Low Degree Of Specificity Research Articles

Mutant Variants of the Substrate-Binding Protein DppA from Escherichia coli Enhance Growth on Nonstandard γ-Glutamyl Amide-Containing Peptides.

The import of nonnatural molecules is a recurring problem in fundamental and applied aspects of microbiology. The dipeptide permease (Dpp) of Escherichia coli is an ABC-type multicomponent transporter system located in the cytoplasmic membrane, which is capable of transporting a wide range of di- and tripeptides with structurally and chemically diverse amino acid side chains into the cell. Given this low degree of specificity, Dpp was previously used as an entry gate to deliver natural and nonnatural cargo molecules into the cell by attaching them to amino acid side chains of peptides, in particular, the γ-carboxyl group of glutamate residues. However, the binding affinity of the substrate-binding protein dipeptide permease A (DppA), which is responsible for the initial binding of peptides in the periplasmic space, is significantly higher for peptides consisting of standard amino acids than for peptides containing side-chain modifications. Here, we used adaptive laboratory evolution to identify strains that utilize dipeptides containing γ-substituted glutamate residues more efficiently and linked this phenotype to different mutations in DppA. In vitro characterization of these mutants by thermal denaturation midpoint shift assays and isothermal titration calorimetry revealed significantly higher binding affinities of these variants toward peptides containing γ-glutamyl amides, presumably resulting in improved uptake and therefore faster growth in media supplemented with these nonstandard peptides.IMPORTANCE Fundamental and synthetic biology frequently suffer from insufficient delivery of unnatural building blocks or substrates for metabolic pathways into bacterial cells. The use of peptide-based transport vectors represents an established strategy to enable the uptake of such molecules as a cargo. We expand the scope of peptide-based uptake and characterize in detail the obtained DppA mutant variants. Furthermore, we highlight the potential of adaptive laboratory evolution to identify beneficial insertion mutations that are unlikely to be identified with existing directed evolution strategies.

Brainstem audiometry as a diagnostic tool in psychiatry: Preliminary results from a blinded study

BackgroundSome prior studies of brainstem audiometry have found illness-specific aberrations, suggesting that this procedure can be of use to clinicians in diagnosing certain psychiatric illnesses.AimsThe study aimed to examine the diagnostic properties of a brain stem audiometry procedure (SD-BERA®) for patients suffering from schizophrenia and bipolar disorder.MethodsA blinded study including 12 patients with schizophrenia, 12 patients with bipolar disorder, and 12 healthy controls was performed in 2014/2015. The patients were recruited from psychiatric specialist services and a primary care office in the County of Troms, Norway. The patients and controls were examined with brainstem audiometry. The clinical diagnoses were not known to the researchers who analysed the brain stem audiometry data at the Swedish company SensoDetect. Sensitivity and specificity for each group (compared to healthy controls) was calculated.ResultsThe brain stem audiometry procedure had a high degree of sensitivity (1.00), but a lower degree of specificity (0.45) when patients suffering from bipolar disorder were compared to healthy controls. For the diagnosis of schizophrenia, the brain stem audiometry procedure had a high degree of specificity (0.91), but a lower degree of sensitivity (0.33) when patients were compared to healthy controls.ConclusionsThis method may help clinicians by lending support to a clinically suspected diagnosis of schizophrenia. The relatively low specificity for bipolar disorder could suggest that the method needs further development before it can be useful clinically when the diagnosis of bipolar disorder is suspected. Further scientific testing is needed to verify these findings.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Hirschman meets Williamson: Relationship-specific investment and loyalty

In Albert Hirschman’s theory, loyalty plays a key role in the equilibrium between exit and voice. This article extends economic (rational choice) analysis to the emergence of loyalty, which Hirschman considers an exogenous factor. This is accomplished by linking Williamson’s theory of specific investment to Hirschman’s model. Three cases are distinguished: (1) loyalty is due to specific investment; (2) loyalty is due to (intermediate) factors influenced by specific investment; and, (3) loyalty is independent of specific investment. A simple model formalizes the first case. A paradoxical dynamic of loyalty is identified: a lower degree of specificity may lead to a weakening of loyalty in the short run but astrengthening of loyalty in the long run. An application to the process of European integration is sketched.

