Alterations in membrane surfaces induced by attachment of carbohydrates

We have examined the behavior of the dry phospholipid dipalmitoylphosphatidylcholine (DPPC) in the presence of several carbohydrate derivatives. These carbohydrate derivatives possess a hydrophobic portion which is incorporated directly into the DPPC membrane and a hydrophilic portion which places the carbohydrate structure at the membrane interface with the surrounding matrix. In the presence of these derivatives, the physical properties of the membrane are altered. These alterations are evident in changes observed in the phosphate and carbonyl vibrational modes of the phospholipid portion of the membrane. In addition, the phase transition behavior of the lipid is significantly altered as evidenced by a reduction in the gel to liquid-crystalline phase transition temperature. These results are consistent with those previously reported for free carbohydrates interacting with membranes in which a water replacement hypothesis has been used to explain the behavior. The attachment of carbohydrates to the membrane enhances these effects by localizing the agent responsible for these alterations at the membrane interface.     

Immunoglobulin complementarity-determining region grafting by recombinant polymerase chain reaction to generate humanised monoclonal antibodies

We describe an approach to rapidly generate humanised monoclonal antibodies by grafting rodent complementarity-determining regions onto human immunoglobulin frameworks using recombinant polymerase chain reaction (PCR) methodology. The approach was applied to grafting a rat complementarily-determining region onto a human framework and amplifying the entire humanised heavy chain. The terminal oligodeoxyribonucleotide primers incorporated restriction sites to allow forced cloning into plasmid vectors for sequencing and expression. No nucleotide errors were introduced into the 1463-bp sequence even after sequential applications of PCR.     

Functional redundancy imparts process stability to acidic Fe(II)-oxidizing microbial reactors

In previous work, lab-scale reactors designed to study microbial Fe(II) oxidation rates at low pH were found to have stable rates under a wide range of pH and Fe(II) concentrations. Since the stirred reactor environment eliminates many of the temporal and spatial variations that promote high diversity among microbial populations in nature, we were surprised that the reactors supported multiple taxa presumed to be autotrophic Fe(II) oxidizers based on their phylogeny. Metagenomic analyses of the reactor communities revealed differences in the metabolic potential of these taxa with respect to Fe(II) oxidation and carbon fixation pathways, acquisition of potentially growth-limiting substrates and the ability to form biofilms. Our findings support the hypothesis that the long-term co-existence of multiple autotrophic Fe(II)-oxidizing populations in the reactors are due to distinct metabolic potential that supports differential growth in response to limiting resources such as nitrogen, phosphorus and oxygen. Our data also highlight the role of biofilms in creating spatially distinct geochemical niches that enable the co-existence of multiple taxa that occupy the same apparent metabolic niche when the system is viewed in bulk. The distribution of key metabolic functions across different co-existing taxa supported functional redundancy and imparted process stability to these reactors.     

An on-farm investigation of beef suckler herds using an animal welfare index (AWI)

Background  

Beef suckler farms (194 farms throughout 13 counties) were assessed once with housed cattle and once with cattle at grass using an animal welfare index (AWI). Twenty-three of the 194 farms were revisited a year later and re-evaluated using the AWI and the Tier-Gerechtheits-Index 35L/2000 (TGI35L/2000). Thirty-three indicators were collected in five categories: locomotion (5 indicators); social interactions (between animals) (7), flooring (5), environment (7) and Stockpersonship (9). Three indicators relating to the size of the farm were also collected.     

Factors affecting the stability of dry liposomes

Previous studies have shown that liposomes can be preserved in the dry state in the presence of certain sugars, of which trehalose is particularly effective. There have been some discrepancies in results obtained by the various laboratories in which this phenomenon has been studied, both with respect to the efficacy of the sugars tested and the degree to which the dry vesicles can be stabilized. We show here that several factors that affect the stability of the dry liposomes may be responsible for the discrepancies between measurements by different laboratories. These factors include: (1) Size: small, sonicated vesicles are comparatively very unstable, and retain no more than 70% of trapped solute after drying, even in extremely high concentrations of sugars. Very large vesicles are similarly unstable. (2) Charge: a small amount of negatively charged lipid in the bilayer significantly increases stability. (3) Stabilizing sugar: the comparative efficacy of the sugar used varies with the size of the vesicles. (4) Dry-mass ratio. It is the dry-mass ratio between the stabilizing sugar and lipid that is important in the preservation during freeze-drying, not the concentration of either lipid or sugar in bulk solution.     

Long-term preservation of dried phosphofructokinase by sugars and sugar/zinc mixtures

We have demonstrated that sugars and suger/zinc mixtures can be used to preserve the activity of dried phosphofructokinase (PFK) during long-term storage over CaSO4. After 9 weeks in the presence of either 200 mM sucrose or 200 mM trehalose little loss of PFK activity was noted, with almost 60% of the original prefreeze-dry activity recovered when samples were rehydrated. Even reducing sugars protected the dried enzyme throughout the entire storage period. Of the sugars tested, 200 mM lactose provided the most stability to PFK; at the end of the dry storage, over 80% of the initial activity was recovered. With either 200 mM maltose or 400 mM glucose, about 40% of the initial activity was recovered at the end of the experiment. With all the sugars tested, the addition of 0.6 mM Zn2+ to sugar/PFK mixtures enhanced the stability of the enzyme, and no long-term adverse effects of the metal ion on enzyme activity were noted.     

Information transmission in non-visual fingertip matching along a horizontal track in the median plane

Non-visually triggered arm movements over a horizontal table at shoulder height were analysed by an Information Theory approach according to a method suggested by Sakitt et al. (1983) and Sakitt (1980). The movement track was along the subject's median line and was indicated by a vertical metal ridge fixed to the table. The observer passively moved the subject's left index finger along the left side of the ridge to the target position. The blindfolded subject then had to move his right index finger along the right side of the ridge to match the left finger position. Direct contact between the two fingers was prevented by the ridge. We compared our results, which involve the transmission of information through the arm and shoulder joints of both arms, whith those of Sakitt et al. which involved just one elbow joint. We supplemented our experimental results with simulations and show that the value for the transmitted information, obtained using the method of analysis suggested by Sakitt et al., is very dependent upon the number of trials, and number and spacing of the targets. Sakitt et al. suggest that the Information Theory approach permits easy comparison between different tasks and different observers. Our results suggest that comparisons should be made with caution.     

Mechanism of Enhanced Immature Dengue Virus Attachment to Endosomal Membrane Induced by prM Antibody

1. Download high-res image (403KB)
2. Download full-size image