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The milk-alkali syndrome. A reversible form of acute renal failure.

The milk-alkali syndrome became rare with the advent of modern ulcer therapy with nonabsorbable antacids, histamine2 blockers, and sucralfate. An increased frequency of this syndrome seems likely with the growing popularity of the use of calcium carbonate as an antacid or as calcium supplementation to prevent osteoporosis. We treated five patients who had six episodes of the milk-alkali syndrome; four of these cases were diagnosed between 1990 and 1992. All patients were ingesting massive quantities of calcium and absorbable alkali and were unaware of the toxic effects of these compounds. All patients presented with the triad of hypercalcemia, metabolic alkalosis, and renal failure. All metabolic abnormalities were corrected, and renal function improved with appropriate supportive measures and cessation of calcium and alkali ingestion. In two patients, the renal failure was so severe that dialysis was necessary. In four patients, either the serum amino-terminal parathyroid hormone or 1,25-dihydroxycholecalciferol levels were appropriately decreased in response to hypercalcemia. The serum carboxy-terminal parathyroid hormone levels were increased because of renal failure. Since both physicians and patients are often unaware of the calcium and alkali content of many nonprescription medicines, the diagnosis of the milk-alkali syndrome, a reversible cause of renal failure, can be missed if a detailed history of such intake is not elicited. Measurement of the serum amino-terminal parathyroid hormone and 1,25-dihydroxycholecalciferol levels may help differentiate milk-alkali syndrome from primary hyperparathyroidism.

Acute Kidney Injury↗

Alkali burn-induced synthesis of inflammatory eicosanoids in rabbit corneal epithelium.

PURPOSE: Alkali burning of the rabbit cornea is a well-established model for the study of anterior surface inflammation, neovascularization, and wound-healing processes. 12-hydroxyeicosanoids have been implicated as mediators of such responses. 12(S)-hydroxyeicosatetraenoic acid (12[S]-HETE) is a lipoxygenase-derived arachidonate metabolite and 12(R)-hydroxyeicosatetraenoic acid (12[R]-HETE) is formed by a cytochrome P450 monooxygenase; both give rise to the potent angiogenic factor 12(R)-hydroxyeicosatrienoic acid (12[R]-HETrE). In this study, the authors correlate the pattern of their synthesis in the corneal epithelium with the inflammatory response after alkali injury. METHODS: New Zealand albino rabbits were anesthetized and alkali burns created with 10-mm filter paper discs (1 N NaOH for 2 minutes). Corneas were then rinsed; 1 to 7 days later, corneal epithelium was scraped and used to assess 14C-arachidonic acid conversion to 12-HETE and 12-HETrE enantiomers in the presence of NADPH by chiral high-pressure liquid chromatography. The inflammatory response secondary to the alkali burn was quantified through area measurements of reepithelialization and neovascularization. RESULTS: Alkali burn induced a time-dependent production of corneal epithelial 12-HETE and 12-HETrE. A marked increase in 12-HETE and 12-HETrE synthesis was evident at day 2 (from 22 +/- 7 to 139 +/- 22 ng/hour) after injury, increasing to 800 +/- 68 ng/hour at day 7. Chiral analysis revealed a time-dependent synthesis of the R and S enantiomers of 12-HETE (24% R, 76% S) and 12-HETrE (72% R, 28% S). Total arachidonate metabolism, as well as the formation of 12(R)-HETrE, correlated with the area of neovascularization (P < 0.01 and P < 0.02, respectively). CONCLUSIONS: The results demonstrate that surviving and regenerating epithelium has an increased capacity of synthesizing 12(S)-HETE and 12(R)-HETE and that maximal production of 12(R)-HETrE, a known direct and indirect angiogenic factor, coincides with neovascularization in this model. Thus, the lipoxygenase and cytochrome P450-dependent activities increased in a time-dependent manner, indicating the potential involvement of both pathways in the inflammatory response to alkali burn. The formation of significant quantities of 12(R)-HETE and 12(R)-HETrE is a novel finding in this alkali injury model.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

Mechanisms of killing spores of Bacillus subtilis by acid, alkali and ethanol.