Emotion Dysregulation as a Core Feature of Borderline Personality Disorder: Comparison of the Discriminatory Ability of Two Self-Rating Measures

Background/Aims: There is growing evidence that emotion dysregulation (ED) is a core feature of borderline personality disorder (BPD). The present study examines whether a self-rating measure, the ED Scale, lets us distinguish between individuals with BPD and those diagnosed with other mental disorders in a way similar to that of a borderline-related screening measure, the German version of the McLean Screening Instrument for Borderline Personality Disorders (MSI-BPD). Method: Based on the signal detection theory, receiver operating characteristics as well as reliability and validity indicators are determined in a heterogeneous outpatient sample (n = 168). Results: The values of internal consistency and the validity indicators turned out to be in the expected range. The area under the curve (AUC) for the ED Scale was 0.86, and therefore emerged on a par with the AUC = 0.90 of the MSI-BPD. As required, analyses for both measures revealed equal and high values for sensitivity, as well as corresponding low negative predictive values. There was, however, a lower degree of specificity on the ED Scale as compared to the MSI-BPD. Conclusion: The results support the assumption that ED is a core feature of BPD, but should also be taken into account in the assessment and treatment of other mental disorders.

Low specificity and nested subset structure characterize mycorrhizal associations in five closely related species of the genus Orchis

Most orchid species rely on mycorrhizae to complete their life cycle. Despite a growing body of literature identifying orchid mycorrhizal associations, the nature and specificity of the association between orchid species and mycorrhizal fungi remains largely an open question. Nonetheless, better insights into these obligate plant-fungus associations are indispensable for understanding the biology and conservation of orchid populations. To investigate orchid mycorrhizal associations in five species of the genus Orchis (O. anthropophora, O. mascula, O. militaris, O. purpurea, and O. simia), we developed internal transcribed spacer-based DNA arrays from extensive clone library sequence data sets, enabling rapid and simultaneous detection of a wide range of basidiomycetous mycorrhizal fungi. A low degree of specificity was observed, with two orchid species associating with nine different fungal partners. Phylogenetic analysis revealed that the majority of Orchis mycorrhizal fungi are members of the Tulasnellaceae, but in some plants, members of the Thelephoraceae, Cortinariaceae and Ceratobasidiaceae were also found. In all species except one (O. mascula), individual plants associated with more than one fungus simultaneously, and in some cases, associations with ≥3 mycorrhizal fungi at the same time were identified. Nestedness analysis showed that orchid mycorrhizal associations were significantly nested, suggesting asymmetric specialization and a dense core of interactions created by symmetric interactions between generalist species. Our results add support to the growing literature that multiple associations may be common among orchids. Low specificity or preference for a widespread fungal symbiont may partly explain the wide distribution of the investigated species.

GNL, competizione e sicurezza di approvvigionamento: il segmento dello shipping

- In the last few years, one of the main concerns of European Union in the energetic field has been that of facilitating the safeguard of raw materials' security of supply, especially that of natural gas. Import through LNG chain, that is, through the employment of LNG tankers for gas transportation, has been identified by the European Council as one of the instruments to achieve these goals. In fact, import via LNG does not require, for the importer, such investments as to determine an indissoluble physical tie between producer and buyer, as happens for transport via pipeline (Chernyavs'ka et al., 2002). In other words, investments in pipelines are very specific. Moreover, as they are made in order to support specific transactions, contracts usually take the form of long-term agreements with minimum offtake requirements (take or pay clauses): such contracts definitely contribute to the "cartelization" of the market, hindering competition. Unlike investments in pipelines, those in the LNG chain present a much lower degree of specificity: in fact, even though the construction of a regasification plant is generally tied to the stipulation of a long-term agreement (with take or pay clause), LNG chain costs have significantly decreased over time (until a few years ago) and, moreover, it is getting increasingly common that part of plant capacity is made available for spot transactions. What's more, once the contract is expired and the investment is sunk, the importer may satisfy his gas supply needs on the basis of his relative gains. As far as LNG import contractual practices are concerned, significant changes have started to take places in the last few years, both in terms of agreements' length - average duration has significantly decreased - and in terms of price indexation - in the most developed markets LNG price is tied to gas spot price (IEA, 2006). One of the many possible advantages of transport via LNG is that liquefied gas enables European importers to widen their gas suppliers portfolio. Increased possibilities of choice for importers, the widening of the group of exporting countries, and the increased integration of the European market, thanks to the possibility of redirecting cargoes depending on single countries' supply-demand balance, would contribute decisively to security of supply, market globalization and competition (between importers) in the industry (IEA, 2004). Yet, it must be stressed that import via tanker appears to be competitive with import via pipe only for the medium-long distances. As far as LNG chain is concerned, the element that so far has attracted the least attention, though being not less important than the other two, is certainly shipping. Being the link between the producing/exporting country and the importing country, and having been subject to major changes in the last few years, it is particularly interesting to analyze it singularly, aiming to understand how it is linked to the other elements of LNG value chain, besides studying industry dynamics. This paper will address this issue, aiming also to understand what has been and what will be in the future the evolutionary trajectory of this segment, starting from an analysis of operative and planned gas tankers, their size, their routes and their contractual situation. This analysis can be useful to make hypothesis about the growth of the spot market and, consequently, of market liquidity.Keywords: LNG, gas tankers, security of supply, competition, regasification plants, spot market, natural gas international tradeJEL classifications: L95, K12, F14, L11Parole chiave: GNL, navi gasiere, sicurezza dell'approvvigionamento, competizione, rigassificatori, mercato spot, commercio internazionale di gas naturale

