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International microbiome sequencing initiatives are revealing detailed inventories of diverse bacterial communities across various body sites, diets and human populations (2-4). Complex ecosystems have been forged by co-adaptation over millennia [...], Mammals harbour a complex gut microbiome, comprising bacteria that confer immunological, metabolic and neurological benefits (1). Despite advances in sequence-based microbial profiling and myriad studies defining microbiome composition during health and disease, little is known about the molecular processes used by symbiotic bacteria to stably colonize the gastrointestinal tract. We sought to define how mammals assemble and maintain the Bacteroides, one of the most numerically prominent genera of the human microbiome. Here we find that, whereas the gut normally contains hundreds of bacterial species (2,3), germ-free mice mono-associated with a single Bacteroides species are resistant to colonization by the same, but not different, species. To identify bacterial mechanisms for species-specific saturable colonization, we devised an in vivo genetic screen and discovered a unique class of polysaccharide utilization loci that is conserved among intestinal Bacteroides. We named this genetic locus the commensal colonization factors (ccf). Deletion of the ccf genes in the model symbiont, Bacteroides fragilis, results in colonization defects in mice and reduced horizontal transmission. The ccf genes of B. fragilis are upregulated during gut colonization, preferentially at the colonic surface. When we visualize microbial biogeography within the colon, B. fragilis penetrates the colonic mucus and resides deep within crypt channels, whereas ccf mutants are defective in crypt association. Notably, the CCF system is required for B. fragilis colonization following microbiome disruption with Citrobacter rodentium infection or antibiotic treatment, suggesting that the niche within colonic crypts represents a reservoir for bacteria to maintain long-term colonization. These findings reveal that intestinal Bacteroides have evolved species-specific physical interactions with the host that mediate stable and resilient gut colonization, and the CCF system represents a novel molecular mechanism for symbiosis.

The porins OmpF and OmpC are trimeric [beta]-barrel proteins with narrow channels running through each monomer that exclude molecules >600 Da while mediating the passive diffusion of small nutrients and metabolites across the Gram-negative outer membrane (OM). Here, we elucidate the mechanism by which an entire soluble protein domain (>6 kDa) is delivered through the lumen of such porins. Following high-affinity binding to the vitamin [B.sub.12] receptor in Escherichia coli, the bacteriocin ColE9 recruits OmpF or OmpC using an 83-residue intrinsically unstructured translocation domain (IUTD) to deliver a 16-residue TolB-binding epitope (TBE) in the center of the IUTD to the periplasm where it triggers toxin entry. We demonstrate that the IUTD houses two OmpF-binding sites, OBS1 (residues 2-18) and OBS2 (residues 54-63), which flank the TBE and bind with [K.sub.d]S of 2 and 24 [micro]M, respectively, at pH 6.5 and 25[degrees]C. We show the two OBSs share the same binding site on OmpF and that the colicin must house at least one of them for antibiotic activity. Finally, we report the structure of the OmpF-OBS1 complex that shows the colicin bound within the porin lumen spanning the membrane bilayer. Our study explains how colicins exploit porins to deliver epitope signals to the bacterial periplasm and, more broadly, how the inherent flexibility and narrow cross-sectional area of an IUP domain can endow it with the ability to traverse a biological membrane via the constricted lumen of a [beta]-barrel membrane protein. colicin translocation | intrinsically unstructured protein | protein-protein interaction | transmembrane signalling | isothermal titration calorimetry doi/ 10.1073/pnas.1010780107

T lymphocytes (T cells) orchestrate adaptive immune responses that clear pathogens from infected hosts. T cells recognize short peptides (p) derived from antigenic proteins bound to protein products of the MHC genes. Recognition occurs when T cell receptor (TCR) proteins expressed on T cells bind sufficiently strongly to antigen-derived pMHC complexes on the surface of antigen-presenting cells. A diverse repertoire of self-pMHC-tolerant TCR sequences is shaped during development of T cells in the thymus by processes called positive and negative selection. Combining computational models and analysis of experimental data, we parsed the contributions of positive and negative selection to the design of TCR sequences that recognize antigenic peptides with specificity, yet also exhibit cross-reactivity. A dominant role for negative selection in mediating antigen specificity of mature T cells and a molecular mechanism for TCR recognition of antigen are described. statistical mechanics | T cell antigen specificity | thymic selection

