Evidence of C−H···O Hydrogen Bonds in Liquid 4-Ethoxybenzaldehyde by NMR and Vibrational Spectroscopies

Raman, FTIR, and NMR (both 13C and 17O) spectroscopies are used in a complementary way in order to study the occurrence of C−H···O intermolecular hydrogen bonds in liquid 4-ethoxybenzaldehyde (4EtOB). Additional information concerning the structure of the possible dimers is obtained through ab initio calculations, at the B3LYP/6-31G* level. The strongest evidences of the presence of C−H···O hydrogen bonds in the liquid phase arise from the temperature and solvent intensity dependence of the two bands observed in the νCO region of the vibrational spectra, as well as from the shift to low magnetic field detected for the carbonyl 17O NMR peak at higher dilutions. Further evidence is gathered from the changes observed in the νC-H vibrational modes, the 1JCH concentration dependence detected in the NMR spectra, and ab initio results. The experimental observations are consistent with the decrease of the C−H bond length upon hydrogen-bonding, as predicted for the nonstandard blue-shifting hydrogen bonds. Ab initio calculations predict several possible structures for the dimeric species, with nearly identical energies. The calculated dimerization energy is within the −5.1 to −6.5 kJ mol-1 range, considering both basis set superposition error and zero-point vibrational energy corrections, in agreement with the obtained experimental ΔH value of −5.7 ± 0.5 kJ mol-1

Surfaces mimicking glycosaminoglycans trigger different response of stem cells via distinct fibronectin adsorption and reorganization

We report on the utility of a platform created by self-assembled monolayers to investigate the influence of the degree of sulfation of glycosaminoglycans (GAGs) on their interactions with fibronectin (Fn) and the impact of these interactions on the adhesion and morphology of human adipose derived stem cells (ASCs). We used the label-free QCM-D, AFM and SPR to follow the changes in the protein adlayer in close proximity to the substrates surface and QCM-D in combination with live imaging to characterize the adherent cells. Our results suggest that Fn interactions with GAGs are governed by both H-bonding and electrostatic forces. Strong electrostatic interactions cause irreversible change in the protein conformation, while the weaker H-bonding only partially restricts the protein flexibility, allowing Fn reorganization and exposure of its binding sites for ASC adhesion. These findings imply that a delicate balance between these two types of forces must be considered in the design of biomaterials that mimic GAGs.We acknowledge EU for financial support (FP7/2007-2013, under Grants REGPOT-CT2012-316331-POLARIS and ERC- 2012-ADG-20120216-321266 for the project ComplexiTE). I.P. is thankful to the Portuguese Foundation for Science and Technology (IF/00032/2013). The authors are very grateful to Dr. Raquel Teixeira for her help with the treatment and discussion of the MP-SPR data

Structures and Vibrational Spectra of CH,OCH,CH,OH : The

Ab initio calculations at the MP2/6-31G* and MP2/6-31G*//6-31G* levels have been carried out for the monomer of 2-methoxyethanol (CH,OCH,CH,OH). The MP2/6-31G* results indicate that the two more stable conformers (tGg’ and gGg‘) display intramolecular hydrogen bonds directed from the hydroxy H atom to one of the lone pairs of the ether 0 atom, and that the tGg’ conformer is 6.3 kJ mol-’ more stable than the gGg’ conformer. As the MP2/6-31G* and MP2/6-3lG*//6-31G* calculations do not yield results differing by more than a few tenths of a kJ mol-‘, it is concluded that the structure-sensitive and the dynamic correlation corrections are far from being additive. While the optimization of geometry for the correlated wavefunction generally leads to increase of bond lengths and reduction of bond angles, on the whole the geometrical parameters undergo similar changes in different conformers. Ab initio harmonic 6-31G* derived force fields were used to perform normal mode analyses for the more stable conformers. The calculated v(CH) frequencies are found to correlate linearly with some of the ab initio calculated CH bond lengths. An interpretation of the FTIR and Raman spectra for the liquid phase consonant with the structural and vibrational ab initio results is presented. Two spectral features observed both in Raman and in FTIR spectra and associated with v(0H) in monomeric species are ascribed to conformers, in accord with the theoretical and experimental results. On the whole, both the structural and the vibrational results presented point to a distinction between the hydrogen-bonded G-type conformers (tGg’ and gGg‘) and the higher energy T-type conformers (tTg and tTt)

The impact of overnight orthokeratology on accommodative response in myopic subjects