I mercati internazionali dell'energia

- The paper analyzes recent market trends in the oil and natural gas sector. For the latter, a focus on the European gas market is then presented, whose consumption has grown considerably in these last ten years. As for the oil sector this paper investigates the key elements that have shaped its market in these years. As for oil consumption, we show that in these last 15 years China, India and the Middle East are the main responsible for the increase in World consumption. On the other hand, European OECD Countries have consistently reduced (almost 9%) their oil demand. This is due both to the dematerialization of their economy and their significant improvements in energy efficiency. As for energy intensity, in fact, Europe by far is the most efficient region in the World. On the other hand, OPEC has drastically raised its share of total production: at present the cartel accounts for more than 40% of overall production. OPEC members were the only producers to meet World's needs as oil demand expanded. The difficulties of other producers to keep up with the demand originated in the nineties, when no investment in new production capacity was brought about due to low oil prices. In the end of 2008, anyway, recession has eased the situation: for the first time in fifteen years, demand has not grown, compared to 2007 consumption. Recession has also shrunk prices, which, as soon as the demand started decreasing, have collapsed by almost 70%. As for the gas sector, the paper focuses on the European market where, after ten years from the beginning of the liberalization process, competition is still missing. In particular, the paper discusses whether LNG can bring about the competition so desperately needed. Unlike investments in pipelines, those in the LNG chain present a much lower degree of specificity, since the importer is not physically tied with the producer; moreover, it is getting increasingly common that part of the plant capacity is made available for spot transactions. It is also worth mentioning that for the time being LNG seems to represent the sole possibility for new competitors to enter the market according to the lack of capacity on international import pipelines. Long term import take or pay contracts held by gas incumbents play a pre-emption activity on transit pipelines and access can not be granted to third parties. Moreover, LNG could enable traditional European importers to widen their gas suppliers' portfolio, also considering that some producing countries (i.e. stranded gas) can be reached only via sea. Increased possibilities of choice for importers, the widening of the group of exporting countries, and the increased integration of the European market, thanks to the possibility of redirecting cargoes depending on single countries' supply-demand balance, would contribute decisively to security of supply, market globalization and competition in the industry. The paper presents also a cost plus comparison among different LNG supplies and those from new Russian fields, demonstrating that LNG will be even more convenient than those supplies coming from Eastern Siberia. Finally, it is important to highlight that the lack in new liquefaction capacity could undermine the growth of a florid LNG market.Key words: Oil and gas sector, liberalization, LNG.JEL classifications: Q40, Q41, Q43, Q48.Parole chiave: Mercato del petrolio e del gas, liberalizzazione e GNL.

The specificity and the constraints on NP-external placement of quantity expressions in Japanese

Abstract It is generally agreed that, in Japanese, NP-external placement of quantity expressions (often referred to as ‘quantifier float’) can occur with noun phrases in the nominative and accusative cases and sometimes with ni-marked cases, and most of the accounts have been syntactically based. Interpreting approximate quantity as one of the indicators of a low degree of specificity (less commitment on the part of the speaker to refer to particular entities), this study examines these statements in a wider context of a correlation between a low degree of specificity and the permissibility of NP-external constructions occurring with noun phrases marked by ni and even other oblique cases. The study supports the validity of the hypothesis by examples found in a CD corpus and on the Internet and by the result of a large scale native speaker grammaticality test, suggesting that perception of grammaticality is sensitive to semantic factors such as the degree of specificity.

