Dan Nieves’ paper on an easy and accessible method to covalently conjugate proteins, sugars and indeed pretty much any biomoleucle onto nanoparticles has just come out in Chem. Commun.

At the heart of the method is the installation of a maleimide onto the nanoparticle surface. Since the ligands that are used to form the protective self-assembled monolayer on the gold nanoparticle possess thiols to allow bonding to the metal, this requires an indirect method. Dan approached this by incorporating an azide at the end of one of the ligands. After the ligand shell is formed on the nanoparticle, the azide can easily be converted to a maleimide by reaction with a strained cyclooctyne (copper-free click chemistry, which is useful for biomolecules, since Cu+ is quite reactive). The maleimide can then be reacted with a thiol on a protein (Dan used fibroblast growth factor-2) or indeed any other molecule.

Highlighting the versatility of the approach, Dan also conjugated an oligosaccharide derived from heparin to gold nanoparticles this way. The oligosaccharide had previously been derivatised by Nina Azmi, so that it had a maleimide at its reducing end (thiol chemistry is orthogonal to the reactivity of other groups on this class of sugars, so particularly useful). The ligand shell of the nanoparticles, on which we have spent a lot of effort in the past, is resistant to ligand exchange by dithiothreitol (the present paper and here). So a quick reaction of the maleimide with dithiothreitol, and we have a thiol on the outside of the nanoparticle ligand shell, which in turn reacts with the maleimide on the oligosaccharide.

The ligand shell allows control of the stoichiometry of nanoparticle functionalisation, so Dan made 1:1 conjugates, which will be particularly useful for future functional studies.

We are excited by this work, because hitherto we have been restricted to non-covalent conjugation. A perpetual worry is that the exchange of the hexahistidine tagged protein on the nickel-NTA-nanoparticle for an endogenous protein with a histidine patch. We know there is real potential for this, because, when you run a cell lysate over a nickel-NTA column, there are plenty of untagged proteins that bind rather well. With covalent conjugation, this is one worry we can lay to rest.

In the case of proteins, cysteine can often be mutated to serine without affecting function and/or a cysteine can be introduced genetically as an N-terminal tag, again without affecting function. This allows rational chemical genetic covalent coupling of proteins to nanoparticles by Dan’s method, which provides scope for applications in functional work in cells. For sugars and nucleic acids, the thiol chemistry is, as noted above, completely orthogonal to the groups that occur naturally on these molecules, so nanoparticle conjugation can be designed very precisely and simply.

On December 31 2013 I posted my New Year’s resolution: to only review manuscripts from open access or learned society journals.

My reasoning was that open access will only be the norm if we stop giving that which is most precious, our time, to closed access journals. I really think the wider community needs to start to be selective in reviewing. It is far easier to implement than the radical re-alignment of library journal subscriptions. Continue Reading »

This post is entirely inspired by a Tweet that appeared in my stream via @stuartcantrill, a request for ideas on the future of chemistry. My (instant) response was that we have to replace everything with materials derived from waste biomass. After finishing my morning check of information systems and my coffee, it was time to get on my bike and cycle to the university. This set off the lateral neuronal activity that my brain engages in when I cycle – the worse the traffic, the more lateral activity… Continue Reading »

The sadly predictable hyping of things nano reached a nadir recently with the promotion of silver nanoparticles (aka “silver bullet”) as a treatment for ebola virus. There has been a great discussion of this and other aspects of silver nanoparticles by Andrew Maynard (here, here for ebola and here for the essential Risk Bites video).

It may surprise some, but until a few weeks ago, there was no simple, direct published method to quantify non-destructively silver nanoparticles. Yet, the non-destructive quantification of silver nanoparticles is essential to any experiment that aims to prepare and use these in a biological context. Without it any experimental work is likely to be qualitative and simple things, such as determining the stoichiometry of functonalisation, become difficult. Indeed, so important is simple quantification of nanoparticles that we validated and published a method for gold nanoparticles in 2007 that has been very well received by the community and which we use daily in the lab. Continue Reading »

Last week at Retraction Watch (RW) there was a post on a paper in elife by Andrew Stern, Arturo Casadevall, Grant Steen, and Ferric Fang that put a figure on the cost of research misconduct, using misconduct officially identified by the ORI.

A number of comments on RW, including my own, highlighted that the study necessarily (because it had to use hard data) resulted in an underestimate of the financial cost of misconduct by a least a factor of 10. I thought it useful to summarise my views in what follows. Continue Reading »

Policing the police

The end of this week has seen two very insightful postings on science and governance by Stephen Curry and Neuroskeptic.

Stephen Curry’s post “Who governs science” has what is for me a pithy summary of how science works: “No-one is in charge … …. That structure, or rather, lack of structure has not been arrived at by design but reflects the organic emergence of the scientific enterprise over the past several hundred years… …It poses challenges for good governance but is at the same time a source of great strength.

Continue Reading »

The burden of proof

This post has been stimulated by a post on PubPeer entitled “A crisis of trust
This post should be required reading for all engaged in research and in the management of the institutions involved in research, including funders and journal editors. I made a brief comment, relating to a sentence that is some way down the post:

“This could be done if together we invert the burden of proof. It should be your responsibility as a researcher to convince your peers, not theirs to prove you wrong”. Continue Reading »


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