AIMS: To determine the mechanisms of killing of Bacillus subtilis spores by ethanol or strong acid or alkali. METHODS AND RESULTS: Killing of B. subtilis spores by ethanol or strong acid or alkali was not through DNA damage and the spore coats did not protect spores against these agents. Spores treated with ethanol or acid released their dipicolinic acid (DPA) in parallel with spore killing and the core wet density of ethanol- or acid-killed spores fell to a value close to that for untreated spores lacking DPA. The core regions of spores killed by these two agents were stained by nucleic acid stains that do not penetrate into the core of untreated spores and acid-killed spores appeared to have ruptured. Spores killed by these two agents also did not germinate in nutrient and non-nutrient germinants and were not recovered by lysozyme treatment. Spores killed by alkali did not lose their DPA, did not exhibit a decrease in their core wet density and their cores were not stained by nucleic acid stains. Alkali-killed spores released their DPA upon initiation of spore germination, but did not initiate metabolism and degraded their cortex very poorly. However, spores apparently killed by alkali were recovered by lysozyme treatment. CONCLUSIONS: The data suggest that spore killing by ethanol and strong acid involves the disruption of a spore permeability barrier, while spore killing by strong alkali is due to the inactivation of spore cortex lytic enzymes. SIGNIFICANCE AND IMPACT OF THE STUDY: The results provide further information on the mechanisms of spore killing by various chemicals.

Acids↗

Alkali-labile sites and post-irradiation effects in single-stranded DNA induced by H radicals.

Single-stranded phiX174 DNA in aqueous solutions has been irradiated in the absence of oxygen, under conditions in which only H radicals react with the DNA. It was shown that H radical reactions result in breaks, which contribute approximately 10 per cent inactivation. Further, two types of alkali-labile sites are formed. One is lethal and gives rise to single-strand breaks by alkali and is most probably identical with post-irradiation heat damage and contributes about 33 per cent to the inactivation mentioned above. The other consists of non-lethal damage, partly dihydropyrimidine derivatives, and is converted to lethal damage by alkali. This follows from experiments in which the DNA was treated with osmium-tetroxide, which oxidizes thymine to 5,6-dihydroxy-dihydrothymine. Treatment with alkali of this DNA gives the same temperature dependence as found for the non-lethal alkali-labile sites in irradiated DNA. A similar temperature dependence is found for dihydrothymine and irradiated pyrimidines with alkali.

Alkalies↗

Interaction of collagen molecules from the aspect of fibril formation: acid-soluble, alkali-treated, and MMP1-digested fragments of type I collagen.

Collagen type I extracted with acid or digested with pepsin forms fibrils under physiological conditions, but this ability is lost when the collagen is treated with alkaline solution or digested with matrix metalloproteinase 1 (MMP1). When acid-soluble collagen was incubated with alkali-treated collagen, the fibril formation of acid-soluble collagen was inhibited. At 37 degrees C, at which alkali-treated collagen is denatured, the lag time was prolonged but the growth rate of fibrils was not affected. At 30 degrees C, at which the triple helical conformation of alkali-treated collagen is retained, the lag time was prolonged and the growth rate reduced. Heat-denatured alkali-treated collagen and MMP1-digested fragments have no inhibitory effect on the fibril formation of acid-soluble collagen. This means that the triple helical conformation and the molecular length are important factors in the interaction of collagen molecules and that alkali-treated collagen acts as a competitive inhibitor for fibril formation of collagen. We found that alkali-treated collagen and MMP1-digested fragments form fibrils that lack the D periodic banding pattern and twisted morphology under acidic conditions at the appropriate ionic strength. We also calculated the relative strengths of hydrophobic and electrostatic interactions between collagen molecules. When the hydrophobic interaction between linear collagen molecules was considered, we found a pattern of periodic maximization of the interactive force including the D period. On the other hand, the electrostatic interaction did not show the periodic pattern, but the overall interaction score affected fibril formation.

