vis spectra were measured for APHB. Their anticancer activity was determined experimentally, for human carcinoma cell lines pertaining to liver, Colorectal, and lung. Barrier heights, around six rotating bonds in APHB were computed. Optimized structure parameters, general valence force field, harmonic vibrational fundamentals, potential energy distribution, infrared and Raman intensities, frontier molecular orbital (FMO) parameters, NLO behaviour, NBO characteristics and molecular electrostatic surface potential (MESP) were determined using DFT/B3LYP/6-311++G(d,p) level of theory. TD-DFT was used to compute absorption maxima (λmax) of electronic transitions for the molecule in DMSO‑d6 solvent. Frontier molecular orbitals were used to understand origin of UV–Vis spectrum and chemical reactivity of the molecule. Good agreement was found between measured and computed structure parameters, IR, Raman and UV–Vis spectra. The rms error between experimental and theoretical vibrational frequencies was 9.5 cm−1, for APHB. All vibrational fundamentals were assigned unambiguously. The computations demonstrated that the molecule was good for NLO applications, which was substantiated by NBO analysis. Existence of bifurcated intramolecular hydrogen bond was predicted for APHB.

Unexplored Isomerization Pathways of Azobis(benzo-15-crown-5): Computational Studies on a Butterfly Crown Ether.

Computational studies on trans → cis and cis → trans isomerizations of photoresponsive azobis(benzo-15-crown-5) have been reported in this work. The photoexcited ππ* state (S2) of the trans isomer relaxes through the planar S2 minimum and the planar S2/S1 conical intersection (both situated around 9 kcal/mol below the vertically excited S2 state) arising along the N═N stretching coordinate. The nπ* state (S1) of this isomer has both planar and rotated (clockwise and anticlockwise) minima, which may lead to a torsional conical intersection (S0/S1) geometry having a <CNNC dihedral angle value close to 90°. This rotational isomerization path is found to have an energy barrier. It has been noticed that an N-N-out-of-plane motion coupled with the torsion can bring down the barrier and may facilitate the isomerization process. On the other hand, the vertically excited S1 state of the cis-isomer undergoes a barrierless path to reach a torsional conical intersection (S0/S1) geometry (<CNNC = 88°), responsible for the trans-isomer formation. The cis-S2/S1 CI (conical intersection) torsional geometry (<CNNC = 45°) is situated around 16 kcal/mol above the vertically excited ππ* state of the cis-isomer and not reachable on S2 photoexcitation. The two optimized torsional S2 minima of this system are close to the S1 surface and seem to be involved in the S2-S1 internal conversion. A less efficient concerted inversion photoisomerization path through a linear geometry has also been identified. The thermal cis → trans isomerization has been found to undergo an inversion motion, which forms a less stable trans isomer. Possible differences between the isomerization channels of this azobis(benzo-15-crown-5) and the unsubstituted azobenzene system have also been highlighted in the work.

Syntheses, Characterization and X-ray Crystal Structure of Trinuclear NiII—NaI—NiII Assembled with Salen-type Schiff Base

The present investigation describes the synthesis and structural study of a metal-zinc ligand [NiL].H2O, which was used to generate a trinuclear complex formulated as {Ni(m-L)Na(m-L)Ni}.(SCN)0.6.(Cl)0.4. The title compound crystallizes in the tetragonal space group I41/acd with the following unit cell parameters: a = 185403(5) Å, c = 51.925(2) Å, V = 17849.0(3) Å3, Z = 16, R1 = 0.074 and wR2 = 0.209. Each organic molecule acts as a hexadentate ligand and bridges Ni(II) and Na(I). For both Ni(II) cations the coordination environment around the metal center can be described as distorted square planar. The Na(I) cation is eight coordinated and the polyhedron around the sodium ions is best described as a distorted square anti-prism. The means planes of the two phenyl rings with a methoxy substituent form a dihedral angle of 3.870(4)°, while the dihedral angle values of these mean planes with the means plane of the central phenyl ring are, respectively, 11.233(4)° and 14.138(3)°. The Zn–Na distance is 3.4285(7) Å. Weak hydrogen bonds involving C—H as donor and Cl, S or O as acceptor are observed.

Conformational Search for the Building Block of Proteins Based on the Gradient Gravitational Search Algorithm (ConfGGS) Using Force Fields: CHARMM, AMBER, and OPLS-AA.

