Determination of the Mental Adjustment Status of Refugee Children in Primary School Age: The Case of Turkey

INTRODUCTION

This research was conducted as a descriptive study to determine the mental adjustment status of refugee children aged 6 to 14 in Duzce.

METHOD

The sample of the study consisted of 163 refugee children. Data were collected through face-to-face interviews with primary caregivers of children using the Hacettepe Mental Adjustment Scale. The collected data were analyzed in the SPSS 22.0 database using percentages, Mann Whitney U, Kruskal-Wallis H, and chi-square tests.

RESULTS

Adjustment problems were detected in 25.8% of the children participating and behavioral problems were detected in over half (52.4%).

DISCUSSION

In line with the findings obtained from the research, it has been suggested to form a team of mental health experts, including psychiatric nurses, who have adopted the principles of transcultural care to make early diagnosis and effective treatment of psychiatric diseases of refugee children.

Content analysis of suicide prevention web pages from perspective of preventive psychiatric approaches

Suicide is a serious public health problem; however, suicides are preventable with evidence-based and often low-cost interventions. This study analyzes the online content of suicide prevention and helps websites in the context of preventive psychiatry. The universe and sample of the research consisted of 147 web pages whose links can be found on the most widely used international social media platforms and websites dedicated to suicide prevention. To conduct the content analysis, the crisis hotline guide prepared by the World Health Organization for suicide prevention and the guide prepared for media professionals were used in the data collection form created by the researchers. The majority of the websites were of European origin and were prepared by mental health and suicide prevention associations for suicide prevention and crisis intervention. Telephone helplines were the most common means of communicating with consultants via the web page. On the basis of the research findings, suggestions were generated regarding the scope, content, and sustainability of web pages for crisis intervention and suicide prevention prepared at the national and international levels.

Salmon calcitonin and amyloid beta: two peptides with amyloidogenic capacity adopt different conformational manifolds in their unfolded states

The molecular conformations of salmon calcitonin in aqueous solution have been investigated by exploiting the different influences of excitonic coupling on the amide I band profile in the isotropic and anisotropic Raman, FTIR, and vibrational circular dichroism spectra of a polypeptide. The N-terminal loop, caused by a disulfide bridge between cysteines at positions 1 and 7, was modeled by performing a conformational search by molecular mechanics calculations. The remaining part of the peptide chain was modeled as a mixture of three sequences containing different fractions of residues adopting poly-l-proline II (PPII), extended beta-strand, and alpha-helix-like conformations. This yielded an excellent reproduction of the experimentally observed amide I' band profiles. A comparison with recent data on the beta-amyloid fragment Abeta(1)(-)(28) revealed a lower PPII content and more conformational heterogeneity for calcitonin. Thus, our results underscore the notion that individual structural propensities of amino acid residues give rise to structural differences between the unfolded states of even long peptide chains, at variance with expectations based on a random or statistical coil model.

Conformational Analysis of XA and AX Dipeptides in Water by Electronic Circular Dichroism and 1H NMR Spectroscopy

We measured the temperature-dependent electronic circular dichroism (ECD) spectra of AX, XA, and XG dipeptides in D2O. The spectra of all XA and AX peptides indicate a substantial population of the polyproline II (PPII) conformation, while the ECD spectra of LG, KG, PG, and AG were found to be quantitatively different from the alanine-based dipeptides. Additional UV absorption data indicate that the ECD spectra of the XG peptides stem from electronic coupling between the peptide and the C-terminal group, and that spectral differences reflect different orientations of the latter. We also measured the 1H NMR spectra of the investigated dipeptides to determine the 3JHalphaNH coupling constants for the C-terminal residue. The observed temperature dependence of the ECD spectra and the respective room-temperature 3JHalphaNH coupling constants were analyzed by a two-state model encompassing PPII and a beta-like conformation. The PPII propensity of alanine in the XA series is only slightly modulated by the N-terminal side chain, and is larger than 50%. As compared to AA, XA peptides containing L, P, S, K V, E, T, and I all cause a relative stabilization of the extended beta-strand conformation. The PPII fractions of XA peptides varied between 0.64 for AA and 0.58 for DA, whereas the PPII fractions of AX peptides were much lower. From the investigated AX peptides, only AL and AQ showed the expected PPII propensity. We found that AT, AI, and AV clearly prefer an extended beta-strand conformation. A quantitative comparison of AA, AAA, and AAAA revealed a hierarchy AAAA > AAA approximately AA for the PPII population, in agreement with predictions from MD calculations and results from Raman optical activity studies (McColl et al. J. Am. Chem. Soc. 2004, 126, 5076).