Acids↗

Alkali-resistant bacteria in root canal systems.

The aim of this study was to isolate and identify alkali-resistant bacteria from the dentin of infected root canals. Bacteria from homogenized dentin powder made up from infected root canal walls from human teeth were cultured on buffer-enriched Brain Heart Infusion agar supplemented with 4% sheep blood (BHI-blood agar), adjusted to pH 7.0, 9.0 or 10.0. Incubation took place for 7 days at 37 degrees C in an anaerobic glove box. Bacterial strains selected according to colony and morphology were subcultured in buffer-enriched BHI broth adjusted to pH 9.0, 10.0 or 11.0 to confirm their growth as alkali-resistant bacteria. Polymerase chain reaction amplification using specific primer sets and 16S rDNA sequence analysis was performed for identification of alkali-resistant isolates. In the present study, 37 teeth extracted from 37 patients were used for preparation of the dentin powder samples. Bacteria were detected in 25 samples when standard BHI-blood agars (pH 7.0) were used. Of these, 29 strains from 15 samples were alkali resistant, 25 strains growing at pH 9.0 and 4 at pH 10.0. The alkali-resistant strains included Enterococcus faecium (10 strains) and Enterococcus faecalis (2 strains), Enterobacter cancerogenus (1 strains), Fusobacterium nucleatum (1 strains), Klebsiella ornithinolytica (2 strains), Lactobacillus rhamnosus (2 strains), Streptococcus anginosus (2 strains), Streptococcus constellatus (3 strains), and Streptococcus mitis (2 strains). Three strains were also identified as bacteria of genus Firmicutes or Staphylococcus at the genus level. The present study showed that many bacterial species in infected root canal dentin were alkali-resistant at pH 9.0 and/or pH 10.0, and belonged mainly to the genus Enterococcus.

Adolescent↗

Acquisition of alkali-soluble fluoride by enamel through treatment with NaF-containing toothpastes in vitro.

The first aim of the present study was to examine if alkali-soluble fluoride (calcium fluoride-like material and adsorbed fluoride) forms when a NaF-containing toothpaste is applied on human enamel surface in vitro. The centrifuged supernatants of toothpastes dissolved in distilled water were used and four different commercial NaF-containing toothpastes were tested. The second aim was to investigate if pyrophosphate would interfere with the deposition of alkali soluble fluoride. The formation of alkali-soluble fluoride was determined by chemical analysis and visualized by scanning electron microscopy (SEM). It was ascertained that all tested toothpastes contained free fluoride according to the manufacturers' specifications. It was shown that they promoted deposition of alkali soluble fluoride on the enamel surface. The amount of deposited material increased with the time of exposure. The clinical effect of a NaF-containing toothpaste may thus well depend on an initial formation of alkali-soluble fluoride. Fluoride from this reservoir may adsorb onto the enamel crystals and inhibit further demineralization or increase the rate of remineralization during cariogenic challenges. It was also demonstrated that pyrophosphate did not interfere with the deposition of alkali soluble fluoride.

Adsorption↗

Effects of acid and alkali on the light absorption, energy transfer and protein secondary structures of core antenna subunits CP43 and CP47 of photosystem II.

