INDOR study of 1H?1H inter-ring couplings in naphthalene derivatives

The ¹H n.m.r. spectra of two naphthalene derivatives have been completely analysed. The advantages of the INDOR technique have been illustrated in the determination, magnitudes and signs, of small couplings in complex spin systems. A splitting of 0.07 Hz has been resolved in the 100 MHz spectrum of 1,2-dichloro-3 nitronaphthalene. The signs of the inter-ring coupling constants alternate with the number of intervening bonds.     

The complete analysis of the 1H NMR spectra of quinoline and two of its derivatives. sign determinations of inter-ring coupling constants by means of the INDOR technique

The complete ¹H NMR spectral analyses of quinoline and two of its derivatives (4,7-dichloroquinoline and 8-nitroquinoline) have been performed. All the long-range coupling constants were determined both in magnitude and sign. In determining the signs the INDOR technique was very useful and successful, allowing the resolution of transitions as close as a few hundredths of a Hz. The signs of the inter-ring coupling constants alternate with the number of intervening bonds, according to McConnell's rule, except the all-trans⁶J couplings. A linear relationship has been found between the ¹H?¹H and ¹⁹F?¹⁹F inter-ring coupling constants for which the spin polarization is transmitted almost exclusively via the π-electron system.     

Multilamellar LipoCEST Agents Obtained from Osmotic Shrinkage of Paramagnetically Loaded Giant Unilamellar Vescicles (GUVs)

Moving from nano‐ to micro‐systems may not just be a matter of scale, but it might imply changes in the properties of the systems that can open new routes for the development of efficient MRI contrast agents. This is the case reported in the present paper, where giant liposomes (giant unilamellar vesicles, GUVs) loaded with Ln^III complexes have been studied as chemical exchange saturation transfer (CEST) MRI contrast agents. The comparison between nanosized liposomes (small unilamellar vesicles, SUVs) and GUVs sharing the same formulation led to differences that could not be accounted for only in terms of the increase in size (from 100–150 nm to 1–2 μm). Upon osmotic shrinkage, GUVs yielded a saturation‐transfer effect three order of magnitude higher than SUVs consistent with the increase in vesicles volume. Confocal microscopy showed that the shrinkage of GUVs resulted in multilamellar particles whereas SUVs are known to yield asymmetrical, discoidal shape.     

Iterative analysis of the 1H NMR spectra of naphthalene (AA′ A″ A‴ BB′ B″ B‴ system) and two of its derivatives

The ¹H NMR spectra of naphthalene as an eight spin system, and two of its derivatives, 2,4-dichloro- and 2,4-dinitro-1-naphthol, have been completely analysed. The Indor technique has been very useful in the determination of the signs and magnitudes of very small coupling constants. An improved version of the Laocoon 3 program has greatly facilitated the spectral analysis through, first, the knowledge of the dependence of each transition upon the spectral parameters; second, some modifications in the iterative loop which avoid failure of convergence, and, third, the use of a slightly modified diagonalization subroutine which saves 20% CPU computer time. Our data suggest a rather small substituent effect on intra-ring couplings of the unsubstituted ring. The inter-ring coupling constants display a negative or positive sign according to an even or odd number of intervening bound, except the all-trans ⁶J which is positive. No substituent effect on the inter-ring couplings has been observed, except a small effect for the all-trans ⁶J.     

On the convergence of iterative computation in the LAOCOON 3 program

The reasons which sometimes cause failure of convergence in the iteration of NMR spectra by LAOCOON 3 are discussed. The problem can be avoided by retaining the sequence of the eigenfunctions throughout the iterative process. In addition, assignment of the lines to start the iterative analysis can be facilitated by considering the dependence of the transitions on the NMR parameters in the simulation stage. LAOCOON 3, modified and extended to handle eight spin systems, has been successfully tested in the iterative analysis of the ¹H NMR spectrum of naphthalene.     

