Characterisation of chromatography adsorbents for antibody bioprocessing

Currently the purification of monoclonal antibodies for therapeutic purposes is reliant on protein A affinity chromatography. The rapid growth of this class of therapeutic and their high value makes the understanding of protein A chromatography an important target. There is a range of commercially available protein A chromatography media. The main differences between these media are the support matrix type, the pore size, the particle size, the amount of ligand attached to the matrix and the kind of protein A modification. The differences in these factors give rise to differences in compressibility, chemical and physical robustness, diffusion resistance and binding capacity of the adsorbents. The ideal media would have high specificity, high mass transfer and binding capacity, low non-specific adsorption and ligand leakage, incompressibility, resistance to alkaline condition for sanitization, chemical stability and cost effectiveness. Current resins offer a compromise, which balances what is achievable in respect of these features giving rise to an array of different solutions. Measurement of these parameters is often complex and agreed standards have yet to be determined. The objective of this study is to further develop understanding of these measurements for the assessment of the matrix performance. This thesis employs a suite of techniques to characterise commercial and prototype adsorbents. The adsorbents that will be looked at are MabSelect (GE Healthcare), MabSelect Xtra (GE Healthcare), Prosep Ultra (Millipore), Protein A immobilised on 4CL Sepharose (GE Heatlhcare) in house and a prototype adsorbent with a Protein A mimic ligand (Millipore). Both down-scaled techniques of fixed bed chromatography, together with supporting analysis of equilibrium and dynamic behaviours are used. The latter will adopt standard and novel ‘wet chemistry’ approaches together with the increasingly adopted techniques of laser scanning confocal microscopy. Experiments are carried out using hIgG to study the static capacity, adsorption equilibrium and dynamic capacity of adsorbents. Other techniques will be used to study the kinetic uptake and desorption rates of adsorbents in different conditions. A novel approach using confocal microscopy is used to further understand the adsorption behaviour of individual beads of different sizes. The main results that were drawn from these techniques are that MabSelect Xtra had the highest static capacity of 61.8mg/ml. It also showed the highest dynamic capacity at 2 mins, 4 mins and 8 mins residence time (0.66cm Omnifit column, bed height 6cm) when compared to other adsorbents. This is mainly due to the more porous nature of the MabSelect Xtra beads, which increased the surface area available for Protein A ligand immobilisation. From the adsorption equilibrium data the Kd values ranged from 181nM to 36nM. Such low values are expected by affinity adsorbents such as these. The uptake rate curves were similar for all the adsorbents. Hence the difference in particle size, pore size, the type of ligand or the material of the adsorbent itself did not have an effect on the uptake rate when carried out in a batch mode. A similar behaviour was shown for the desorption curves. The confocal analysis using a flow cell showed that all the adsorbents showed a shrinking core effect except for the prototype where the hIgG didn’t penetrate into the bead and was only attached to the surface of the bead. It was found that the adsorption rate to the centre of each bead was linear. The different particle sizes within any particular type of matrix and also across different matrix did not result in different diffusion rates. From the adsorption curves produced it was seen that smaller beads reached saturation much faster than larger beads at any given time. This technique can have great benefits in understanding how individual beads of different adsorbents behave in different circumstances

Investigation into Pharmacological Profile and Mechanism of Action of Abscisic Acid with Reference to it's Possible Therapeutic Usefulness

Not availabl

ભારતમાં ઉદ્યોગ સાહસિક્તાના વિકાસનો વિશ્ર્લેષણાત્મક અભ્યાસઃ (ગુજરાતના ખાસ સંદર્ભમાં)

Not availabl

The Small Scale Velocity Dispersion of Galaxies: A Comparison of Cosmological Simulations

The velocity dispersion of galaxies on small scales ($r\sim1h^{-1}$ Mpc), $\sigma_{12}(r)$, can be estimated from the anisotropy of the galaxy-galaxy correlation function in redshift space. We apply this technique to ``mock-catalogs'' extracted from N-body simulations of several different variants of Cold Dark Matter dominated cosmological models to obtain results which may be consistently compared to similar results from observations. We find a large variation in the value of $\sigma_{12}(1 h^{-1} Mpc)$ in different regions of the same simulation. We conclude that this statistic should not be considered to conclusively rule out any of the cosmological models we have studied. We attempt to make the statistic more robust by removing clusters from the simulations using an automated cluster-removing routine, but this appears to reduce the discriminatory power of the statistic. However, studying $\sigma_{12}$ as clusters with different internal velocity dispersions are removed leads to interesting information about the amount of power on cluster and subcluster scales. We also compute the pairwise velocity dispersion directly and compare this to the values obtained using the Davis-Peebles method, and find that the agreement is fairly good. We evaluate the models used for the mean streaming velocity and the pairwise peculiar velocity distribution in the original Davis-Peebles method by comparing the models with the results from the simulations.Comment: 20 pages, uuencoded (Latex file + 8 Postscript figures), uses AAS macro

