Current indications for endoscopic submucosal dissection of early gastric cancer.

The development of endoscopic treatment technology has further promoted the minimally invasive treatment of early gastric cancer (EGC). Endoscopic treatment has achieved better therapeutic effects in terms of safety and prognosis and is the preferred treatment method for patients who meet the indications for endoscopic treatment. However, the consequent problem is that some patients receiving endoscopic treatment may undergo non-curative resection, and the principle of follow-up management for non-curative resection patients deserves further attention. In addition, there are still debates on how to improve the accuracy of clinical staging, select a reasonable treatment method for patients who meet the expanded indications for endoscopic treatment, manage patients with positive endoscopic surgical margins, conduct research on function-preserving surgery, and manage the treatment of EGC under the current situation in China. Consequently, we aim to review current indications for endoscopic submucosal dissection of EGC in order to better inform treatment options.

Nanosphere [Ag(SR)]n: coordination polymers of Ag+ with a combination of hydrophilic and hydrophobic thiols.

We propose to create nanospheres in aqueous solutions from coordination polymers of Ag+ with a combination of a hydrophilic and a hydrophobic thiol, of diameter ca. 2.7 nm in the case of using cysteine and n-butanethiol. A spectral probe for the formation of the nanospheres is a reversal of the CD signal at 253 nm from negative in the case of cysteine alone to positive when cysteine and n-BuSH are both employed, together with an amplification.

Chiral Recognition by Flexible Coordination Polymers of Ag+ with a Cysteine-Based Chiral Thiol Ligand That Bears a Binding Site.

We report a new scheme for chiral recognition using coordination polymers of Ag+ with a chiral thiol ligand that contains a binding group. N-Benzoyl-l-cysteine ethyl ester equipped with a boronic acid group at the para position of the phenyl ring forms coordination polymers with Ag+ in alkaline aqueous solutions that exhibit excellent selectivity toward a d-glucose enantiomer over l-glucose, while the coordination polymers from the d-cysteine-based thiol ligand are specific for l-glucose. It is assumed that a conformation change occurs upon interaction of a saccharide molecule with the polymeric chain receptor, for which the next binding is promoted, leading to the highly effective chiral recognition, despite the flexible nature of the polymeric receptor.

Helical nanofibers of N-(perfluorooctanoyl)cysteine ethyl ester in coordination polymers of Ag.

We propose using the formation of coordination polymers of Ag+ to probe differences between the perfluorinated alkyl chain and the alkyl chain by deriving a thiol ligand, N-(perfluoroalkanoyl)cysteine. Rapid formation in EtOH of P-/M-helical nanofibrils of high thermostability was found for N-(perfluorooctanoyl)-l-/d-cysteine ethyl esters at the µM level upon mixing with Ag+, but not for the octanoyl counterpart. This difference was also observed in terms of circular dichroism-enantiomeric excess dependence.

Balancing interactions in proline-based receptors for chiral recognition of l-/d-DOPA.

Proline based receptors (1-14) attached with phenylboronic acid and benzaldehyde binding groups at the N-/C- or C-/N-termini of the proline residue were created for chiral recognition of l-/d-DOPA, in an attempt to examine if balancing the two binding events would influence the recognition. By changing the positions of boronic acid and aldehyde groups substituted on the phenyl rings (1-4, 5-8) and the site at which phenylboronic acid and benzaldehyde moieties attached respectively to the N- and C-termini or C- and N-termini of the proline residue (1-4vs.5-8), and by introducing an electron-withdrawing fluorine atom in the phenyl ring of the weaker binder the benzaldehyde moiety (11vs.1, 14vs.5), we were able to show that a better balance of the two binding events does improve the chiral recognition. This finding can only be made with the current version of receptors that were equipped with two different binding groups. Together with the finding that the chiral recognition performance in mixed organic-aqueous solutions is tunable by varying the solvent composition, we have now arrived at a protocol for designing proline based receptors for extended applications in chiral recognition.