PCILO calculation on the ansa conformation of hexahydrorifamycin S

PCILO calculation on the conformation of the 16, 17, 18, 19, 28, 29 hexahydrorifamycin S points to an ansa chain conformation of the C(12)–C(28) fragment from the alternatives given by a previous ¹H NMR spectroscopic study.The energetically favoured conformation of the C(19)–N fragment has also been determined.     

Substituent effects on 33S NMR chemical shifts in sulphones

The ³³S NMR spectra of some selected sulphones demonstrate additive substituent-induced chemical shift (SCS) effects. In dimethyl sulphone (1), replacement of a methyl group by a vinyl or a phenyl group causes an SCS effect of ?7 to ?8.5 ppm or ?4 to ?5 ppm, respectively. The ³³S chemical shift in 1 is also sensitive to substitution of methyl protons. The ß-substituent effect for methyl and phenyl groups is in the range +7 to +8 ppm and +5.5 to +6 ppm, respectively.     

Photodynamic Therapy with Zinc Phthalocyanine Inhibits the Stemness and Development of Colorectal Cancer: Time to Overcome the Challenging Barriers?

Photodynamic therapy (PDT) is a light-based cancer therapy approach that has shown promising results in treating various malignancies. Growing evidence indicates that cancer stem cells (CSCs) are implicated in tumor recurrence, metastasis, and cancer therapy resistance in colorectal cancer (CRC); thus, targeting these cells can ameliorate the prognosis of affected patients. Based on our bioinformatics results, SOX2 overexpression is significantly associated with inferior disease-specific survival and worsened the progression-free interval of CRC patients. Our results demonstrate that zinc phthalocyanine (ZnPc)-PDT with 12 J/cm² or 24 J/cm² irradiation can substantially decrease tumor migration via downregulating MMP9 and ROCK1 and inhibit the clonogenicity of SW480 cells via downregulating CD44 and SOX2. Despite inhibiting clonogenicity, ZnPc-PDT with 12 J/cm² irradiation fails to downregulate CD44 expression in SW480 cells. Our results indicate that ZnPc-PDT with 12 J/cm² or 24 J/cm² irradiation can substantially reduce the cell viability of SW480 cells and stimulate autophagy in the tumoral cells. Moreover, our results show that ZnPc-PDT with 12 J/cm² or 24 J/cm² irradiation can substantially arrest the cell cycle at the sub-G1 level, stimulate the intrinsic apoptosis pathway via upregulating caspase-3 and caspase-9 and downregulating Bcl-2. Indeed, our bioinformatics results show considerable interactions between the studied CSC-related genes with the studied migration- and apoptosis-related genes. Collectively, the current study highlights the potential role of ZnPc-PDT in inhibiting stemness and CRC development, which can ameliorate the prognosis of CRC patients.     

Detection of taurine in biological tissues by (33)S NMR spectroscopy.

The potential of (33)S NMR spectroscopy for biochemical investigations on taurine (2-aminoethanesulfonic acid) is explored. It is demonstrated that (33)S NMR spectroscopy allows the selective and unequivocal identification of taurine in biological samples. (33)S NMR spectra of homogenated and intact tissues are reported for the first time, together with the spectrum of a living mollusc. Emphasis is placed on the importance of choosing appropriate signal processing methods to improve the quality of the (33)S NMR spectra of biological tissues.     

Indor and 1H-NMR. Studies of the Ansa Conformation of Hexahydrorifamycin S

The study of 16, 17, 18, 19, 28, 29-hexahydrorifamycin S by ¹H-NMR. spectroscopy using INDOR at 100 MHz and homodecoupling at 270 MHz has shown that the conformation of the ansa fragment C(20)-C(27) and the position of this fragment relative to the naphthoquinone chromophore are practically the same as those of rifamycin S. This finding rules out the hypothesis that the lower activity of the hydrogenated rifamycins could be due to a different conformation.