Vibrio vulnificus biotype 3 has been implicated as the causative pathogen of an ongoing disease outbreak that erupted in Israel in 1996. Recent work based on multi-locus sequence typing (MLST) showed that V. vulnificus biotype 3 is genetically homogeneous. The aim of this study was to investigate the existence of subpopulations within this homogeneous biotype by characterizing the surface antigens and analysing the sequence diversity of selected outer-membrane protein (OMP)-encoding genes. Rabbit antisera were prepared against biotype 1, 2 and 3 strains. The results of the slide-agglutination test, dot-blot assay (using fresh and boiled cells), and immunoblotting of lipopolysaccharides (LPS) and OMPs were evaluated. By slide-agglutination and dot-blot assays all biotype 3 strains agglutinated with the selected biotype 3 strain. This homogeneity was supported by immunoblot analysis of the LPS. Analysis of OMP patterns revealed that all three biotypes share a considerable number of common bands that are antigenically related. Cluster analysis of DNA sequence data from selected OMP-encoding genes showed that biotype 3 strains form a genetically distinct and homogeneous clone. The homogeneity of surface antigens and the lack of any sequence diversity among both housekeeping and OMP-encoding genes reaffirms the highly clonal nature of biotype 3 and suggests that it has only recently descended from the parent population of V. vulnificus.

A study used alpha-varOmega-alkanediol dimethylsulfonate esters to consider the role of cationic purine on DNA sequence specificity.

A range of water-soluble piperazinylcarbonyloxyethyl derivatives of anthracene and pyrene were prepared to study their interactions with DNA.

Research was conducted to examine the tailoring of the S1 pocket of subtilisin Bacillus lentus to also accept small hydrophobic, positively charged and negatively charged P1 residues. A simple technique of steric and electrostatic complementarity was applied to achieve the broadened P1 tolerance. Results provide an encouraging initial validation of the practical effectiveness of the chemically modified mutant enzymes strategy for generating complementary electrostatic and steric enzyme-substrate interactions.

The conserved amino-terminal 4-3 hydrophobic (heptad) repeat embedded within the gp41 ectodomain of HIV-1 exhibits trimerization specificity. This is evident in an experiment in which the buried core residues of the heptad repeat was introduced into the first and fourth positions of the GCN4 leucine-zipper dimerization domain. Results show that the mutant peptides fold into trimeric, helical structures as indicated by circular dichroism and equilibrium sedimentation centrifugation.

The modification of the P2 specificity of the conserved amino acid substrate Gly(super 101) by excluding the bulky P2 side chain of the substrate was investigated. Gly(super 101) was replaced by valine, alanine or leucine for the engineering of S2 site of aqualysin I, a microbial thermophilic alkaline serine protease. Experimental results showed that the catalytic efficiencies of the enzyme for bulky amino acid residues in P2 site decreased dramatically due to mutation. Gly(super 101) was modified to be glycine preferable.

