R1 R4 Research Articles

Molecular Dynamics Simulation of Kv Channel Voltage Sensor Helix in a Lipid Membrane with Applied Electric Field

In this article, we present the results of the molecular dynamics simulations of amphiphilic helix peptides of 13 amino-acid residues, placed at the lipid-water interface of dipalmitoylphosphatidylcholine bilayers. The peptides are identical with, or are derivatives of, the N-terminal segment of the S4 helix of voltage-dependent K channel KvAP, containing four voltage-sensing arginine residues (R1–R4). Upon changing the direction of the externally applied electric field, the tilt angle of the wild-type peptide changes relative to the lipid-water interface, with the N-terminus heading up with an outward electric field. These movements were not observed using an octane membrane in place of the dipalmitoylphosphatidylcholine membrane, and were markedly suppressed by 1), substituting Phe located one residue before the first arginine (R1) with a hydrophilic residue (Ser, Thr); or 2), changing the periodicity rule of Rs from at-every-third to at-every-fourth position; or 3), replacing R1 with a lysine residue (K). These and other findings suggest that the voltage-dependent movement requires deep positioning of Rs when the resting (inward) electric field is present. Later, we performed simulations of the voltage sensor domain (S1–S4) of Kv1.2 channel. In simulations with a strong electric field (0.1 V/nm or above) and positional restraints on the S1 and S2 helices, S4 movement was observed consisting of displacement along the S4 helix axis and a screwlike axial rotation. Gating-charge-carrying Rs were observed to make serial interactions with E183 in S1 and E226 in S2, in the outer water crevice. A 30-ns-backward simulation started from the open-state model gave rise to a structure similar to the recent resting-state model, with S4 moving vertically ∼6.7 Å. The energy landscape around the movement of S4 appears very ragged due to salt bridges formed between gating-charge-carrying residues and negatively charged residues of S1, S2, and S3 helices. Overall, features of S3 and S4 movements are consistent with the recent helical-screw model. Both forward and backward simulations show the presence of at least two stable intermediate structures in which R2 and R3 form salt bridges with E183 or E226, respectively. These structures are the candidates for the states postulated in previous gating kinetic models, such as the Zagotta-Hoshi-Aldrich model, to account for more than one transition step per subunit for activation.

Modulation of Escherichia coli DNA Methyltransferase Activity by Biologically Derived GATC-flanking Sequences

Escherichia coli DNA adenine methyltransferase (EcoDam) methylates the N-6 position of the adenine in the sequence 5'-GATC-3' and plays vital roles in gene regulation, mismatch repair, and DNA replication. It remains unclear how the small number of critical GATC sites involved in the regulation of replication and gene expression are differentially methylated, whereas the approximately 20,000 GATCs important for mismatch repair and dispersed throughout the genome are extensively methylated. Our prior work, limited to the pap regulon, showed that methylation efficiency is controlled by sequences immediately flanking the GATC sites. We extend these studies to include GATC sites involved in diverse gene regulatory and DNA replication pathways as well as sites previously shown to undergo differential in vivo methylation but whose function remains to be assigned. EcoDam shows no change in affinity with variations in flanking sequences derived from these sources, but methylation kinetics varied 12-fold. A-tracts immediately adjacent to the GATC site contribute significantly to these differences in methylation kinetics. Interestingly, only when the poly(A) is located 5' of the GATC are the changes in methylation kinetics revealed. Preferential methylation is obscured when two GATC sites are positioned on the same DNA molecule, unless both sites are surrounded by large amounts of nonspecific DNA. Thus, facilitated diffusion and sequences immediately flanking target sites contribute to higher order specificity for EcoDam; we suggest that the diverse biological roles of the enzyme are in part regulated by these two factors, which may be important for other enzymes that sequence-specifically modify DNA.

