Serine carboxypeptidases contain a conserved catalytic triad of serine, histidine, and aspartic acid active-site residues. These enzymes cleave the peptide bond between the penultimate and C-terminal amino acid residues of their protein or peptide substrates. The Arabidopsis Genome Initiative has revealed that the Arabidopsis genome encodes numerous proteins with homology to serine carboxypeptidases. Although many of these proteins may be involved in protein turnover or processing, the role of virtually all of these serine carboxypeptidase-like (SCPL) proteins in plant metabolism is unknown. We previously identified an Arabidopsis mutant, sng1 (sinapoylglucose accumulator 1), that is defective in synthesis of sinapoylmalate, one of the major phenylpropanoid secondary metabolites accumulated by Arabidopsis and some other members of the Brassicaceae. We have cloned the gene that is defective in sng1 and have found that it encodes a SCPL protein. Expression of SNG1 in Escherichia coli demonstrates that it encodes sinapoylglucose:malate sinapoyltransferase, an enzyme that catalyzes a transesterification instead of functioning like a hydrolase, as do the other carboxypeptidases. This finding suggests that SCPL proteins have acquired novel functions in plant metabolism and provides an insight into the evolution of secondary metabolic pathways in plants.

The phenylpropanoid enzyme 4-coumarate:coenzyme A ligase (4CL) is considered necessary to activate the hydroxycinnamic acids for the biosynthesis of the coniferyl and sinapyl alcohols subsequently polymerized into lignin. To clarify the role played by 4CL in the biosynthesis of the guaiacyl (G) and syringyl (S) units characteristic of angiosperm lignin, we generated 4CL antisense Arabidopsis lines having as low as 8% residual 4CL activity. The plants had decreases in thioglycolic acid-extractable lignin correlating with decreases in 4CL activity. Nitrobenzene oxidation of cell walls from bolting stems revealed a significant decrease in G units in 4CL-suppressed plants; however, levels of S lignin units were unchanged in even the most severely 4CL-suppressed plants. These effects led to a large decrease in the G/S ratio in these plants. Our results suggest that an uncharacterized metabolic route to sinapyl alcohol, which is independent of 4CL, may exist in Arabidopsis. They also demonstrate that repression of 4CL activity may provide an avenue to manipulate angiosperm lignin subunit composition in a predictable manner.

Root surface roughness, resulting from calculus removal by hand curette, ultrasonic curette and rotating diamond or Roto-Pro points, was examined by combined use of microroughness measurements and scanning electron microscopy (SEM). Mandibular incisors were placed in a jaw model with a rubber "gingiva" in an attempt to simulate a clinical situation. After cleaning with the various instruments, the surface roughness was measured by an industrial profilometer followed by SEM evaluation. A microroughness index (MRI) was developed and showed that the instruments could be separated into three groups, where the hand curette produced least roughness, followed by the Roto-Pro instrument, while the ultrasonic curette and the diamond left the most uneven surfaces. A SEM roughness index (SRI) based on defined criteria, corresponded well with the results from the profilometer measurements, except that using this index the diamond scored higher than the ultrasonic curette. This was probably due to considerable calculus remnants remaining in the ultrasonic specimens. Characteristic features of the root surface morphology of the cleaned teeth are described. It is concluded that the combined use of microroughness measurements and SEM is of considerable value in this type of studies since more information may be obtained than by any of these methods used separately.

The efficiency of calculus removal and the amount of lost tooth substance resulting from the use of hand curette, ultrasonic curette and rotating diamond and Roto-Pro points were examined by scanning electron microscopy (SEM). Root surfaces of mandibular incisors placed in a jaw model were cleaned of adhering deposits, photographed by SEM and evaluated at a standard magnification by three examiners. Scores were given for remaining calculus (RCI) and loss of tooth substance (LTSI) according to defined index criteria. The results revealed that calculus removal was most complete following diamond instrumentation, whereas the ultrasonic curette was least efficient in this respect. Hand curette, ultrasonic curette and Roto-Pro removed about the same amount of tooth substance whereas the diamond removed considerably more than the others. The diamond regularly removed all the cementum and left deep instrumental marks in the dentin; it seems advisable to avoid the use of such instruments in periodontal depuration.

The electrification of automotive powertrains in recent years has been driving the development of internal combustion engines towards reduced volumes with higher power outputs. These changes place extreme demands on engine materials. Engineers employ the computer-aided engineering approach to design reliable and cost-effective engines. However, this approach relies on accurate knowledge of the material deformation and fatigue characteristics during service-like loading. The present study seeks to investigate the effect of dwell times on the deformation and fatigue behaviour of the A356-T7 + 0.5 wt.% Cu alloy used to cast cylinder heads. In particular, we study the effect of dwell time duration at various temperatures. A combined fatigue-dwell testing procedure, with the dwell at the maximum compressive strain, replicates the service conditions. It is found that the material exhibits a stress relaxation behaviour with a decreasing relaxation rate. At lower temperatures, the load level influences the relaxation more than at elevated temperatures. However, the dwell does not significantly affect the hardening behaviour or the life of the tested alloy. Finally, we model the time-dependent material behaviour numerically. The Chaboche model, combined with a Cowper–Symonds power-law, is found to capture the visco-plastic deformation behaviour accurately.