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The formation of three isostructural co-crystals that utilize iodoperchlorobenzene as a dual halogen-bond donor is reported. These molecular solids are held together by the combination of I⋯N and Cl⋯N halogen bonds to form one-dimensional polymeric chains. Curiously, these co-crystals are isostructural to a series of related solids based upon the isosteric halogen-bond donor 1,4-diiodoperchlorobenzene. It is noteworthy that the co-crystal containing trans-1,2-bis(4-pyridyl)ethylene undergoes a near quantitative [2 + 2] cycloaddition reaction.

The Wolkenstein&rsquo, s theory of catalysis and the d-band theory of formation chemical bonds between transition metal catalysts and adsorbates were used to develop the approach applied to the kinetics of CO oxidation by gold nanoparticles. In the model, within the framework of the mechanism of the reaction going through dissociative adsorption of oxygen molecules and reaction with gas-phase CO molecules, weak and strong chemisorption states of intermediates (O, CO2) were taken into account in the kinetic equations by introducing reversible electronic steps corresponding to electron transfers between the intermediates and the catalyst. As a result, we obtain the expression for the reaction rate, which exhibits a volcano-shape dependence upon the size of the gold nanoparticles at the conditions when the intermediates fractions are not small compared to the empty active sites of the catalyst. It is supposed that the approach can be also applied to the Langmuir-Hinshelwood mechanism.

C–H···N hydrogen bonds support an intermolecular [2 + 2] photodimerization in the solid state. The photocycloaddition occurs in a co-crystal of composition (tbrb)·(4,4′-bpe) (where tbrb = 1,2,4,5-tetrabromobenzene; 4,4′-bpe = trans-1,2-bis(4-pyridyl)ethylene) that consists of one-dimensional (1D) chains that self-assemble to form corrugated sheets. Stacking of 4,4′-bpe between sheets conforms to the topochemical postulate of Schmidt. The alkene reacts to form rctt-tetrakis(4-pyridyl)cyclobutane (4,4′-tpcb) stereoselectively and in quantitative yield. C–H···N hydrogen bonds also support the assembly of the components in (tbrb)·(4,4′-azo) (where: 4,4′-azo = 4,4′-azopyridine) into planar sheets. Density-functional theory calculations reveal identical face-to-face stacks of tbrb to aide in the stabilization of the structures of the co-crystals.

The Ising model, describing mathematically phase transitions between disordered and ordered states in ferromagnets and binary alloys, has been applied to the freezing process of water confined inside the carbon nanotube. To take into account the rearrangement of water molecules inside the carbon nanotube to retain their hydrogen bonds in competition with van der Waals interactions with carbon atoms of the nanotube, an additional term has been introduced into the formula for the ordering parameter in water. Inclusion of this hydrophobic effect which depends exponentially upon the diameter of the tube within the Ising model yields an expression for the dependence of freezing temperature of water inside the CNT upon its diameter. According to the model, the smaller the diameter of the tube, the higher freezing temperature of water molecules. These theoretical results are in a good agreement with the experimental data.

Amino alcohols are important ligands for the asymmetric catalytic hydroamination of aminoallenes to form chiral pyrrolidines. Herein, we report the crystal structures of two chiral amino alcohols, D-N-(2-Adamantyl)phenylglycinol and L-N-(2-Adamantyl)diphenylphenylalinol, that function as ligands within transition metal complexes that catalyze the hydroamination of aminoallenes. Both molecules crystallize in the noncentrosymmetric orthorhombic space group P212121. Inter- and intramolecular hydrogen bonding plays an important role in stabilizing each alcohol in the solid state in the absence of a transition metal. The presence of these hydrogen bonds has been verified by single crystal X-ray diffraction and their overall strength determined by computational methods.