Distribution of lipopolysaccharide core types among avian pathogenic Escherichia coli in relation to the major phylogenetic groups

Five distinct lipopolysaccharide (LPS) core types, namely R1–R4 and K12 have been identified in Escherichia coli. The aims of this study were to determine, primarily by means of PCR, the distribution of those oligosaccharide core types among avian pathogenic E. coli and their relationship to phylogenetic groups. To identify putative avian pathogenic E. coli, serum resistance and the presence of three virulence genes encoding temperature sensitive haemagglutinin ( tsh), increased serum survival ( iss) and colicin V ( cvaC) were determined. Of the 143 clinical isolates examined 62% possessed the R1 core, 22% were R3, 13% were R4 and 3% were R2. Fifty commensal isolates consisted of 58% with R1 core, 38% with R3 core, 4% with R4 core, and none with R2. None of the isolates were of K12 core type. The distribution of core oligosaccharide types in clinical and commensal isolates were not statistically significant ( P = 0.51). Three genes, tsh, iss and cvaC were found in E. coli of all four core types. The genes tsh ( P < 0.001) and iss ( P = 0.03412) were significantly associated with the R4 core oligosaccharide type. The isolates containing R4 core type LPS were mainly confined to phylogenetic group D. The widespread R1 core type showed less ability to possess virulence genes and 83% were in the phylogenetic group A. Results of this study indicated that E. coli with R1, R2, R3 and R4 were important in causing infections in chickens and further, the E. coli with R4 core type were less common among commensals, possessed more virulence genes and were related to phylogenetic groups pathogenic for poultry.

Linkage‐dependent contribution of repeat peptides to self‐aggregation of three‐ or four‐repeat microtubule‐binding domains in tau protein

Although one of the priorities in Alzheimer's research is to clarify the filament formation mechanism for the tau protein, it is still unclear how it is transformed from a normal structure in a neuron. To examine the linkage-dependent contribution of each repeat peptide (R1-R4) to filament formation of the three- or four-repeat microtubule-binding domain (MBD) in the tau protein, four two-repeat peptides (R12, R13, R23 and R34) and two three-repeat peptides (R123 and R234) were prepared, and their in vitro self-aggregation was investigated by thioflavin S fluorescence and circular dichroism measurements, and by electron microscopy in neutral buffer (pH 7.6). Comparison of these aggregation behaviors with previous results for single-repeat peptides and wild-type 3RMBD (R134) and 4RMBD (R1234) indicated that (a) the two-repeat R23, not the R2 or R3 single repeat, forms the core structure in self-aggregation of 4RMBD, whereas that of 3RMBD comprises the R3 single repeat, (b) co-existence of R1 and R4 repeats is necessary for the aggregation behavior inherent in 3RMBD and 4RMBD, whereas the R1 or R4 repeat alone functions as a repressor or modifier of the filament formation, (c) 4RMBD aggregation is accompanied by R1-driven transition from random and alpha-helix structures to a beta-sheet structure, whereas 3RMBD aggregation involves three-repeat R134-specific transition from a random structure to an alpha-helix structure without the participation of a beta-sheet structure, and (d) the peptides that include the R1 repeat form a long filament irrespective of the absence or presence of the R4 repeat, whereas those that include the R4 repeat, but not the R1 repeat, form a relatively short filament. To the best of our knowledge, a systematic study of the linkage-dependent contribution of each repeat peptide to the paired helical filament formation of tau MBD has not been carried out previously, and thus the present information is useful for understanding the essence of the filament formation of tau MBD.

Structural properties of the DNA-bound form of a novel tandem repeat DNA-binding domain, STPR

Fibroin-modulator-binding protein 1 (FMBP-1) is a predicted transcription factor of the silkworm fibroin gene. The DNA-binding domain of FMBP-1 consists of four almost perfect tandem repeats of 23 amino acids each (R1-R4), and is referred to as the score and three amino acid peptide repeat (STPR) domain. This characteristic domain is conserved in eukaryotes, but the DNA-binding mode is not known. In this study, the structural properties of the DNA-bound form of the STPR domain were characterized. The combined experiments indicated that the STPR domain bound to the DNA duplex with a 1:1 binding ratio. The specific DNA caused considerable changes in the thermal unfolding profile and the digestion pattern of the STPR domain. These data suggested that the domain adapts a quite rigid helix-rich structure in the DNA-bound state, even though it moves flexibly in the absence of DNA. Furthermore, mutual induced-fit conformational change was also observed in DNA. Finally, we determined the DNA-binding surface of the STPR third repeat (R3) by alanine scanning mutagenesis; a particular site, composed of hydrophobic and hydrophilic residues, was identified. Notably, the substitution of Arg-9 in R3 with alanine residue, which is located in the middle of the surface, drastically abolished the alpha-helix-inducing and DNA-binding abilities. From these results, we predicted the DNA-binding mode of the STPR domain.

