Amino acid/zwitterion equilibria II: vibrational and NMR studies of substituted thiazolidine-4-carboxylic acids

Howard-Lock, H. E.; Lock, C. J. L.; Martins, Maria de Lurdes

doi:10.1139/v91-252

Cited by 8 publications

(5 citation statements)

References 4 publications

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“…pH = 7 was the least preferred environment during LE. It may be explained by the fact that during the LE performed at pH = 7, DPA occurs in a relatively high concentration (compared to the reaction at pH = 4) in the form of a zwitterion, and in this form amino acids have the lowest solubility (Howard-Lock et al 1991). Additionally, NPs functionalized at pH = 7were not stable in time.…”

Section: Resultsmentioning

confidence: 99%

Surface modification of cadmium-based nanoparticles with d-penicillamine—study of pH influence on ligand exchange reaction

et al. 2020

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Semiconducting nanoparticles (NPs) find applications in many fields, with a recent focus on medicine and biology. Functionalization of the surface of NPs is necessary, and one of the most commonly employed techniques is ligand exchange (LE). In this paper, the study of pH influence on LE reaction for different types of cadmium-based NPs (quantum dots, nanorods, and nanoplates) is presented. Hydrophobic NPs were transferred to the nonorganic medium by functionalization with D-penicillamine (DPA). The LE procedure was conducted at four different pH levels (4, 7, 9, and 11), and obtained hydrophilic NPs were dispersed in phosphate buffer. Results show that the most effective procedure resulted from a reaction carried at pH = 4; however, NPs with higher photoluminescence intensity were obtained when pH = 11 was used. Comparable emission was achieved from samples at pH = 4 and pH = 9. The least effective transfer, resulting in unstable NPs, occurred when the procedure was conducted at pH = 7.

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Section: Resultsmentioning

confidence: 99%

Surface modification of cadmium-based nanoparticles with d-penicillamine—study of pH influence on ligand exchange reaction

et al. 2020

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“…This was not surprising, since the α -amino acids are normally present in solutions in their zwitterionic form [10]. In order to obtain further structural information, 13 C NMR spectroscopy studies on 1 (in the range between -20 and 230 ppm) were undertaken.…”

Section: Resultsmentioning

confidence: 99%

Rare-earth metal complexes derived from the acids Ph2C(X)CO2H (X= OH, NH2): Structural and ring opening polymerization (ROP) studies

Collins

Santoro

Prior

et al. 2021

Journal of Molecular Structure

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Treatment of Ln(NO 3 ) 3 . 6H 2 O (Ln = La, Ce) with an equimolar amount of 2,2'-diphenylglycine (DpgH) in ethanol afforded the corresponding hexacoordinated complexes (DpgH ± ) 3 Ln(NO 3 ) 3 . H 2 O (DpgH ± = zwitterionic 2,2'-diphenylglycine, Ln = La ( 1 ), Ce). The spectroscopic and structural features of these compounds have been investigated.Similar reactions with the related benzilic acid (BenzH 2 ) were unsuccessful. The catalytic behaviour of 1 and 2 in the homo-and copolymerization of ε -caprolactone ( ε -CL) and rac -lactide ( r -LA) has been investigated herein. In the case of ε -CL, the two complexes exhibited comparable activity, allowing for complete monomer conversion under aerobic and solvent-free conditions at 150°C in 24 h. With respect to the ROP of r -LA, 1 was found to be completely inactive, while only 8% conversion was achieved in the presence of 2 . Liquid oligomers were isolated during ε -CL/ r -LA co-polymerization in the presence of both complexes. The catalytic activity of the pre-ligands DpgH and BenzH 2 ( i.e. metal-free) was also examined. Interestingly, only BenzH 2 was found to be active, although it required a higher catalyst loading and the presence of benzyl alcohol as co-activator.

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“…To prove this hypothesis, it was necessary to understand the difference in the basicity of amine of Hcy/Cys derived heterocycles. Previously, the basicity of the amine of thiazolidine-4-caroboxylc acids has been studied [126][127][128][129] but the basicity of the amine of the Hcyderived thiazinane-4-carboxylic acids had not been reported. Therefore, a series of 5- Table 4.1.…”

Section: Resultsmentioning

confidence: 99%

Development of an Optical Method for the Detection of Homocysteine as a Disease Biomarker Using Fluorescein-Aldehydes

Barve¹

2000

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Homocysteine is a natural occurring aminothiol. It is an intermediate product in the metabolism of methionine. Methionine is an essential amino acid required for protein synthesis. Metabolic irregularities disrupt homocysteine levels in plasma. Elevated homocysteine levels are directly linked to folate and cobalamin (vitamin B12) deficiencies, and are an independent risk factor for cardiovascular diseases. High homocysteine levels have also been associated with Alzheimer's, osteoporosis, renal failure, cancer, birth defects and pregnancy complications. The association of elevated homocysteine levels with cardiovascular disease and other diseases has generated great interest in the detection of homocysteine.An optical method for the detection of homocysteine has been developed using fluorescein mono-and dialdehydes. Selectivity for homocysteine was achieved based on the characteristic differences between 5-and 6-membered ring heterocyclic amines formed upon the reaction with fluorescein mono-and dialdehydes. 6-membered ring homocysteine-derived thiazinane-4-carboxylic acids were found to be more basic than 5-membered cysteine-derived thiazolidine-4-carboxylic acids. Fluorescence enhancement in response to homocysteine was thus attained by tuning pH and excitation wavelengths.

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Amino acid/zwitterion equilibria II: vibrational and NMR studies of substituted thiazolidine-4-carboxylic acids

Cited by 8 publications

References 4 publications

Surface modification of cadmium-based nanoparticles with d-penicillamine—study of pH influence on ligand exchange reaction

Surface modification of cadmium-based nanoparticles with d-penicillamine—study of pH influence on ligand exchange reaction

Rare-earth metal complexes derived from the acids Ph2C(X)CO2H (X= OH, NH2): Structural and ring opening polymerization (ROP) studies

Development of an Optical Method for the Detection of Homocysteine as a Disease Biomarker Using Fluorescein-Aldehydes

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