Due to its proximity of Hg(II) atoms, electron-withdrawing properties and inherent accessibility to electrophilic sites on the molecular surface, trimeric perfluoro-ortho-phenylenemercury, (o-C6F4Hg)3, has demonstrated a capacity to form supramolecular adducts with a variety of neutral and anionic substrates. Often within these complexes the Lewis acid, (o-C6F4Hg)3, interacts with a Lewis base rather than itself in the solid state via various supramolecular interactions. Among these, perfluorophenyl–perfluorophenyl interactions have been utilized in the construction of various supramolecular materials; however, within these molecular complexes, this category of non-covalent interaction is not often observed. Even though these perfluorophenyl–perfluorophenyl interactions have been used to produce new materials, their overall strength has not been generally reported in the literature. In this contribution, we highlight not only the synthesis, structural and spectroscopic properties of a novel binary supramolecular adduct between (o-C6F4Hg)3 and 4-chlorobenzaldehyde (4-ClBA) [(o-C6F4Hg)3(4-ClBA)] 1, but also report on the overall strength of the perfluorophenyl–perfluorophenyl interaction energies determined by means of computational chemistry. The carbonyl group of the 4-ClBA substrate was found to interact with all three mercury atoms within (o-C6F4Hg)3 via Hg⋯O contacts. An infrared spectroscopic analysis of 1 demonstrated a lower wavenumber for the carbonyl stretching frequency when compared to that for the free substrate confirming the presence of these Hg⋯O interactions.

Background: Polychlorinated biphenyls (PCBs) manufactured in Anniston, Alabama, from 1929 to 1971 caused significant environmental contamination. The Anniston population remains one of the most highly exposed in the world. Objectives: Reports of increased diabetes in PCB-exposed populations led us to examine possible associations in Anniston residents. Methods: Volunteers (n = 774) from a cross-sectional study of randomly selected households and adults who completed the Anniston Community Health Survey also underwent measurements of height, weight, fasting glucose, lipid, and PCB congener levels and verification of medications. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationships between PCBs and diabetes, adjusting for diabetes risk factors. Participants with prediabetes were excluded from the logistic regression analyses. Results: Participants were 47% African American, 70% female, with a mean age of 54.8 years. The prevalence of diabetes was 27% in the study population, corresponding to an estimated prevalence of 16% for Anniston overall; the PCB body burden of 35 major congeners ranged from 0.11 to 170.42 ppb, wet weight. The adjusted OR comparing the prevalence of diabetes in the fifth versus first quintile of serum PCB was 2.78 (95% CI: 1.00, 7.73), with similar associations estimated for second through fourth quintiles. In participants < 55 years of age, the adjusted OR for diabetes for the highest versus lowest quintile was 4.78 (95% CI: 1.11, 20.6), whereas in those ≥ 55 years of age, we observed no significant associations with PCBs. Elevated diabetes prevalence was observed with a 1 SD increase in log PCB levels in women (OR = 1.52; 95% CI: 1.01, 2.28); a decreased prevalence was observed in men (OR = 0.68; 95% CI: 0.33, 1.41). Conclusions: We observed significant associations between elevated PCB levels and diabetes mostly due to associations in women and in individuals < 55 years of age.

Human salivary secretions are supersaturated with respect to basic calcium phosphates but spontaneous precipitation of these salts from saliva, or surface-induced precipitation of calcium phosphates onto dental enamel, does not normally occur. This unexpected stability has been attributed to the inhibitory activities of two kinds of salivary phosphoproteins: statherin and the acidic, proline-rich phosphoproteins (PRP). Investigation of the structure-function relationships of statherin, the most potent inhibitor of primary (spontaneous) and secondary (seeded) precipitation of calcium phosphate salts in human saliva has been limited to studies of peptide segments obtained from the native peptide by specific proteolysis. Solid phase peptide synthesis (SPPS) is a useful and potentially more flexible alternative. Phosphoserine residues (positions 2 & 3) play critically important roles in the precipitation-inhibition activities of statherin, but SPP synthesis of these phosphorylated peptides is precluded because of the instability of phosphoserine residues in the presence of HF. Thus, this peptide was synthesized by solution-phase methods. The dipeptide possessed substantial inhibitory activity in assays for inhibition of both primary and secondary precipitation of calcium phosphate salts, but was not as active as either N-terminal tryptic hexapeptide of statherin or intact statherin. Syntheses of other model phosphorylated peptides are underway to expand the structure-function relationships.

