The influence of the soil structure and moisture content on the number of bacteria and the degree of nitrification

ИзгчалоAЬ одноврeмeнноe дeйствиe сBрCкСC@ы поGвKi и Aодeрeа влаBи на количe бактeрий и интeнсивноAтЬ нитрифика. ции в гумуA-карбонаBной почвe. Путeм просeиваниHя образцоCпочвы чeрeз сиBа были в044B;цeлeны слeдующиe фракции: I — агрeгaаты мeнЬшe 1 мм; II — агрeгаты размe@ами в 1—2; мм; III — аг@eгаты размeрами в 2—3 мм; IV — агтeгаBы размeрами в 3—4 мм; V — агрeгаBы размeрами в 4—5 мм. Образцы брали три @аза а год. Для опрeДeлeния количeства бактeрий полЬзовалисЬ прямым мeтодeм флуорeсцeнтной м0438;H043A;H0440;H043E;скопии по Strugger в модификации по Seifert. Пeрeд опрeдeлeниeм биогeнности образцы насыщли влагой до заранee установлeнного уровня и инкCбировали 48 час. при тeмпeратгрe 20° С Нитрификацию опрeдeлOли послe 14-днeвной ?нкгбации образFов, насKщeнных влвгой до опрeдeлeнного уровня и хранившихся в тeрмостатe пр? 20° А. Бы;ло установлeно, что количeство бактeрий зависит от содeржания влаги и 043F;очти нe зависит оB размeров агрeгатов (рис. 1). ИнтeнсивностЬ нитрификации зависит как от содeржаниO влаги, так ? оB размeров агр;eгатов. НаиболЬHая интeнсивностЬ наблюдаласЬ в слу чаe агрeгатов пe@вой фракции, т. e. при диамeтрах мeнЬHe 1 мм. С гвeличeниeм диамeтров агрeгатов интeнсивностЬ нитрификации постeпeнно поннжаласЬ (@ис. 2). Понижeниe интeнсивности нитрификации отличалосЬ опрeдeлCнной правилЬностЬю, инаосновании ee анализа мы пришли к выводу, что инBeнсивностЬ нитрификаFии прямо пропорFионадЬна вeдиGинe спeцифичeAкой повeрхносBи агрeгатов. ДоказатdдЬство зтого привeдeно на рис. З. Для протeрки того, как на интeнсивносBЬ нитрификации дeйствуeт радмeлЬчeниe агрeгатов, мы поставнди опыт, при котором апрeгаBы V фракции были размeлЬчeны до размeров I фракции. Послe измeлЬчeниO интeнсивностЬ ниBририкаFии знаGиBeлЬно повысиласЬ (рис. 4).     

Effect of temperature and ionic environment on the specific binding of 3H(—)sulpiride to membranes from different rat brain regions

Sulpiride is an antipsychotic drug endowed with the properties of a dopamine antagonist. The failure of sulpiride to inhibit neostriatal dopamine stimulated adenylate cyclase activity indicated that this drug is a selective D₂ receptor antagonist. In this study we used a novel synthesized ²H(—)sulpiride with very high specific activity (72 Ci/mol) and characterized the temperature sensitivity of the binding sites labeled by this compound. Kinetic analysis of ³H(—)sulpiride binding in rat striatum showed unstable behavior when incubation was performed at 37 or 30°C. However when experiments were carried out at 15 or 10°C, binding reached a stable steady-state within 10 min. Scatchard analysis of binding isotherms obtained at 10°C showed a 5-fold increase in the maximum number of binding sites and a decrease in K_d values to one-third those obtained at 37°C. Pharmacological characterization of the binding sites labeled by ³H(—)sulpiride at 10°C showed a greater affinity for antagonists but not for agonists than 37°C. Under both experimental condition, ³H(—)sulpiride binding sites were Na⁺ and GTP-sensitive. The temperature sensitive binding phenomenon appeared to be area specific. ³H(—)sulpiride binding sites in tissues other than from striatum were influenced less or not at all by changes in incubation temperature.     