Proteins are linear polymers built from a repertoire of 20 different amino acids, which are considered building blocks of proteins. The diversity and versatility of these 20 building blocks with regard to their conformations are key to adopting three-dimensional structures that facilitate proteins to undergo important mechanistic biological processes in living systems. The present investigation reports a conformational search of 20 different amino acids, building blocks of proteins, using three different force fields, CHARMM, AMBER, and OPLS-AA, implemented in the gradient gravitational search algorithm. The search technique (ConfGGS) includes the contribution from both bonded and nonbonded terms using Cartesian coordinates. The efficiency of such conformational searches has also been compared with other optimization algorithms: DE/Best, DE/Rand, and PSO algorithms with respect to computational time and accuracy based on the minimum number of iteration steps and computed lowest mean absolute error (MAE) and mean standard deviation (MSD) values for dihedral angles of respective near-optimal structures. Moreover, the ConfGGS technique has also been extended to an ordered protein fragment (PQITL) extracted from HIV-1 protease (PDB ID: 1YTH), an intrinsically disordered protein fragment, i.e., an amyloid-forming segment (AVVTGVTAV), from the NAC domain of Parkinson's disease protein α-synuclein, residues 69-77 (PDB ID: 4RIK), the experimental NMR atomic-resolution structure of α-synuclein fibrils (PDB ID: 2N0A), and a disulfide bond-containing protein fragment sequence (PCYGWPVCY), residues 59-67 (PDB ID: 6Y4F) toward structure prediction as a close homologue compared with experimental accuracy, using the CHARMM force field. The MolProbity validation results for the protein fragment (PQITL) obtained by ConfGGS/CHARMM are in better agreement with the native protein fragment structure of HIV-1 protease (PDB ID: 1YTH). Furthermore, the computed results have also been compared with the coordinates obtained from the AlphaFold network.

PREDICTION OF DIPROPYL SULFONE PROPERTIES BY DENSITY FUNCTIONAL THEORY METHODS: CONFORMATIONAL ANALYSIS AND SIMULATED IR SPECTRUM

In this work, the conformational and vibrational analysis of dipropyl sulfone in its isolated gaseous state with identification of all stable conformers, their energy and degeneracy, relative population determined by Boltzmann distribution, as well as IR spectra have been performed by density functional theory (DFT) methods. Several DFT methods and basis sets were tested. It was demonstrated that the various local and hybrid DFT functionals such as well-known B3LYP, regardless of the size of basis sets, completely fail in the prediction of correct molecular structures, let alone the IR spectra. It was found that only long-range corrected hybrid density functionals, combined with decently sized basis sets are capable to predict correct values of dihedral angles between non-bonded atomic groups: the most important coordinates in conformational analysis. Thus, wB97XD/6-311++G(2df,2pd) method/basis set combination appears to be the best method for the titled system both in terms of geometry and IR spectra prediction. A detailed analysis of the potential energy surface revealed the existence of 28 distinct conformers with various populations at 298 K, which have significant impact in the simulated IR spectra. The linear scaling equation (LSE) fitting methodology was successfully adopted for the calibration of wavenumbers and achievement of the best match between theoretical and experimental absorption regions of functional groups in sulfones. Moreover, in the construction of the simulated IR spectra, the Lorentzian broadening of each calculated mode with different full widths at half maximum was considered to obtain extinction coefficients, thus more realistic ε(ν) dependency, that is directly comparable with experimental spectra. The authenticity of the results obtained have been verified by comparison with existing experimental literature data on sulfones.

Synthesis of 5- and 7-hydroxy indolizidin-2-one prostaglandin-F2α modulators and activity on myometrial contractility towards development of agents for delaying preterm birth.

In pursuit of more effective-labor delaying tocolytic agents, the prostaglandin F2α (PGF2α) receptor (FP) modulator PDC113.824 [(6S)-2] represents a potent lead for developing therapy to treat preterm birth. Derivatives of FP modulator (6S)-2 were synthesized, possessing respectively 5- and 7-hydroxyl groups on the indolizidin-2-one amino acid (I2 aa) residue. The effects of the alcohol substituents were examined in a PGF2α-induced myometrial contraction assay. Based on knowledge of dihedral angle values of model I2 aa peptides from X-ray analyses, the results of the study indicate respectively encouraging and limited potential for creating improved tocolytic agents by modifications at the 5- and 7-positions.