The cocrystal containing 1,2,4,5-tetracyanobenzene (TCNB) and trans-1,2-bis(4-pyridyl)ethylene (4,4′-BPE) has been realised (TCNB)·(4,4′-BPE) 1. Compound 1 produces a two-dimensional sheet based on two different types of C–H···N hydrogen bonds. Each molecule within the cocrystal functions as both a donor and an acceptor of hydrogen bonds. Weak hydrogen bonds such as these, acting as the driving force to produce a polymeric assembly, are not investigated as frequently as stronger and more traditional O–H···O and O–H···N hydrogen bonds within multicomponent cocrystals. The existence of the different types of C–H···N hydrogen bonds was confirmed by single-crystal X-ray diffraction as well as infrared spectroscopy. The overall interaction energies for both types of hydrogen bonds were determined by computational calculations at various levels of theory.

We introduced vapor corrosion inhibitor (VCI) into a disk drive to improve the resistance of the components to corrosion in repeated condensation cycles. VCI also significantly reduced the defect smears in the disks during accelerated life test. VCI is well known to cover up exposed metal surfaces. Thus the first means by which a VCI prevents corrosion is by forming a hydrophobic adsorbed film over exposed metal (e.g. Co, Cu) alloy. VCI also blocks the pathway for metal dissolution into the electrolyte.

Two stereocontrolled synthetic approaches towards 5-(S)-amino-1,2,4,5,6,7-hexahydro-azepino [3,2,1-hi] indole-4-one-2- (S)-carboxylic acid 1, based on intramolecular Friedel-Crafts acylations, are reported. This conformationally restricted tricyclic dipeptidomimetic has been applied to the design of a potent and orally active inhibitor of angiotensin-converting enzyme (ACE).

The primary objective of this research was to develop relationships which predict tool wear from measured cutting forces. Different cutting speeds and feed rates were examined. The workpiece materials used were a medium-carbon steel and a titanium alloy. A synthetic cutting fluid was used with a 9.525 mm drill and a 6.350 mm drill, for drilling the medium-carbon steel and the titanium alloy, respectively. Preliminary testing was conducted to find the optimal values for cutting speeds and feed rates. The main drilling tests were performed using the cutting conditions resulting from the preliminary tests. Statistical analysis of the results of the main drilling tests showed that the axial force was significant at the 5 per cent level in models for both materials. It also showed that the moment about the vertical axis was significant at the 5 percent and the 15 per cent levels in the models for the titanium alloy and the medium-carbon steel, respectively. The model for the smaller holes drilled into the more homogeneous material, the titanium alloy, was more accurate in predicting tool wear.

Background: Self-perceived lactose intolerance may result in adverse dietary modifications; thus, more studies are needed to understand the prevalence of self-perceived lactose intolerance and how it relates to calcium intake and selected health conditions. Objective: The objective was to examine the effects of selfperceived lactose intolerance as it relates to calcium intake and specific health problems that have been attributed to reduced intakes of calcium and dairy foods in a nationally representative multiethnic sample of adults. Design: This was a cross-sectional study in a national sample of 3452 adults. The relation between self-perceived lactose intolerance, calcium intakes, and physician-diagnosed health conditions was analyzed by using linear regression analyses. Results: Of the total sample, 12.3% of respondents perceived themselves to be lactose intolerant. The age-adjusted prevalence of selfperceived lactose intolerance was 7.8% for non-Hispanic whites, 20.1% for non-Hispanic blacks, and 8.8% for Hispanics. Respondents with self-perceived lactose intolerance had significantly lower (P , 0.05) average daily calcium intakes from dairy foods than did those without self-perceived lactose intolerance. A significantly higher (P , 0.05) percentage of respondents with self-perceived lactose intolerance than of respondents without self-perceived lactose intolerance reported having physician-diagnosed diabetes and hypertension. The odds of self-reported physician-diagnosed diabetes or hypertension decreased by factors of 0.70 and 0.60, respectively, for a 1000-mg increase in calcium intake from dairy foods per day. Conclusion: Self-perceived lactose-intolerant respondents had a significantly lower calcium intake from dairy foods and reported having a significantly higher rate of physician-diagnosed diabetes and hypertension. Am J Clin Nutr doi: 10.3945/ajcn.110.009860.