The effects of acid and alkali treatment on the light absorption, energy transfer and protein secondary structure of the photosystem II core antenna CP43 and CP47 of spinach were investigated by the absorption spectra, fluorescence emission spectra and circular dichroism spectra. It has been found that acid treatment caused the appearance of absorption characteristic of pheophytin a (Pheo a), whereas alkali treatment induced a new absorption peak at 642 nm. The energy transfer between beta-carotene and chlorophyll a (Chl a) in CP43 was easily disturbed by alkali, whereas in CP47 was readily affected by acid. As to the effects on the secondary structure of proteins in CP43 and CP47, effects of acid were far less than those of alkali. Both acid and alkali disturbed the microenvironment of Chl a and interfered exciton interaction between Chl a molecules. It was suggested that acid and alkali affect the light absorption, energy transfer and protein secondary structure of CP43 and CP47 in a different way. H+ can permeate into the internal space of alpha-helix, change Chl a into Pheo a and disturb the microenvironment of pigments without damaging the secondary structure of protein, whereas OH- can induce the protein unfolding at first, then saponify Chl a to chlorophyllide and disturb the microenvironment of pigments.

Acids↗

[Experimental study on the treatment of corneal melting after alkali burn with GM 6001].

OBJECTIVE: To eva1uate the effect of synthetic inhibitors of matrix metalloproteinases (GM 6001) on the prevention of melting of rabbit corneas after alkali burn. METHODS: Severe and moderate rabbit alkali burns were made by different concentrations of NaOH. Corneas with severe or moderate alkali injuries were topically treated with 400 mg/L or 200 mg/L GM 6001 for 30 days. Vehicle was used as control. All corneas were evaluated for melting, opacity and other pathological changes. RESULTS: After severe alkali burns, all of the 8 corneas of the control group melted in 13 +/- 5 days, and 2 corneas perforated. Only did 2 corneas melt in 19 +/- 4 days after burn and not perforate in 400 mg/L GM 6001 group. The rates of corneal melting and perforation in 400 mg/L GM 6001 group were lower than that of the control (P < 0.05), and the initial time of melting was later than that of the control (P < 0.0l). After moderate alkali burn, all of the 6 corneas of control melted in 14 +/- 6 days, and 1 cornea perforated. Only did 2 of 200 mg/L GM 6001 treated corneas melt in 19 +/- 4 days without perforation after burn. The rate of corneal melting and the degree of corneal opacity were lower in 200 mg/L GM 6001 treated than that of the control, the difference being significant (P < 0.0l). Histologic section of GM 6001 treated corneas revealed much less collagen fiber destruction and inflammatory cell infiltration than that of the control. CONCLUSION: GM 6001 not only can prevent and delay the corneal melting after alkali burn, but also can reduce the destruction of corneal collagen fibers and infiltration of inflammatory cells in the corneal tissue.

Alkalies↗

Alkali secretion by isolated rabbit gastric mucosa: effects of non-steroidal anti-inflammatory drugs and prostaglandins.

The effects of aspirin, indomethacin and prostaglandins E2 and F2 alpha on the secretory and electrical activity of isolated rabbit gastric mucosa have been studied. Serosal side application of indomethacin (10(-5) M) or aspirin (3 X 10(-3) M) inhibited alkali secretion by fundic mucosa (mean +/- SE: 0.55 +/- 0.06 to 0.12 +/- 0.06 mumol X cm-2 X h-1, n = 6, p less than 0.01 and 0.28 +/- 0.06 to 0.11 +/- 0.03 mumol X cm-2 X h-1, n = 7, p less than 0.02 respectively) and antral mucosa (0.80 +/- 0.03 to 0.53 +/- 0.21 mumol X cm-2 X h-1, n = 5, p less than 0.01 and 0.75 +/- 0.23 to 0.47 +/- 0.20 mumol X cm-2 X h-1, n = 8, p less than 0.01 respectively). Mucosal and serosal side application of prostaglandin E2 or F2 alpha (10(-10) to 10(-4) M) had no effect on gastric alkali secretion. Serosal side 16,16 dimethyl E2 (10(-6) M) stimulated alkali secretion by fundic mucosa (0.90 +/- 0.20 to 1.50 +/- 0.30 mumol X cm-2 X h-1, n = 6, p less than 0.01) and abolished the inhibition of alkali production caused by indomethacin in fundic and antral mucosae. Inhibition of alkali secretion by aspirin was not modified by 16,16 dimethyl E2 pretreatment. The findings suggest that mucosal damage by aspirin and indomethacin may be mediated by inhibition of alkali secretion and that the protective action of various prostaglandins are only partly related to effects on this secretion.