Biosorption of Pb(II) from contaminated water onto Moringa oleifera biomass: kinetics and equilibrium studies

Abstract

The present study aims at evaluating a batch scale biosorption potential of Moringa oleifera leaves (MOL) for the removal of Pb(II) from aqueous solutions. The MOL biomass was characterized by FTIR, SEM, EDX, and BET. The impact of initial concentrations of Pb (II), adsorbent dosage, pH, contact time, coexisting inorganic ions (Ca²⁺, Na⁺, K⁺, Mg²⁺, CO₃^2?, HCO₃^?, Cl^?), electrical conductivity (EC) and total dissolved salts (TDS) in water was investigated. The results revealed that maximum biosorption (45.83?mg/g) was achieved with adsorbent dosage 0.15?g/100?mL while highest removal (98.6%) was obtained at adsorbent biomass 1.0?g/100?mL and pH 6. The presence of coexisting inorganic ions in water showed a decline in Pb(II) removal (8.5% and 5%) depending on the concentrations of ions. The removal of Pb(II) by MOL decreased from 97% to 89% after five biosorption/desorption cycles with 0.3?M HCl solution. Freundlich model yielded a better fit for equilibrium data and the pseudo-second-order well described the kinetics of Pb(II) biosorption. FTIR spectra showed that –OH, C–H, –C–O, –C?=?O, and –O–C functional groups were involved in the biosorption of Pb(II). The change in Gibbs free energy (ΔG = ?28.10?kJ/mol) revealed that the biosorption process was favorable and thermodynamically driven. The results suggest MOL as a low cost, environment-friendly alternative biosorbent for the remediation of Pb(II) contaminated water.     

Optimization of Nitrate and Manganese Removal by Bacterium Pseudomonas sp. H117 in Mixotrophic Condition

Previous study has revealed that Pseudomonas sp. H117 could exhibit excellent performance on autotrophic and heterotrophic denitrification in polluted groundwater. However, a novel character of simultaneous denitrification and manganese removal by the bacteria remained to be further explored. In this study, we investigated optimum conditions of nitrate and Mn(II) removal by the strain H117 in mixotrophic condition. Different factors (temperature, initial pH, nitrate concentration, and Mn(II) concentration) were investigated and optimized by response surface methodology (RSM), demonstrating that the highest nitrate removal ratio (100%) in the mixotrophic condition occurred at the temperature of 30.20?°C, pH of 6.90, and Mn(II) concentration of 61.81?mg/l. Meanwhile, the optimal Mn(II) removal (73.34%) conditions were at the temperature of 29.33?°C, pH of 7.22, and nitrate concentration of 20.74?mg/l. Furthermore, microbial development pattern, cellular metabolites, and bioprecipitation were characterized by the excitation emission matrix (EEM), meteorological chromatography analysis, and scanning electron microscopy (SEM) methods, respectively. These results demonstrated that strain H117 can have good adaptability to the environment, thus exhibiting an efficient ability for bioremediation of groundwater polluted by nitrate and Mn(II).     

Effect ofpH on the formation of Compounds II and III of horseradish peroxidase

The formation of Compounds II and III of horseradish peroxidase from Compound I and potassium ferrocyanide and from Compound II and excess hydrogen peroxide, respectively, was studied as a function ofpH at 25°C and a constant ionic strength of 0.11. The yield of Compound II obtained increases progressively with increase inpH; a mixture of Compounds I and II is produced at acidicpH. Pure Compound III is obtained at allpH values, but the highest yield is obtained atpH values between 6.0 and 7.0. The yield of p-670, formed when Compound III is allowed to stand for 60 min, decreases with increase inpH, while the decay of Compound III also decreases with increase inpH. Therefore p-670 is the decay product of Compound III.     