Conformational ensemble of amyloid-forming semenogelin 1 peptide SEM1(68–107) by NMR spectroscopy and MD simulations

SEM1(68–107) is a peptide corresponding to the region of semenogelin 1 protein from 68 to 107 amino acid position. SEM1(68–107) is an abundant component of semen, which participates in HIV infection enhanced by amyloid fibrils forming. To understand the causes influencing amyloid fibril formation, it is necessary to determine the spatial structure of SEM1(68–107). It was shown that the determination of SEM1(68–107) structure is complicated by the non-informative NMR spectra due to the high intramolecular mobility of peptides. The complementary approach based on the geometric restrictions of individual peptide fragments and molecular modeling was used for the determination of the spatial structure of SEM1(68–107). The N- (SEM1(68–85)) and C-terminuses (SEM1(86–107)) of SEM1(68–107) were chosen as two individual peptide fragments. SEM1(68–85) and SEM1(86–107) structures were established with NMR and circular dichroism CD spectroscopies. These regions were used as geometric restraints for the SEM1(68–107) structure modeling. Even though most of the SEM1(68–107) peptide is unstructured, our detailed analysis revealed the following structured elements: N-terminus (70His-84Gln) forms an α-helix, (86Asp-94Thr) and (101Gly-103Ser) regions fold into 310-helixes. The absence of a SEM1(68–107) rigid conformation leads to instability of these secondary structure regions. The calculated SEM1(68–107) structure is in good agreement with experimental values of hydrodynamic radius and dihedral angles obtained by NMR spectroscopy. This testifies the adequacy of a combined approach based on the use of peptide fragment structures for the molecular modeling formation of full-size peptide spatial structure.

DFT simulation of barrier heights, infrared and Raman spectra, and investigation of vibrational characteristics of 2-((2-aminopyridin-3-yl) methylene) hydrazinecarbothioamide and its N-methyl variant

ABSTRACT Fourier transform infrared spectra, for 2-((2-aminopyridin-3-yl) methylene) hydrazinecarbothioamide (APHT) and 2((2-aminopyridin-3-yl) methylene)-N-methylhydrazinecarbothioamide (APMHT), were recorded in the spectral range 4000–400 cm−1. Their Raman counterparts were measured in the spectral region 4000–50 cm−1. Preliminary values of dihedral angles around five rotating bonds C–NH2 pyridyl C–CN, N–N, N–CS and C–NH2 aliphatic in APHT, required for initiating geometry optimization, were obtained by pairing successive bonds and evaluating torsional potential energy for various values of dihedral angle around these bonds in the entire conformational space spanning 0° to 360°. Barrier heights, around five rotating bonds in APHT and six rotating bonds in APMHT were computed, making torsional scans in conformational space from 0° to 360°. This indicated existence of two rotational isomers for APMHT. General valence force field, harmonic vibrational fundamentals, potential energy distribution (PED), along with infrared and Raman intensities were determined using DFT/B3LYP/6-311++G(d,p) level of theory for both the molecules. Good agreement was found between measured and simulated spectra, for APHT and APMHT. This was also true for corresponding Raman spectra. The rms error between experimental and theoretical vibrational frequencies was 9.00 and 6.70 cm−1, for APHT and APMHT, respectively. All vibrational fundamentals were assigned unambiguously, on the basis of computed PED, eigenvectors, and literature range for the first time. These assignments were further supported by comparing with attribution of corresponding bonds in the parent molecule pyridine and a related molecule 2-((2-aminopyridin-3-yl)methylene)-N-ethylhydrazinecarbothioamide, wherever possible.

Synthesis, structural, spectroscopic, intermolecular interactions, kinetic stability, charge transfer method with DNA bases and electronic properties of (E)-3-(2-ethoxyphenyl)-5-(3-(2-methoxyphenyl)-4methylthiazol-2(3H)-ylidene)-2-thioxothiazolidin-4-one: Computational and experimental approach