The pupose of this project was to develop a model for predicting surface finish of drilled holes for different feed rates, cutting speeds, fluid concentrations, and drill diameters. A regression equation was developed for a linear model using data collected from a 25experimental design. Aluminium 390 was used as the workpiece material. Feed rate, fluid concentration, and the interaction between feed rate and drill diameter were significant at the 5% level. Cutting speed and drill diameter were not significant within the ranges tested.

The primary objective of this research was to compare the surface finish resulting when using a semi-synthetic cutting fluid to that of a premium soluble oil. The secondary objective was to determine the effects of drill diameter, cutting speed, and fluid concentration on surface finish. The surface measurements were made on the walls of 6.350 and 9.525 mm lind holes drilled 25.4 mm into aluminium 390. Each cutting fluid was introduced using a flood application. Additional factors in the experimental design for each cutting fluid included two levels of cutting speed and two levels of fluid concentration. Variations in drill diameter, cutting speed, and the interaction between these factors were significant with respect to surface finish for both the semi-synthetic fluid and the soluble oil. Fluid concentration for the semi-synthetic fluid also had a significant effect on the surface finish. The surface finish produced while using the semi-synthetic fluid was approximately the same as that with the soluble oil.

The fluorescence and phosphorescence of proteins and polypeptides is the sum of the contributions from the three aromatic amino acids tryptophan, tyrosine, and phenylalanine. The work on protein and polypeptide luminescence prior to 1971 has been reviewed in detail by Longworth. Another fine account of the early work, emphasizing tryptophan and tyrosine, is the monograph by Konev. An excellent review on tyrosine fluorescence in proteins and model peptides, for the period up to 1975, is given by Cowgill. In 1984, Creed reviewed the photophysics and photochemistry of tyrosine and its simple derivatives, including a thorough coverage of steady-state fluorescence and a brief discussion of triplet-state properties, but did not include any work on proteins or polypeptides. The first quantitative studies of the excited-state properties of the three aromatic amino acids were carried out in the 1950s. The low-temperature phosphorescence of the aromatic amino acids was initially observed by Debye and Edwards in 1952, and phosphorescence emission spectra were reported by Steele and Szent-Gyorgyi in 1957. In 1953, Weber postulated that the fluorescence of the aromatic amino acids should occur in the near-ultraviolet region of the electromagnetic spectrum. In 1956, independently and almost simultaneously, Duggan and Udenfriend and Shore and Pardee reported the results of their investigations of protein fluorescence. At the same time

Current logic has it that the problem of climate change is caused by the emission of several so-called greenhouse gases, or GHGs for short, of which carbon dioxide (CO2) is the most important. CO2 emissions result from different human activities, but the burning of fossil fuels is by far its major source. The emissions, together with the emissions of other GHGs, are supposed to cause increasing concentrations of GHGs in the atmosphere, which might result in climate change and a rise in the earth’s mean temperature. Concern about this scenario has led to different policy proposals to curb those GHG emissions, especially CO2 emissions. One example of clear commitment is the policy goal set by the European Union to emit the same amount of carbon dioxide in the year 2000 as in 1990. To reach this goal, the Commission has proposed a package of instruments which includes a hybrid energy/carbon tax or excise.

The experimental data and theoretical calculations presented herein support the mechanism for C n + C 1 and C n + C 2 chain growth in oxygenate synthesis in which the efficient and dominant aldol addition with oxygen retention reversal is caused by bonding of alkoxide oxygen of the intermediate 1,3-keto-alkoxide to the alkali ion while the carbonyl group is released for hydrogenation by a cis-trans isomerization thereof. This isomerization is sterically suppressed by alkyl substituents on the carbonyl carbon, viz . in reactions of secondary alcohols or ketones. The role of alkali promoter is to activate the beta carbon of the reacting aldehyde or ketone and to add a second aldehyde. The heavy alkali render the cistrans keto-alkoxide transition more facile than light alkali, with the result that both the rate of the C-C bond formation and the selectivity of the path involving oxygen retention increase as the size of the alkali cation increases.