Effect ofpH on the formation of Compounds II and III of horseradish peroxidase

The formation of Compounds II and III of horseradish peroxidase from Compound I and potassium ferrocyanide and from Compound II and excess hydrogen peroxide, respectively, was studied as a function ofpH at 25°C and a constant ionic strength of 0.11. The yield of Compound II obtained increases progressively with increase inpH; a mixture of Compounds I and II is produced at acidicpH. Pure Compound III is obtained at allpH values, but the highest yield is obtained atpH values between 6.0 and 7.0. The yield of p-670, formed when Compound III is allowed to stand for 60 min, decreases with increase inpH, while the decay of Compound III also decreases with increase inpH. Therefore p-670 is the decay product of Compound III.     

Mechanism of the interactions of aliphatic alcohols with bovine serum albumin in the ternary systems—1H n.m.r. study: 1. Aqueous solutions BSA-alcohols-urea

The molecular mechanism of the interaction of aliphatic alcohols (A) with bovine serum albumin (BSA) protein was studied in aqueous solutions at increasing concentrations (0–8 m) of urea (U). ¹H n.m.r. spectra of alcohols were monitored in D₂O in the control binary systems (A—U) and (A—BSA), and in the ternary systems (A—U—BSA) at pH 7.0. Marked and selective broadening of the n.m.r. lines of alcohols in the system (A—BSA) was reduced upon addition of urea, indicating that alcohols are poorly bound by urea-denaturated BSA. The reduction in the ability to associate with BSA depends on chain position of the alcohol molecule and is much higher for α-methylenes (next to ?OH) than for other proton groups. Besides this reduction seems to be a two-step phenomenon dependent upon urea concentration. The results obtained can be explained by competition in formation by the peptide linkages of a protein of the hydrogen bonds with ?OH group of alcohols or fragments of urea molecules.     

Energy transfer and the distribution of excitation energy in the photosynthetic apparatus of spinach chloroplasts

Equations are derived from our model of the photochemical apparatus of photosynthesis to show that the yield of energy transfer from Photosystem II to Photosystem I, ?_T(II→Iz), can be obtained from measurements on an individual sample of chloroplasts frozen to ?196 °C by comparing the sum of two specifically defined fluorescence excitation spectra with the absorption spectrum of the sample. Then, given that value of ?_T(II→I), the fraction of the quanta absorbed by the photochemical apparatus which is distributed initially to Photosystem I, α, can be determined as a function of the wavelength of excitation from the same fluorescence excitation spectra. The results obtained in this study of individual samples of chloroplasts frozen to ?196 °C in the absence of divalent cations, namely, that ?_T(II→I) varies from a minimum value of 0.10 when the Photosystem II reaction centers are all open to a maximum value of 0.25 when the centers are all closed and that α has a value of about 0.30 which is almost independent of wavelength for wavelengths shorter than 675 nm (α increases rapidly toward unity at wavelengths longer than 675 nm), agrees quite well with results obtained previously from comparative measurements of chloroplasts frozen to ?196 °C in the presence and absence of divalent cations.     

H2O2 as a DNA fragmenting agent in the alkaline elution interstrand crosslinking and DNA-protein crosslinking assays

A method for DNA fragmentation by H2O2 in the DNA alkaline elution procedure is described. Treatment of cell suspensions for 1 h with 100 microM H2O2 or 5 mM H2O2 at 0-1 degree C resulted in DNA breakage equivalent to doses of 300 and 3000 rad of gamma-rays, respectively. The elution profiles were reproducible and H2O2 was used for measurements of interstrand crosslinks and DNA-protein crosslinks induced in HeLa cells by mitomycin C, cis-diamminedichloroplatinum(II), and trans-diamminedichloroplatinum(II). The comparison of data obtained with the use of H2O2 and gamma-rays has shown that both methods have similar sensitivity and reproducibility.     

The oxidation-reduction potentials of compound I/compound II and compound II/ferric couples of horseradish peroxidases A2 and C.