In the current paper, the new molecule (E)-3-(2-Ethoxyphenyl) -5-(3-(2methoxyphenyl) -4 methylthiazol-2(3H) -ylidene) -2-thioxothiazolidin-4-one (EMTh2) was synthesized and characterized using FT-IR, UV-vis, NMR, and X-ray diffraction experimental techniques. The experimental structure was determined from single-crystal X-ray diffraction data at low temperature (173 K). The compound crystallizes in the monoclinic system and space group P21/c with cell parameters: a=11.1100(5) Å, b=13.0597(6) Å, c=15.2343(7) Å, β=103.480(5)°, Z=4. R= 0.0512 was the final value for 4372 observed reflections. The two thiazol rings are coplanar, while the ethoxyphenyl and methoxy phenyl rings are essentially perpendicular to these rings with dihedral angle values of 107.2° for C4-N2-C8-C13 and 101.7° for C3-1-C15-C20. All theoretical calculations are performed using DFT with B3LYP functional and 6-31G(d,p) basis set. Both theoretical and experimental molecular structures were investigated and compared to one another. Furthermore, Hirshfeld surface analysis was performed to display surface contours and 2D-fingerprint plots were used to obtain contributions of the most important intermolecular interactions. The theoretical UV-vis spectrum was computed in chloroform as a solvent using the TD-DFT method. 1H and 13C-NMR chemical shifts were calculated using the GIAO approximation and the results were compared to the experimental ones. In addition, natural bond orbital (NBO), global reactivity parameters, MPA and NPA atomic charges, molecular electrostatic potential, Fukui functions were estimated using the same level of theory. The interactions between the investigated molecule and DNA bases (mainly adenine, cytosine, guanine, and thymine) were explored using the electrophilicity-based charge transfer method.

Theoretical investigation of fused N-methyl-dithieno-pyrrole derivatives in the context of acceptor-donor-acceptor approach.

In this work we have theoretically investigated the optoelectronic properties of a series of acceptor–donor–acceptor type molecules by employing density functional theory formalism. We have used 1,1-dicyano-methylene-3-indanone as the acceptor unit and a fused N-methyl-dithieno-pyrrole as the donor unit. We have calculated the values of dihedral angle, inter-ring bond length, bond length alteration parameters, HOMO–LUMO gap, ionization potential, electron affinity, partial density of states, reorganization energies for holes and electrons, charge transfer rate for holes and electrons of the seven types of compounds designed via molecular engineering. Calculated IP and EA values manifest that PBDB-C2 shows excellent charge transportation compared to others. Absorption spectra of the designed compounds have been studied using the time-dependent density functional theory method. From the calculation of reorganization energy it is confirmed that our designed molecules behave more likely as donor materials. Our calculated results also reveal that compounds with electron donating substituents at the acceptor units show higher value of λmax. Absorption spectra of donor/acceptor blends show similar trends with the isolated compounds. Observed lower exciton binding energy values for all the compounds indicate facile charge carrier separation at the donor/acceptor interface. Moreover, the negative values of Gibb's free energy change also indicate the ease of exciton dissociation of all the designed compounds. The photovoltaic characteristics of the studied compounds infer that all the designed compounds have the potential to become suitable candidate for the fabrication of organic semiconductors. However, PBDB-C2 and PBDB-C4 with the highest PCE of 18.25% can become the best candidate for application in photovoltaics.

Conformational Properties of Glycosaminoglycan Disaccharides: A Molecular Dynamics Study.

The structure and conformation of glycosaminoglycans (GAGs) are of central importance to understand the mechanisms behind their functions in biological systems. Due to the inherent chemical and structural heterogeneity of GAGs, focusing on longer, naturally existing GAG chains hinders drawing conclusions on the influence of the chemical functionalization on the basic conformational degree of freedom, that is, the dynamic shape of glycosidic linkage present in the particular disaccharide repeating unit. In the present study, we have considered the complete set of 106 GAG-related disaccharides, being potential building blocks for longer GAG chains (including hyaluronan, chondroitin, keratan, dermatan, and heparan). Both the unfunctionalized units and all possible combinations of either partially or fully sulfated derivatives contribute to this number. The unbiased and enhanced sampling molecular dynamics simulations provide a link to understand the influence of sulfation on the conformational properties of GAG glycosidic linkages. Residue-residue hydrogen bonding is not significant for either the glycosidic linkage conformation or its flexibility. It was found that in the majority of cases, the dominating conformation of the linkage is weakly affected by sulfation and the main role is played by the steric and stereoelectronic effects. However, there exist numerous cases where sulfation increases the contribution of alternative conformations to a nonnegligible extent and, in some rare cases (restricted to disaccharides building heparan), leads to the reorientation of the glycosidic linkage. The identified sulfation sites, being the most important in this context, are C6 and C3 at the GlcNAc residue. Finally, the full set of free energy maps relying on the glycosidic dihedral angle values for diverse GAG disaccharides are provided; they may be used for further studies, focused on longer GAG chains.

