A structure-function analysis of the icosahedral RNA bacteriophage fr coat protein (CP) assembly was undertaken using linker-insertion, deletion and substitution mutagenesis. Mutations were specifically introduced into either pre-existing or artificially created restriction enzyme sites within fr CP gene expressed in Escherichia coli from a recombinant plasmid. This directs synthesis of wild type protein that undergoes self-assembly and forms capsid-like particles indistinguishable morphologically and immunologically from native phage particles. A series of fr CP variants containing sequence alterations in the regions which are (i) exposed on the external surface of capsid or (ii) located on the contacting areas between CP subunits were obtained and their assembly properties investigated. The majority of mutants demonstrated reduction of assembly ability and formed either CP dimers (mutations at residues 2, 10, 63 or 129) or both dimer and capsid structures (residue 2 or 69). The exceptions were variants demonstrating normal assembly and containing insertions at residues 2, 50 or 129 of the fr CP. A third type of assembled structure was formed by a variant with a single amino acid substitution I104T. The alpha A-helix region (residues 97-111) is particularly sensitive to mutation and any alteration in this region decreases accumulation of mutant protein in E. coli. The relative contributions of particular fr CP domains in maintenance of capsid structural integrity as well as the possible capsid assembly mechanism are discussed.

Simple SummaryCurrently, several alternative protein sources are under investigation for replacing soybean meal in poultry diets. One alternative is larvae meal of the black soldier fly (Hermetia illucens) with a specific sulfur amino acid composition. The larvae meal is limiting in sulfur amino acids supply and provides a wide methionine:cysteine ratio of 61:39. Currently, it is not known whether the insect meal has an impact on the optimal ratio of methionine to cysteine in broiler chicken diets. The methionine:cysteine ratio significantly influences animal growth and welfare. Both methionine and cysteine excess and deficiency can lead to an impaired feed intake, growth, and feed efficiency. Therefore, the aim of this study was to investigate whether the optimal methionine:cysteine ratio is modulated when a high inclusion rate of partly defatted Hermetia illucens meal is applied. The results show that a methionine:cysteine ratio of 50:50 yields superior growth and dietary protein quality. It can be concluded that the insect meal under study is a promising alternative protein source without modulating the optimal methionine:cysteine ratio in broiler chicken diets.AbstractThe dietary methionine:cysteine (Met:Cys) ratio (MCR) is an important factor influencing the optimal growth of chickens. Therefore, this study aimed to contribute to the assessment of the optimal dietary MCR in diets with the complete replacement of soybean meal (SBM) by a partly defatted larvae meal of Hermetia illucens (HM). A growth study with 240 male meat-type chickens (Ross 308) was conducted, also assessing the body nutrient deposition both at the end of the starter (day 21) and the grower (day 35) period. Birds were fed experimental diets based on wheat, maize, and insect meal (23%/21% HM in starter/grower diets). Sulfur amino acids were created as the limiting AA in diets with graded MCR (40:60; 45:55; 50:50; 55:45; 60:40). The control diet contained SBM instead of HM with a MCR of 50:50. The current results based on growth parameters, dietary protein quality, and Met efficiency data gave support to the previous assumption of an ideal MCR of 50:50, which was also valid in diets with a high proportion of insect meal. The lowest MCR of 40:60 led to significantly impaired feed intake and growth of the birds, while the response to the highest MCR (60:40) was moderate.

Um die Abweichungen des Anstrengungszustandes von dem gem. Stabtheorie berechneten zu begrenzen, werden windbelastete schlanke Kreiszylinderschalen mit Ringsteifen versehen. Die deutsche Fachnorm fordert mindestens eine ausreichend dimensionierte Kopfversteifung. Es fehlen gegenwärtig gesicherte technische Regeln, für welche Belastung diese Ringsteifen zu bemessen sind und welche Mindeststeifigkeiten gewährleistet sein müssen. Im Beitrag wird gezeigt, daß das Tragverhalten der Ringversteifungen als Funktion der langwelligen Lösung der Semimembrantheorie beschrieben werden kann. Davon ausgehend werden Regelungsvorschläge für die anzusetzende Einflußlänge und die einzuhaltenden Mindeststeifigkeiten entwickelt.

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