IR vibrational CD (VCD) has been observed for the cyclic pentapeptide cyclo-(-Gly-Pro-Gly-D -Ala-Pro-) in solution in CDBr3. The observed VCD spectra do not resemble the VCD features of any of the previously reported peptide secondary structures, such as α-helical, “random coil,” or sheet structures, and might be due to the β-turn contained in this molecule. To shed light onto the origin of the observed spectra, VCD intensity calculations, based on the solution and solid-state structures of cyclo-(-Gly-Pro-Gly-D-Ala-Pro-), have been carried out. In addition, calculated VCD data for pure β-turns are discussed. © 1992 John Wiley & Sons, Inc.

The modelling of radionuclide release from waste forms is an important part of the performance assessment of a potential, high-level radioactive waste repository. Since spent fuel consists of UO2 containing actinide elements and other fission products, it is necessary to determine the principal parameters affecting UO2 dissolution and quantify their effects on the dissolution rate before any prediction of long term release rates of radionuclides from the spent fuel can be made. As pan of a complex matrix to determine the dissolution kinetics of UO2 as a function of time. pH, carbonate/bicarbonate concentration and oxygen activity, we have measured the dissolution rates at 25°C of: a) UO2.00 pellets; b) UO2.000 powder and c) synthetic dehydrated schoepite. UO3.H2O using a single-pass flow through system in an argon-atmosphere glove box Mixtures of carbonate, and bicarbonate buffers with concentrations ranging from 0.0002 M to 0.02 M and pH values from 8 to 11 have been used. Argon gas mixtures containing oxygen (from 0.002 to 0.2 ann) and carbon dioxide (from 0 to 0.011 atm) were bubbled through the buffers to stabilize their pH values.

The accuracy and reliability of difference NMR spectroscopy can be substantially improved by a simple correction based on changes in the lineshape of an internal reference line. This reference lineshape adjusted (RLSA) method is experimentally demonstrated to behave according to theoretical predictions under variations in drift of the main magnetic field, in rf power, in homogeneity of the main field, in spinning side bands, in detector phase, and in sweep rate. The RLSA method is experimentally demonstrated to automatically compensate for changes in all these instrumental parameters provided H, is sufficiently small that saturation is avoided. In addition, the internal reference must be constant in composition, concentration, and resonance position, and must be totally resolved from the rest of the spectrum. Under these conditions, the RLSA method is shown to give difference spectra that are visibly superior to simple difference spectra.

Results from theoretical studies of dimethyl diselenide (H3C–Se–Se–CH3) by semiempirical and ab initio molecular orbital (MO) methods are reported. The CNDO/2 method was employed for the semiempirical studies, and the restricted Hartree–Fock (RHF) method, in which an augmented STO‐3G basis set was used, for the ab initio studies. Total energy E was calculated as a function of a chosen internal coordinate (bond length, bond angle or torsion angle) by the CNDO/2 method while all other internal coordinates were held at fixed values. In addition, a geometric optimization in which selected internal coordinates were permitted to vary simultaneously was performed. The heights of the cis and trans torsional (rotational) barriers were calculated by the CNDO/2 method and found to be greatly exaggerated. More realistic values were calculated by the RHF method, in which an augmented STO‐3G basis set was used. The heights calculated by both MO methods were compared to the corresponding ones calculated by similar metho...

