Carl Leung

• PhD
• Research Associate at Birkbeck, University of London

Pore forming proteins are widely used weapons of attack and defence in all domains of life. In the course of their action, they are released as monomers, bind to the target membrane, and assemble into oligomeric transmembrane pores. Our understanding of these processes has been enhanced by atomic force microscopy studies of membrane pore formation,...

Structural variability and flexibility are crucial factors for biomolecular function. Here we have reduced the invasiness and enhanced the spatial resolution of atomic force microscopy (AFM) to visualize, for the first time, different structural conformations of the two polynucleotide strands in the DNA double helix, for single molecules under near...

Surface charges play a key role in determining the structure and function of proteins, DNA, and larger biomolecular structures. Here we report on the measurement of the electrostatic surface potential of individual DNA and avidin molecules with nanometer resolution using Kelvin probe force microscopy. We also show, for the first time, the surface p...

Atmospheric aerosol formation is known to occur almost all over the world, and the importance of these particles to climate and air quality has been recognized. Although almost all of the processes driving aerosol formation take place below a particle diameter of 3 nanometers, observations cover only larger particles. We introduce an instrumental s...

Perforin is a key protein of the vertebrate immune system. Secreted by cytotoxic lymphocytes as soluble monomers, perforin can self-assemble into oligomeric pores of 10-20 nm inner diameter in the membranes of virus-infected and cancerous cells. These large pores facilitate the entry of pro-apoptopic granzymes, thereby rapidly killing the target ce...

Based on soft-touch atomic force microscopy, a method is described to reconstruct the secondary structure of single extended biomolecules, without the need for crystallization. The method is tested by accurately reproducing the dimensions of the B-DNA crystal structure. Importantly, intramolecular variations in groove depth of the DNA double helix...

Nanostructured surfaces are surface architectures with lateral features of size 1–100 nm, precisely the size scale of biological molecules, e.g. proteins. Immobilisation of single protein molecules by selective binding to a surface nanofeature suggests a new generation of experiments and represents the ultimate limit for biochip analysis. We demons...

Electrostatic forces and potentials are keys in determining the interactions between biomolecules. We have recently imaged the topography and electrostatic surface potential of nucleic acid molecules on silicon surfaces using Kelvin probe force microscopy (KPFM). Here, we demonstrate KPFM imaging on insulating surfaces like mica, which provides acc...

Frequency-modulation atomic force microscopy (FM-AFM) relies on an accurate tracking of the resonance frequency of a scanning probe. It is now used in environments ranging from ultrahigh vacuum to aqueous solutions, for slow and for fast imaging, with probes resonating from a few kilohertz up to several megahertz. Here we present a versatile experi...

Understanding and controlling protein adsorption on surfaces is fundamental to many biological processes ranging from cell adhesion to the fabrication of protein biochips. In general, proteins need to retain their 3D conformation to perform their intended functions. However, when they are presented with a solid surface, complex interactions ranging...

We have employed liquid phase atomic force microscopy (AFM) to explore the immobilization of green fluorescent protein (GFP) molecules on films of size-selected gold clusters pinned on the surface of graphite. Previous studies indicated covalent binding between such clusters and a variety of proteins. For GFP, strong binding does not occur, but tap...

In this Opinion article, we describe a nanotechnology-based approach to immobilize and orient proteins onto surfaces using atomic clusters prepared by physical methods. This is relevant to future protein biochips where dilute arrays of protein binding sites, each designed to immobilize no more than one protein molecule, would be ideal. In the case...

Atmospheric aerosol formation is known to occur almost all over the world, and the importance of these particles to climate and air quality has been recognized. Although almost all of the processes driving aerosol formation take place below a particle diameter of 3 nanometers, observations cover only larger particles. We introduce an instrumental s...

The atomic force microscope (AFM), operating in contact mode, has been employed in buffer solution to study two proteins; (i) green fluorescent protein (GFP), from the hydromedusan jellyfish Aequorea victoria; and (ii) human oncostatin M (OSM), in the presence of size-selected gold nanoclusters pinned on to a highly oriented pyrolytic graphite subs...

Protein immobilization by nanocluster films is a new route to stabilize individual protein molecules and complexes for single-molecule measurements such as liquid-phase atomic force microscopy (AFM) imaging (see Figure). The sub-monolayer films of size-selected Au clusters present protein binding sites of arbitrary density.