Novel and Mild Route to Phthalocyanines and 3‐Iminoisoindolin‐1‐ones via N,N‐Diethylhydroxylamine‐Promoted Conversion of Phthalonitriles and a Dramatic Solvent‐Dependence of the Reaction

AbstractRefluxing a mixture of phthalonitrile C6R1R2R3R4(CN)2 1 (R1–R4=H), or its substituted derivatives 2 (R1, R3, R4=H, R2=Me), or 3 (R1, R4=H, R2, R3=Cl) (1 equiv.) and N,N‐diethylhydroxylamine, Et2NOH, (4 equivs.) in methanol for 4 h results (Route A) in precipitation of the symmetrical (6 and 8) and an isomeric mixture of unsymmetrical (7) phthalocyanines, isolated in good (55–65 %) yields. The reaction of phthalonitriles 1, 2, or 4 (R1, R3, R4=H, R2=NO2) (4 equivs.) with Et2NOH (8 equivs.) in the presence of a metal salt MCl2 (M=Zn, Cd, Co, Ni) (1 equiv.) in n‐BuOH or without solvent results in the formation of metallated phthalocyanine species (9–17). Upon refluxing in freshly distilled dry chloroform, phthalonitrile 1 or its substituted analogues 2, 3 or 5 (R1–R4=F) (1 equiv.) react with N,N‐diethylhydroxylamine (2 equivs.) affording 3‐iminoisoindolin‐1‐ones 18–21 (Route B) isolated in good yields (55–80 %). All the prepared compounds were characterized with C, H, and N elemental analyses, ESI‐MS, IR, and compounds 18–21 also by 1D (1H, 13C{1H}), and 2D (1H,15N‐HMBC and 1H,13C‐HMQC, 1H,13C‐HMBC) NMR spectroscopy.

Pilot-scale experiment on anaerobic bioreactor landfills in China

Developing countries have begun to investigate bioreactor landfills for municipal solid waste management. This paper describes the impacts of leachate recirculation and recirculation loadings on waste stabilization, landfill gas (LFG) generation and leachate characteristics. Four simulated anaerobic columns, R1–R4, were each filled with about 30 tons of waste and recirculated weekly with 1.6, 0.8 and 0.2 m 3 leachate and 0.1 m 3 tap water. The results indicated that the chemical oxygen demand (COD) half-time of leachate from R1 was about 180 days, which was 8–14 weeks shorter than that of R2–R4. A large amount of LFG was first produced in R1, and its generation rate was positively correlated to the COD or volatile fatty acid concentrations of influent leachates after the 30th week. By the 50th week of recirculation, the waste in R1 was more stabilized, with 931.2 kg COD or 175.6 kg total organic carbon released and with the highest landfill gas production. However, this contributed mainly to washout by leachate, which also resulted in the reduction of LFG generation potential and accumulation of ammonia and/or phosphorus in the early stage. Therefore, the regimes of leachate recirculation should be adjusted to the phases of waste stabilization to enhance efficiency of energy recovery. Integrated with the strategy of in situ leachate management, extra pre-treatment or post-treatment methods to remove the nutrients are recommended.

Fluorescence-coupled CD conformational monitoring of filament formation of tau microtubule-binding repeat domain

To clarify the contribution of the three- or four-repeated peptide moiety in tau microtubule-binding domain (MBD) to paired helical filament (PHF) formation, conformational transition accompanied by heparin-induced filament formation was investigated stepwise for four repeat peptides (R1–R4), one three-repeated R1–R3–R4 peptide (3RMBD), and one four-repeated R1–R2–R3–R4 peptide (4RMBD) using a combination of thioflavin S fluorescence and circular dichroism (CD) measurements in a neutral buffer (pH 7.6). The comparison of the fluorescence profile of each repeat peptide with those of 3RMBD and 4RMBD showed the synergistic contribution of R1–R4 to PHF formation of MBD. The CD spectrum measured as a function of filament formation time indicates that: (i) two conformational transitions occur for the filament formations of R3 (from the random structure to the β-sheet structure) and 3RMBD (from the random structure to the α-helix structure), (ii) the filament formations of R2 and 4RMBD proceed via the synchronized conformational transitions of the α-helix and random structures, and (iii) the filament formation of 4RMBD is dependent on the aggregation behavior of R2. These data are useful for elucidating the MBD conformational transition in tau PHF formation.

