Comparison of chromatographic ion-exchange resins IV. Strong and weak cation-exchange resins and heparin resins

A comparative study was performed on heparin resins and strong and weak cation exchangers to investigate the pH dependence, efficiency, binding strength, particle size distribution, static and dynamic capacity, and scanning electron microscopy pictures of chromatographic resins. The resins tested include: Heparin Sepharose FF, SP Sepharose FF, CM Sepharose FF, Heparin Toyopearl 650 m, SP Toyopearl 650 m, CM Toyopearl 650 m, Ceramic Heparin HyperD M, Ceramic S HyperD 20, and Ceramic CM HyperD F. Testing was performed with four different proteins: anti-FVII Mab (IgG), aprotinin, lysozyme, and myoglobin. Dependence of pH on retention was generally very low for proteins with high isoelectric point (pI), though some decrease of retention with increasing pH was observed for CM Ceramic HyperD F and S Ceramic HyperD 20. Binding of anti-FVII Mab with pI < 7.5 was observed on several resins at pH 7.5. Efficiency results show the expected trend of increasing dependence of the plate height with increasing flow rate of Ceramic HyperD resins followed by Toyopearl 650 m resins and the highest flow dependence of the Sepharose FF resins corresponding to their pressure resistance. Determination of particle size distribution by two independent methods, coulter counting and SEM, was in good agreement. Binding strength of cation-exchange resins as a function of ionic strength varies depending on the protein. Binding and elution at high salt concentration may be performed with Ceramic HyperD resins, while binding and elution at low salt concentration may be performed with model proteins on heparin resins. Employing proteins with specific affinity for heparin, a much stronger binding is observed, however, some cation exchangers may still be good substitutions for heparin resins. Dynamic capacity at 10% breakthrough compared to static capacity measurements and dynamic capacity displays that approximately 40-80% of the total available capacity is utilized during chromatographic operation depending on flow rate. A general good agreement was obtained between results of this study and data obtained by others. Results of this study may be used in the selection of resins for testing during protein purification process development.     

The rα-structure of thieno[2,3-b] thiophene. A 1H-NMR study in a nematic phase including 13C-satellites in natural abundance

The ¹H-NMR spectrum of thieno[2,3-b]thiophene in a nematic phase has been recorded and analysed. The ¹H,¹³C dipole—dipole couplings were obtained from ¹³C satellites in natural abundance. The indirect ¹H,¹H and ¹H,¹³C spin—spin coupling constants were determined from an isotropic sample. The dipole—dipole couplings were corrected for harmonic vibrational contribution. The corrected dipole—dipole couplings were used to evaluate the r_α-structure of the molecule.     

Asymmetric hydrocyanation of hydrazones catalyzed by lanthanide--PYBOX complexes

[reaction: see text] The asymmetric addition of HCN to hydrazones is catalyzed in high yield and good-to-excellent enantioselectivity by the easily prepared (PhPYBOX)ErCl3 complex. This constitutes the first example of asymmetric catalytic hydrocyanation of hydrazones.     

Comparison of ethanol-soluble proteins from different rye (Secale cereale) varieties by two-dimensional electrophoresis

The major storage proteins from six rye varieties, grown under the same conditions in 1997 and 1998 in Rønhave, Denmark, were analyzed by two‐dimensional (2‐D) polyacrylamide gel electrophoresis. The proteins were extracted from ground rye kernels with 70% ethanol and separated by 2‐D electrophoresis. The gels were scanned, compared using ImageMaster® software and the data sets were analyzed by principal component analysis (PCA) using THE UNSCRAMBLER software. Afterwards MATLAB was used to make a cluster analysis of the varieties based on PCA. The analysis of the gels showed, that the protein patterns (number of different proteins and their isoelectric points and molecular weights) from the six rye varieties were different. Based on the presence of unique cultivar‐specific spots it was possible to differentiate between all six varieties if the two harvest years were investigated separately. When the results were combined from the two years five varieties could be differentiated. The results from the PCA confirmed the finding of the unique spots and cluster analysis was made in order to illustrate the results. The combination of the results from 2‐D electrophoresis and other grain characteristics showed that one protein spot was located close to the parameters bread volume and bread height.     

Spectroscopic investigation of metal dimercaptodithiolenes and selenium analogs

The optical absorption, reflectance and resonance Raman spectra of (Bu₄N)_x M(C₃X₅)₂ (where x=2,1 or 0 < x < 1 and M=Pt,Pd,Ni,Hg etc. and X=S or Se) are described. The strong solvent effects(x=2), strong resonance Raman peaks (x=1)and a metallic behaviour ( 0 < × < 1,or x=1,2 after I₂-doping) are the main features.