The biotin-binding site of streptavidin was modified to alter its ligand-binding specificity. In natural streptavidin, the side chains of N23 and S27 make two of the three hydrogen bonds with the ureido oxygen of biotin. These two residues were mutated to severely weaken biotin binding while attempting to maintain the affinity for two biotin analogs, 2-iminobiotin and diaminobiotin. Redesigning of the biotin-binding site used the difference in local electrostatic charge distribution between biotin and these biotin analogs. Free energy calculations predicted that the introduction of a negative charge at the position of S27 plus the mutation N23A should disrupt two of the three hydrogen bonds between natural streptavidin and the ureido oxygen of biotin. In contrast, the imino hydrogen of 2-iminobiotin should form a hydrogen bond with the side chain of an acidic amino acid at position 27. This should reduce the biotin-binding affinity by approximately eight orders of magnitude, while leaving the affinities for these biotin analogs virtually unaffected. In good agreement with these predictions, a streptavidin mutant with the N23A and S27D substitutions binds 2-iminobiotin with an affinity ([K.sub.a]) of 1 x 106 [M.sup.-1], two orders of magnitude higher than that for biotin (1 x [10.sup.4] [M.sup.-1]). In contrast, the binding affinity of this streptavidin mutant for diaminobiotin (2.7 x [10.sup.4] [M.sup.-1]) was lower than predicted (2.9 x [10.sup.5] [M.sup.-1]), suggesting the position of the diaminobiotin in the biotin-binding site was not accurately determined by modeling.

The functional role of an omega loop of cholesterol oxidase was evaluated by constructing a deletion mutant of cholesterol oxidase. The findings indicated that the tip of the loop is essential for packing, while the tail of the cholesterol determines the substrate specificity at C17. Thus, the loop is essential for movement of cholesterol from the lipid bilayer, with tip residues developing a hydrophobic pathway between the active site and the lipid membrane to support movement of substrate and product.

Research was conducted to examine the specificities of eight pairs of PCR assays for the detection of Cryptosporidium parvum, C muris, C baileyi andd C maleagridis. C parvum and C meleagridis could not be differentiated from each other despite being genetically similar at each of the eight loci analyzed by DNA amplification. Results suggest that caution should be practised in the interpretation of data from water sample analysis studied using the techniques.

Research was conducted to examine the substrate specificity of the oligopeptide transport system of Lactococcus lactis. A chemically defined medium with various mixtures of free amino acids was used to study the growth of L lactis Prt- MG1363. The addition of a mixture with all of the seven amino acids necessary for L lactis MG1363 led to a sevenfold increase in the maximum population density of the strains. Results indicate the strains' ability to sustain growth with the preferential use of hydrophobic basic peptides and their inability to use large, acidic peptides.

As a step in the design of directed toxins, aimed at cells that overexpress HER receptors, particularly breast carcinoma cells, we studied the properties of a chimera of diphtheria toxin (DT) and heregulin [Beta]1. The EGF-like growth hormone heregulin is a ligand for the HER3 and HER4 receptors and their heterodimers with HER2. The 60-residue EGF-like domain (hrg) of heregulin elicits a biological response and binds to these receptors primarily through its N terminus. We tested a fusion protein in which hrg replaces the C-terminal receptor-binding domain of DT (DT(389)hrg) and an alternative design in which this domain is fused to the N terminus of DT(389). Of those two constructs, the N-terminal fusion was not active as a directed toxin but elicited a growth response. The C-terminal fusion of hrg to DT(389) yielded a functional toxin and showed cell line specific cytotoxicity that is consistent with heregulin specificity. The binding of hrg to its cognate receptor is not impaired as shown by receptor activation, direct binding, and competition with free hrg. Cytotoxicity is dependent on high-affinity binding of DT-(389)hrg to HER3 and HER4 receptors and is not mediated by HER2 overexpression alone. For those cell lines exhibiting high-affinity binding sites, the level of cytotoxicity correlates with the rate of internalization. Thus DT(389)hrg chimeras offer a possible avenue toward directed toxins against cells that overexpress HER receptors.

Site-specific DNA-protein interactions can be studied using experimental and computational methods. Experimental approaches typically analyze a protein-DNA interaction by measuring the free energy of binding under a variety of conditions. Computational methods focus on alignments of known binding sites for a protein, and, from these alignments, make estimates of the binding energy. Understanding the relationship between these two perspectives, and finding ways to improve both, is a major challenge of modern molecular biology.

