No abstract

Biological and artificial molecules and assemblies capable of supramolecular recognition, especially those with nucleobase pairing, usually rely on autonomous or collective binding to function. Advanced site-specific recognition takes advantage of cooperative spatial effects, as in local folding in protein-DNA binding. Herein, we report a new nucleobase-tagged metal-organic framework (MOF), namely ZnBTCA (BTC=benzene-1,3,5-tricarboxyl, A=adenine), in which the exposed Watson-Crick faces of adenine residues are immobilized periodically on the interior crystalline surface. Systematic control experiments demonstrated the cooperation of the open Watson-Crick sites and spatial effects within the nanopores, and thermodynamic and kinetic studies revealed a hysteretic host-guest interaction attributed to mild chemisorption. We further exploited this behavior for adenine-thymine binding within the constrained pores, and a globally adaptive response of the MOF host was observed.

No abstract

A novel, sensitive DNA hybridization detection protocol, based on DNA-quantum dots nanoconjugates coupled with electrochemical impedance spectroscopy (EIS) detection, is described. The amino-linked ss-DNA probe was covalently immobilized onto a self-assembled mercaptoacetic acid monolayer modified gold electrode; after hybridization with the target ssDNA-CdS nanoconjugates, EIS was used to detect the change of interfacial electrontransfer resistance (R et ) of the redox marker, [Fe(CN) 6 ] 4À/3À , from solution to transducer surface. The results showed that when target ssDNA-CdS nanoconjugates hybridized with probe oligonucleotide, a double helix film formed on the electrode, a remarkably increased R et value was observed. Only complementary DNA sequence had an obvious signal compared with three-base mismatched or non-completely matched sequences under the optimized experimental conditions. Due to having more negative charges, space resistance and the semiconductor property, CdS nanoparticle labels on target DNA could improve the sensitivity to two orders of magnitude when compared with non-CdS tagged DNA sequences.

scattering, etc., the one based on luminescence possesses the merits of fast response, excellent spatial resolution, and high sensitivity, which translate into great advantages for microfluidic and bioimaging applications. [2] Particularly, by employing the intensity ratio of two independent emissions in the same materials, luminescent ratiometric thermometers (LRTs) are independent of sensor concentration, excitation power, and drifts of the optoelectronic systems. These unique characteristics ensure accurate and reliable temperature sensing. [3] On the other hand, temperature is a crucial parameter for monitoring protoplast events in order to track the cellular pathology and physiology as well as understand the treatments and diagnoses. Hence, the development of biocompatible temperature probes is highly desired. Various types of material-based thermometers have been developed for monitoring temperature at the cellular level, including europium (III) complexes, nanomaterials, polymers, quantum dots, and biomaterial microcantilevers. [4,5] Metal-organic frameworks (MOFs) are one of the most promising thermochromic materials due to their remarkable structural diversities and tunable luminescent properties. Light-emitting species such as metal ions and organic ligands can be periodically integrated into the framework; this unique characteristic along with high porosity effectively prevent aggregation-induced luminescence quenching and make MOF materials excellent candidates for encapsulating other luminescent species. For example, lanthanide ions, luminescent dyes, and quantum dots could be encapsulated in MOFs for applications in color control and temperature sensing. [4d,e,f,9b] Many cases of LRT-MOFs based on lanthanide ions have received much attention for their interesting temperaturedependent luminescence properties. [3a,4b,5b,6,7] More recently, LRT-MOFs constructed with mixed lanthanide ions (usually Tb 3+ and Eu 3+ ) have been reported by Qian and Chen et al. with improved sensing performance and sensitivity. [1b,c,3a,4b,7] However, scarcity of rare earth metals could limit their extensive applications of any kind. Therefore, it is equally challenging to explore LRT-MOFs constructed with readily available and inexpensive metals in this line of work. For monitoring temperature at the cellular level, exploring LRT-MOFs with biocompatibility, although still in its nascency, is of great significance. Luminescent ratiometric thermometers (LRTs) based on the emission intensity ratio with self-reference functions guarantee a temperature sensing of fast response, high precision, and excellent spatial resolution. For monitoring temperature at the cellular level, the use of metal-organic frameworks (MOFs) as probes, especially biocompatible ones, is still in its nascency. By employing a biological MOF, Zn 3 (benzene-1,3,5-tricarboxyl) 2 (adenine)(H 2 O) (ZnBTCA), as a host and thermosensitive fluorescent dyes as guests, a series of dye@ZnBTCA is synthesized and studied as potential LRT materials, featuring a...