Tailoring FPOX enzymes for enhanced stability and expanded substrate recognition

Fructosyl peptide oxidases (FPOX) are deglycating enzymes that find application as key enzymatic components in diabetes monitoring devices. Indeed, their use with blood samples can provide a measurement of the concentration of glycated hemoglobin and glycated albumin, two well-known diabetes markers. However, the FPOX currently employed in enzymatic assays cannot directly detect whole glycated proteins, making it necessary to perform a preliminary proteolytic treatment of the target protein to generate small glycated peptides that can act as viable substrates for the enzyme. This is a costly and time consuming step. In this work, we used an in silico protein engineering approach to enhance the overall thermal stability of the enzyme and to improve its catalytic activity toward large substrates. The final design shows a marked improvement in thermal stability relative to the wild type enzyme, a distinct widening of its access tunnel and significant enzymatic activity towards a range of glycated substrates.

Light-Based Anti-Biofilm and Antibacterial Strategies

Biofilm formation and antimicrobial resistance pose significant challenges not only in clinical settings (i.e., implant-associated infections, endocarditis, and urinary tract infections) but also in industrial settings and in the environment, where the spreading of antibiotic-resistant bacteria is on the rise. Indeed, developing effective strategies to prevent biofilm formation and treat infections will be one of the major global challenges in the next few years. As traditional pharmacological treatments are becoming inadequate to curb this problem, a constant commitment to the exploration of novel therapeutic strategies is necessary. Light-triggered therapies have emerged as promising alternatives to traditional approaches due to their non-invasive nature, precise spatial and temporal control, and potential multifunctional properties. Here, we provide a comprehensive overview of the different biofilm formation stages and the molecular mechanism of biofilm disruption, with a major focus on the quorum sensing machinery. Moreover, we highlight the principal guidelines for the development of light-responsive materials and photosensitive compounds. The synergistic effects of combining light-triggered therapies with conventional treatments are also discussed. Through elegant molecular and material design solutions, remarkable results have been achieved in the fight against biofilm formation and antibacterial resistance. However, further research and development in this field are essential to optimize therapeutic strategies and translate them into clinical and industrial applications, ultimately addressing the global challenges posed by biofilm and antimicrobial resistance.

Donor-Acceptor Stenhouse Adduct Displaying Reversible Photoswitching in Water and Neuronal Activity

The interest in the photochromism and functional applications of donor-acceptor Stenhouse adducts (DASAs) soared in recent years owing to their outstanding advantages and flexible design. However, their low solubility and irreversible conversion in aqueous solutions hampered exploring DASAs for biology and medicine. It is notably unknown whether the barbiturate electron acceptor group retains the pharmacological activity of drugs such as phenobarbital, which targets γ-aminobutyric acid (GABA)-type A receptors (GABA_ARs) in the brain. Here, we have developed the model compound DASA-barbital based on a scaffold of red-switching second-generation DASAs, and we demonstrate that it is active in GABA_ARs and alters the neuronal firing rate in a physiological medium at neutral pH. DASA-barbital can also be reversibly photoswitched in acidic aqueous solutions using cyclodextrin, an approved ingredient of drug formulations. These findings clarify the path toward the biological applications of DASAs and to exploit the versatility displayed in polymers and materials science.

Recent Approaches to the Identification of Novel Microtubule-Targeting Agents

Microtubules are key components of the eukaryotic cytoskeleton with essential roles in cell division, intercellular transport, cell morphology, motility, and signal transduction. They are composed of protofilaments of heterodimers of α-tubulin and β-tubulin organized as rigid hollow cylinders that can assemble into large and dynamic intracellular structures. Consistent with their involvement in core cellular processes, affecting microtubule assembly results in cytotoxicity and cell death. For these reasons, microtubules are among the most important targets for the therapeutic treatment of several diseases, including cancer. The vast literature related to microtubule stabilizers and destabilizers has been reviewed extensively in recent years. Here we summarize recent experimental and computational approaches for the identification of novel tubulin modulators and delivery strategies. These include orphan small molecules, PROTACs as well as light-sensitive compounds that can be activated with high spatio-temporal accuracy and that represent promising tools for precision-targeted chemotherapy.