Alkalies↗

Urinary citrate, bone resorption and intestinal alkali absorption in stone formers with fasting hypercalciuria.

Reduced citrate in urine and increased fasting excretion of calcium are abnormalities frequently reported in stone forming (SF) patients. Increased dietary acid (or reduced alkali) introduction or absorption may be a potential cause of both these pathological findings. To test this hypothesis, we studied 64 SF patients (32 with fasting hypercalciuria (FH) and 32 without FH (NFH)). After a basal evaluation for nephrolithiasis, while on a 500 mg calcium diet, they were evaluated for: (1) daily intestinal alkali absorption (IAA), by urinary electrolyte excretion; (2) basal concentrations of PTH, calcitonin (CT) and 1,25(OH)2-VitD; (3) oral calcium load for evaluation of changes in calcium and hydroxyproline urinary excretions; (4) intestinal calcium absorption (18 patients), with double curve analysis (stable Sr as tracer); and (5) changes in citrate excretion after an alkali load (50 mEq of a mixture of calcium gluconate, lactate and carbonate) in 10 patients. The results demonstrated: (1) FH stone formers had reduced citrate excretion and lower mean IAA levels than NFH stone formers; (2) FH stone formers also had higher bone resorption levels with lower PTH and higher CT levels; (3) IAA levels were related to both citrate excretion and bone turnover indices; and (4) the increases in citrate excretion after oral alkali load were strictly related to basal IAA values (index of alkali absorption and/or generation after oral load), demonstrating that a different absorptive capacity of alkali rather than a different dietary content may underlie these metabolic abnormalities.

Adult↗

Recognition by two-dimensional thin-layer chromatography and densitometric quantification of alkali-labile gangliosides from the brain of different animals.

A simple method for recognition and quantification of alkali-labile gangliosides is described. The method was worked out using authentic alkali-labile gangliosides in pure form (9-O-Ac-GT1b; 9-O-Ac-GQ 1b; lactone form of GD 1b) and applied to ganglioside mixtures from the brain of mouse, rat, rabbit, pig, and pigeon. The method consists of two-dimensional thin-layer chromatography on silica gel high-performance thin-layer chromatography plates employing the same solvent, chloroform/methanol/0.2% aqueous CaCl2, 50/40/10, for both runs. Prior to the second run the plate is exposed at room temperature for 5 h to ammonia vapors in order to split alkali-labile linkages. At the end of chromatography alkali-stable gangliosides appear lined along a diagonal starting from the origin; the spots corresponding to alkali-labile gangliosides lie out of the diagonal and can be individually detected and quantified on the basis of their sialic acid content. Up to 15 different spots, corresponding to as many alkali-labile gangliosides, can be recognized by this procedure.

Animals↗

Characteristics of polymorphonuclear leukocyte infiltration into the alkali burned eye and the influence of sodium citrate.

Polymorphonuclear leukocytes (PMNs) are considered to play a central role in the corneal ulceration process subsequent to an alkali burn. We have described the time course of PMN infiltration into the ocular tissues following an alkali burn. In addition, we examined the effect of sodium citrate upon the accumulation of PMNs in the alkali burned cornea. The accumulation of PMNs into the cornea and iris-ciliary body was quantified by measuring myeloperoxidase (MPO), an enzyme marker for these inflammatory cells. Leukocytes in aqueous humor aspirates and corneal washes were counted directly under a microscope. In the alkali burned cornea, we found an initial transient, yet substantial, infiltration of PMNs, peaking at about 12-24 hr and limited to the peripheral cornea; this subsided by about 72 hr. By 14 days, the MPO activity, and hence the number of leukocytes, had risen again, and by 21 days the level had increased by several fold. Qualitatively similar biphasic patterns of leukocyte infiltration were observed in the iris-ciliary body and aqueous humor. Leukocyte numbers in corneal washes only increased between 4-24 hr following the alkali burn. The exceptionally high degree of leukocyte infiltration into the cornea at 21 days corresponded with the presence of ulceration. Topical administration of sodium citrate (10%) inhibited the early and late phase of PMN accumulation in the alkali burned cornea, i.e. at 24 hr (-63%) and 21 days (-92%). The inhibition of PMN infiltration by sodium citrate correlates with the reduced corneal ulceration observed following treatment with this compound.