Side Chain Dependence of Intensity and Wavenumber Position of Amide I‘ in IR and Visible Raman Spectra of XA and AX Dipeptides

A series of AX and XA dipeptides in D2O have been investigated by FTIR, isotropic, and anisotropic Raman spectroscopy at acidic, neutral, and alkaline pD, to probe the influence of amino acid side chains on the amide I' band. We obtained a set of spectral parameters for each peptide, including intensities, wavenumbers, half-widths, and dipole moments, and found that these amide I' parameters are indeed dependent on the side chain. Side chains with similar characteristic properties were found to have similar effects on the amide I'. For example, dipeptides with aliphatic side chains were found to exhibit a downshift of the amide I' wavenumber, while those containing polar side chains experienced an increase in wavenumber. The N-terminal charge causes a substantial upshift of amide I', whereas the C-terminal charge causes a moderate decrease of the transition dipole moment. Density functional theory (DFT) calculations on the investigated dipeptides in vacuo yielded different correlations between theoretically and experimentally obtained wavenumbers for aliphatic/aromatic and polar/charged side chains, respectively. This might be indicative of a role of the hydration shell in transferring side chain-backbone interactions. For Raman bands, we found a correlation between amide I' depolarization ratio and wavenumber which reflects that some side chains (valine, histidine) have a significant influence on the Raman tensor. Altogether, the obtained data are of utmost importance for utilizing amide I as a tool for secondary structure analysis of polypeptides and proteins and providing an experimental basis for theoretical modeling of this important backbone mode. This is demonstrated by a rather accurate modeling for the amide I' band profiles of the IR, isotropic Raman, and anisotropic Raman spectra of the beta-amyloid fragment Abeta(1-82).

Abeta(1-28) fragment of the amyloid peptide predominantly adopts a polyproline II conformation in an acidic solution

To structurally characterize the nonaggregated state of the amyloid beta peptide, which assembles into the hallmark fibrils of Alzheimer disease, we investigated the conformation of the N-terminal extracellular peptide fragment Abeta(1-28) in D(2)O at acidic pD by utilizing combined FTIR and isotropic and anisotropic Raman spectra measured between 1550 and 1750 cm(-1). Peptide aggregation is avoided under the conditions chosen. The amide I' band was found to exhibit a significant noncoincidence effect in that the first moment of the anisotropic Raman and of the IR band profile appears red-shifted from that of the isotropic Raman scattering. A simulation based on a coupled oscillator model involving all 27 amide I' modes of the peptide reveals that the peptide adopts a predominantly polyproline II conformation. Our results are inconsistent with the notion that the monomeric form of Abeta(1-28) is a totally disordered, random-coil structure. Generally, they underscore the notion that polyproline II is a characteristic motif of the unfolded state of proteins and peptides.

Preferred peptide backbone conformations in the unfolded state revealed by the structure analysis of alanine-based (AXA) tripeptides in aqueous solution

We have combined Fourier transform IR, polarized Raman spectroscopy, and vibrational CD measurements of the amide I' band profile of alanyl-X-alanine tripeptides in (2)H(2)O to obtain the dihedral angles of their central amino acid residue. X represents glycine, valine, methionine, histidine, serine, proline, lysine, leucine, tryptophan, tyrosine, and phenylalanine. The experimental data were analyzed by means of a recently developed algorithm, which exploits the excitonic coupling between the amide modes of the two peptide groups. The results were checked by measuring the respective electronic CD spectra. The investigated peptides can be sorted into three classes. Valine, phenylalanine, tryptophan, histidine, and serine predominantly adopt an extended beta-strand conformation. Cationic lysine and proline prefer a polyproline II-like structure. Alanine, methionine, glycine, and leucine populate these two conformations with comparable probability. Our results are in variance with the prediction of the random-coil model, but supportive of Flory's isolated-pair hypothesis. We combined the obtained structural propensities of the investigated residues and similar information about other residues in the literature (i.e., glutamate, aspartate, isoleucine, and glutamine) to predict possible conformations of the monomeric amyloid beta peptide A beta(1-42) in aqueous solution, which reproduces results from most recent spectroscopic studies. Thus, it is demonstrated that the unfolded state of peptides can be understood in terms of the intrinsic structural propensities of their amino acid residues.