International Scientific Collaboration Is Needed to Bridge Science to Society: USERN2020 Consensus Statement

Scientific collaboration has been a critical aspect of the development of all fields of science, particularly clinical medicine. It is well understood that myriads of benefits can be yielded by interdisciplinary and international collaboration. For instance, our rapidly growing knowledge on COVID-19 and vaccine development could not be attained without expanded collaborative activities. However, achieving fruitful results requires mastering specific tactics in collaborative efforts. These activities can enhance our knowledge, which ultimately benefits society. In addition to tackling the issue of the invisible border between different countries, institutes, and disciplines, the border between the scientific community and society needs to be addressed as well. International and transdisciplinary approaches can potentially be the best solution for bridging science and society. The Universal Scientific Education and Research Network (USERN) is a non-governmental, non-profit organization and network to promote professional, scientific research and education worldwide. The fifth annual congress of USERN was held in Tehran, Iran, in a hybrid manner on November 7–10, 2020, with key aims of bridging science to society and facilitating borderless science. Among speakers of the congress, a group of top scientists unanimously agreed on The USERN 2020 consensus, which is drafted with the goal of connecting society with scientific scholars and facilitating international and interdisciplinary scientific activities in all fields, including clinical medicine.

Biohybrid Electrospun Membrane for the Filtration of Ketoprofen Drug from Water

A current challenge in materials science and biotechnology is to express a specific and controlled functionality on the large interfacial area of a nanostructured material to create smart biohybrid systems for targeted applications. Here, we report on a biohybrid system featuring poly(vinyl alcohol) as the supporting synthetic polymer and bovine serum albumin as the biofunctional element. The optimal processing conditions to produce these self-standing composite membranes are determined, and the composition and distribution of the bioactive agent within the polymeric matrices are analyzed. A post-processing cross-linking using glutaraldehyde enables this functional membrane to be used as a chemical filter in aqueous environments. By demonstrating that our mats can remove large amounts of ketoprofen from water, we show that the combination of a BSA-induced biofunctionality with a nanostructured fibrous material allows for the development of an efficient biohybrid filtering device for the large and widely used family of nonsteroidal anti-inflammatory drugs (NSAIDs). The crystal structure of the complex between BSA and ketoprofen is determined for the first time and confirms the interaction between the two species.

Dodecagonal plasmonic quasicrystals for phage-based biosensing

In this work, we fabricate and characterize a novel sensitive two-dimensional surface enhanced Raman spectroscopy (SERS) substrate made of plasmonic nanocavities in a photonic quasicrystal arrangement characterized by a 12-fold rotational symmetry. Our SERS device is capable of detecting chemisorbed bacteriophages at a femtomolar range. Most importantly, the paper presents for the first time a study on the procedure to functionalize the plasmonic quasicrystal with bacteriophages of the Podoviridae family. The immobilization of the phages on the plasmonic substrate has been studied and verified through SERS measurements. A new stable peak, visible in the SERS spectra at 1326 cm^-1 at a greater than 60 times amplification, confirms the immobilization of the phages on the substrate. This functionalization approach can be used also for other types of phages or plasmonic sensors and hence, our achievements could allow the development of novel systems for the specific detection of different species of bacteria.

Light-induced dipole moment modulation in diarylethenes: a fundamental study

The dipole moment of photochromic diarylethenes is determined in solution for both the coloured and uncoloured forms by measuring the capacitance of a capacitor filled with a photochromic solution as a dielectric material. Diarylethenes with different substituents are investigated and the modulation of the dipole moment is related to their chemical structures. We determine a modulation of the dipole moment up to 4 Debye. We discuss the model used to obtain the dipole moment from the capacitance measurements and we compare the experimental results with the outcomes from DFT calculations. The results highlight the importance of conformational effects in the description of the dipole moment of diarylethenes.

Tip‐mould microcontact printing for functionalisation of optical microring resonator

We present an approach to functionalise optical microring resonators as hybridisation platforms, using tip‐mould reactive microcontact printing process. Derived from reactive microcontact printing using an ad hoc mould of polydimethylsiloxane (PDMS), the method functionalises single microring resonator with a target‐specific capture agent. The authors report the functionalisation of silicon nitride (SiN) 200 μ m diameter microring resonator with single‐strand DNA and the hybridisation detection of 100 nM target analyte, while concurrently monitoring not‐functionalised microring as a control sensor. Results show that the functionalisation approach permits to address single microring resonators with mutual distance lower than 100 μ m with high precision, enabling a better integration of multiple spotting zones on the chip concerning traditional functionalisation procedures.