Ligands with greater affinity and enhanced selectivity for the SH3 domain of the tyrosine kinase Src were discovered by using the solution structure of the SH3 domain to design biased libraries. Spatially separated molecules were prepared using split-pool synthesis and designed to complement the topography of the specificity pocket. The procedure also yielded non-natural ligands that bind selectively to the SH3 domain of the tyrosine kinase Hck.

Research was conducted to study the binding specificity in protein-protein recognition in the colicin DNase-immunity protein system. Focus of the research was on a class of toxins in the E group colicins which have the ability to kill Escherichia coli cells by the action of an endonuclease domain. Results indicate that specificity in the colicin-immunity system is controlled by a dual recognition mechanism wherein stabilizing interactions from the conserved regions of an immunity protein are considered as the binding site anchor.

By using a protein-design algorithm that quantitatively considers side-chain packing, the effect of specific steric constraints on protein design was assessed in the core of the streptococcal protein G [Beta]1 domain. The strength of packing constraints used in the design was varied, resulting in core sequences that reflected differing amounts of packing specificity. The structural flexibility and stability of several of the designed proteins were experimentally determined and showed a trend from well-ordered to highly mobile structures as the degree of packing specificity in the design decreased. This trend both demonstrates that the inclusion of specific packing interactions is necessary for the design of native-like proteins and defines a useful range of packing specificity for the design algorithm. In addition, an analysis of the modeled protein structures suggested that penalizing for exposed hydrophobic surface area can improve design performance.

Molecular replacement experiments are performed to study the structures of the HIV-1 protease triple mutant and simian immunodeficiency virus (SIV) protease in complex with the analog inhibitor SB203386. Results show that that inhibition capability of SB203386 decreases when used in the HIV-1 protease triple mutant and SIV protease. The data also HIV protease ligand specificity is imparted by residues outside of the catalytic pocket.

The cloned alpha-1,3-L-fucosyltransferases, FT III, FT IV, and FT V, have unique specificities for blood group type 2-based carbohydrate ligands and antigenic determinants. FT V participates more in the production of Lewis y than Lewis x. FT IV is very effective in synthesizing both 3'-sulfo Lewis x and Lewis x in mucin-type branched chains. Both FT III and FT V are more effective in synthesizing 3'-sulfo Lewis x than 3'-sialyl Lewis x. FT IV is more effective in synthesizing 6-sulfo Lewis x than the other two.

MRP is a recently isolated ATP-binding cassette family transporter. We previously reported transfection studies that established that MRP confers multidrug resistance [Kruh, G. D., Chan, A., Myers, K., Gaughan, K., Miki, T. & Aaronson, S. A. (1994) Cancer Res. 54, 1649-1652] and that expression of MRP is associated with enhanced cellular efflux of lipophilic cytotoxic agents [Breuninger, L. M., Paul, S., Gaughan, K., Miki, T., Chan, A., Aaronson, S. A. & Kruh, G. D. (1995) Cancer Res. 55, 5342-5347]. To examine the biochemical mechanism by which MRP confers multidrug resistance, drug uptake experiments were performed using inside-out membrane vesicles prepared from NIH 3T3 cells transfected with an MRP expression vector. ATP-dependent transport was observed for several lipophilic cytotoxic agents including daunorubicin, etoposide, and vincristine, as well as for the glutathione conjugate leukotriene [C.sub.4] ([LTC.sup.4]). However, only marginally increased uptake was observed for vinblastine and Taxol. Drug uptake was osmotically sensitive and saturable with regard to substrate concentration, with [K.sub.m] values of 6.3 [[micro]molar], 4.4 [[micro]molar], 4.2 nM, 35 nM, and 38 [[micro]molar], for daunorubicin, etoposide, vincristine, [LTC.sub.4], and ATP, respectively. The broad substrate specificity of MRP was confirmed by the observation that daunorubicin transport was competitively inhibited by reduced and oxidized glutathione, the glutathione conjugates S-(p-azidophenacyl)-glutathione (APA-SG) and S-(2,4-dinitrophenyi)glutathione (DNP-SG), arsenate, and the LTD4 antagonist MK571. This study establishes that MRP pumps unaltered lipophilic cytotoxic drugs, and suggests that this activity is an important mechanism by which the transporter confers multidrug resistance. The present study also indicates that the substrate specificity of MRP is overlapping but distinct from that of P-glycoprotein, and includes both the neutral or mildly cationic natural product cytotoxic drugs and the anionic products of glutathione conjugation. The widespread expression of MRP in tissues, combined with its ability to transport both lipophilic xenobiotics and the products of phase II detoxification, indicates that the transporter represents a widespread and remarkably versatile cellular defense mechanism.

