The Buoyant Behavior of Viral and Bacterial DNA in Alkaline CsCl

In equilibrium density gradient centrifugation, the banding polymer species is electrically neutral. The banding species for a negative polyelectrolyte with a polyanion P_(n)^(-z)n (where n is the degree of polymerization, and z the titration charge per monomer unit) in a CsCl salt gradient is CS_(zn)P_n. If the ion P_(n)^(-z)n is itself a weak acid, it may be titrated to the state P_(n)^(-(Zn+y)) by CsOH; the banding species is then Cs_(zn+y)P_n. Because of the large mass and high effective "density" of a Cs^+ ion, it is to be expected that the buoyant density in a CsCl gradient of a polymer acid will be increased by such a partial alkaline titration with CsOH. This expectation has been confirmed for polyglutamic acid (where z = 0 at low pH). The guanine and thymine monomer units of DNA are weak acids. The present communication is concerned with the increase in buoyant density of DNA in alkaline CsCl solutions. It is well known that the guanine and thymine protons are more readily titrated in denatured DNA than in native DNA. We find that the buoyant density of denatured DNA and of single strand ϕX-174 DNA gradually increases as the pH of the solution is increased beyond pH 9.8. The density of native DNA is not affected until a critical pH > 11 is reached, where the DNA abruptly denatures and increases in density. Similar increases in buoyant density have been observed independently by Baldwin and Shooter in their studies of 5BU[overbar]-substituted DNA's in alkaline solutions

Effects of chlorinated seawater on decapod crustaceans and Mulinia larvae

Eggs and larvae of decapod crustaceans and embryos of Mulinia laterulis were exposed to chlorinated seawater for varying periods in continuous flow systems. Mortality, developmental rate, and general behavior were recorded

Stress and subfertility in dairy cows

In commercial dairy cattle farming, stressful disease conditions, such as high somatic cell count (SCC), poor body condition score (BCS) or lameness, are associated with subfertility. The objective of this thesis is to identify key areas in the reproductive cycle associated with each condition which contribute to this subfertility. Cows 30-80 days post partum from two commercial dairy farms were scored for SCC, BCS and lameness over a 5 week period prior to the implementation of an oestrous synchronization programme. Blood and milk sampling, trans-rectal ultrasonography and oestrus behaviour monitoring were conducted. Follicular development from emergence to deviation was unaffected as all cows produced a dominant follicle, which continued to grow beyond lOmm. In the following period, mean follicular growth, maximum follicular diameter and time to ovulation were not influenced by any of the 3 conditions (p> 0.05). In the animals that ovulated (irrespective of clinical status), follicles grew faster and achieved a greater diameter than in the animals that failed to ovulate (p< 0.05). Fewer lame animals ovulated compared to healthy animals (p< 0.05) and fewer high SCC animals with concurrent lameness ovulated than cows with only high SCC (p< 0.05) In cows with high SCC, progesterone concentrations prior to PG injection, over the peri-ovulatory period, on Days 5 and 7 or during the mid luteal phase after ovulation were unaffected, as was mean oestradiol concentration prior to ovulation. In the cows that ovulated, the dominant follicle grew at the same rate and ovulated at a similar size and at the same time regardless of high SCC, lameness or both. High SCC cows tended to (p< 0.07) and lame cows did express an oestrus of lower intensity and had a lower maximum intensity score than healthy animals (p< 0.05). High SCC cows started displaying oestrus signs and stood to be mounted (STBM) later than their healthy counterparts (p< 0.05) while lame animals displayed oestrus and STBM earlier than non lame cows (p< 0.05)

Quantifying the Reversible Association of Thermosensitive Nanoparticles

Under many conditions, biomolecules and nanoparticles associate by means of attractive bonds, due to hydrophobic attraction. Extracting the microscopic association or dissociation rates from experimental data is complicated by the dissociation events and by the sensitivity of the binding force to temperature (T). Here we introduce a theoretical model that combined with light-scattering experiments allows us to quantify these rates and the reversible binding energy as a function of T. We apply this method to the reversible aggregation of thermoresponsive polystyrene/poly(N-isopropylacrylamide) core-shell nanoparticles, as a model system for biomolecules. We find that the binding energy changes sharply with T, and relate this remarkable switchable behavior to the hydrophobic-hydrophilic transition of the thermosensitive nanoparticles

Identification and structural characterisation of a partially arabinosylated lipoarabinomannan variant isolated from a Corynebacterium glutamicum ubiAmutant

Arabinan polysaccharide side-chains are present in both Mycobacterium tuberculosis and Corynebacterium glutamicum in the heteropolysaccharide arabinogalactan (AG), and in M. tuberculosis in the lipoglycan, lipoarabinomannan (LAM). Herein, we show by quantitative sugar and glycosyl linkage analysis that C. glutamicum possesses a much smaller LAM version, Cg-LAM, characterised by single t-Araf residues linked to th