Animals↗

Comparison of induction and repair of adducts and of alkali-labile sites in human lymphocytes and granulocytes after exposure to ethylating agents.

A comparative study has been made of the induction and repair of adducts and alkali-labile sites in the DNA of human lymphocytes and granulocytes exposed to the ethylating agents N-ethyl-N-nitrosourea (ENU) and diethyl sulphate (DES). To evaluate these damages, the human blood cells were treated with highly 3H-labelled ENU and DES, and the resulting 3H-ethyl adducts were analysed via HPLC. Alkali-labile sites introduced in the DNA during treatment with non-radioactive ENU and DES were detected by alkaline elution with fluorometric quantitation of the DNA in the eluted fractions. All known adducts induced by ENU and DES could be detected by the HPLC methods applied. Furthermore, these adducts were separated from a number of unidentified compounds, because of the improved resolution on the columns used. Most of the adducts were rather persistent during a subsequent incubation period of up to 20 h after treatment, but some partly disappeared (7-ethyladenine and 3-ethyladenine). The induction of alkali-labile sites in lymphocytes and granulocytes was very similar, but the kinetics of the removal of these sites appeared to be quite different. In granulocytes there was hardly any repair, whereas in lymphocytes, particularly after ENU treatment, a substantial and relatively fast repair was observed. Induction of alkali-labile sites in human lymphocytes and granulocytes occurred also at 0 degrees C; the data suggest that this kind of damage is not a result of enzymic repair processes. A comparison of the induction and the repair of alkali-labile sites in lymphocytes and granulocytes with those of the various ethyl adducts did not give a clue as to the identity of the adduct that could be responsible for the lability towards alkali.

Alkylating Agents↗

Chemistry of the alkali-labile lesion formed from iron(II) bleomycin and d(CGCTTTAAAGCG).

Two sets of products are formed from DNA upon treatment with Fe(II).bleomycin + O2. One set, which is believed to derive from a C-4' hydroperoxy derivative of the DNA deoxyribose moiety, includes the four possible base propenals, as well as DNA oligomers having deoxynucleoside 3'-(phosphoro-2"-O-glycolates) at their 3'-termini. The other set of products consists of free bases and alkali-labile lesions, the latter of which had not previously been characterized structurally. By use of the self-complementary dodecanucleotide d(CGCTTTAAAGCG) having a site modified by Fe-bleomycin three nucleotides from the 5'-end, it has been possible to characterize the alkali-labile product as a C-4' hydroxyapurinic acid. When the bleomycin-treated dodecanucleotide was treated with agents that effected decomposition of the alkali-labile lesion, products of the form CpGpx were obtained, and these proved useful for structural characterization of the alkali-labile lesion. Treatment with alkali produced CpGpx, where x was 2,4-dihydroxycyclopentenone. Alternatively, treatment with hydrazine provided a pyridazine derivative, and aqueous alkylamines led to formation of CpGp itself. The structures of all dinucleotides produced from the alkali-labile lesion were verified by direct comparison with authentic synthetic samples.

Base Sequence↗

A Convenient Synthetic Strategy toward Heavy Alkali Metal Bis(trimethylsilyl)phosphides: Crystal Structures of the Ladder-Type Polymers [A(thf)P(SiMe(3))(2)](infinity) (A = K, Rb, Cs).