In their recent report, Yumay Chen et al present data suggesting that the BRCA1 gene product is excluded from the nucleus in sporadic breast and ovarian cancer and i certain [...]

Techniques for purifying Brucella native haptens (NH) that would have high levels of serotological activity from B. abortus and B. melitensis are presented. Their results were compared with those obtained by acid hydrolysis of the S lipopolysaccharide (LPS). 13C nuclear magnetic resonance analysis showed that NHs obtained using the new approach exhibited a spectrum of homopolymer consistent with that of the LPS O chain. High performance liquid chromatography and thin layer chromatography showed heterogeneity in NH purified from whole cells but not in PS.

A study was conducted on the role of the carboxyl-terminal domain of enzyme I of the Escherichia coli phosphoenolpyruvate:sugar phosphotransferase system for phosphoryl donor specificity. Results showed that the isolated amino-terminal domain, EIN, can be stably expressed in Escherichia coli through an expression vector developed for the production of large quantities of EIN.

The immunoglobulin kappa gene 3' enhancer (E3') suppresses V(sub kappa)-J(sub kappa) recombination and restricts it to the pre-B developmental stage of B cells. The B/T specificity of V(sub kappa)-J(sub kappa) recombination is controled by the PU.1 binding domain in E3'. A mutation in the PU.1 domain causes recombination in both B and T cells. Deletion of E3' causes rearrangement of the kappa gene in the early pro-B stage of B cells.

A stringent specificity for adenosine triphosphate and an ability to discriminate between nicked and gapped DNAs at the substrate binding step were noted in an investigation of the specificity and fidelity of the viral enzyme vaccinia DNA ligase using purified recombinant ligase and synthetic duplex DNA substrates containing a single strand discontinuity. Findings reveal that the ligase was fairly tolerant of mismatches at a nick involving the 5' phosphate donor terminus, but was blocked strongly by mismatches at the 3' OH acceptor terminus, particularly by purine-purine mispairs.

The neonatal Fc receptor (FcRn) transports maternal IgG from ingested milk in the gut to the bloodstream of newborn mammals. An FcRn dimer was observed in crystals of the receptor alone and of an FcRn-Fc complex, but its biological relevance was unknown. Here we use surface plasmon resonance-based biosensor assays to assess the role of FcRn dimerization in IgG binding. We find high-affinity IgG binding when FcRn is immobilized on a biosensor chip in an orientation facilitating dimerization but not when its orientation disrupts dimerization. This result supports a model in which IgG-induced dimerization of FcRn is relevant for signaling the cell to initiate endocytosis of the IgG-FcRn complex.

Thy-1, a member of the immunoglobulin superfamily, is one of the most abundant glycoproteins on mammalian neurons. Nevertheless, its role in the peripheral or central nervous system is poorly understood. Certain monoclonal antibodies to Thy-1 promote neurite outgrowth by rodent central nervous system neurons in vitro, suggesting that Thy-1 functions, in part, by modulating neurite outgrowth. We describe a binding site for Thy-1 on astrocytes. This Thy-1-binding protein has been characterized by immunofluorescence with specific anti-idiotype monoclonal antibodies and by three competitive binding assays using (i) anti-idiotype antibodies, (ii) purified Thy-1, and (iii) Thy-1-transfected cells. The Thy-1-binding protein may participate in axonal or dendritic development in the nervous system.