Palladium-Catalyzed Direct C2-Biarylation of Indoles.

Biaryl and indole units are important structural motifs in several bioactive molecules and functional materials. We have accomplished straightforward access to C2-biarylated indole derivatives through palladium-catalyzed C-H activation strategy with a broad range of substrate scope in yields of 24 to 92%. Besides, the UV/visible absorption and fluorescence properties of the ensuing products were explored. The calculated higher dihedral angle and rotational barrier values for the selected C2-biarylated indoles show that these compounds may display atropisomerism at room temperature.

Twisted intramolecular motion arrested in aggregated state emission and the nonlinear optical properties of pyrene pyrazoline derivatives

Heterocyclic pyrene pyrazoline moieties containing similar structures but with differences in thiophene (PPT), furan (PPF) and pyridine (PPP) substitutions at the terminal molecules were synthesized. Their aggregation behaviour in THF-water mixtures was investigated and results demonstrated that PPT and PPP exhibited aggregation-induced emission (AIE), whereas PPF exhibited aggregation-induced blue-shifted emission (AIBSE). PPT and PPP provided red-shifted emission, while PPF had observed blue-shifted emission at high water fractions of 70-90%, confirming that aggregation effects played a major role in the molecular structure. Two emission peaks from locally excited and twisted intramolecular charge transfer confirmed the twisted nature from the dihedral angle values of the free reorganized molecules that were completely restricted in high water fractions due to molecular aggregation. This was further confirmed from colour Commission Internationale de l'Eclairage values as well as dynamic light scattering analysis. Third-order nonlinear optical properties were studied using a Nd:Yag laser beam Z-scan technique at 532 nm. The open aperture Z-scan revealed that PPT and PPF towards the peak point endured strong saturable absorption, whereas PPP indicated a strong reverse saturable absorption process. The AIE and AIBSE mechanisms from undergoing restricted twisting intramolecular motion in the aggregated luminogens provide great insight into new developments in AIEgen materials for these optoelectronic materials.

Spatial Structure of the Acth-(6-9)-PGP Molecule

The spatial structure of ACTH-(6-9)-PGP molecule has been investigated using theoretical conformational analysis method. Amino acid sequence of the N-terminal pentapeptide fragment of His-Phe-Arg-Trp-Pro of this molecule conforms to the fragment 6-9 of ACTH hormone. Calculations of conformational states of this molecule are carried out regarding nonvalent, electrostatic and torsional interactions and the energy of hydrogen bonds. The spatial structure of the His-Phe-Arg-Trp-Pro-Gly-Pro molecule was estimated on the low–energy conformations of the N-terminal tetrapeptide fragment His-Phe-Arg-Trp and C-terminal tripeptide fragment Pro-Gly-Pro of this molecule. It is shown that the spatial structure of heptapeptide molecule can be presented by 11 low-energy forms of the main chain. The low–energy conformations of this molecule, the values of dihedral angles of the backbone and side chains of the amino acid residues were founded and the energies of intra- and inter-residual interactions were determined.

Spatial Structure of the Acth-(6-9)-PGP Molecule

The spatial structure of ACTH-(6-9)-PGP molecule has been investigated using theoretical conformational analysis method. Amino acid sequence of the N-terminal pentapeptide fragment of His-Phe-Arg-Trp-Pro of this molecule conforms to the fragment 6-9 of ACTH hormone. Calculations of conformational states of this molecule are carried out regarding nonvalent, electrostatic and torsional interactions and the energy of hydrogen bonds. The spatial structure of the His-Phe-Arg-Trp-Pro-Gly-Pro molecule was estimated on the low–energy conformations of the N-terminal tetrapeptide fragment His-Phe-Arg-Trp and C-terminal tripeptide fragment Pro-Gly-Pro of this molecule. It is shown that the spatial structure of heptapeptide molecule can be presented by 11 low-energy forms of the main chain. The low–energy conformations of this molecule, the values of dihedral angles of the backbone and side chains of the amino acid residues were founded and the energies of intra- and inter-residual interactions were determined.