The reversibility of the stepwise reduction of Compound I to the ferric state via Compound II was confirmed in horseradish peroxidases A2 and C. The values of E'o (compound I/Compound II) and E'O (Compound II/ferric) were measured from equilibrium data coupled with the K2IrCl6-K3IrCl6 system in a narrow region of pH near 6.3. The ferric enzymes were also oxidized by ferricyanide to Compound II at alkaline pH and the values of E'O (Compound II/ferric) were measured from the equilibrium data. The pH dependence of E'O (Compound II/ferric) was in accord with the equation: E'O = EO + 0.058 log (Kr[H+] + [H+]2)/(KO + [H+]), where Kr and KO are proton dissociation constants in the ferric enzyme and Compound II, respectively. The pH-E'O (Compound I/Compound II) curves were likewise obtained from the equation, E'O = EO + 0.058 log (Kr + [H+]), where Kr is the proton dissociation constant in Compound II. The forward and backward rate constants were measured in each of one-electron transfer reactions of the peroxidases with the K2IrCl6-K3IrCl6 system at various pH values. The E'O values calculated on the assumption that the ratio of the rate constants equals the equilibrium constant were compared with those obtained from the equilibrium data.     

Packing analysis of carbohydrates and polysaccharides. V. Crystal structures of two polymorphs of pachyman triacetate

The crystal structures of two polymorphic forms of pachyman triacetate, the fully acetylated derivative of a naturally occuring β-(1 → 3)-D -glucan, were determined by a combination of stereochemical and x-ray diffraction analysis. The two polymorphs could be obtained depending on the temperature and the degree of stretching of film specimens of the substance: polymorph I resulted from stretching 25–50% at 125°C and polymorph II resulted from further stretching to 300% at 215°C. Both polymorphs had previously been shown to have sixfold helical chain conformations, but of unequal pitch. Subsequent detailed structure refinement performed with bond lengths, bond angles, conformational angles, and helix-packing parameters as refinement variables, and the simultaneous minimization of packing and conformational energy and the crystallographic R-factor as refinement criteria, resulted in a complete determination of the two crystal structures. Pachyman triacetate I was found to be a right-handed helix packing with antiparallel polarity and space group P2₁2₁2₁ symmetry (unit-cell parameters a = 11.0, b = 19.0, c (fiber repeat) = 22.38 Å). The acetate groups were nearly planar and the O(2) and O(4) acetates were oriented in such a fashion that the carbonyl double-bond nearly eclipsed the corresponding C—H bond of the ring. The O(6) was in the tg position and its acetate was oriented in such a fashion that the bond sequence C(6)—O(6)—C(6C)—C(6M) was nearly trans-planar, with the carbonyl double-bond bisecting the tetrahedral angle formed by C(6) and its two hydrogens. The final R = 0.221. Pachyman triacetate II was similarly found to be a right-handed helix, but packing as a 50:50 mixture of parallel and antiparallel polarities (unit-cell parameters a = 11.49, b = 20.13, c (fiber repeat) = 18.6 Å). The acetate positions in pachyman triacetate II were substantially the same as in pachyman triacetate I. The final R for the 50:50 mixture was 0.234. Probable reasons for the change in packing polarities are discussed, as are the difficulties encountered in the structure refinement of acetate derivatives.     

Characterization of the product radical structure in the Co(II)-product radical pair state of coenzyme B12-dependent ethanolamine deaminase by using three-pulse 2H ESEEM spectroscopy