To determine the mechanism and pathway of entry of polar nonelectrolytes into bile, we studied first the permeation of [3H]H2O, [14C]urea, [14C]erythritol, [14C]mannitol, [3H]sucrose, [3H]inulin and [3H]dextran across an isolated, in situ perfused segment of the guinea pig's extrahepatic bile duct. All of these molecules, except [3H]dextran, permeated the bile duct. The diffusive permeability coefficients (cm per sec per 106) ranged from 248 for [3H]H2O to 1.2 for [3H]inulin. On the basis of these results, we formulated two models of solute biliary excretion. In Model I, permeation across both the canaliculus and ductule/duct was assumed to be by simple diffusion. In Model II, solute was assumed to enter the canaliculus by convection and diffusion, and the ductule/duct by diffusion. Reflection coefficients and/or permeability coefficients for the canalicular membrane were then determined by fitting the equations describing these processes to the bile-to-plasma ratios of [14C] erythritol, [14C]mannitol, [3H]sucrose and [3H]inulin observed at different rates of bile flow produced by partially clamping the bile duct cannula and subsequently infusing taurodehydrocholate. Only when convection was included as a mechanism of canalicular permeation (Model II) was excellent fitting observed. In such a case, the reflection coefficients and permeability coefficients for the carbohydrates in question were similar to those reported for other transporting epithelia. Cholestasis produced by taurolithocholate (10 to 40 μmoles per kg, i.v.) was associated with an irreversible increase in both the sieving coefficient and permeability coefficient for [3H]sucrose and [3H]inulin, even when the inhibition of bile flow was fully reversible. The permeability to [14C] erythritol and [14C]mannitol was either not affected or minimally increased. These findings suggest that, in the guinea pig: (i) solutes as large as [3H]inulin enter the biliary tree both at the canaliculus and bile ductule/duct; (ii) [14C]erythritol and [14C]mannitol gain access into the canalicular lumen primarily by convection, whereas [3H]sucrose and [3H]inulin permeate mainly by diffusion; (iii) distal permeation of these carbohydrates is small, and accounts for 1 to 11% of their total biliary entry; (iv) the canalicular membrane permeability to [3H]sucrose and [3H]inulin is not functionally important in bile secretion, and (v) a fraction of canalicular bile flows through the transjunctional shunt pathway.

The resonances of six of the seven backbone amide protons of [8-arginine]vasopressin (AVP) and of all four nonequivalent backbone amide protons of gramicidin S (GS) in D2O were assigned by decoupling of the amide protons from their respective vicinal Cα protons while exchange of the amide protons for deuterons was occurring. The simple pulsed Fourier transform method involving only a (π/2-FID) sequence of pulses was used. This method of assigning resonances of exchangeable protons is termed on-the-fly decoupling. Values for the chemical shifts of the amide protons (δNH) and for the coupling constants between vicinal amide and Cα protons of AVP in D2O are shown to be quite similar to the corresponding ones previously published for [8-lysine]vasopressin in H2O at a slightly different acidity and temperature [J. D. Glickson, D. W. Urry, and R. Walter, Proc. Nat. Acad. Sci. USA 69, 2566 (1972)]. Values for the δNHS of GS in D2O are shown to be quite similar to the corresponding ones previously published for this peptide in CH3OH at the same temperature [D. W. Urry, in “The Enzymes of Biological Membranes” (A. Martonosi, Ed.), Vol. 1, pp. 31–69, Plenum, New York, 1976]. It is concluded that on-the-fly decoupling can be used to assign resonances of exchangeable protons in compounds dissolved at millimolar concentrations in solvents with exchangeable deuterons and that the spectral simplification that results when signals from rapidly exchanging protons are not observed may be advantageous.

This study reports the synthesis and biological activities of 1-desamino, 7-lysine-(4-azidobenzoyl), 8-arginine vasotocin (d7-N3-AVT). This compound was found to be biologically active in the rat antidiuretic assay (20 U/mg), to behave as an antagonist of vasopressin in the rat pressor assay (pA2 = 6.6), and to yield a half-maximal hydroosmotic response in the isolated toad urinary bladder at a bath concentration of 2.4 X 10(-8) M. When toad bladders were exposed to d7-N3-AVT in the presence of long wavelength UV light, the hydroosmotic response persisted in spite of prolonged and repeated periods of washout. By contrast, the hydroosmotic response in control bladders after stimulation with d7-N3-AVT in the absence of UV irradiation was fully reversed within 15 min of washout. A membrane preparation derived from bladders that had been photolabeled with d7-N3-AVT and washed for 1 h specifically bound 325 fmol [3H]vasopressin/mg protein. Matched bladders exposed to the analog in the absence of UV irradiation and washed for 1 h specifically bound 591 fmol [3H]vasopressin per mg of protein. These studies indicate that d7-N3-AVT binds covalently to hydroosmotic receptors of toad urinary bladder and forms a complex that is functional in triggering an increase in the permeability to water of the epithelium. This analog may prove useful in the isolation and purification of vasotocin receptors in lower vertebrates.