The conformation of tetraalanine in water determined by polarized Raman, FT-IR, and VCD spectroscopy

The present article reports the conformation of cationic tetraalanine in aqueous solution. The determination of the dihedral angles of the two central amino acid residues was achieved by analyzing the amide I' band profile in the respective polarized visible Raman, Fourier transform-IR, and vibrational circular dichroism (VCD) spectra by means of a novel algorithm which utilizes the excitonic coupling between the amide I modes of nearest neighbor and second nearest peptide groups. It is an extension of a recently developed theory (Schweitzer-Stenner, R. Biophys. J., 2002, 83, 523-532). UV electronic circular dichroism (ECD) spectra of the peptides were used to validate the results of the structure analysis. The analyses yielded the dihedral angles (phi(12), psi(12)) = (-70 degrees, 155 degrees ) and (phi(23), psi(23)) = (-80 degrees, 145 degrees ). The obtained values are very close to the Ramachandran coordinates of the polyproline II helix (PPII). The data suggest that this is the conformation predominantly adopted by the peptide at room temperature. This notion was corroborated by the corresponding electronic circular dichroism spectrum. Tetraalanine exhibits a higher propensity for PPII than trialanine for which a 50:50 mixture of polyproline II and an extended beta-strand-like conformation was obtained from recent spectroscopic studies (Eker et al., J. Am. Chem. Soc. 2002, 124, 14330-14341). The temperature dependence of the CD spectra rule out that any cooperativity is involved in the strand if PPII transition. This led to the conclusion that solvent-peptide interactions give rise to the observed PPII stability. Our result can be utilized to understand why the denaturation of helix-forming peptides generally yields a PPII rather than a heterogeneous random conformation.

The structure of tri-proline in water probed by polarized Raman, Fourier transform infrared, vibrational circular dichroism, and electric ultraviolet circular dichroism spectroscopy

Tripeptidesserve as model systems for understanding the so-called random-coil state of peptides and proteins. While it is well known that polyproline or proline-rich polypeptides adopt the very regular polyproline-II (PPII) or left-handed 3(1)-helix conformation, it was thus far not clear whether this is also the predominant structure adopted by proline-containing tripeptides. To clarify this issue, we have investigated the amide I' band profile in the ir, isotropic, and anisotropic Raman, and vibrational circular dichroism (VCD) spectrum of cationic and zwitterionic tri-proline in D(2)O. The data were analyzed by modifying a recently developed algorithm, which allows one to obtain the central dihedral angles of tripeptides from the amide I' band intensities (R. Schweitzer-Stenner, Biophysical Journal, 2002, Vol. 83, pp. 523-532). Our analysis revealed that the peptide adopts a nearly canonical PPII structure in water with psi and phi values in the range of 175 degrees -165 degrees and -70 degrees -(-80 degrees ), respectively. This is fully confirmed by the respective electronic ultraviolet-CD spectra. Our result indicates that the strong PPII propensity of trans proline results from local interactions between the pyrrolidine ring and the backbone and is not due to any long-range interactions.

Tripeptides with Ionizable Side Chains Adopt a Perturbed Polyproline II Structure in Water†

The present paper reports the conformations of the acidic and basic homotripeptides triglutamate, triaspartate, and trilysine in aqueous solution to better understand their relevance for the structure of disordered proteins and protein segments and for a variety of protein binding processes. The determination of the dihedral angles of the central amino acid residue was achieved by analyzing the amide I band profile of the respective polarized visible Raman, Fourier transform infrared (FT-IR), and vibrational circular dichroism (VCD) spectra by means of recently developed algorithms [Schweitzer-Stenner, R. (2002) Biophys. J. 83, 523-532; Eker et al. (2002) J. Am. Chem. Soc. 124, 523-532]. The results were validated by measuring the UV electronic circular dichroism (ECD) spectra of the peptides. The analyses revealed that a polyproline II-like conformation is predominant at room temperature. For triaspartate and triglutamate the dihedral angles of phi = -70 degrees, psi = 165 degrees and phi = -60 degrees, psi = 160 degrees were obtained, respectively. A similar conformation, i.e., phi = -50 degrees, psi = 170 degrees, was obtained for trilysine, which is at variance with the earlier reported left-handed turn structure. The ECD spectrum of charged tripeptides displayed symmetric negative and positive couplets at 190 and 210 nm, which are interpreted as indicating a somewhat, perturbed polyproline II conformation, in agreement with the obtained dihedral angles. Comparison with literature data shows that the investigated tripeptides are ideal model systems for understanding the local conformation of functionally relevant K3, K2X, E3, and D3 segments in a variety of different proteins.