Effect of resin hydrophilicity and temperature on water sorption of dental adhesive resins

This study examined the effects of copolymer hydrophilicity and temperature on water sorption and solubility characteristics of five copolymer blends of increasing degree of hydrophilicity using gravimetric measurements. Six resin disks (15 mm in diameter×1 mm in thickness) were prepared from each copolymer blend and were stored in deionised water at 23, 37 and 55 °C. Water sorption and solubility of the resin disks were measured before and after water immersion and desiccation. Multiple regression analysis of water sorption was performed on two independent variables, copolymer hydrophilicity and temperature. Maximum water sorption increased significantly with Hoy's total cohesive energy density ( δ t ), Hoy's solubility parameter for polar forces ( δ p ) and hydrogen bonding ( δ h ), but was not influenced by temperature. However, a significant positive relationship was observed between diffusion coefficients (obtained using Fick's law of diffusion) and temperature. The water absorption activation energy was 10 kJ/mol for the most hydrophilic copolymer blend R5 and 35–51 kJ/mol for copolymer blends R1–R4. The positive relationship between maximum water uptake and copolymer hydrophilicity suggests that water molecules diffuse through the polymer matrices by binding successively to the polar sites via hydrogen bonding. Such water sorption may determine the durability of resin–dentine bonds.

Biofilm reactor technology for low temperature anaerobic waste treatment: microbiology and process characteristics

The microbial composition, methanogenic activity and architecture of particulate and fixed biofilms within four anaerobic hybrid reactors, R1–R4, operating at psychrophilic temperatures were investigated. The reactors treated low-strength (1 g COD l−1; R1) and high-strength (10 g COD l−1; R2–R4) wastewaters from the food-processing sector (R1, R2 – whey; R3 – sucrose; R4 – volatile fatty acids). Successful start-up and long-term psychrophilic operation was observed for all four reactors, with COD removal efficiencies of 80–99% achieved at 12–20 °C at organic loading rates of 1.3–20 kg COD m−3 d−1. The formation and maintenance of a well-settling granular sludge bed and an attached biofilm were shown to occur under psychrophilic conditions, an important consideration for the successful implementation of low temperature biofilm reactor technology. Culture-independent molecular techniques (terminal restriction fragment length polymorphism, clone library analysis and 16S rRNA gene sequencing) revealed that microbial population structure could be a key factor in reactor performance, with changes in the community structure of the three high-strength reactors preceding granular instability and a subsequent decline in COD removal efficiency. Biomonitoring of microbial population structure and dynamics within anaerobic reactors may, therefore, allow for the early recognition of potential operational problems.

Possible Role of Each Repeat Structure of the Microtubule-Binding Domain of the Tau Protein in In Vitro Aggregation

Although one of the priorities in Alzheimer's research is to clarify the filament formation mechanism of the tau protein, it is currently unclear how it is transformed from a normal structure in a neuron. To examine which part and what structural change in the tau protein are involved in its transformation into a pathological entity, the initial in vitro self-aggregation features of each repeat peptide (R1-R4) constituting a three- or four-repeat microtubule-binding domain (3RMBD or 4RMBD) in the tau protein was investigated by measuring both the fluorescence and light scattering (LS) spectra on the same instrument, because these MBD domains constitute the core moiety of the tau paired helical filament (PHF) structure. The conformational features of the R1 and R4 peptides in trifluoroethanol were also investigated by (1)H-NMR and molecular modeling analyses and compared with those of the R2 and R3 peptides. The analyses of the LS spectra clarified (i) the self-aggregation rates of R1-R4, 3RMBD and 4RMBD at a fixed concentration (15 mM), (ii) their minimum concentrations for starting filament extension, and (iii) the concentration dependence of their self-aggregations. The fluorescence analyses showed that the R2 and R3 peptides have high self-aggregation abilities at the extension and nucleation steps, respectively, in their filament formation processes. It was shown that the R2 repeat exhibits a positive synergistic effect on the aggregation of 4RMBD. The R1 and R4 repeats, despite their weak self-aggregation abilities, are necessary for the intact PHF formation of tau MBD, whereas they exerted a negative effect on the R3-driven aggregation of 3RMBD. The conformational analyses showed the importance of the amphipathic conformational features of the R1 to R4 peptides, and the intermolecular disulfide bonding abilities of the R2 and R3 peptides for the PHF formation. On the basis of the present spectral and conformational results, the possible role of each repeat structure in the dimeric formation of MBD at the initial in vitro aggregation stage is discussed.