Three arginine-vasopressin (AVP) analogues in which the proline residue in position 7 was substituted with 4-hydroxyproline were synthesized by solid-phase techniques, and their biological activities were evaluated by antidiuretic, pressor, and uterotonic bioassays. The [7-trans-4-hydroxy-L-proline]AVP, the 1-desamino[7-trans-4-hydroxy-L-proline]AVP, and the 1-desamino[7-cis-4-hydroxy-L-proline]AVP analogues showed a high antidiuretic and strikingly high uterine activity, a sharp decrease in pressor activity, and a better antidiuretic and uterine to pressor selectivity than the parent compound, arginine-vasopressin. The uterine activities are the highest so far assayed in AVP analogues with replacements in position 7.

The time-resolved fluorescence properties of phenol and straight-chained phenol derivatives and tyrosine and simple tyrosine derivatives are reported for the pH range below neutrality. Phenol and straight-chained phenol derivatives exhibit single exponential fluorescence decay kinetics in this pH range unless they have a titratable carboxyl group. If a carboxyl group is present, the data follow a two-state, ground-state, Henderson-Hasselbalch relationship. Tyrosine and its derivatives with a free carboxyl group display complex fluorescence decay behavior as a function of pH. The complex kinetics cannot be fully explained by titration of a carboxyl group; other ground-state processes are evident, especially since tyrosine analogues with a blocked carboxyl group are also multiexponential. The fluorescence kinetics can be explained by a ground-state rotamer model. Comparison of the preexponential weighting factors (amplitudes) of the fluorescence decay constants with the 1H NMR determined phenol side-chain rotamer populations shows that tyrosine derivatives with a blocked or protonated carboxyl group have at least one rotamer exchanging more slowly than the radiative and nonradiative rates, and the fluorescence data are consistent with a slow-exchange model for all three rotamers, the shortest fluorescence decay constant is associated with a rotamer where the carbonyl group can contact the phenol ring, and in the tyrosine zwitterion, either rotamer interconversion is fast and an average lifetime is seen or rotamer interconversion is slow and the individual fluorescence decay constants are similar.

Peripheral blood specimens were obtained from 50 patients with various stages of breast cancer (I-II = 7, III = 6, IV = 24, treated and NED = 13), and 20 biochemical tests were performed. There are significant differences of hemoglobin, LDH, SGPT, serum protein, albumin, and alpha globulin values between patients with early (I, II, NED) and late (III, IV) lesions. Among patients with stage IV diseases, those patients with bony metastases had significantly higher values of alkaline phosphatase, alpha-1 globulin, IgA, and C-reactive protein than those with nonosseous lesions. Neither CEA nor pregnancy-associated alpha-2 glycoprotein showed any correlation with different stages or sites of breast cancer in these small series of patients.

The primary objective of this research project was to compare the tool wear resulting when a semi-synthetic cutting fluid was used, to that from use of a premium soluble oil. The secondary objective was to determine the effects of cutting speed, drill diameter, and fluid concentration, on tool wear. The experiments contained two key elements: (1) cast aluminium alloy 390 was used as the workpiece material and (2) deep-hole drilling to a depth greater than two diameters was performed. Numerous drilling tests were performed with each cutting fluid using a flood application. To meet the primary objective, an experiment was designed for each cutting fluid and the wear on the lands of twist drills was measured. The secondary objective utilized a statistically-designed 23 factorial experiment which evaluated the effects that moderate and relatively high cutting speeds, two drill diameters, and two levels of fluid concentration, had on tool wear. After analysis of the test results, it was concluded that concentration had the most significant effect on land wear when the experimentally-formulated semi-synthetic cutting fluid was used. Cutting speed was the most significant factor when drilling with the commercially-available premium soluble oil. Tool wear while using the semi-synthetic fluid was slightly less than that for the premium soluble oil.

Steady-state and time-resolved fluorescence properties of the single tyrosyl residue in oxytocin and two oxytocin derivatives at pH 3 are presented. The decay kinetics of the tyrosyl residue are complex for each compound. By use of a linked-function analysis, the fluorescence kinetics can be explained by a ground-state rotamer model. The linked function assumes that the preexponential weighting factors (amplitudes) of the fluorescence decay constants have the same relative relationship as the 1H NMR determined phenol side-chain rotamer populations. According to this model, the static quenching of the oxytocin fluorescence can be attributed to an interaction between one specific rotamer population of the tyrosine ring and the internal disulfide bridge.