Stable conformations of tripeptides in aqueous solution studied by UV circular dichroism spectroscopy

Determination of the precise solution structure of peptides is of utmost importance to the understanding of protein folding and peptide drugs. Herein, we have measured the UV circular dichroism (UVCD) spectra of tri-alanine dissolved in D(2)O, H(2)O, and glycerol. The results clearly show the coexistence of a polyproline II or 3(1)-helix and a somewhat disordered flat beta-strand conformation, in complete agreement with recent predictions from spectroscopic data (Eker et al. J. Am. Chem. Soc. 2002, 124, 14 330-14 341). A thermodynamic analysis revealed that enthalpic contributions of about 11 and 17 kJ/mol stabilize polyproline II in D(2)O and H(2)O, respectively, but at room temperature they are counterbalanced by entropic contributions, which clearly favor the more disordered beta-strand conformation. It is hypothesized that this delicate balance is the reason for the variety of structural propensities of amino acid residues in the absence of nonlocal interactions. The isotope effect yielding a higher occupation of polyproline II in H(2)O with respect to D(2)O strongly suggests that a hydrogen-bonding network involving the peptide and water molecules in the hydration shell plays a major role in stabilizing this conformation. The equilibrium between polyproline II and beta-strand is practically maintained in glycerol, which suggests that glycerol can substitute water as stabilizing solvent for the polyproline II conformation. We also measured the UVCD spectra of tri-valine and tri-lysine (both at acidic pD) in D(2)O and found them to adopt a flat beta-strand and left-handed turn structure, respectively, in accordance with recent analyses of vibrational spectroscopy data. Generally, the present study adds substantial evidence to the notion that the so-called random coil state of peptides is much more structured than generally assumed.

Tripeptides adopt stable structures in water. A combined polarized visible Raman, FTIR, and VCD spectroscopy study

We have measured the band profile of amide I in the infrared, isotropic, and anisotropic Raman spectra of L-alanyl-D-alanyl-L-alanine, acetyl-L-alanyl-L-alanine, L-vanyl-L-vanyl-L-valine, L-seryl-L-seryl-L-serine, and L-lysyl-L-lysyl-L-lysine at acid, neutral, and alkaline pD. The respective intensity ratios of the two amide I bands depend on the excitonic coupling between the amide I modes of the peptide group. These intensity ratios were obtained from a self-consistent spectral decomposition and then were used to determine the dihedral angles between the two peptide groups by means of a recently developed algorithm (Schweitzer-Stenner, R. Biophys. J. 2002, 83, 523-532). The validity of the obtained structures were checked by measuring and analyzing the vibrational circular dichroism of the two amide I bands. Thus, we found two solutions for all protonation states of trialanine. Assuming a single conformer, one obtains a very extended beta-helix-like structure. Alternatively, the data can be explained by the coexistence of a 3(1)(PII) and a beta-sheet-like structure. Acetyl-L-alanyl-L-alanine exhibits a structure which is very similar to that obtained for trialanine. The tripeptide with the central D-alanine adopts an extended structure with a negative psi and a positive phi angle. Trivaline and triserine adopt single beta(2)-like structures such as that identified in the energy landscape of the alanine dipeptide. Trilysine appears different from the other investigated homopeptides in that it adopts a left-handed helix which at acid pD is in part stabilized by hydrogen bonding between the protonated carboxylate (donor) and the N-terminal peptide carbonyl. Our result provides compelling evidence for the capability of short peptides to adopt stable structures in an aqueous solution, which at least to some extent reflect the intrinsic structural propensity of the respective amino acids in proteins. Furthermore, this paper convincingly demonstrates that the combination of different vibrational spectroscopies provides a powerful tool for the determination of the secondary structure of peptides in solution.

Dihedral angles of trialanine in D2O determined by combining FTIR and polarized visible Raman spectroscopy

We have measured the polarized visible Raman and FTIR spectra of trialanine and triglycine in D(2)O at acid, neutral, and alkaline pD. From the Raman spectra we obtained the isotropic and the anisotropic scattering. A self-consistent spectral analysis of the region between 1550 and 1800 cm(-1) was carried out to obtain the intensities, frequencies, and halfwidths of the respective amide I bands. A model was developed by means of which the intensity ratios of the amide I bands in all spectra and the respective frequency differences were utilized to determine the orientational angle theta between the peptide groups and the strength of excitonic coupling between the corresponding amide I modes. By exploiting results from a recent ab initio study on triglycine (Torii, H; Tasumi, M. J. Raman Spectrosc. 1998, 29, 81), we used these parameters to determine the dihedral angles phi and psi between the peptide groups. Our results show that trialanine adopts a 3(1)-helical structure in D(2)O for all of its three protonation states. The structure is insensitive to the carboxylate protonation and changes only slightly with N-terminal protonation. Triglycine is structurally more heterogeneous in the zwitterionic and the cationic state. Our spectral analysis suggests that 3(1)-helices coexist with right-handed alpha-helical and/or with beta-turn conformations. The N-terminal protonation stabilizes the 3(1)-structure. Our study provides compelling evidence that tripeptides adopt stable conformations in aqueous solution and that they are suitable model systems to investigate the initiation of secondary structure formation.