Death receptors, Fas and TRAIL receptors, are involved in human osteoclast apoptosis

Survival and apoptosis are crucial aspects of the osteoclast life cycle. Although osteoclast survival has been extensively studied, little is known about the mechanisms involved in human osteoclast apoptosis. In the present study, cord blood monocytes (CBMs) were used as the source of human osteoclast precursors. When cultured in the presence of M-CSF and RANKL, CBMs formed multinucleated cells that expressed RANK and calcitonin receptor, and were able to resorb bone. These cells expressed TRAIL receptors (R1–R4). Surprisingly, although TRAIL-receptor expression was not detectable in osteoclasts from normal bone, osteoclasts from myeloma specimens did express TRAIL receptors to a variable extent. Significantly, we have shown for the first time that this pathway is indeed functional in human osteoclasts, and that apoptosis occurred and was significantly greater in the presence of TRAIL. In addition, we have shown that a Fas-activating antibody is also able to induce osteoclast apoptosis, as did TGFβ, whereas the survival factor M-CSF decreased apoptosis. Overall, these findings suggest that death receptors, TRAIL receptors and Fas, could be involved in osteoclast apoptosis in humans.

Crystal Structure of CD14 and Its Implications for Lipopolysaccharide Signaling

Lipopolysaccharide, the endotoxin of Gram-negative bacteria, induces extensive immune responses that can lead to fatal septic shock syndrome. The core receptors recognizing lipopolysaccharide are CD14, TLR4, and MD-2. CD14 binds to lipopolysaccharide and presents it to the TLR4/MD-2 complex, which initiates intracellular signaling. In addition to lipopolysaccharide, CD14 is capable of recognizing a few other microbial and cellular products. Here, we present the first crystal structure of CD14 to 2.5 angstroms resolution. A large hydrophobic pocket was found on the NH2-terminal side of the horseshoe-like structure. Previously identified regions involved in lipopolysaccharide binding map to the rim and bottom of the pocket indicating that the pocket is the main component of the lipopolysaccharide-binding site. Mutations that interfere with lipopolysaccharide signaling but not with lipopolysaccharide binding are also clustered in a separate area near the pocket. Ligand diversity of CD14 could be explained by the generous size of the pocket, the considerable flexibility of the rim of the pocket, and the multiplicity of grooves available for ligand binding.

Effect of settling time on aerobic granulation in sequencing batch reactor

The essential role of hydraulic settling time in the formation of aerobic granules was studied in four column sequencing batch reactors (R1–R4). Results showed that aerobic granules were successfully cultivated and became dominant only in the R4 operated at the shortest settling time of 5 min, while a mixture of aerobic granules and suspended sludge was observed in R1–R3 run at settling times of 20, 15 and 10 min, respectively. After the steady state was achieved, the respective settling times of R1–R3 was shortened from 20 to 5 min, from 15 to 2 min and from 10 to 1 min; as the result, aerobic granules completely displaced suspended sludge in these three reactors after two-week operation. It was found that cell surface hydrophobicity was improved significantly at short settling times. Analyses of the polyvalent metals contents in aerobic granules showed that the accumulation of calcium in aerobic granules was related to the settling time, however, the total content of iron, magnesium and aluminium in aerobic granules was much pretty lower than the granule calcium content and almost remained constant. It is obvious that a short settling time favours aerobic granulation, and one may expect to manipulate the formation and characteristics of aerobic granules by controlling settling time.

The spatial window of the perceptual template and endogenous attention

One primary function of spatial attention is to exclude external noise [e.g., Psychol. Sci. 11(2) (2000) 139], especially in the region of the target stimulus [J. Vis. 2(4) (2000) 312]. What is not known is the spatial profile of external noise exclusion in the vicinity of the target and how this depends upon attention. The spatial region around an oriented Gabor target was segmented into four concentric rings (R1–R4). Psychometric functions were measured for orientation discrimination with external random Gaussian noise in all combinations of rings (e.g., R1 alone; R1+R2; etc.). Regions with larger impact on performance are weighted more heavily in the perceptual template. In an orientation discrimination task in periphery the effective noise regions aligned closely with the high contrast regions of the target Gabor, with attention reducing the effective noise across the spatial template. The combined effects of external noise regions were well-modeled by a (non-linear) perceptual template model (PTM) [Vis. Res. 38(9) (1998) 1183]. In another experiment in attended fovea, the results were similar to those in periphery, but exhibited additional ability to selectively weight clear spatial regions.