A model for oxytocin has been previously proposed in which residues 3 and 4 occupy the corner positions in a beta turn (Urry, D. W., & Walter, R (1971) Proc. Natl. Acad. Sci. U.S.A. 68, 956). The analogue [Pro(3),Gly(4)]-oxytocin (PGO) was used in proton magnetic resonance (1H NMR) studies designed to probe the contribution of these corner positions in forming a beta turn. Comparison of various 1H NMR parameters obtained at 220 MHz for backbone amide protons of PGO with those for the corresponding protons of oxytocin suggests that, to a first approximation, these two peptides may have similar backbone conformations in )CD3)2SO. Theoretically, the L-Pro lead toGly sequence in positions 3 and 4 of PGO would allow the formation of either a type I or type II beta turn. The two coupling constants between vicinal amide and C alpha protons for Gly(4) of PGO in (CD3)2SO are compatible with a type II beta turn in which 04, the dihedral angle about the bond between the backbone C alpha and N' atoms of Gly4, is appromximately +92 degrees, but not with a type I beta turn. A survey of peptides studied in other laboratories by X-ray and/or 1H NMR with reported type II beta turns with L-Pro lead toGly or Gly lead to Gly sequences in the corner positions revealed a close correlation between chemical shifts and vicinal coupling constants for the glycl residue in the second corner position. It is suggested that this criterion can form an additional basis for the characterization of beta turns. More studies are needed to determine the particular type of beta turn manifest in the cyclic moiety of oxytocin per se, although a reasonable working hypothesis is that oxytocin, similar to PGO, has a type II beta turn.

1. 1. Isolated hemibladders of the fresh-water turtle, Pseudemys scripta, were bathed on both surfaces by an oxygenated Na+-free choline-Ringer solution (17 mM HCO3−-Krebs buffer) and were maintained in a short-circuited state. Forward (mucosal to serosal) clearance of 22Na+ was measured. Clearance (μl/h) was defined as the forward flux (nmoles/h) per unit of mucosal Na+ concentration (mM). When serosal [Na+] < 0.5 mM and mucosal [Na+] < 0.1 mM, clearance progressively and spontaneously decreased at an average rate of 29%/h. 2. 2. During the period of progressive decline, nonradioactive 23Na+ was added only to the mucosal fluid to a final concentration ranging between 1 and 10 mM. Following this addition, clearance changed from a state of spontaneous decline to one of progressive increase. The average rate of increase was 37%/h. 3. 3. The period of progressive increase (slow cis-stimulation) lasted an average of 2 h; afterwards clearance spontaneously began to decrease progressively. 4. 4. On the average, the peak value of clearance was 2.2 times the value of clearance at the time 23Na+ was added. 5. 5. Even during the period of decline, the clearance did not return to the level at which it would have been if Na+ had not been added to the mucosal fluid. 6. 6. Washout of 22Na+ from the tissue pool subsequent to the addition of mucosal 23Na+ was eliminated as the explanation for the observed increase in clearance. 7. 7. Concomitant changes in short-circuiting current independently confirmed the validity of the slow cis-stimulation but also suggested that the movement of ions other than Na+ may have been affected by slow cis-stimulation.

Discharge into Columbia River is proposed; laboratory studies showed that slime growths in receiving stream could be controlled if wastes were discharged intermittently into river of sufficient volume and high velocity.

A standard addition method is described for the determination of vanadium in brines by atomic absorption spectroscopy with a nitrous oxide-acetylene flame. Sample pH is adjusted to 1.0 with concentrated hydrochloric acid and the vanadium is directly extracted with 5% cupferron in methyl isobutyl ketone (MIBK). The ketone layer is then aspirated into the flame and the recorded absorption values are plotted as a function of the concentration of the added metal. As little as 2.5 μg l −1 of vanadium can be detected under the conditions of the procedure. Tungsten and tin interfere when present in excess of 5 and 10 μg ml −1 , respectively. The concentrations of the two interfering ions normally found in brines are well below interference levels.