Molecular structural features of the product radical in the Co(II)-product radical pair catalytic intermediate state in coenzyme B(12)- (adenosylcobalamin-) dependent ethanolamine deaminase from Salmonella typhimurium have been characterized by using X-band three-pulse electron spin-echo envelope modulation (ESEEM) spectroscopy in the disordered solid state. The Co(II)-product radical pair state was prepared by cryotrapping holoenzyme during steady-state turnover on excess 1,1,2,2-(2)H(4)-aminoethanol or natural abundance, (1)H(4)-aminoethanol. Simulation of the (2)H/(1)H quotient ESEEM (obtained at two microwave frequencies, 8.9 and 10.9 GHz) from the interaction of the unpaired electron localized at C2 of the product radical with nearby (2)H nuclei requires four types of coupled (2)H, which are assigned as follows: (a) a single strongly coupled (effective dipole distance, r(eff) = 2.3 A) (2)H in the C5' methyl group of 5'-deoxyadenosine, (b) two weakly coupled (r(eff) = 4.2 A) (2)H in the C5' methyl group, (c) one (2)H coupling from a beta-(2)H bonded to C1 of the product radical (isotropic hyperfine coupling, A(iso) = 4.7 MHz), and (d) a second type of C1 beta-(2)H coupling (A(iso) = 7.7 MHz). The two beta-(2)H couplings are proposed to arise from two C1-C2 rotamer states of the product radical that are present in approximately equal proportion. A model is presented, in which C5' is positioned at a distance of 3.3 A from C2, which is comparable with the C1-C5' distance in the Co(II)-substrate radical pair intermediate. Therefore, the C5'methyl group remains in close (van der Waals) contact with the substrate and product radical species during the radical rearrangement step of the catalytic cycle, and the C5' center is the sole mediator of radical pair recombination in ethanolamine deaminase.     

Correlating ch bond cleavage with molybdenum reduction in xanthine oxidase

We have performed a computational study of substrate C?H bond activation in enzymes of the XO family. The C?H H-atom for all XO substrates studied is transferred to the terminal sulfido at the transition state with near neutral charge, and this is consistent with both Mo?S π→ C?H σ* and C?H σ→Mo?S π* donor?acceptor interactions activating the C?H bond. A C?H bond scission and Mo reduction appear to be highly correlated along the reaction coordinate for all XO substrates studied, with Mo reduction being a continuous and exponential function of C?H bond breaking along the reaction coordinate.     

Determination of the antihypertensive agent 1-(2-aminoethyl)-3-(2,6-Dichlorophenyl)thiourea in plasma and urine by high-performance liquid chromatography

A rapid, sensitive and specific normal-phase (adsorption) high-performance liquid chromatographic (HPLC) assay was developed for the determination of 1-(2-aminoethyl)-3-(2,6-dichlorophenyl)thiourea [I] in plasma and urine. The assay involves the extraction of the compound into methylene chloride from plasma or urine buffered to pH 10, and the HPLC analysis of the residue dissolved in methylene chloride—methanol—heptane (85:10:5). A 10-μm silica gel column was used with methylene chloride—methanol—heptane—ammonium hydroxide (85:10:5:0.1) as the eluting solvent. The effluent was monitored at 254 nm and quantitation was based on the peak height vs. concentration technique. The assay has a recovery of 64.5 ± 4.5% (S.D.) from plasma and 96.0 ± 6.3% (S.D.) from urine in the concentration range of 0.1–2 μg per ml and 2–40 μg per 0.1 ml of plasma and urine, respectively, with a limit of detection of 0.05–0.1 μg [I] per ml of plasma using a 1-ml specimen and 0.1 μg per ml urine using a 0.1-ml specimen, respectively. The assay was applied to the determination of plasma levels and urinary excretion of the compound [I] in dog following the oral administration of 28.8 mg of [I] · maleate per kg body weight.The HPLC assay was also used to determine the stability of [I] and for the measurement of a potential degradation product, clonidine [II] [2-(2,6-dichlorophenylamino)-2-imidazoline] in pooled human plasma stored at ?17°C, and pooled human urine stored at ?17°C and ?90°C, respectively.     