Engineered nanopatterned substrates for high-sensitive localized surface plasmon resonance: an assay on biomacromolecules

In this paper, we report on novel iso-Y-shaped-nanopillar based photonic crystals (PCs) engineered for plasmonic lab-on-a-chip advanced diagnostics. The iso-Y shaped units are selected on the basis of their plasmonic properties, analyzed numerically and experimentally. We show that by accurately choosing the nanopillar shape, dimensions and their geometrical disposal it is possible to obtain efficient optical 2D structures for biomolecule detection by high-sensitive localized surface plasmonic resonance (LSPR). In particular, an assay is realized by using bovine serum albumin (BSA), a widely recognized model for biosystem studies. BSA was simply deposited on a self-assembled monolayer (SAM) of 4-mercaptobenzoic acid (4-MBA) previously grown-up on the plasmonic substrate. We demonstrate that the geometries considered allow the design of LSPR nano-assays working in the visible-NIR region based on both intensity interrogation and the resonance peak shift permitting the sensing of BSA with a limit of detection in the order of picomoles (LOD = 233 pM).

Plasmonic Nanocavities-based Aperiodic crystal for Protein-Protein Recognition SERS sensors

The revelation of protein-protein interactions is one of the main preoccupations in the field of proteomics. Nanoplasmonics has emerged as an attractive surface-based technique because of its ability to sense protein binding under physiological conditions in a label-free manner. Here, we present a detailed experimental study of the use of aperiodic photonic nanocavities for plasmonic Surface Enhanced Raman Scattering (SERS) protein detection and recognition. The plasmonic crystal is designed on a 2D Thue-Morse array configuration. The SERS nanosensor is coated with a proper self-assembled monolayer to covalently bind Bovine Serum Albumin that is a well known model to study biological (specifically, protein) systems. The performance of the nanosensor is assessed by recording a new Raman (SERS) peak in the fingerprint region and by a giant enhancement of the SERS signal intensity, both reported and discussed.

Reactive Microcontact Printing of DNA Probes on (DMA-NAS-MAPS) Copolymer-Coated Substrates for Efficient Hybridization Platforms

High-performing hybridization platforms fabricated by reactive microcontact printing of DNA probes are presented. Multishaped PDMS molds are used to covalently bind oligonucleotides over a functional copolymer (DMA-NAS-MAPS) surface. Printed structures with minimum width of about 1.5 μm, spaced by 10 μm, are demonstrated, with edge corrugation lower than 300 nm. The quantification of the immobilized surface probes via fluorescence imaging gives a remarkable concentration of 3.3 × 10(3) oligonucleotides/μm(2), almost totally active when used as probes in DNA-DNA hybridization assays. Indeed, fluorescence and atomic force microscopy show a 95% efficiency in target binding and uniform DNA hybridization over printed areas.

Structured beam diffraction

We report on the observation of a modulated pattern induced by a single laser beam in a polymeric film. In spite of the simple geometrical configuration, the analysis of the far field diffraction pattern allows a sensitive retrieving of the wavelength of the recording beam and of its incidence angle, pointing out the high information content of the recorded spot. A theoretical model is presented which satisfactorily explains the observed behavior. It takes into account the interaction of structured light with structured matter with the same symmetries and spatial modulation frequencies close to each other. This result shows a feature of the interaction between structured light and structured matter which has not been explored yet.

High-performance Nanocavities-based Meta-crystals for Enhanced Plasmonic Sensing

We report on a novel procedure of fabrication to easily obtain highly reproducible nanocavities-shaped photonic crystals with strong plasmonic performances. Thus, we also report on the morphological and optical characterization of the obtained structures. They are classifiable as 2-layers (organic and inorganic) photonic crystals based on iso-Y-shaped nano-cavities. Such novel designed structures are compelling candidates for the development of highly sensitive biosensors due to their unique surface plasmon resonances (SPRs) and SPR enabled surface-enhanced Raman spectroscopy (SERS). The planar photonic crystal comprises a polymeric (ZEP520A) layer (thickness ~80 nm) sandwiched between a layer of gold (~50 nm thickness) and a glass substrate. For what concerns the cavities’ shape, iso-Y units are chosen on the basis of their third order nonlinearity and are coupled in hexagonal-based configuration to produce extended meta-structures. The substrates are functionalized with a probe made by a self-assembling monolayer (SAM) of 4-mercaptobenzoic acid (4-MBA). The average SERS Enhancement Factor >106 and SPR sensitivity of ~300 nm/RIU confirm that the proposed 2-layers iso-Y meta-structure is very suitable for high sensitive label-free plasmonic sensing.

