Unravelling Supramolecular Photocycloaddition: Cavitand-Mediated Reactivity of 3-(Aryl)Acrylic Acids.

The supramolecular photocycloaddition (PCA) of 3-(phenyl)acrylic acid has been extensively pursued by chemists to study weak interactions and synthesize substituted cyclobutanes. The stereo- and regioselectivity of the products in a supramolecularly affected reaction are often used as a probe for assessing the nature of weak interactions and/or molecular ambience of the reactants. However, some crucial aspects of this chemistry have often remained underexplored in the past, especially within the context of interpreting strength and directionality of interactions based on reaction outcomes.

The genus Lernaeenicus Lesueur (Copepoda, Siphonostomatoida, Pennellidae) in India: a checklist with notes on its taxonomy and ecology.

Members of the pennellid genus Lernaeenicus Lesueur, 1824 (Copepoda, Siphonostomatoida) have frequently been recorded from commercially important fishes collected along the coasts of India. Marine fish hosts from landing centres at Nagapattinam and Parangipettai Tamil Nadu, southeast coast of India, were examined for parasitic copepods between January 2011 and December 2013. A total of nine species including three unidentified species of Lernaeenicus were recorded: (1) L.

Magnesium pyrophosphates in enzyme mimics of nucleotide synthases and kinases and in their prebiotic chemistry.

Derivatives of ribosyl pyrophosphate have been synthesized, and examined with magnesium salts in the coupling of the ribose unit to various nucleophiles, including pyrazole and 2-chloroimidazole. Only with the magnesium salt present did they generate the ribosyl cation by binding to the leaving group and then couple the ribose derivative with nucleophiles. The role of magnesium salts in phosphorylation of methanol by ATP was also examined.

Catalysis of glyceraldehyde synthesis by primary or secondary amino acids under prebiotic conditions as a function of pH.

The synthesis of an excess of D-glyceraldehyde by coupling glycolaldehyde with formaldehyde under prebiotic conditions is catalyzed by L amino acids having primary amino groups at acidic pH's, but at neutral or higher pH's they preferentially form L-glyceraldehyde. L Amino acids having secondary amino groups, such as proline, have the reverse preferences, affording excess L-glyceraldehyde at low pH but excess D-glyceraldehyde at higher pHs. Detailed mechanistic proposals make these preferences understandable.

Chloride sensing via suppression of excited state intramolecular proton transfer in squaramides.

A new design strategy is described for chloride ion sensors based on suppression of excited state intramolecular proton transfer in squaramides as a fluorescence "turn on" mechanism.

A cucurbit[8]uril sponge.

This paper describes a convenient approach to quantitative removal of the synthetic host cucurbit[8]uril (Q8) from aqueous mixtures using a sepharose resin coated in memantine groups to selectively sequester Q8 in the presence of competing hosts and guests. The "Q8 sponge" can separate Q8 from Q6 and reverse the Q8-mediated dimerization of peptides.

Nanomolar binding of peptides containing noncanonical amino acids by a synthetic receptor.

This paper describes the molecular recognition of phenylalanine derivatives and their peptides by the synthetic receptor cucurbit[7]uril (Q7). The 4-tert-butyl and 4-aminomethyl derivatives of phenylalanine (tBuPhe and AMPhe) were identified from a screen to have 20-30-fold higher affinity than phenylalanine for Q7. Placement of these residues at the N-terminus of model tripeptides (X-Gly-Gly), resulted in no change in affinity for tBuPhe-Gly-Gly, but a remarkable 500-fold increase in affinity for AMPhe-Gly-Gly, which bound to Q7 with an equilibrium dissociation constant (K(d)) value of 0.

Cucurbit[8]uril rotaxanes.

The synthesis of [2]rotaxanes, each comprising a viologen core threaded through a cucurbit[8]uril (Q8, Figure 1) macrocycle and stoppered by tetraphenylmethane groups, and their binding to second guests as inclusion complexes in organic and aqueous media are described. Stoppering was observed to have little effect on binding. Chemical modification of the threaded guest was used to control solubility and binding characteristics, thus demonstrating a novel approach to making artificial receptors with readily modifiable properties.

Determining protease substrate selectivity and inhibition by label-free supramolecular tandem enzyme assays.

An analytical method has been developed for the continuous monitoring of protease activity on unlabeled peptides in real time by fluorescence spectroscopy. The assay is enabled by a reporter pair comprising the macrocycle cucurbit[7]uril (CB7) and the fluorescent dye acridine orange (AO). CB7 functions by selectively recognizing N-terminal phenylalanine residues as they are produced during the enzymatic cleavage of enkephalin-type peptides by the metalloendopeptidase thermolysin.

Carbonyl groups as molecular valves to regulate chloride binding to squaramides.

Environment-sensitive binding of anions to synthetic receptors is important for the functional mimicry of ion channels. We describe new squaramide-based chloride ion receptors whose anion binding cavity can be opened and closed by using carbonyl groups as valves. In nonpolar solvents, the carbonyls preclude chloride binding via intramolecular hydrogen bonding with the squaramide NHs.

Copper-mediated synthesis of tertiary diaryl squaramides.

Tertiary aryl squaramides were synthesized by using copper catalyzed C-N bond-formation with L-proline as the ligand. Symmetrical diaryl squaramides could be prepared in a one-pot reaction by using excess aryl bromide with varying yields. Unsymmetrical derivatives were prepared by sequential arylation.