A study conducted on the expression of the antigens, serotype A and B, of Candida albicans shows that the serotype A is more reactive in acidic medium while serotype B is more reactive in alkaline medium. Indirect immunofluorescence shows that the monoclonal antibody B9E and the polyclonal monospecific antiserum against the antibody 6 in vitro react with the cell walls of the serotype A yeast cells but not with serotype B. However spectrofluorometry shows similar reactivity of both the serotypes.

NMR experiments help identify the specific urea binding sites of urea with two globular proteins, bovine pancreatic trypsin inhibitor (BPTI) and PEC-60. Examination of the nuclear Overhauser effects reveals the preferential binding of urea of pockets and grooves on the protein surfaces. The interaction is weak and very short-lived on a nanosecond time scale, and this short life suggests that urea exhibits no significant kinetic barrier in protein folding-unfolding reactions. Analysis of amide proton chemical shifts help determine the binding constants, which are less than one.

AS6, a serotype of Rhizobium leguminosarum bv. trifolii, is found in more than 50% of field-grown subclover root nodules and between 33 and 78% in nodules of certain annual clover species. The release of serotype AS from senescing nodules during the spring accounts for the increase in clover rhizosphere population, but AS21 and AP17 are also largely found. The dominance of AS6 in root nodules of certain annual clover species could be attributed to host preferences and symbiotic effective characteristics.

Immunohistochemical study of perivascular connective tissue mast cells (CTMCs) from the ear and skin of BALB/cJ mice, using anti-mouse mast cell protease, revealed a coexpression of mMCP-2 and mMCP-5 in the granules of perivascular CTMCs. The ears of four strains of BALB/cJ mice contained high concentration of mMCP-2. The +/+ strains of mice also differed from the BALB/cJ mice with regard to their perivascular CTMCs and serosal mast cells.

The importance of tyrosine phosphorylation during ligand-induced internalization of membrane immunoglobulin (mIg) and its critical role for activating B cells as antigen presenting cells were investigated. Two tyrosine phosphorylation specific inhibitors inhibited mIg modulation on the cell surface and suppressed ligand-induced receptor internalization. These findings indicated that tyrosine phosphorylation in the B cells occured as a consequence of crosslinking mIg and was needed for internalization of mIg-ligand complexes. The results supported the essential role of tyrosine phosphorylation in the function of B lymphocytes.

Considerable progress has been made in the characterization of immunoglobulin genes from several lower vertebrate taxa. Isolation and identification of immunoglobulin genes in phylogenetically primitive species is based predominantly on heterologous cross-hybridization. The unit, clustered organization of heavy chain segmental elements observed in the germline of the horned shark (Hinds and Litman, 1986) has also been found in another elasmobranch. Studies to determine whether the clustered organization is universal throughout the entire cartilaginous fish assemblage are ongoing. In contrast, the ray-fined (bony) fishes appear to posses a mammalian-type heavy chain gene organization. Additionally, immunoglobulin genes are being characterized in two relict fish species whose exact systematic relationships are unknown. Isolation of putative immunoglobulin genes from the phylogenetically-ancient hagfish is being attempted using a PCR-based approach. Other ongoing or future research efforts involve characterization of lower vertebrate light chain genes, heavy chain isotype evolution, and the divergence of the immunoglobulins and T-cell antigen receptors.

The colonial marine hydroid Hydractinia has a sophisticated allorecognition and effector system. Unlike may unitary organisms (i.e., vertebrates) which lack a current context for allorecognition, there is the potential for strong selection pressure for allorecognition and response in Hydractinia. Hydractinia colonies use allorecognition in intraspecific competition for two dimensional space; space is an absolute requirement for Hydractinia to successfully complete its life-cycle and thus interactions for space are of central importance for Hydractinia. Studies of the mechanisms, molecules, and genes involved in allorecognition in Hydractinia may contribute to our understanding of the evolution of allorecognition in the metazoa.