Highly homogeneous core–sheath polyaniline nanofibers obtained by polymerisation on a wire-shaped template

Homogeneous and defect-free PANI nanofibrous membranes were demonstrated with oxidative polymerization on a Nylon 6 electrospun wire-shaped template.

Modeling absorbance-modulation optical lithography in photochromic films

A kinetic model describing the conversion of a photochromic layer under complex illumination conditions is applied to absorbance-modulation optical lithography to determine the influence of the material characteristics on the confinement to subdiffraction dimensions of the transmitted dose. We show that the most important parameters are the intensity ratio between the confining and writing beams, the overall absorption at the writing wavelength, the relative absorption coefficients, and the photoreaction quantum yields at the two wavelengths. As the confining beam ultimately determines the transferred dose pattern, we conclude that the modulation of the writing beam is not strictly necessary to produce subwavelength apertures.

Photochromic Electret: A New Tool for Light Energy Harvesting

In this paper, a photochromic electret for light energy harvesting is proposed and discussed. Such electret directly converts the photon energy into electric energy thanks to a polarization modulation caused by the photochromic reaction, which leads to a change in dipole moment. Theoretical concepts on which the photochromic electret is based are considered with an estimation of the effectiveness as a function of material properties. Finally, an electret based on a photochromic diarylethene is shown with the photoelectric characterization as a proof of concept device.

Esthesioneuroblastoma treated with external radiotherapy. Case report

Esthesioneuroblastoma is a rare tumour arising from the olfactory epithelium of the nasal vault which frequently invades the cranial base and orbit. Esthesioneuroblastoma has a bimodal age distribution between 11 and 20 years and between 51 and 60 years. Esthesioneuroblastoma accounts for approximately 1-5% of intranasal cancers. The case is reported of a 79-year-old female patient with a Kadish stage C tumour with a one-year history of headache, nasal obstruction, anosmia, rhinorrhoea and epistaxis. Aim of this study is to analyse the natural history, treatment and prognosis of this tumour, based on a review of the literature.

[Multivariate analysis of prognostic factors and survival in patients with "glioblastoma multiforme"]

PURPOSE

The aim of this study was to evaluate the survival of patients with "glioblastoma multiforme", to analyse the prognostic factors influencing the survival rate and to review recent results in the literature.

MATERIALS AND METHODS

Seventy five patients underwent radiation treatment between May 1998 and April 2003. Among the factors under investigation we ascertained that sex, chemotherapy, conformal treatment, surgery, and the choice of the irradiation area (whole brain or only the involved field) did not influence the survival in a statistically significant manner.

RESULTS

Whereas age and total dose were the 95% statistically significant variables. Hazard ratio of patients older than 58 years compared to younger patients was 1.69. The death risk was 69% in older than younger patients. A greater irradiation dose improved the survival with an increase of the median survival days. The total dose lower than 6000 cGy caused an increase of 81.8% in the death risk. The median survival from the diagnosis to the death was 14.7 months (446 days) and 1-, 2- and 3- year survival rate was 69.3%, 38.4%, and 14.7% respectively.

CONCLUSIONS

The current medical literature and our experience attests that the use of temozolomide improves the survival of these patients.

Rapid mutagenesis and purification of phage RNA polymerases

We have developed plasmid-based expression systems that encode modified forms of T7 RNA polymerase (RNAP) having 6-12 histidine residues fused to the amino terminus. The histidine-tagged RNAPs (His-T7 RNAPS) are indistinguishable from the wild-type (WT) enzyme in nearly all biochemical assays. Similar plasmids that encode His-tagged T3 and SP6 RNAPs have also been constructed. To facilitate site-directed mutagenesis of the RNAP gene, the size of the target plasmid was minimized by using T7 RNAP itself as a selectable marker. BL21 (DCAT4) cells (which carry a chromosomal copy of the chloramphenicol acetyltransferase cat gene under control of a T7 promoter) are resistant to chloramphenicol when functional T7 RNAP is expressed, thus allowing the selection and maintenance of the target plasmid in these cells. Mutagenesis is accomplished by denaturing the plasmid, annealing mutagenic DNA primers, and repairing the plasmid with T4 DNA polymerase. Two DNA primers are used: one corrects a defect in the bla gene, the other introduces the desired mutation into the RNAP gene; 30-85% of the ampicillin-resistant transformants carry the desired mutation in the RNAP gene. By using BL21 (DCAT4) cells as a recipient for transformation the functional integrity of the RNAP gene may conveniently be monitored by assessing the level of chloramphenicol resistance in vivo. Methods for rapid, simultaneous purification of multiple samples of modified (His-tagged) and conventional RNAPs are described. Together, these developments greatly enhance our ability to characterize this important class of enzymes.

