Metal complexes as "protein surface mimetics"

A key challenge in chemical biology is to identify small molecule regulators for every single protein. However, protein surfaces are notoriously difficult to recognise with synthetic molecules, often having large flat surfaces that are poorly matched to traditional small molecules. In the surface mimetic approach, a supramolecular scaffold is used to project recognition groups in such a manner as to make multivalent non-covalent contacts over a large area of protein surface. Metal based supramolecular scaffolds offer unique advantages over conventional organic molecules for protein binding, including greater stereochemical and geometrical diversity conferred through the metal centre and the potential for direct assessment of binding properties and even visualisation in cells without recourse to further functionalisation. This feature article will highlight the current state of the art in protein surface recognition using metal complexes as surface mimetics.

Protein Surface Mimetics: Understanding How Ruthenium Tris(Bipyridines) Interact with Proteins

Protein surface mimetics achieve high-affinity binding by exploiting a scaffold to project binding groups over a large area of solvent-exposed protein surface to make multiple cooperative noncovalent interactions. Such recognition is a prerequisite for competitive/orthosteric inhibition of protein-protein interactions (PPIs). This paper describes biophysical and structural studies on ruthenium(II) tris(bipyridine) surface mimetics that recognize cytochrome (cyt) c and inhibit the cyt c/cyt c peroxidase (CCP) PPI. Binding is electrostatically driven, with enhanced affinity achieved through enthalpic contributions thought to arise from the ability of the surface mimetics to make a greater number of noncovalent interactions than CCP with surface-exposed basic residues on cyt c. High-field natural abundance ¹ H,¹⁵ N HSQC NMR experiments are consistent with surface mimetics binding to cyt c in similar manner to CCP. This provides a framework for understanding recognition of proteins by supramolecular receptors and informing the design of ligands superior to the protein partners upon which they are inspired.

Inhibition of Beclin 1 expression enhances cisplatin-induced apoptosis through a mitochondrial-dependent pathway in human ovarian cancer SKOV3/DDP cells

The purpose of this study was to determine the influence of autophagy on cisplatin-induced ovarian cancer SKOV3/DDP cell line death through regulation of the expression of the autophagy gene, Beclin 1, and to explore the potential mechanism underlying the relationship between autophagy and apoptosis. When compared with a blank control group, the proportion of apoptotic cells undergoing Beclin 1 interfering increased significantly after cisplatin treatment, accompanied by reduction in mitochondrial membrane potential, increase in activities of caspase-9/3 and cytoplasmic cytochrome C, elevation of Bax expression, and reduction in Bcl-2 expression. However, the proportion of apoptotic cells with Beclin 1 overexpression reduced. These findings suggest that Beclin 1 plays an important role in the regulation of potent antitumor activity through a mitochondrial-dependent pathway in SKOV3/DDP cell line, and inhibition of Beclin 1 expression may become a new target for the sensitization therapy of ovarian cancer with cisplatin.

Cytochrome c conjugated to ZnO-MAA nanoparticles: the study of interaction and influence on protein structure

Nanoparticle-protein conjugates have potential for numerous applications due to the combination of the properties of both components. In this paper we studied the conjugation of horse heart cytochrome c with ZnO nanoparticles modified by mercaptoacetic acid (MAA) which may be a material with great potential in anticancer therapy as a consequence of synergic effect of both components. Cyt c adsorption to the ZnO-MAA NPs surface was studied by UV-vis spectroscopy and by a dynamic light scattering in various pH. The results indicate that the optimal pH for the association of protein with modified nanoparticles is in range 5.8-8.5 where 90-96% of cytochrome c was assembled on ZnO-MAA nanoparticles. The interaction of proteins with nanoparticles often results in denaturation or loss of protein function. Our observations from UV-vis spectroscopy and circular dichroism performed preserved protein structure after the interaction with modified nanoparticles.

Beclin 1 Influences Cisplatin-Induced Apoptosis in Cervical Cancer CaSki Cells by Mitochondrial Dependent Pathway

Purpose

To investigate the role of Beclin 1 expression on the cisplatin-induced apoptosis in cervical cancer CaSki cells and to explore the potential mechanism underlying this effect.