Differential solubilization of nuclear glucocorticoid receptors by DNAase I and DNAase II

This study analyzes the sensitivity of nuclear bound glucocorticoid receptors to solubilization from nuclei by DNAase I and DNAase II. Thymocytes were incubated with 10(-8) M [3H]dexamethasone, [3H]cortisol or [3H]triamcinolone acetonide, without or with 10(-6) M unlabelled dexamethasone, for 30 min at 37 degrees C and nuclei from these cells were digested with either DNAase I and DNAase II. DNAase I for 2 h at 3 degrees C leads to solubilization of 60% of the nuclear DNA and release of 10--20% triamcinolone acetonide-receptor, 30--40% dexamethasone-receptor and 85--90% cortisol-receptor. DNAase II at the same enzymatic concentration solubilizes only 10--20% of the nuclear DNA, but releases 40--50% triamcinolone-receptor, 60--70% dexamethasone-receptor and 100% cortisol-receptor. Release of nuclear bound dexamethasone-receptor by DNAase I parallels the solubilization of DNA, reaching maximum values by 2 h at 3 degrees C, whereas maximal release by DNAase II is obtained within 45 min when DNA solubilization is not complete. When nuclei initially extracted with DNAase I are re-extracted with DNAase II, greater than 65% of the DNAase I residual dexamethasone-receptors are solubilized, whereas DNAase I is ineffective in solubilizing DNAase II residual dexamethasone-receptors. DNAase I solubilizes only 30% of the 0.4 M KCl residual dexamethasone-receptor whereas DNAase II digests over 90% of this fraction. DNAase I extracts of nuclear dexamethasone-receptor chromatograph on G-100 Sephadex as a single radioactive peak just after the void volume, whereas DNAase II extracts of nuclear dexamethasone-receptor chromatograph as two peaks of radioactivity, one which is similar to the DNAase I solubilized receptor and a second broad peak of macromolecular bound radioactivity which is smaller in size.     

Spectroscopic studies on bleomycin-iron complexes with carbon monoxide, nitric oxide, isocyanide, azide, and cyanide and comparison with iron-porphyrin complexes

The bleomycin-iron complexes with CO, NO, C2H5NC, OH-, N-3, CN-, and CH3NH2 were characterized by electronic, ESR, 1H-NMR, and M?ssbauer spectroscopies and the findings were compared with the corresponding hemoprotein complexes. The 1H-NMR and M?ssbauer features for the CO and C2H5NC adducts of the bleomycin-Fe(II) complex are consistent with an S = 0 ferrous assignment. The OH-, CH3NH2, and N-3 adducts of the bleomycin-Fe(III) complex show the ESR, 1H-NMR, and M?ssbauer spectra typical of a low-spin Fe(III). The unique M?ssbauer parameters of the bleomycin-Fe(II)-NO complex demonstrate mixing between the NO pi- and the Fe 3d-orbitals. The magnitude of the proton chemical shifts over +/- 50 ppm indicates a high-spin ferric type for the bleomycin-Fe(III)-CN complex. The M?ssbauer parameters (delta EQ = 0.89 and delta = 0.48 mm/s) of the CN- adduct differ substantially from those of typical low-spin hemoprotein-cyanide complexes. Except for the CN- adduct, the M?ssbauer and crystal field parameters of these bleomycin-iron complexes are similar to those of the corresponding hemoprotein complexes.     

Interaction of metal ions with nucleic acids. Interaction of copper(II) with adenosine and its derivatives.

The interaction of copper(II) with adenosine, 2'-deoxyadenosine, 1-methyladenosine, 7-deazaadenosine and AMP was studied by spectroscopic and magnetochemical methods. In non-aqueous medium, copper(II) interacts with adenosine and AMP at N-7 and N-1, and with 1-methyladenosine at N-7 and N-3. The copper ion is not bound to the NH2 group. In aqueous solution, copper(II) interacts both with N-7 and N-1 of adenosine, and in AMP additionally with the phosphate group. The interaction of copper(II) with the heterocyclic part, but not withthe phosphate group, is dependent on the extent of protonation of the molecular. A crystalline AMP-copper(II) complex [Cu(C10H12N5O7P).(H2O)2] was obtained; the phosphate group and probably N-7 are involved in the complex formation.     

