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Ricin is a toxic protein produced in the seeds of the castor bean plant. The toxicity of the protein and the ease in which it can be extracted from the seeds makes it a potential biological warfare agent. There has been extensive work in the development of analytical techniques that can identify the protein robustly and rapidly. On-target tryptic digestion and MALDI MS was used to distinguish ricin from bovine serum albumin and three other type 2 ribsome-inactivating proteins (RIPs), abrin, agglutinin (RCA(120)), and viscumin, using the peptide mass fingerprint. The sequence coverage obtained was enhanced using methanol-assisted tryptic digestion and was particularly useful for the detection of these toxins in complex matrixes. When used in conjunction with intact protein MALDI mass measurement, a positive identification of ricin (or any of the other RIPs) was achieved including confirmation of the integrity of the disulfide bond between the A and B chains. This applicability of this methodology was demonstrated by the identification of ricin in a typical "crude white powder" that may be illicitly produced in a clandestine lab. The analysis on the solubilized sample using this method can be undertaken in around an hour with minimal sample preparation.

Ricin is a highly toxic protein from the seeds of the castor bean plant. Crude extracts from castor beans are toxic by several routes, and there is international concern about the use of these extracts by terrorist organizations. Lethality in aerosolized form has spurred the development of methods for the rapid detection of this protein from air samples that is critical in determining the illicit use of this material. Matrix-assisted laser desorption ionization (MALDI) mass measurement with an automated laser firing sequence was used to detect intact ricin from solutions containing less than 4 microg/mL of ricin in the presence of other endogenous seed proteins. This sensitivity was attained with the addition of 0.01% Tween 80 to the extracts that greatly enhanced the ricin signal. Importantly, this treatment substantially reduces the interference from the castor bean seed storage proteins. Commonly the ricin signal can be completely obscured by the oligomers of seed storage proteins, and this treatment reveals the ricin molecular ion, allowing the analyst to make a judgment as to the ricin content of the extract. This method provides for sensitive and rapid identification of intact ricin from aqueous samples with little sample preparation and is amenable to automatic acquisition.

Caerin 1.1 is a potent broad-spectrum antibacterial peptide isolated from a number of Australian frogs of the Litoria genus. In membrane-like media, this peptide adopts two alpha-helices, separated by a flexible hinge region bounded by Pro15 and Pro19. Previous studies have suggested that the hinge region is important for effective orientation of the two helices within the bacterial cell membrane, resulting in lysis via the carpet mechanism. To evaluate the importance of the two Pro residues, they were replaced with either Ala or Gly. The antibacterial activity of these two peptides was tested, and their three-dimensional structures were determined using two-dimensional NMR spectroscopy and restrained molecular dynamics calculations. The resulting structures indicate that the central hinge angle decreases significantly upon replacement of the Pro residues with Gly and to a further extent with Ala. This trend was mirrored by a corresponding decrease in antibiotic activity, further exemplifying the necessity of the hinge in caerin 1.1 and related peptides. In a broader context, the use of Pro, Gly, and Ala variants of caerin 1.1 has enabled the relationship between conformational flexibility and activity to be directly investigated in a systematic manner.