Evaluation of the BD PHOENIX Automated Microbiology System for Detection of Methicillin Resistance in Coagulase-Negative Staphylococci

The new BD PHOENIX automated microbiology system (Becton Dickinson Diagnostic Systems, Sparks, Md.) is designed for automated rapid antimicrobial susceptibility testing and identification of clinically relevant bacteria. In our study, the accuracy and speed of the BD PHOENIX oxacillin MIC determination for detecting methicillin resistance was evaluated for 200 clinical isolates of coagulase-negative staphylococci (CoNS). Compared to mecA PCR, the BD PHOENIX system detected methicillin resistance with a sensitivity of 99.2%. According to the actual NCCLS oxacillin MIC breakpoint of > or =0.5 microg/ml, the specificity was only 64.9%, attributable to false-positive results in 26 mecA-negative strains, including 16 non-Staphylococcus epidermidis strains. Alternative oxacillin breakpoints of > or =1, > or =2, and > or =4 microg/ml resulted in increased specificities of 83.8, 94.6, and 100% and high sensitivities of 99.2, 99.2, and 96.7%, respectively. Similarly, NCCLS broth microdilution oxacillin MICs exhibited a sensitivity of 100% but a low degree of specificity. However, the previous oxacillin MIC breakpoint of > or =4 microg/ml performed with a sensitivity of 98.4% and a specificity of 98.7%. BD PHOENIX oxacillin MIC results were available after 9 h for 40.5% of the examined CoNS strains and were completed after 17 h. Our results revealed the high reliability of the BD PHOENIX system as a phenotypic method for detection of resistance to oxacillin in mecA-positive CoNS. However, for the improvement of specificity, reevaluation of the optimal oxacillin MIC breakpoint for CoNS appears to be necessary.

Polyanions and the Proteome

The behavior of the proteome reflects spatial and temporal organization both within and without cells. We propose that various macromolecular entities possessing polyanionic character such as proteoglycans, lipid bilayer surfaces, microtubules, microfilaments, and polynucleotides may provide a functional network that mediates a variety of cellular phenomena. The interaction of proteins with this array of polyanions is characterized by a lower degree of specificity than seen with most commonly recognized macromolecular interactions. In this commentary, potential roles for this polyanion network in diverse functions such as protein/protein interactions, protein folding and stabilization, macromolecular transport, and various disease processes are all considered, as well as the use of polyanions as therapeutic agents. The role of small polyanions in the regulation of protein/polyanion interactions is also postulated. We provide preliminary experimental analysis of the extent to which proteins interact with polyanions inside cells using a combination of two-dimensional chromatographic and electrophoretic methods and antibody arrays. We conclude that many hundreds to thousands of such interactions are present in cells and argue that future understanding of the proteome will require that the "polyanion world" be taken into account.

Heredity of specific host-finding behaviour in Schistosoma mansoni miracidia.

Two strains of Schistosoma mansoni were used to investigate the hereditary basis of species-specific host recognition by analysing behavioural responses of miracidia to snail-conditioned water. An Egyptian strain of S. mansoni, capable of distinguishing its host snail Biomphalaria alexandrina from other snails was cycled repeatedly through Biomphalaria glabrata, the intermediate host of a Brazilian strain known to respond even to non-susceptible snails with high intensity. After 5 cycles in the non-natural host, miracidia of the Egyptian strain still retained their preference for the original host snail. In a second experiment, host-finding behaviour of hybrids between these two parasite strains was studied. In the F1 generation, hybrids of both parental combinations showed the same low degree of specificity as the pure-bred Brazilian strain. Approximately one quarter of F2 hybrids proved to be as discriminatory as the Egyptian strain, confirming dominant Mendelian inheritance of non-specificity in schistosome miracidial host-finding behaviour. Moreover, hybrids seem to have lost the ability to develop in B. alexandrina, possibly suggesting a link between host recognition and host compatibility. The heredity of this behavioural trait is of evolutionary and epidemiological significance, since a shift to low host-finding specificity might have been a prerequisite for S. mansoni to acquire new host snails after being introduced to South America by the slave trade.

