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We studied the interaction of poly-l-lysine (PLL) and poly-l-arginine (PLAG) with sodium dodecyl sulfate (SDS) surfactant and the interaction of poly-l-glutamic acid (PLGA) and poly-l-aspartic acid (PLAA) with tetradecyltrimethylammonium bromide (TTAB) surfactant using vibrational circular dichroism (VCD) spectroscopy in the region of C-H stretching vibration and in the Amide I region both in solution and in mulls. A chirality transfer from polypeptides to achiral surfactants was observed in the C-H stretching region, where measurements in solution were impossible. This observation was enabled by a special sample treatment technique using lyophilization and the preparation of mulls. This technique demonstrated itself as an interesting and beneficial tool for VCD measurements. In addition, we observed that SDS changed the secondary structure of PLL to the β-sheet and of PLAG to the α-helix. TTAB disrupted the PLGA and PLAA structure. These results were obtained in the mull but were confirmed by the VCD spectra measured in solution and by electronic circular dichroism. The chirality transfer from the polypeptides to SDS was caused by polypeptides ordered into a specific conformation during the interaction, while in the TTBA system it was induced primarily by the chirality of the amino acid residues.

A new bis[cobalt(II)porphyrin]-Troger's base conjugate was studied as a potential receptor for methyl esters of several amino acids. The conjugate was prepared as racemate, and then resolved via preparative high-performance liquid chromatography (HPLC) on a chiral column. The high affinity to lysine, histidine, and proline methyl esters was found by complexation studies followed by UV-Vis spectroscopy. The studies of pure enantiomers, followed by UV-Vis and electronic circular dichroism spectroscopy, revealed the highest enantioselectivity for lysine methyl ester. Chirality 26:361–367, 2014. © 2014 Wiley Periodicals, Inc.

Although the interactions between bilirubin and serum albumin are among the most studied serum albumin-ligand interactions, the binding-site location and the participation of bilirubin-serum albumin complexes in pathological and physiological processes are under debate. In this article, we have benefited from the chiral structure of bilirubin and used CD spectroscopy to characterize the structure of bilirubin bound to human and bovine serum albumins. We determined that in a phosphate buffer at pH 7.8 there are three binding sites in both human and bovine serum albumins. While the primary binding sites in human and bovine serum albumins bind bilirubin with P- and M-helical conformations, respectively, the secondary binding sites in both albumins bind bilirubin in the P-helical conformation. We have shown that the bonding of bilirubin to the serum albumin matrix is a more favorable process than the self-association of bilirubin under the studied conditions, with a maximum of three bound bilirubins per serum albumin molecule. Although bilirubin bound to the primary binding site has attracted the most attention, the presented results have documented the impact of the secondary binding sites which are relevant in the displacement reactions between BR and drugs and in the phenomena where bilirubin plays antioxidant, antimutagenic, and anti-inflammatory roles.

Self-assembly of molecules is one of the fundamental processes in biology and in supramolecular chemistry. Guanosine (Guo) and its derivatives are among the widely studied molecules because of self-assembly abilities. Their tetrameric associates are the nature of telomeric DNA, and furthermore they are fundamental building blocks of supramolecular reversible gels, which may arise in certain physical and chemical conditions. Although poorly soluble in water, Guo forms interesting structures with guanosine 5'-monophosphate salt (GMP) in the TRIS buffer. We used electronic circular dichroism and vibrational circular dichroism to describe the thermal response of gels formed by the Guo/GMP binary mixture. Using these complementary techniques suitable to study conformational changes of chiral compounds, we obtained information about the involvement of functional groups and weak interactions in the guanosine quartet (G(4)) and stacked G(4) structures.

We studied the interaction of poly-l-lysine (PLL) and poly-l-arginine (PLAG) with sodium dodecyl sulfate (SDS) surfactant and the interaction of poly-l-glutamic acid (PLGA) and poly-l-aspartic acid (PLAA) with tetradecyltrimethylammonium bromide (TTAB) surfactant using vibrational circular dichroism (VCD) spectroscopy in the region of C-H stretching vibration and in the Amide I region both in solution and in mulls. A chirality transfer from polypeptides to achiral surfactants was observed in the C-H stretching region, where measurements in solution were impossible. This observation was enabled by a special sample treatment technique using lyophilization and the preparation of mulls. This technique demonstrated itself as an interesting and beneficial tool for VCD measurements. In addition, we observed that SDS changed the secondary structure of PLL to the β-sheet and of PLAG to the α-helix. TTAB disrupted the PLGA and PLAA structure. These results were obtained in the mull but were confirmed by the VCD spectra measured in solution and by electronic circular dichroism. The chirality transfer from the polypeptides to SDS was caused by polypeptides ordered into a specific conformation during the interaction, while in the TTBA system it was induced primarily by the chirality of the amino acid residues.