This study aimed to evaluate the effects of two months of orthokeratology (OK) treatment in the accommodative response of young adult myopes. Twenty eyes (21.8 ± 1.8 years) were fitted with the Paragon CRT® 100 LENS to treat myopia between −1.00 and −2.00 D. Low- and high-contrast visual acuity (LCDVA and HCDVA), central objective refraction, light disturbance (LD), and objective accommodative response (using the Grand Seiko WAM-5500 open-field autorefractometer coupled with a Badal system) were measured at baseline (BL) before lens wear and after 1, 15, 30, and 60 nights of OK. Refractive error correction was achieved during the first fifty days of OK lens wear, with minimal changes afterwards. LD analysis showed a transient increase followed by a reduction to baseline levels over the first 30 nights of treatment. The accommodative response was lower than expected for all target vergences in all visits (BL: 0.61 D at 1.00 D to 0.96 D at 5.00 D; 60 N: 0.36 D at 1.00 D to 0.79 D at 5.00 D). On average, the accommodative lag decreases over time with OK lens wear. However, these differences were not statistically significant (p > 0.050, repeated-measures ANOVA and Friedman test). This shows that overnight OK treatment does not affect objectively measured the accommodative response of young, low myopic eyes after two months of treatment stabilization.This research was supported by the Portuguese Foundation for Science and Technology (FCT) PTDC/FIS-OPT/0677/2014, the Strategic Funding UID/FIS/04650/2013 at Center of Physics, UMinho, and predoctoral grant SFRH/BD/136684/2018 to A.A.S

Hydrogen-Bonded Dimers of CH3OCH2CH2OH: Ab Initio Structures and Multivariate Analysis

Structures and vibrational frequencies of relevant hydrogen-bonded dimers of 2-methoxyethanol are obtained at the 3-21G*//Ah41 level (the 3-21G* basis set included polarization functions deliberately added to second period atoms) and the results analyzed by standard multivariate methods. Dimers built from the same pair of isolated monomers belong to the same homologous series. The most stable dimer is obtained from the most stable conformations of both monomers, has a 10-membered intermolecular ring with a boat-chairboat conformation, and presents a zero dipole moment. In addition, the most stable dimers of the three homologous series have 10-membered rings with relatively symmetric conformations and zero or very low dipole moments. The energies of the monomers in these dimers-monomers with geometries frozen in the dimer-are close to the isolated and relaxed monomers energies. Generally speaking, OH 0 and CH 0 hydrogen bonds are found to contribute appreciably for the stability of the dimers. In particular, for the second most stable dimer, two of the three CH -0 hydrogen bonds are shorter than the intramolecular OH- 0 bond for the isolated monomer. Multivariate analysis of all the results shows that the 0. *H-0 angle is highly correlated with the H-0 bond length and that the COC and OCC angles are also highly correlated for both monomers, hence confirming that each monomer in a dimer keeps essentially the same conformation it has in the isolated monomer. The first and second principal components include all the highly correlated variables and account for 45% of the total variance. 3-D plots of the three most important principal components confirm a strong structural resemblance both for 10-membered ring dimers of homomeric series, Le., formed by the same monomers, and for the more stable dimers in each homologous series. In addition, among the heteromeric dimers with seven membered rings, the ones whose first conformation is G or G’ are less stable and located in a separate group

Retinal response of low myopes during orthokeratology treatment

The aim of this study was to evaluate the changes in retinal activity during orthokeratology (OK) treatment in 20 myopic eyes. Pattern electroretinography (PERG) and visual evoked potential (VEP) were assessed with the RETI-port/scan21 (Roland Consult, Wiesbaden, Germany). Measurements were taken at baseline (BL) and 1 night (1N), 15 nights (15N), 30 nights (30N), and 60 nights (60N) of OK lens wear. Repeated measures analysis of variance (ANOVA) and the Friedman test were used. Twenty eyes (23.20 ± 3.46 years, 70% female) with visual acuity ≤ 0.00 logMAR in post-treatment showed that despite a slight increase in retinal and cortical response amplitude, observed with both PERG and VEP, respectively, immediately after the initial treatment, these differences found were not statistically significant during the 60 days of OK treatment, despite a statistically significant increase in N95 response with PERG. This shows that retinal and cortical visual-related electrical activity is maintained or slightly increased during OK treatment.This research was supported by the Portuguese Foundation for Science and Technology (FCT) PTDC/FIS-OPT/0677/2014, the Strategic Funding UID/FIS/04650/2013 at Center of Physics, UMinho, and predoctoral grant SFRH/BD/136684/2018 to A.A.

Encerramento de diastemas com restaurações diretas : caso clínico

Poster apresentado no XXV Congresso da Ordem dos Médicos Dentistas. 10-12 Novembro 2016, Exponor, Matosinhos, PortugalN/

Identificação de genótipos de bananeira resistentes ao mal-do-Panamá a partir da avaliação em área infestada e em casa de vegetação.

O mal-do-Panamá, causado por Fusarium oxysporum f. sp. cubense (Foc), é considerada uma das mais destrutivas doenças que acometem a bananicultura mundial. As cultivares utilizadas no Brasil, em especial a ?Prata-Anã? e ?Pacovan? são suscetíveis ao mal-do-Panamá, ou tem apresentado relatos crescentes de áreas acometidas pelo patógeno

Influencia do PRD (irrigação com secamento parcial do sistema radicular) e RDI (irrigação com déficit hídrico controlado) na qualidade de frutos de Laranjeira 'Pera'.

qUALIDADE DE FRUTO E RAI