We examined via simulation 3 representative types of bison (Bison bison)-brucellosis management schemes that have been proposed for the Grand Teton National Park (NP) bison herd: (1) vaccinating female calves, (2) vaccinating females of all ages, and (3) testing and removing seropositive animals, combined with vaccinating female calves or females of all ages. Sensitivity analysis demonstrated that model predictions are relatively robust to likely errors in estimates of key parameters under assumptions representing Grand Teton NP. Simulations predict that, after 20 years, the proportion of the Grand Teton NP herd seropositive for Brucella could be reduced from 69% (current level) to, at best, 20% under any of the 3 management schemes evaluated. Our examination of the relationship among brucellosis transmission rate, vaccine efficacy, and vaccine delivery rate indicated that reducing the percentage of seropositive animals to

Urea treatment fails to recover the heat-inactivated antigenic components of staphylococcal enterotoxin A (SEA) from heat-processed mushrooms and meat products. Food samples treated with urea show lower rates of recovery of toxins than those without urea treatment. The heat resistance of the native SEA serological components is three times the heat resistance of the purified toxin. However, heating to a F(sub o) of 4 to 18 or autoclaving at 121.1 degree celsius breaks down about 92 to 94% of the antigenicity of the toxin.

The monoclonal antibody IgG-alpha5 have been widely to identify Na+/K+ pump. Ultrastructure, Na+/K+ pump localization, and effects of mercury on Na+,K+-ATPase immunoreactivity were investigated in the branchial cavity of Palaemon elegans. Each branchial cavity contains 8 pairs of phyllobranchiate gills, 3 epipodites and a branchiostegite which comprises two irregular thick epithelia. Na+,K+-ATPase (Na+/K+ pump) specific labelling was detected only in the axial zone of the epithelial cells of the gills. Two layers of the epipodites epithelium and the branchiostegite inner epithelium showed a very strong Na+,K+-ATPase immunofluorescence and they appear as the main site of osmoregulation. Ultrastructuraly, these epithelium cells present ionocytes characters and possess numerous Na+/K+ pump on baso-lateral membranes. The number of immunofluorescence cells decreased from 91% in controls to 23% in mercury exposed Palaemon. Ultrastructuraly, mercury exposure increases levels of necrosis and apoptosis of ionocytes and disturbs the Na+/K+ pump. These results confirm that osmoregulatory capacity can be used to detect environmental disturbances in the shrimp P. elegans.

Research was conducted to determine the three-dimensional structure of ginger rhizome (GP-II) by X-ray crystallography to a resolution of 2.1 angstroms. The objective is to provide an explanation for the specificity of GP-II toward proline-containing peptides and to compare its structure with those of other cysteine proteases. The structure of GP-II was solved through molecular replacement to 2.1 angstrom resolution and the active site was identified.

Research was conducted to examine whether the carrier ligand specificity of replicative bypass could be determined either by the DNA polymerases that catalyze translesion replication or by the damage-recognition proteins that selectively bind to the Pt-DNA adducts and block translesion synthesis. Primer extension experiments were carried out with enzymes from all four DNA polymerase families. Results illustrate that both DNA polymerases and damage-recognition proteins can impart specificity to replicative bypass of Pt-DNA adducts.

A study conducted by Francisco Lozano et al. on the selection of cells expressing optimized antibodies in the immune system provide experimental support for the advantages offered by antibody-producing cells' single antibody specificity. They examined transgene copy expression in hybridomas obtained from immunized transgenic mice and found that somatic mutation occurred in most of the transgenes, making them distinguishable at the mRNA level. Their findings indicate that antibody-producing cells have several mechanisms for modulating antibody gene expression patterns and that the antibody response selects strongly for monospecific cells.