Vibrational circular dichroism (VCD) spectra of (+)-α-pinene solutions in carbon tetrachloride have been measured in the range of volume fractions 5–100% (v/v) in the mid-infrared region. The concentration dependence measured was statistically analyzed with the aim of obtaining a reliable correlation between the VCD band areas and the concentrations of individual enantiomers. The quality of the spectra was estimated by means of noise spectra which were defined as half the difference of the two following blocks of scans. In addition to this, the enantiomeric purity was studied. This study was carried out for both (+)- and (−)-α-pinene enantiomers in the range of the percent enantiomeric excess in the interval 10–100%. The relationship between VCD intensity and enantiomeric purity was determined by least-square regression and statistically evaluated. All measurements performed in this study were intended as a basic tool for testing of a new commercial VCD setup from Bruker. Chirality 12:199–203, 2000. © 2000 Wiley-Liss, Inc.

A new bis[cobalt(II)porphyrin]-Tröger's base conjugate was studied as a potential receptor for methyl esters of several amino acids. The conjugate was prepared as racemate, and then resolved via preparative high-performance liquid chromatography (HPLC) on a chiral column. The high affinity to lysine, histidine, and proline methyl esters was found by complexation studies followed by UV-Vis spectroscopy. The studies of pure enantiomers, followed by UV-Vis and electronic circular dichroism spectroscopy, revealed the highest enantioselectivity for lysine methyl ester.

Although the interactions between bilirubin and serum albumin are among the most studied serum albumin-ligand interactions, the binding-site location and the participation of bilirubin-serum albumin complexes in pathological and physiological processes are under debate. In this article, we have benefited from the chiral structure of bilirubin and used CD spectroscopy to characterize the structure of bilirubin bound to human and bovine serum albumins. We determined that in a phosphate buffer at pH 7.8 there are three binding sites in both human and bovine serum albumins. While the primary binding sites in human and bovine serum albumins bind bilirubin with P- and M-helical conformations, respectively, the secondary binding sites in both albumins bind bilirubin in the P-helical conformation. We have shown that the bonding of bilirubin to the serum albumin matrix is a more favorable process than the self-association of bilirubin under the studied conditions, with a maximum of three bound bilirubins per serum albumin molecule. Although bilirubin bound to the primary binding site has attracted the most attention, the presented results have documented the impact of the secondary binding sites which are relevant in the displacement reactions between BR and drugs and in the phenomena where bilirubin plays antioxidant, antimutagenic, and anti-inflammatory roles.

Self-assembly of molecules is one of the fundamental processes in biology and in supramolecular chemistry. Guanosine (Guo) and its derivatives are among the widely studied molecules because of self-assembly abilities. Their tetrameric associates are the nature of telomeric DNA, and furthermore they are fundamental building blocks of supramolecular reversible gels, which may arise in certain physical and chemical conditions. Although poorly soluble in water, Guo forms interesting structures with guanosine 5'-monophosphate salt (GMP) in the TRIS buffer. We used electronic circular dichroism and vibrational circular dichroism to describe the thermal response of gels formed by the Guo/GMP binary mixture. Using these complementary techniques suitable to study conformational changes of chiral compounds, we obtained information about the involvement of functional groups and weak interactions in the guanosine quartet (G(4)) and stacked G(4) structures.

The stereoselective complexation of tert-butylcarbamoyl quinine and tert-butylcarbamoyl quinidine selectors (SOs) with 3,5-dinitrobenzoyl (DNB) derivatives of D- and L-alpha amino acids (DNB-Ala, DNB-Val, DNB-Leu, and DNB-Ile) as well as achiral DNB-Gly has been studied by vibrational circular dichroism (VCD) spectroscopy in the spectral region of CH stretching vibrations. All the complexes of SOs and sterically compatible enantiomers of derivatized amino acid selectands (SAs) showed induced circular dichroism (ICD) bands in the region of aromatic CH stretching vibrations, indicating the occurrence of a π–π interaction between the aromatic moieties of SA and SO. To our knowledge, this is the first report in which a π–π interaction was observed by VCD spectroscopy in this spectral region. No ICD bands were disclosed in the spectra of the sterically incompatible SA and SO complexes. The spectral pattern in the region of aliphatic CH stretching vibrations showed interaction-induced conformational adaptations in sterically favorable SA and SO complexes. No such spectral changes were observed for any of the sterically incompatible complexes. The DNB-Gly complexes exhibited spectral patterns similar to those observed for sterically favorable pairs of SOs and chiral SAs. Chirality, 2011. © 2010 Wiley-Liss, Inc.

Vibrational circular dichroism (VCD) spectra are reliable indicators of the spatial structure of chiral molecules. The specific and characteristic feature of vibrational spectroscopy, and therefore also of VCD, where the energy of some vibrational modes is predominantly focused to a specific part of the molecule, enables monitoring both the structure of the molecule dissolved in different solvents and under different physicochemical conditions and molecular interactions. This minireview deals with recent contributions covering structural information on the bioinspired interactions obtained by means of VCD, especially in the following areas: interaction of DNA with biomolecules and biogenic metals, guanine tetramers and quadruplexes, biointeractions of bile pigments, and polypeptide and protein interactions with other biomolecules. Chirality 21:E215–E230, 2009. © 2009 Wiley-Liss, Inc.