Reduction of phenol content and toxicity in olive oil mill waste waters with the ligninolytic fungus Pleurotus ostreatus

Olive oil mill waste waters (OMW) constitute a major environmental problem because of the large amount produced and the toxicity of the phenolic compounds present. Several of these aromatic compounds can be assimilated to many of the components of lignin. Only few microorganisms, mainly “white-rot” basidiomycete, are able to degrade lignin by means of oxidative reactions catalysed by phenol oxidases and peroxidases. Both the low degree of specificity which characterizes these enzymes, and the structural relationships of many aromatic pollutants with the natural substrates of the enzymes, have suggested the use of ligninolytic organisms and of their enzymes for the treatment of these kinds of substrates. This paper investigates the ability of the “white-rot” basidiomycete Pleurotus ostreatus and particularly of the phenol oxidases it produces in the detoxification of OMW phenol compounds. Treatment of OMW with purified phenol oxidase showed a significant reduction of phenolic content, but no decrease of its toxicity was observed when tested on Bacillus cereus. Otherwise, the effect of processing OMW with the entire microorganism resulted in a noticeable detoxification of the waste with concomitant abatement of the phenol content.

DNA-binding properties of the yeast transcriptional activator, Gcr1p

In Saccharomyces cerevisiae the GCRI gene product is required for high-level expression of genes encoding glycolytic enzymes. In this communication, we extend our analysis of the DNA binding properties of Gcr1p. The DNA-binding domain of Gcr1p binds DNA with high affinity. The apparent dissociation constant of the Gcr1p DNA-binding domain for one of its specific binding sites (TTTCAGCTTCCTCTAT) is 2.9 x 10(-10) M. However, competition experiments showed that Gcr1p binds this site in vitro with a low degree of specificity. We measured a 33-fold difference between the ability of specific competitor and DNA of random sequence to inhibit the formation of nucleoprotein complexes between Gcr1p and a radiolabeled DNA probe containing its binding site. DNA band-shift experiments, utilizing probes of constant length in which the positions of Gcr1p-binding sites are varied relative to the ends, indicated that Gcr1p-DNA nucleoprotein complexes contain bent DNA. The implications of these findings in terms of the combinatorial interactions that occur at the upstream activating sequence elements of genes encoding glycolytic enzymes are discussed.

Sugar sensing in higher plants.

Sugar repression of photosynthetic genes is likely a central control mechanism mediating energy homeostasis in a wide range of algae and higher plants. It overrides light activation and is coupled to developmental and environmental regulations. How sugar signals are sensed and transduced to the nucleus remains unclear. To elucidate sugar-sensing mechanisms, we monitored the effects of a variety of sugars, glucose analogs, and metabolic intermediates on photosynthetic fusion genes in a sensitive and versatile maize protoplast transient expression system. The results show that sugars that are the substrates of hexokinase (HK) cause repression at a low concentration (1 to 10 mM), indicating a low degree of specificity and the irrelevance of osmotic change. Studies with various glucose analogs suggest that glucose transport across the plasma membrane is necessary but not sufficient to trigger repression, whereas subsequent phosphorylation by HK may be required. The effectiveness of 2-deoxyglucose, a nonmetabolizable glucose analog, and the ineffectiveness of various metabolic intermediates in eliciting repression eliminate the involvement of glycolysis and other metabolic pathways. Replenishing intracellular phosphate and ATP diminished by hexoses does not overcome repression. Because mannoheptulose, a specific HK inhibitor, blocks the severe repression triggered by 2-deoxyglucose and yet the phosphorylated products per se do not act as repression signals, we propose that HK may have dual functions and may act as a key sensor and signal transmitter of sugar repression in higher plants.

Electroencephalogram and Epilepsy

In spite of its low degree of specificity and its poor sensibility, the electroencephalogram has remained, for half a century, the epileptologist's working tool. In this paper, the places of simple activation procedures are recalled, especially sleep activations. Recent studies have shown that EEG is important in diagnosis assessment and in treatment management.

Modulation of beta-cell activity and its influence on islet cell antibody (ICA) and islet cell surface antibody (ICSA) reactivity.