Plurisegmental vestibulocerebellar projections and other hindbrain cerebellar afferents in midterm chick embryos: biotinylated dextranamine experiments in vitro

The vestibular neuronal groups that project to the cerebellum were mapped in midterm chick embryos (10–11 days in “ovo”) through “ in vitro ” retrograde tracing experiments. Massive unilateral deposits of biotin-dextranamine were placed at the basis of the cerebellum to label the cerebellar peduncles. Separate rostral and caudal vestibulo-cerebellar groups were identified, with predominance of contralateral neurons. We tentatively identified the rhombomeric location of both groups, as well as their topography within the conventional cytoarchitectonically-defined vestibular nuclei, by comparison with previously established segmental fate maps. The rostral group extended from rhombomeres 1–4 (r1–r4) and was restricted mainly to the superior vestibular nucleus. The caudal group stretched from r6 to pseudorhombomere “r8” and was related to the descending and medial vestibular nuclei. The less abundant ipsilateral vestibulocerebellar neurons had a similar topography. The crossing axons of the rostral vestibulocerebellar neurons formed a distinct rostral vestibulocerebellar decussation, restricted to the floorplate of rhombomere 2. The axons of the caudal vestibulocerebellar population mostly decussated associated to the deep cochlear commissure. The present results extend the “segmental hodological mosaic” of defined projection-neuron groups identified within the avian vestibular nuclear complex: The vestibulocerebellar projecting neurons as a type appear iterated from r1 to r4 and from r6 to pseudorhombomere “r8,” albeit showing in their arrangement peculiarities related to single segmental domains, particularly rostrally. In contrast, the vestibulospinal groups are located more restrictedly in r4–r6, while the vestibulo-ocular projecting neurons extend from r1 to “r7.” Only r4 and r6 contain elements of all three hodological types. The organization of the three vestibular projection populations studied to date seems comparable in chicken and frogs and may be a conserved feature in vertebrates.

Fibroblast growth factor receptor‐3 null mice exhibit a delay in the development of oligodendrocytes and myelination

Fibroblast growth factors (FGFs) comprise of a family of twenty‐three members which bind to four receptor tyrosine kinases (R1–R4). They induce a broad spectrum of biological effects in a variety of cell types, including neurons and glia in the CNS. In oligodendrocytes (OLs), FGF‐2 elicits a number of specific responses depending on their stage of development. During OL development in vitro, the expressions of FGF‐receptor mRNAs are differentially regulated. R1 mRNA increases gradually along with OL maturation, whereas R3 and R2 mRNAs peak at the OL progenitor and mature OL stages, respectively, suggesting a differential roles of these receptors in OL development. R3 is also expressed by astrocytes. To determine the roles of R3 during OL development and myelination in vivo, we have employed mice lacking functional R3 (R3‐null). During myelination (P7, P9, P13), reduced numbers of differentiated OLs and myelinated fibers are observed in the brains of R3 null mice compared to wild type mice. Moreover, up‐regulation of glial fibrillary acidic protein‐positive astrocytes is found in the cerebellum and spinal cord of R3 null mutants. However, the number of OL progenitors (PDGF‐Ra), BrdU incorporation, and cell survival (TUNEL assay) are all comparable, and R3‐null myelin in adult mice appears to be similar to that of wild type mice. In mixed primary cultures of post‐natal R3 null brain (that have few if any neurons), OLs exhibit a delay in differentiation similar to that observed in vivo. In summary, our results elucidate regulatory roles of FGF‐R3 in mouse brain, in particular with regard to its roles in the timing of OL maturation and myelin formation (MS Society, Canada, NIH NS38878‐03).

How much does it hurt? Pediatric pain measurement for doctors, nurses, and parents.