Restoration of lipopolysaccharide-mediated B-cell response after expression of a cDNA encoding a GTP-binding protein

Previous analysis of hybrid progeny derived from lipopolysaccharide (LPS) responder and nonresponder inbred mouse strains demonstrated that a single genetic locus controlled responsiveness to LPS. Using a differential functional screening approach, we report the isolation of a cDNA that has sequence homology to a GTP-binding protein. Expression of the cDNA in splenic B cells of C3H/HeJ nonresponder, endotoxin-resistant mice resulted in polyclonal B-cell activation in response to LPS stimulation. Thus a GTP-binding protein may be involved in LPS stimulation in B cells and perhaps other cell types.

RFLP-based genetic relationships of Einkorn wheats

To study the relationships between different species of the Einkorn group, 55 different accessions ofTriticum monococcum,T. boeoticum,T. urartu,T. sinskajae,T. thaoudar andT. aegilopoides were analyzed. Fifteen anonymous probes and four clones corresponding to storage protein genes were used for detecting restriction fragment length polymorphisms (RFLPs). The DNA was restricted with the restriction enzymesAluI,HaeIII,RsaI andTaqI. The 25 probe/enzyme combinations employed yielded a total of 488 polymorphic fragments. Statistical analyses were performed using Jaccard's coefficient of similarity and principal coordinate analysis. Different values of similarity within the three main taxa,monococcum,boeoticum andurartu, were obtained; the grouping at the species level was quite well reflected by the RFLP analysis done here. The coincidence between RFLP data and the subspecies classification of theT. monococcum group was only partial. OneT. urartu accession is clearly different from all of the other 54 accessions. The need for an RFLP based revision of the Einkorn taxonomy is evident.

Lipopolysaccharide nonresponder cells: the C3H/HeJ defect

Since its initial discovery as endotoxin resistant, the C3H/HeJ mouse has been extensively studied and used as a comparative model to help reveal the mechanism under genetic control which governs host responses to endotoxin. Most of the research has focused on the B lymphocyte and macrophage of this strain which fail to be activated by LPS. Recently, specific LPS binding proteins have been isolated on lymphocytes and other cells; however a receptor which transduces an activation signal has not been isolated as yet from responder cells which is missing or altered on C3H/HeJ nonresponder cells. Investigations into the signal transduction pathways used by C3H/HeJ B cells when they are activated by a protein mitogen have been found to be similar to those used by LPS responder cells when activated by LPS. Protein kinase C and tyrosine kinase, which phosphorylate signal proteins in cells have been found to be operative in C3H/HeJ and C3H/OuJ B cells. In both cases, DNA synthesis is shut off by either PKC or PTK blockade; however, PTK inhibition will also block activation of PKC stimulated DNA synthesis, indicating tyrosine kinase initiated phosphorylation may regulate the PKC signal pathway. Further analysis of the proteins that are phosphorylated in LPS responder and LPS nonresponder B cells is needed before conclusions can be drawn as to whether the defect in C3H/HeJ cells resides in the signal pathway leading to gene activation and proliferation. Nevertheless, the notion of a missing or defective signal receptor still remains as a working hypothesis to explain C3H/HeJ cell hyporesponsiveness to LPS. Isolation of the Lpsn gene and its product will provide the evidence needed for a clearer understanding of how LPS reacts with cells.

Suppression of C3H/HeJ cell activation by lipopolysaccharide endotoxin

Earlier studies in our laboratory showed that the lipopolysaccharide (LPS) of Salmonella typhi, which fails to activate B lymphocytes of C3H/HeJ mice, can suppress proliferation and polyclonal antibody synthesis by these cells when they are stimulated by polyclonal activators. In order to determine what stage of the cell cycle was blocked, resting B cells from C3H/HeJ spleens were activated by using different mitogens in the presence of inhibitory concentrations of LPS and analyzed by flow cytometry, using acridine orange to stain DNA and RNA. LPS was found to inhibit the progression of cells into the G1 stage of the cell cycle. Furthermore, [3H]uridine uptake studies showed that RNA synthesis is inhibited during the early phase of activation. These results indicate that inhibition by LPS of the signalling process occurs during a critical period of the cell cycle when the cells become susceptible to the inhibitory effects of LPS. To examine whether LPS acts only on B cells or whether it can suppress other immunocompetent cells from C3H/HeJ mice, studies were carried out on activated thymocytes and macrophages. LPS was found to inhibit thymocyte proliferation stimulated by concanavalin A or the combination of phorbol myristate acetate and ionomycin. Prostaglandin E2 synthesis by macrophages was also blocked by LPS. Thus, LPS is a potent inhibitor of the functioning of the major immunocompetent cells of C3H/HeJ mice.

