Cytophaga johnsonae displays many features that make it an excellent model of bacterial gliding motility. Unfortunately, genetic analyses of C. johnsonae, or any related gliding bacteria, were not possible because of a complete lack of selectable markers, cloning vectors, transposons, and convenient methods of gene transfer. As a first step toward a molecular analysis of gliding motility of C. johnsonae, we developed these genetic techniques and tools. Common broad-host-range plasmids and transposons did not function in C. johnsonae. We identified one Bacteroides transposon, Tn4351, that could be introduced into C. johnsonae on plasmid R751 by conjugation from Escherichia coli. Tn4351 inserted in the C. johnsonae genome and conferred erythromycin resistance. Tn4351 insertions resulted in auxotrophic mutations and motility mutations. We constructed novel plasmids and cosmids for genetic analyses of C. johnsonae. These cloning vectors are derived from a small cryptic plasmid (pCP1) that we identified in the fish pathogen Cytophaga psychrophila D12. These plasmids contain the ermF (erythromycin resistance) gene from Tn4351 and a variety of features that facilitate propagation and selection in E. coli and conjugative transfer from E. coli to C. johnsonae.

Polyphenols are secondary plant compounds showing anticarcinogenic effects both in vitro and in animal experiments and may thus reduce the risk of colorectal cancer in man. The identification of polyphenol metabolites formed via their passage through the small intestine of healthy ileostomy subjects after apple juice consumption is presented. Identification and quantification of polyphenols and their metabolites were performed using HPLC-DAD as well as HPLC-ESI-MS/MS. Total procyanidin content (TPA) was measured, and additionally the mean degree of polymerization (DPm) of the procyanidins was determined in the apple juice and ileostomy effluents. As products of polyphenol metabolism, D-(-)-quinic acid and methyl esters of caffeic acid and p-coumaric acid are liberated from the corresponding hydroxycinnamic acid esters. 1-Caffeoylquinic acid and 3-caffeoylquinic acid were determined as products of isomerization. Phloretin 2'-O-glucoside (phloridzin) and phloretin 2'-O-xyloglucoside were metabolized into the corresponding aglycons phloretin and phloretin 2'-O-glucuronide and all were found in the ileostomy effluent. Ninety percent of the consumed procyanidins were recovered in the ileostomy effluent and therefore would reach the colon under physiologic circumstances. The DP m was reduced (DP m of apple juice=5.7) and varied depending on the time point of excretion. The gastrointestinal passage seems to play an important role in the colonic availability of apple polyphenols.

Recently, contamination of honey with pyrrolizidine alkaloids (PA) has been reported as potential health risk. Therefore, it was of interest to develop a reliable tool for selective and quantitative determination of PA in honey. Sample preparation of the novel method comprises strong cation exchange SPE (SCX-SPE), followed by two reduction steps using zinc and LiAlH(4), as well as subsequent silylation. During this procedure the separated PA are converted into the necin backbone, the common structural feature of PA toxicity, which is analyzed by GC-MS in the SIM mode. The procedure was validated using PA from extracts of Senecio vernalis as well as authentic PA standards including their corresponding N-oxides. The PA content of honey samples was quantified with heliotrine as internal standard. The method was applied to generate a dataset in order to evaluate the potential risk of PA contamination especially for retail honeys available on the German/European market. No selection criteria in terms of floral or geographical origin were applied on the samples before analysis. In total, 216 commercially available floral honey samples were analyzed. Among them 19 samples contained PA, in the range of 0.019-0.120 microg/g, calculated as retronecine equivalents. The reported method facilitates the selective determination of PA without the need to identify each individual PA independently. The PA contamination of honey is expressed in terms of a single sum parameter and no background information such as foraged plants and pollen analysis is necessary. The LOQ is 0.01 ppm with a S/N of 7:1.

Well-defined, monodisperse homopolymer comb architectures with varied number and length of the branches under linear and nonlinear deformation were synthesized and examined to determine the effect of branching on different rheological properties. The correlation of the rheological properties with the comb topology is of special interest for the determination of the degree of branching. Therefore, well-defined polystyrene-based comb polymers with systematically varied number and molecular weight of the branches, narrow polydispersities, and a controlled, but low, number of branches (typically 0.1–1 mol % branches per backbone) were synthesized and compared with data from polystyrene combs of the Roovers series that have a higher number of branches (>1 mol % branches per backbone). To investigate the rheological properties in detail, various linear and nonlinear techniques were applied. Within the linear regime, the reduced van Gurp–Palmen plot (δ vs |G*|/G N 0) was used to identify critical points that illustrated the influence of the branch molecular weight and number of branches on the resulting rheological properties. In the nonlinear regime large amplitude oscillatory shear (LAOS) measurements were performed to obtain the nonlinear parameter Q 0(ω) via a quadratic scaling law from FT-rheology. An intrinsic nonlinear master curve based on the Q 0(ω) parameter reflected the relaxation hierarchy and was shown to be a sensitive method to extract information on the different relaxation time scales. The nonlinear shear measurements were complemented by uniaxial extensional measurements to quantify the strain hardening effect and how the strain hardening was affected by branch relaxation. The results obtained from the uniaxial extensional measurements could be correlated to relaxation times obtained from the intrinsic nonlinear master curve Q 0(ω). Pom-pom constitutive model predictions were performed for the comparison with experimental data for extensional rheology with focus on the strain hardening behavior and for LAOS with focus on the nonlinear parameter Q 0(ω) as a function of increasing number and molecular weight of the branches in the pom-pom molecule. A comparison of the applied rheological methods(1) small amplitude oscillatory shear (SAOS) in the linear regime, (2) LAOS in combination with FT-rheology, and (3) extensional rheology in the nonlinear regimeillustrated the detection limits as well as the advantages and disadvantages of each technique toward the investigation of rare, but entangled branched comb polymer topologies.