Supramolecular chirality of coordination polymers of Ag+ with a chiral thiol ligand that bears a ß-turn structure.

We report coordination polymers forming from Ag+ and a chiral thiol ligand that bears a ß-turn structure, exhibiting supramolecular chirality showing both the majority rules effect (MRE) and the racemate rules effect (RRE).

Proline-Based Boronic Acid Receptors for Chiral Recognition of Glucose.

Chiral recognition remains a major challenge in the area of molecular receptor design. With this research, we set out to explore the use of proline-based receptors for chiral recognition. Importantly, the proline structure allows for the introduction of at least two different binding groups due to the availability of both an amine and carboxylic acid group. Here we report a proof-of-concept exploration into the chiral recognition of d/l-glucose as a model chiral species, which prefers to bind to at least two boronic acid groups. We evaluated several proline-based receptors incorporating two phenylboronic acid groups, respectively, at the N- and C-termini of the amino acid residue, via amide bonds. We confirmed that the receptors exhibited chiral recognition using CD, 1H NMR, and 19F NMR spectroscopy. Given the derivation diversity available, our strategy to use proline-based receptors for chiral recognition holds significant promise for extension to other chiral systems.

Short Azapeptides of Folded Structures in Aqueous Solutions.

Building folded short peptides that are driven by the intramolecular hydrogen bonding in aqueous solutions remains challenging because of their highly competitive intermolecular hydrogen-bonding interactions with water solvent molecules that would have favored the extended conformations. Here, we show folded ß-turn structures in acyl amino acid-based N-amidothioureas, the nonclassic azapeptides, in aqueous solutions, as well as in solid-state and organic solvents, by X-ray crystal structures, DFT calculations, 1D and 2D NMR spectra, and absorption and CD spectra. The achiral phenylthiourea chromophore acts as a CD reporter for the ß-turn structure that communicates the chirality of the amino acid residue to the achiral thiourea moiety and the relative intensity of the intramolecular hydrogen bond that stabilizes the turn structure. The amidothiourea moiety represents a versatile structural framework for folded short peptides in aqueous environments.

Folded short azapeptide for conformation switching-based fluorescence sensing.

Herein, we report a conformation switching-based fluorescence sensing scheme using dipeptide-based amidothioureas (azapeptides) that contain a folded ß-turn structure. Amidothiourea is equipped at its two termini with an electron acceptor and an electron donor or two fluorophores, such that it exhibits enhanced exciplex or excimer emission because of the turn structure in which the two termini are brought into close proximity; on the other hand, it exhibits a dramatic ratiometric fluorescence response upon anion binding to the thiourea moiety because of the resultant extended conformation of the anion binding complex.

Ag+ coordination polymers of a chiral thiol ligand bearing an AIE fluorophore.

We report that in the Ag+ coordination polymers of a chiral thiol ligand containing an AIE fluorophore, tetraphenylethene (TPE), the TPE chromophores experience H-type aggregation, and yet a substantial enhancement of the fluorescence is observed, though to a lesser extent than that in the aggregates of the thiol ligand itself, which undergoes J-type aggregation. We show that this is not due to the difference in the freedom of the rotation of the fluorophore in the two types of aggregate, but is due to a small increase in the radiation rate constant in the coordination polymers while the much higher radiationless rate constant remains more or less unchanged.

ß-Turn structure in glycinylphenylalanine dipeptide based N-amidothioureas.

Transforming the C-terminal amide of a glycinylphenylalanine dipeptide into N-amidothiourea affords a ß-turn structure in the formed dipeptide based N-amidothioureas, which can be readily identified by an induced CD signal from the achiral phenylthiourea chromophore.

Amino acid based chiral N-amidothioureas. Acetate anion binding induced chirality transfer.

N-Amidothioureas generated from amine-dimethylated natural L-phenylalanine and its D-enantiomer bearing a chiral carbon that is by 2 atoms or 3 chemical bonds away from the anion binding site establish chiral communication upon acetate anion binding to the thiourea moiety.