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it, but when you can not measure it, when you cannot express it in numbers, your knowledge is of a meager and unsat isfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the state of science whatever the matter may be. Lord Kelvin quoted by Lewis Thomas I In order to manage pain in any patient, it is essen tial to be able to measure the outcomes of treatment. Without measurement, it is impossible to research new drugs or treatment techniques, just as it is impos sible to treat individual patients without knowing whether the treatment is working. Health centre accreditation now requires that processes for assessing and documenting pain be in place, 2 and patients and their families are being educated about the need for proper pain assessment and management. The Canadian Pain Society has issued a position paper which states, in part, that "routine assessment is essen tial for effective management" and that "health pro fessionals have a responsibility to assess pain routinely, to believe patients' pain reports, to document them, and to intervene in order to prevent pain" .3 The International Society for the Study of Pain has defined pain as ...an unpleasant sensory and emo tional experience associated with actual or potential tis sue damage, or described in terms of such damage...", and goes on to say that "pain is always subjective". 4 The gold standard for pain measurement is selfireport; the patient's own description of his or her own sensa tions and the personal interpretation of those feelings. With children, it can be a complex task to acquire that data, and developmental level, behaviour, and family influences must be taken into consideration. Why are children special? It has been recognized for almost two decades that children are frequently under medicated for postoper ative and disease pain.5 Although this pattern resulted in part from an unsubstantiated fear of potent anal gesics, it was, to a large extent, a result of the failure to recognize the degree, or even the presence, of pain in children. Children often can't or won't express their feelings and degree of pain if anything, they may underrate their own pain because of fear of the conse quences. However, we have a professional obligation and a social responsibility to protect children. Looked at objectively, one cannot imagine a situation in which one would say "it would be a good idea to cause that child some pain", yet health professionals often ratio nalize the "benefits" either of the pain ("he might as well get used to it"), or of the intervention that is causing the pain. It has never been demonstrated that pain has a beneficial effect, and the evidence for harm from pain itself is mounting. Even brief episodes of pain in the newborn period may have profound long term consequences. Taddio showed that un anes thetized circumcision of newborns resulted in increased crying and behavioural response to the pain of the immunization needle four to six months later. G Anand's landmark work demonstrated the increases in morbidity and mortality that result from inadequate opioid use during and after major surgery in infants. 7,8 Thus, it becomes extremely important to ensure that we recognize and treat pain in infants and children to the greatest extent possible, and to do that, we have to measure it. A recent edited text has brought together work by many of the experts in the field. 9 Measurement techniques What pa Hen ts say... Selfireport is the "gold standard" for pain measure ment. The concept that only the patient can really understand what he/she is feeling is embodied in the From the Department of Anesthesia, Dalhousie University, IWK Health Centre, Halifax, Nova Scotia, Canada. Address correspondence to: Dr. Allen Finley, Pediatric Anesthesia, IWK Health Centre, 5850 University Avenue, Halifax, Nova Scotia, Canada B3J 3G9. Phone: 902 428 2708; Fax: 902 428 2709; E mail: allen.itnley@dal.ca CAN J ANESTH 2001 / 48:6 / pp R1 R4

Chiral Methyl‐Branched Surfactants and Phospholipids: Synthesis and Properties

The number of methyl groups on the acyl groups of phosphatidylcholines 1 (R1–R4 = H, CH3) determines their surfactant characteristics. Differential calorimetric investigations show that little or even no branching leads to ordered gel phases. The behavior of the compounds at the water–air interface is also determined by these structural factors.

Performance of Anaerobic Reactors during Pseudo-Steady-State Operation

Four anaerobic reactors were studied for the purposes of this work: two anaerobic fluidized bed reactors (AFBR) using diatomaceous earth and granular activated carbon as immobilization media (R1 and R2, respectively), a packed-bed reactor (R3), and a suspended growth reactor (R4). A nutrient-supplemented wastestream with glucose as the main carbon source was treated. Successful reactor start-up was achieved for all four anaerobic reactors. These reactors were able to handle organic loading rates of more than 12000, 7500, 6000 and 650 mg dm−3 day−1 for R1–R4, respectively. Anaerobic fluidized bed reactors were less affected by interruptions and adverse operating conditions than were packed-bed and suspended growth reactors. Immobilized cell reactors and, specifically, AFBRs were clearly superior to conventional high-rate digesters. This enhanced performance is primarily due to the very high cell retention ability of such reactors. High total organic carbon (TOC) removal efficiencies were achievable under pseudo-steady state operation. Removal efficiencies above 98% were observed for all reactors. Specific biogas production rates of 1·5–1·7, 1·4–1·7, 1·1–1·5 and 0·9–1·3 dm3 of methane per gram of TOC removed for R1–R4, respectively, were attained. A consistent biogas methane content of 52·5–55·9% was observed. Biomass concentrations of 84, 91, 21 and 1·9 g VS dm−3 were measured for R1–R4, respectively. Extremely high biomass concentrations in AFBRs were possible due to the high available specific surface area. © 1997 SCI.