A water network within a protein: temperature-dependent water ligation in H64V-metmyoglobin and relaxation to deoxymyoglobin

The sperm whale myoglobin mutant H64V, where the distal histidine is mutated to valine, is known to be five coordinated in the ferric state at room temperature and physiological pH. A change of the ligation in this H64V-Mbmet has been observed by optical absorption spectroscopy as a function of temperature from 20 K to 300 K. Above the dynamical transition at about 180 K one observes the temperature-dependent equilibrium between five- and six-ligated heme. Below the dynamical transition the equilibrium is frozen-in at about 50% of six-coordinate molecules. The water ligation of the iron occurs at temperatures where protein-specific motions are present, as monitored by M?ssbauer spectroscopy. The X-ray structures of H64V-Mbmet at 300 K and 110 K are reported with a resolution of 1.5 A and 1.3 A, respectively. The measurements at high resolutions are possible owing to crystallization in the space group P2(1), whereas all mutant myoglobins studies up to now have been carried out with crystals in the space group P6. The overall structure at both temperatures is very close to the native myoglobin. The binding of water at the sixth coordination site at lower temperatures is possible owing to a stabilizing water network extending from the protein surface to the active centre. The reduction of the H64V-Mbmet by electrons obtained by X-ray irradiation of the water-glycerol solvent at 85 K produces an intermediate low-spin state of the water-ligated molecules where Fe(II) retains the six-fold coordination. M?ssbauer spectroscopy shows that the relaxation of the metastable low-spin state to high-spin H64V-Mbdeoxy with dissociation of the Fe(II)-H(2)O bond starts at about 115 K and is completed at about 170 K. Differences in the dynamics properties of the native and mutant myoglobin and the connection to the dynamical transition around 180 K are discussed.     

Mass spectrometric analysis of permethylated glycosphingolipids II. Comparative studies on different blood-group active and related erythrocyte membrane glycosphingolipids

Three isomeric ceramide tetrasaccharides — P blood-group active globoside, lacto-N-neotetraosyl ceramide as ABH blood-group precursor, both isolated from human erythrocytes and “asiologanglioside” from human brain as reference standard — and two ceramide pentasaccharides — H blood-group active glycosphingolipid, obtained from blood-group B active ceramide hexasaccharide of human B erythrocytes after α-galactosidase treatment and ceramide pentasaccharide from rabbit erythrocytes with B-like blood-group activity — were investigated by mass spectrometry after permethylation. The carbohydrate moiety exhibits differences not only concerning the sugar sequence but also with regard to the position of some glycosidie linkages: Oligosaccharides containing N-acetylhexosamine substituted at position 4 produce spectra that are distinctly different from those containing C-3 substituted N-acetylhexosamines, thus allowing the differentiation between type 1 and type 2 carbohydrate chains. Moreover, oligosaccharide ions with a hexose at the cleavage site exhibit a fragmentation pattern different from those with a N-acetylhexosamine at the “reducing terminal”. The intensity ratio between parent ion and parent ion — 32 mass units is Q ? 3 in the first case, whereas in the latter case Q is <1. The Q-values are given for 14 oligosaccharide ions. Differences in the composition of the ceramide residues can also be deduced from the mass spectra.     

Binding of iron(II) ions to the pentose sugar 2-deoxyribose

Iron(II) ions are able to form a weak complex (apparent equilibrium constant about 10(2) at pH 7.4 and 25 degrees C) with 2-deoxyribose over a range of pH values, including pH 7. Evidence for this complex formation has been obtained by spectrophotometric experiments and by studies of Fe(II) oxidation. Iron(II) ions bound to deoxyribose seem to react with H2O2, in a site-specific reaction, to form hydroxyl radicals (.OH) that immediately damage the deoxyribose molecule.