Insulin-dependent diabetes mellitus (IDDM) is associated with the formation of autoantibodies against different antigens in the islets of Langerhans, so-called islet cell antibodies (ICA). The expression of a major autoantigen, the beta-cell specific enzyme glutamic acid decarboxylase (GAD), is glucose-dependent in vitro and correlated to insulin release in vitro. In this study the expression of islet autoantigens was examined in vivo and the relationship between beta-cell function and islet cell surface antibody (ICSA) reactivity was tested. Rats were fed for 10 days with glipizide or diazoxide, in order to stimulate or inhibit insulin release, respectively. Frozen sections of pancreata were incubated with ten ICA-positive IDDM sera and analyzed by indirect immunofluorescence. Two sera with a "beta-cell restricted" staining, five with an "all-islet cell" staining and three with a "mixed" pattern were employed. In all three groups, the highest end-point titres were obtained when pancreata of rats treated with glipizide were used. Intermediate titres were seen in control animals and the lowest titres were observed on pancreata from diazoxide-treated rats, regardless of the serum used. In contrast to these observations, no correlation between ICSA reactivity and islet cell activity could be demonstrated. Conflicting results concerning ICSA in previous reports and our failure to show a glucose regulation of ICSA reactivity, indicate that ICSA is a phenomenon with a low degree of specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and substrate specificity of a T4 phage intron-encoded endonuclease

The T4 phage td intron-encoded endonuclease (I-Tev I) cleaves the intron-deleted td gene (td delta I) 23 nucleotides upstream of the intron insertion site on the noncoding strand and 25 nucleotides upstream of this site on the coding strand, to generate a 2-base hydroxyl overhang in the 3' end of each DNA strand. I-Tev I-157, a truncated form in which slightly more than one third (88 residues) of the endonuclease is deleted, was purified to homogeneity and shown to possess endonuclease activity similar to that of I-TEV I, the full-length enzyme (245 residues). The minimal length of the td delta I gene that was cleaved by I-Tev I and I-Tev I-157 has been determined to be exactly 39 basepairs, from -27 (upstream in exon1) to +12 (downstream in exon2) relative to the intron insertion site. Similar to the full-length endonuclease, I-Tev I-157 cuts the intronless thymidylate synthase genes from such diverse organisms as Escherichia coli, Lactobacillus casei and the human. The position and nature of the in vitro endonucleolytic cut in these genes are homologous to those in td delta I. Point mutational analysis of the td delta I substrate based on the deduced consensus nucleotide sequence has revealed a very low degree of specificity on either side of the cleavage site, for both the full-length and truncated I-TEV I.

Characterisation of the discriminative stimulus properties of flumazenil

Rats were trained to discriminate flumazenil (15 mg/kg i.p.) from vehicle in a two-lever, food-reinforced, operant conditioning procedure. Substitution tests were performed with a wide dose range of flumazenil and of several benzodiazepines and non-benzodiazepine compounds possessing behavioural effects similar to or opposite to those of benzodiazepine agonists. The results indicate that low doses of flumazenil have behavioural effects, that the flumazenil cue has a low degree of specificity and is most strongly related to the stimulus properties of benzodiazepines.

Principles of frequency-domain fluorescence spectroscopy and applications to cell membranes.

Fluorescence spectroscopy is often used to study the dynamic and hydrodynamic properties of proteins, membranes, and nucleic acids (Cundall and Dale, 1980; Lakowicz, 1983, 1986; Visser, 1985; Demchenko, 1986). More recently, the sensitivity of fluorescence detection, and advances in two-di-mensional detectors have resulted in increased emphasis on the use of fluo-rescence microscopy to obtain a more detailed understanding of cellular phenomena (Taylor et al., 1986). An unfavorable characteristic of fluorescence is the relatively low degree of specificity. The emission spectra of fluorophores often overlap on the wavelength scale, and the emission spectra of different fluorophores are often similar in shape. A further complication is that the emission may be complex due to the presence of multiple environments in a membrane, several fluorophores in a macromolecule, or the intrinsically complex emission of macromolecules or even simple molecules like tryptophan.

Solid-phase enzyme immunoassay for detection of Chlamydia trachomatis.

The prototype of a solid-phase enzyme immunoassay for the detection of Chlamydia trachomatis antigen was tested in 403 men and 135 women attending a venereal disease clinic. Culture on HeLa 229 cells was used as reference method. In men the overall sensitivity and specificity of the enzyme immunoassay was 70% and 98.5% respectively. In the 158 men with non-gonococcal urethritis the sensitivity and specificity was 73% and 96.5% respectively, in the 31 men with post-gonococcal urethritis 82% and 100%, in the 48 men with gonococcal urethritis 67% and 100%, in the 125 men with discharge but normal urinary sediment 54% and 99.1% and in the 41 men with no signs or symptoms 50% and 100%. In women the sensitivity and specificity of the assay was 70% and 92% respectively. On account of the low degree of sensitivity in both men and women and the low degree of specificity in women the prototype of the enzyme immunoassay is not yet considered suitable for clinical use. An improved model is being developed.