A porous anionic metal-organic framework, bio-MOF-1, constructed using adenine as a biomolecular building block is described. The porosity of this material is evaluated, its stability in biological buffers is studied, and its potential as a material for controlled drug release is investigated. Specifically, procainamide HCl is loaded into the pores of bio-MOF-1 using a simple cation exchange process. Exogenous cations from biological buffers are shown to affect the release of the adsorbed drug molecules.

The synthesis and structure of Co(2)(ad)(2)(CO(2)CH(3))(2) x 2 DMF x 0.5 H(2)O (bio-MOF-11) is described. Pyrimidine and amino groups of adeninate (ad) decorate the pores of the framework. The porosity of this material was studied, and its CO(2) and H(2) adsorption properties were evaluated. bio-MOF-11 exhibits a high heat of adsorption for CO(2) (approximately 45 kJ/mol), a high CO(2) capacity (approximately 6 mmol/g, 273 K), and exceptional selectivity for CO(2) over N(2) at 273 K (81:1) and 298 K (75:1).

We have created unique near-infrared (NIR)-emitting nanoscale metal-organic frameworks (nano-MOFs) incorporating a high density of Yb 3+ lanthanide cations and sensitizers derived from phenylene. We establish here that these nano-MOFs can be incorporated into living cells for NIR imaging. Specifically, we introduce bulk and nano-Yb-phenylenevinylenedicarboxylate-3 (nano-Yb-PVDC-3), a unique MOF based on a PVDC sensitizer-ligand and Yb 3+ NIRemitting lanthanide cations. This material has been structurally characterized, its stability in various media has been assessed, and its luminescent properties have been studied. We demonstrate that it is stable in certain specific biological media, does not photobleach, and has an IC 50 of 100 μg/mL, which is sufficient to allow live cell imaging. Confocal microscopy and inductively coupled plasma measurements reveal that nano-Yb-PVDC-3 can be internalized by cells with a cytoplasmic localization. Despite its relatively low quantum yield, nano-Yb-PVDC-3 emits a sufficient number of photons per unit volume to serve as a NIR-emitting reporter for imaging living HeLa and NIH 3T3 cells. NIR microscopy allows for highly efficient discrimination between the nano-MOF emission signal and the cellular autofluorescence arising from biological material. This work represents a demonstration of the possibility of using NIR lanthanide emission for biological imaging applications in living cells with single-photon excitation.uminescent reporters emitting in the near-infrared (NIR) region of the electromagnetic spectrum are highly advantageous for biological imaging applications for several reasons. Biological material has low autofluorescence in the NIR window, which allows facile discrimination between the desired signal of the reporter and the background, leading to an enhanced signalto-noise ratio and improved detection sensitivity (1). Additionally, NIR light scatters less than visible light, and therefore results in increased optical imaging resolution (2, 3). Finally, NIR photons interact less with biological material compared with visible photons, thus decreasing the risk of disturbing or damaging the biological systems being observed.NIR reporters, such as cyanine dyes (4, 5) and quantum dots (6), have previously been shown to be useful for biological imaging applications. However, these materials have broad emission bands that limit their ability to be easily discriminated from the background fluorescence. Additionally, cyanine dyes exhibit limited photostability and quantum dots can display blinking emission, making it difficult to conduct repeated or long-term experiments for such purposes as tracking a moiety or monitoring a process.Several lanthanide cations emit in the NIR and have some advantages with respect to organic fluorophores and semiconductor nanocrystals. Lanthanide cations have narrower emission bandwidths than organic fluorophores and semiconductor nanocrystals. Their emission wavelengths are not affected by the environment, allowing them to be used in a broad ra...

No abstract

No abstract

No abstract

The design of metal-organic frameworks (MOFs) incorporating near-infrared emitting ytterbium cations and organic sensitizers allows for the preparation of new materials with tunable and enhanced photophysical properties.

Despite the promise of amide bond isosteres for improving the resistance toward degradation by exoproteases by several orders of magnitude, the use of nonhydrolyzable substitutes for the amide group has often led to disappointing decreases in biological activity. 1 The frequent lack of success with ground-state amide bond mimetics stands in contrast to the very promising use of hydroxyethylene protease inhibitors as mimics of the tetrahedral intermediate in amide bond hydrolysis. 2 Nonetheless, the development of effective amide bond isosteres holds considerable promise as a stepping stone toward the rational design of small molecule analogues of bioactive oligo-and polypeptides. Analogues such as thiomethylene and aminomethylene isosteres, however, exchange the conformationally restricted amide function with highly flexible single bonds. Disubstituted (E)-alkene isosteres 1 provide a better fit for the C i -(R)-C i+1 (R) distance (3.8 Å) but are inadequate mimetics of the electrostatic potential surface as well as the backbone φ,ψ-dihedral angles. Gellman and co-workers designed the tetrasubstituted (E)-alkene Gly-Gly dipeptide mimetic 2 to induce conformational rigidification and promote -hairpin formation. 3 More recently, Hoffman and co-workers reported the use of gauche pentane interactions for the design of -hairpin analogue 3. 4 We were interested in exploring the use of trisubstituted (E)-alkene isosteres such as 4 as -turn mimetics. A combination of A 1,3 -and A 1,2 -strain leads to considerable restrictions in φ,ψ-dihedral angles in these substrates, and the Ramachandran plot of the methylalkene isostere of alanine is closely related to the parent amino acid. 5 In contrast, the disubstituted (E)-alkene analogue is conformationally much more flexible. Even greater steric restrictions are observed for a trifluoromethylated derivative 5 where only ca. 15% of the Ramachandran plot area remains within 15 kJ/mol of the energy minimum. Methylalkene moieties are abundant in terpenes and polypropionate natural products and have indeed been shown to serve as surrogates of backbone amide functions in enzymeinhibitor complexes. 6The mimicry of the electronic properties of the amide bond represents perhaps the most challenging parameter for effective isostere design. Electrostatically, the (trifluoromethyl)alkene represents a better match of the amide bond than any other common alkene isostere ( Figure 1).Efficient synthetic approaches toward diastereomerically and enantiomerically pure alkene peptide isosteres are under intense investigation. 8 A particularly promising convergent pathway utilizes the S N 2′-addition of cuprate reagents to alkenyl aziridines and allylic mesylates. 9 The former approach has also been applied to solid-phase synthesis. 10 We have now extended these methods toward a general synthesis of methyl-and (trifluoromethyl)alkene isosteres and, for the first time, systematically compared the solid state conformations of these peptide mimetics.Swern oxidation of the epoxy alcohol 6, obtained in...