Immunomodulation of C3H/HeJ cells by endotoxin associated protein and lipopolysaccharide endotoxin

Protein kinase C plays a vital role in the activation of C3H/HeJ B lymphocytes by endotoxin associated protein; however, it is unlikely that G proteins are involved in the early signals stimulated by EP. On the other hand, LPS suppresses C3H/HeJ B cell DNA synthesis induced by EP which may be the result of PKC down regulation. LPS inhibits C3H/HeJ B cells from progressing through the G1 phase of the cell cycle blocking RNA synthesis within the first 12 hr after the cells are stimulated. Finally, this inhibition extends to activation of the arachidonic acid metabolism in C3H/HeJ macrophages and T cell proliferation to a limited extent.

Roles of protein kinase C and G proteins in activation of murine resting B lymphocytes by endotoxin-associated protein

Endotoxin-associated protein (EP) from the outer membrane of gram-negative bacteria is a potent immunomodulator. To examine the mechanism of EP stimulation, the protein kinase C inhibitors H7 and staurosporine were used. Both DNA and RNA synthesis of EP-stimulated murine resting B cells were completely inhibited when inhibitors were added at 0 h, whereas 55 to 76% inhibition of DNA synthesis was observed when H7 was added after 12 h of stimulation. In contrast, HA 1004, which blocks protein kinase A and protein kinase G activity, was relatively ineffective even at high concentrations, suggesting that the activity of protein kinase C is a primary mechanism of EP-induced murine B-cell proliferation. To examine the role of G proteins in EP-induced DNA synthesis in B cells, the effects of pertussis toxin (PT), which inactivates certain G proteins, and the B oligomer of PT (PTB), which does not, were also examined. PT was found to inhibit EP-induced DNA synthesis in a dose-dependent manner. However, PTB also caused equivalent inhibition, suggesting that PTB may be responsible for most of the inhibitory effect seen with the holotoxin. These results serve to question whether G proteins are involved in the signal transduction that occurs during EP-induced DNA synthesis in murine B cells.

Immunogenic endotoxin associated protein from a rough strain of Salmonella

A multimolecular complex of polypeptides found associated with the lipopolysaccharide endotoxin in Salmonella, referred to as endotoxin-associated protein (EP), has been extracted from a rough strain of Salmonella typhimurium which does not synthesize 0 antigens. Since standard methods of extraction applicable to smooth strains of Salmonella were not successful for this rough strain, two modified procedures were developed. The resulting products were similar to smooth EP in terms of their biochemical, physical and mitogenic properties. When the immunogenicity of the rough EP was characterized by a protection assay in mice challenged with virulent Salmonella, it was found that the rough EP preparations were protective; however, they were not as active as the EP from a smooth strain of S. typhimurium.

Inhibition of activated nonresponder C3H/HeJ lymphocytes by lipopolysaccharide endotoxin

The B lymphocytes and macrophages of lipopolysaccharide (LPS) nonresponder C3H/HeJ mice were found to respond to certain R types of LPS endotoxin in a fashion resembling that ordinarily seen with the cells from normal responder mice. DNA synthesis, polyclonal antibody synthesis, and interleukin-1 activity were stimulated by Bordetella pertussis LPS and Salmonella minnesota R595 LPS, although to a lesser extent than with responder cells. Mitogenesis stimulated by both LPSs was inhibited by polymyxin B; this finding provided evidence that any trace endotoxin-associated proteins were not responsible for the activity. Of particular interest was the finding that wild-type smooth LPS actually inhibited activation of the C3H/HeJ B cells not only by the LPS but also by mitogenic proteins, including purified protein derivative of tuberculin. The nonspecific nature of this inhibition and the fact that maximal inhibition occurred some 9 to 12 h into the culture period suggested that the proliferation of the B cells was affected by smooth-type LPS in a manner heretofore unrecognized. These findings permit a new approach to the study of how LPS endotoxin affects cells of the immune system.