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Gold nanoparticles have been available for many years as a research tool in the life sciences due to their electron density and optical properties. New applications are continually being developed, particularly in nanomedicine. One drawback is the need for an easy, real-time quantitation method for gold nanoparticles so that the effects observed in in vitro cell toxicity assays and cell uptake studies can be interpreted quantitatively in terms of nanoparticle loading. One potential method of quantifying gold nanoparticles in real time is by chemisorption of iodine-125, a gamma emitter, to the nanoparticles. This paper revisits the labelling of gold nanoparticles with iodine-125, first described 30 years ago and never fully exploited since. We explore the chemical properties and usefulness in quantifying bio-functionalised gold nanoparticle binding in a quick and simple manner. The gold particles were labelled specifically and quantitatively simply by mixing the two items. The nature of the labelling is chemisorption and is robust, remaining bound over several weeks in a variety of cell culture media. Chemisorption was confirmed as potassium iodide can remove the label whereas sodium chloride and many other buffers had no effect. Particles precoated in polymers or proteins can be labelled just as efficiently allowing for post-labelling experiments in situ rather than using radioactive gold atoms in the production process. We also demonstrate that interparticle exchange of I-125 between different size particles does not appear to take place confirming the affinity of the binding.

Recognition of the adaptive capacity of mammalian skeletal muscle has opened the way to a number of clinical applications. For most of these, the fast, fatigue-susceptible fibres need to be transformed stably to fast, fatigueresistant fibres that express the 2A myosin heavy chain isoform. The thresholds for activity-induced change are size-dependent, so although the requisite patterns of electrical stimulation are known for the rabbit, in humans these same patterns would produce type 1 fibre characteristics, with an undesirable loss of contractile speed and power. We have used histochemistry, immunohistochemistry and electrophoretic separations to evaluate a possible conditioning regime in a large animal model. Stimulation of the porcine latissimus dorsi muscle with a phasic 30-Hz pattern for up to 41 days converted all type 2X and 2A/2X fibres to 2A with only a small increase in the type 1 population, from 17% to 22%. Stimulation for longer periods increased the proportion of type 1 fibres to 52%. Based on this model, stimulation regimes designed to achieve a stable 2A phenotype in humans should deliver fewer stimulating impulses, possibly by a factor of 2, than the pattern assessed here. Any such pattern needs to be tested for at least 8 weeks.

In a screen for myosin-like proteins in embryonic chicken brain, we have identified a novel nuclear protein structurally related to hnRNP-U (heterogeneous nuclear ribonuclear protein U). We have called this protein chURP, for chicken U-related protein. In this screen, chURP was immunoreactive with two myosin antibodies and, in common with the unconventional myosins, bound calmodulin in vitro in both the presence and absence of calcium ions. Determination of 757 amino acids of the chURP sequence revealed that it shares 41% amino acid identity with human and rat hnRNP-U, although chURP and hnRNP-U appear not to be orthologous proteins. ChURP is ubiquitously expressed in the nuclei of all chick tissues and, as one of a growing number of calmodulin-binding proteins to be identified in the nucleus, further highlights the potential of calmodulin as a regulator of nuclear metabolism.Keywords: hnRNP particles; nuclear matrix; calmodulin; hnRNP-U.Protein-coding genes in eukaryotes are transcribed by RNA polymerase II to form nascent transcripts which, because of their wide size distribution and subcellular localization, are known as heterogeneous nuclear (hn)RNAs. As soon as hnRNAs begin to emerge from their genes, they associate cotranscriptionally with a variety of proteins to become heterogeneous nuclear ribonucleoprotein (hnRNP) complexes [1,2]. The macromolecular composition of hnRNP complexes is diverse and includes spliceosomes, which are themselves ribonucleoprotein complexes consisting of a variety of small nuclear (sn)RNAs and associated proteins in the form of snRNPs [3,4]. Those proteins associated with hnRNAs that are not stable components of RNP complexes such as spliceosomes are generally called hnRNP proteins [1,5]. Approximately 20 major hnRNP proteins, designated hnRNP-A1 through -U in order of ascending molecular weight, are typically identified in hnRNP complexes immunopurified from various sources [1,6±10]. The cDNAs for many of these proteins have now been cloned although their functions are not completely understood [1,5,11]. For example, various hnRNP proteins have been demonstrated to possess RNA annealing activity which may be important in both cis and trans interactions during pre-mRNA splicing [12±18], while the same proteins may also be involved in regulating the export of mature mRNAs from the nucleus to the cytoplasm [19±27]. HnRNP proteins therefore appear to have complex functions.Consistent with their proposed roles in vivo, hnRNP proteins have been demonstrated to bind RNA in vitro [1,5,10]. Three distinct RNA-binding domains (RBDs), known as the RNP-CS, KH and RGG box motifs, are represented in the hnRNP proteins, sometimes in combination within one particular polypeptide [28]. For example, hnRNP-A1 contains two RNP-CS motifs and one RGG box. The RNA-binding activity of recombinant hnRNP-U has been mapped to a 26-amino-acid RGG box motif in a C-terminal 112 amino acid domain termed U-gly, as it is rich in glycine residues [29]. Interestingly, hnRNP-U has also been independently charact...