Materials and Methods

After overexpression or partial silencing of Beclin 1 in cervical cancer CaSki cells, the transfected group and the control group were treated with cisplatin for 24 hours. The percentage of apoptotic cells were assessed by flow cytometry. The mitochondrial membrane potential and activities of caspase-8/9/3 were detected by JC-1 fluorescence staining and colorimetry. The expression of cytochrome c was measured using a Western blot. The messenger RNA expression of Bax and Bcl-2 were detected by real-time quantitative reverse transcription polymerase chain reaction.

Results

Expression of Beclin 1 protein was up-regulated in overexpressed transfectants of CaSki cells. After treatment with cisplatin, the Beclin 1 overexpression group led to the decrease of mitochondrial membrane potential and increase of activities of caspase-9 and caspase-3, and showed a greater increase in apoptosis than did the nontransfected group. Furthermore, Beclin 1 overexpression resulted in increased cytoplasmic cytochrome c and Bax expression and decreased mitochondrial cytochrome c and Bcl-2 expression.

Conclusion

Overexpression of Beclin 1 in CaSki cells may influence cisplatin-induced apoptosis by mitochondrial dependent pathway.

Molecular recognition: from solution science to nano/materials technology

In the 25 years since its Nobel Prize in chemistry, supramolecular chemistry based on molecular recognition has been paid much attention in scientific and technological fields. Nanotechnology and the related areas seek breakthrough methods of nanofabrication based on rational organization through assembly of constituent molecules. Advanced biochemistry, medical applications, and environmental and energy technologies also depend on the importance of specific interactions between molecules. In those current fields, molecular recognition is now being re-evaluated. In this review, we re-examine current trends in molecular recognition from the viewpoint of the surrounding media, that is (i) the solution phase for development of basic science and molecular design advances; (ii) at nano/materials interfaces for emerging technologies and applications. The first section of this review includes molecular recognition frontiers, receptor design based on combinatorial approaches, organic capsule receptors, metallo-capsule receptors, helical receptors, dendrimer receptors, and the future design of receptor architectures. The following section summarizes topics related to molecular recognition at interfaces including fundamentals of molecular recognition, sensing and detection, structure formation, molecular machines, molecular recognition involving polymers and related materials, and molecular recognition processes in nanostructured materials.

Protein recognition of hetero-/homoleptic ruthenium(II) tris(bipyridine)s for α-chymotrypsin and cytochrome c

We examined the relationship between the structures of hetero-/homoleptic ruthenium(II) tris(bipyridine) metal complexes (Ru(II)(bpy)(3)) and their binding properties for α-chymotrypsin (ChT) and cytochrome c (cyt c). Heteroleptic compound 1a binds to both ChT and cyt c in 1:1 ratio, whereas homoleptic 2 forms 1:2 protein complex with ChT but 1:1 complex with cyt c. These results suggest that the structure of the recognition cavity in Ru(II)(bpy)(3) can be designed for shape complementarity to the targeted proteins. In addition, Ru(II)(bpy)(3) complexes were found to be potent inhibitors of cyt c reduction and to permeate A549 cells.

Protein surface recognition using geometrically pure Ru(II) tris(bipyridine) derivatives

This manuscript illustrates that the geometric arrangement of protein-binding groups around a ruthenium(II) core leads to dramatic differences in cytochrome c (cyt c) binding highlighting that it is possible to define synthetic receptors with shape complementarity to protein surfaces.

Inhibition of protein-protein interactions using designed molecules

Although many cellular processes depend upon enzymatic reactions, protein-protein interactions (PPIs) mediate a large number of important regulatory pathways and thus play a central role in disease development. In order to understand and selectively inhibit cellular signalling pathways, there is a pressing need for small molecules that target PPIs, particularly in the context of pharmaceutical development. This tutorial review will introduce the relevance of PPIs to chemical biology and highlight the key challenges in designing inhibitors. Some of the successes using conventional approaches to the identification of small-molecule PPI inhibitors will be highlighted, and also the reasons why these approaches have not always proven successful. Several general approaches tailored to particular protein topologies are emerging for the design of scaffolds that inhibit PPIs-these will form the major content of this review. Finally a summary of the challenges to be faced in developing inhibitors of PPIs into drug leads and how these challenges may differ from those encountered with enzyme-like targets will be given.