Chemical Communications Blog

A new tool for the selective detection of dopamine in water, with potential applications to urine and serum, has recently been developed by the Chinese research group led by Fang Zeng and Shuizhu Wu.

The new sensor, with a detection limit of 50 nM, is based on the fluorescence response obtained when dopamine reacts with a molecule containing an o-phtalic hemithioacetal (OPTA). The selectivity of the system over other amino acids and primary amines has been obtained by trapping the OPTA-bearing group within the pores of microporous silica particles and enhanced by anchoring a β-cyclodextrin (β-CD) layer on the surface of the particles.  The β-CD, due to their ability of supporting both hydrogen-bond and hydrophobic interactions, serves as a barrier for most interfering molecules but allows dopamine to reach the pores. The authors believe that this derives from its limited capability of forming both hydrophobic and hydrogen-bonds.

Repeated tests proved that without the β-CD layer the selectivity is lost and that out of 24 potential interfering molecules, among which common amino acids, epinephrine and others, only two (histidine and norepinephrine) gave responses comparable to dopamine. While the results obtained for norepinephrine can be ascribed to the structural similarities to the target molecule, the reason behind the behaviour of the sensor towards histidine are currently unclear.

Dopamine is an important neurotransmitter involved in behavioural responses, sleep regulation, mood and learning processes among others. A malfunction in the dopamine regulating processes and related disruptions are implicated in the attention deficit disorder, Alzheimer`s disease, schizophrenia and psychosis. 

Korean scientists have used graphene sheets to make a transparent and lightweight loudspeaker which, they say, can be attached to windows and computer screens.

Graphene, whose isolation led to the Nobel prize in physics for Andre Geim and Konstantin Novoselov, is a single layer of graphite. Owing to its remarkable mechanical and electronic properties, it is set to revolutionise modern technology and new uses for it are continuously being discovered. However, one of the big challenges is to fabricate large area films of graphene.

Now, Jyongsik Jang and coworkers from Seoul National University have used inkjet printing and vapour deposition to deposit graphene oxide onto poly(vinylidene fluoride) (PVDF), which is then reduced to create a graphene film. This demonstrates not only a new method for making controlled graphene films, but also a new use for the material: for making a thin transparent loudspeaker.

The acoustic actuator consists of a graphene-based transducer connected to the sound source and amplifier

The speaker system consists of a PVDF thin film sandwiched between two graphene electrodes. The speaker works because when an electrical current from the sound source is applied, the converse piezoelectric effect causes the PDVF film to distort, creating sound waves.

Such a system would be easy to install and usable anywhere where sound is needed, Jang explains. They could even eventually be used as noise cancelling devices by creating anti-noise waves (same amplitude but with inverted phase to the original sound).

To read more please visit the Chemistry World website, or download the original ChemComm communication.

DNA bulges occur when one or more extra bases are added on one side of the DNA strain during the transcription process. These bases generally face either inwards or outwards with respect to the main helix. If we imagine DNA as a straight ladder, a bulge would be a half step that fails to reach the other side. DNA bulges, if not corrected after the transcription process, can often lead to mutations and to the rise of diseases and life threatening conditions. Particular DNA bulges are also relevant in the replication of HIV.

Due to the importance and biological significance of these structures, many studies have been conducted towards the development of molecules that specifically target and recognise these modifications. Molecules have been developed to selectively bind to bulges containing Guanine(G), Adenine(A) and aggregates of Cytosine/Thymine(C/T), but very few show high selectivity for T alone.

The group led by Janet R. Morrow, of the University of Buffalo focused on thymine, and developed a Zn(II) based macrocyclic complex that exhibits a higher than 100-fold specificity for T bulges. The complex is based on a modified cyclen backbone with a quinoline-containing pendant arm, which proved essential for the enhanced selectivity and binding abilities.

Another interesting feature emerging from the study is that when tested on oligonucleotides containing single-base bulges in the stem of a hairpin or a duplex structure, binding occurred without damage to the structure of the stem and only when T was in the bulge. Several other oligonucleotides with different bases in the bulge and with thymine in the hairpin stem (no bulge) were tested to further assess the selectivity of the complex, resulting in only one example of reduced binding when the T bulge has a cytosine on both sides.

 NMR titrations were used to follow the binding process thanks to a clear change in the chemical shift of methylenic protons on the base after coordination.

To read the original ChemComm communication, please take a look at:-

Recognition of thymine in DNA bulges by a Zn(II) macrocyclic complex
Imee Marie A. del Mundo, Matthew A. Fountain and Janet R. Morrow
Chem. Commun., 2011, Advance Article

Posted on behalf of Dr. Giorgio De Faveri, Web Writer for Catalysis Science & Technology.