Selection bias in the M_BH-sigma and M_BH-L correlations and its consequences

It is common to estimate black hole abundances by using a measured correlation between black hole mass and another more easily measured observable such as the velocity dispersion or luminosity of the surrounding bulge. The correlation is used to transform the distribution of the observable into an estimate of the distribution of black hole masses. However, different observables provide different estimates: the Mbh-sigma relation predicts fewer massive black holes than does the Mbh-L relation. This is because the sigma-L relation in black hole samples currently available is inconsistent with that in the SDSS sample, from which the distributions of L or sigma are based: the black hole samples have smaller L for a given sigma or have larger sigma for a given L. This is true whether L is estimated in the optical or in the NIR. If this is a selection rather than physical effect, then the Mbh-sigma and Mbh-L relations currently in the literature are also biased from their true values. We provide a framework for describing the effect of this bias. We then combine it with a model of the bias to make an estimate of the true intrinsic relations. While we do not claim to have understood the source of the bias, our simple model is able to reproduce the observed trends. If we have correctly modeled the selection effect, then our analysis suggests that the bias in the relation is likely to be small, whereas the relation is biased towards predicting more massive black holes for a given luminosity. In addition, it is likely that the Mbh-L relation is entirely a consequence of more fundamental relations between Mbh and sigma, and between sigma and L. The intrinsic relation we find suggests that at fixed luminosity, older galaxies tend to host more massive black holes.Comment: 12 pages, 7 figures. Accepted by ApJ. We have added a figure showing that a similar bias is also seen in the K-band. A new appendix describes the BH samples as well as the fits used in the main tex

The Pairwise Peculiar Velocity Dispersion of Galaxies: Effects of the Infall

We study the reliability of the reconstruction method which uses a modelling of the redshift distortions of the two-point correlation function to estimate the pairwise peculiar velocity dispersion of galaxies. In particular, the dependence of this quantity on different models for the infall velocity is examined for the Las Campanas Redshift Survey. We make extensive use of numerical simulations and of mock catalogs derived from them to discuss the effect of a self-similar infall model, of zero infall, and of the real infall taken from the simulation. The implications for two recent discrepant determinations of the pairwise velocity dispersion for this survey are discussed.Comment: minor changes in the discussion; accepted for publication in ApJ; 8 pages with 2 figures include

The Stellar Mass Fundamental Plane: The virial relation and a very thin plane for slow-rotators

Early-type galaxies -- slow and fast rotating ellipticals (E-SRs and E-FRs) and S0s/lenticulars -- define a Fundamental Plane (FP) in the space of half-light radius $R_e$, enclosed surface brightness $I_e$ and velocity dispersion $\sigma_e$. Since $I_e$ and $\sigma_e$ are distance-independent measurements, the thickness of the FP is often expressed in terms of the accuracy with which $I_e$ and $\sigma_e$ can be used to estimate sizes $R_e$. We show that: 1) The thickness of the FP depends strongly on morphology. If the sample only includes E-SRs, then the observed scatter in $R_e$ is $\sim 16\%$, of which only $\sim 9\%$ is intrinsic. Removing galaxies with $M_*<10^{11}M_\odot$ further reduces the observed scatter to $\sim 13\%$ ($\sim 4\%$ intrinsic). The observed scatter increases to the $\sim 25\%$ usually quoted in the literature if E-FRs and S0s are added. If the FP is defined using the eigenvectors of the covariance matrix of the observables, then the E-SRs again define an exceptionally thin FP, with intrinsic scatter of only $5\%$ orthogonal to the plane. 2) The structure within the FP is most easily understood as arising from the fact that $I_e$ and $\sigma_e$ are nearly independent, whereas the $R_e-I_e$ and $R_e-\sigma_e$ correlations are nearly equal and opposite. 3) If the coefficients of the FP differ from those associated with the virial theorem the plane is said to be `tilted'. If we multiply $I_e$ by the global stellar mass-to-light ratio $M_*/L$ and we account for non-homology across the population by using S\'ersic photometry, then the resulting stellar mass FP is less tilted. Accounting self-consistently for $M_*/L$ gradients will change the tilt. The tilt we currently see suggests that the efficiency of turning baryons into stars increases and/or the dark matter fraction decreases as stellar surface brightness increases.Comment: 13 pages, 9 figures, 3 tables, accepted for publication in MNRA

CO Observations of the Interacting Galaxy Pair NGC 5394/95

Peer reviewe

Spitzer Space Telescope IRAC and MIPS observations of the interacting galaxies Ic 2163 and NGC 2207: clumpy emission

Peer reviewe