A series of highly reactive heavy alkali metal phosphides was prepared by treating trimethylsilyl-substituted phosphines with alkali metal tert-butyl alcoholates. The compounds are formed in excellent yield and purity, and the side product can be easily removed in a vacuum. The high synthetic potential of this reaction route was further shown by utilizing excess alkali metal tert-butyl alcoholates in reaction with silyl substituted phosphines. In all cases, only monometalated products were isolated. In the course of this work the crystal structures of the bis(trimethylsilyl)phosphides [K(thf)P(SiMe(3))(2)](infinity), 1a, [Rb(thf)P(SiMe(3))(2)](infinity), 1b, and [Cs(thf)P(SiMe(3))(2)](infinity), 1c, were obtained. The compounds display polymeric ladder-type structures. Compounds 1a,b are isomorphous, while compound 1c displays a slightly altered local geometry. Despite small differences in local geometry, the coordination spheres for the phosphorus atoms and the alkali metal are fairly similar. The five coordinate phosphorus atoms are connected to three alkali metal centers in addition to two trimethylsilyl groups. The alkali metals are four coordinate with ligations to three phosphorus centers in addition to one thf oxygen donor. Compounds 1a-c were characterized using elemental analysis, NMR spectroscopy, and X-ray crystallography. Crystal data with Mo Kalpha (lambda = 0.710 73 Å) at 150 K are as follows: 1a, a = 6.4261(2) Å, b = 12.4119(2) Å, c = 21.5447(4) Å, V = 1718.41(7) Å(3), Z = 4, orthorhombic, space group P2(1)2(1)2(1), 3427 independent reflections, R1 (all data) = 0.0351; 1b, a = 6.5338(2) Å, b = 12.5664(3) Å, c = 21.5537(5) Å, V = 1769.70(8) Å(3), Z = 4, orthorhombic, space group P2(1)2(1)2(1), 4195 independent reflections, R1 (all data) = 0.0776; 1c, a = 11.3515(1) Å, b = 22.3445(3) Å, c = 7.2501(1) Å, beta = 96.017(1) degrees, V = 1828.81(4) Å(3), Z = 4, monoclinic, space group P2(1)/c, 4343 independent reflections, R1 (all data) = 0.0811.

Journal Article↗

Effect of different forms of alkali treatment on specific fermentation inhibitors and on the fermentability of lignocellulose hydrolysates for production of fuel ethanol.

Treatment with alkali, particularly overliming, has been widely used as a method for the detoxification of lignocellulose hydrolysates prior to ethanolic fermentation. However, the mechanisms behind the detoxification effect and the influence of the choice of cation have not been well understood. In this study, a dilute acid hydrolysate of spruce and an inhibitor cocktail consisting of six known inhibitors were used to investigate different alkali detoxification methods. The various treatments included the addition of calcium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia to pH 10.0 and subsequent adjustment of the pH to 5.5 with either sulfuric or hydrochloric acid as well as treatment with the corresponding amounts of calcium, sodium, and potassium as sulfate or chloride salts at pH 5.5. An RP-HPLC method was developed for the separation of 18 different inhibitors in the hydrolysate, including furaldehydes and phenolics. Detection and quantification were carried out by means of UV, DAD, and ESI-MS in negative mode. Treatment of the spruce hydrolysate with alkali resulted in up to approximately 40% decrease in the concentration of furaldehydes. The effects on the aromatic compounds were complex. Furthermore, SFE was performed on the precipitate formed during alkali treatment to evaluate the inhibitor content of the precipitate, and the following RP-HPLC analysis implied that potential inhibitors were removed mainly through conversion rather than through filtration of precipitate. Parallel experiments in which sulfuric acid or hydrochloric acid was used for acidification to pH 5.5 after alkali treatment indicated that the choice of anion did not affect the removal of inhibitors. Detoxification with calcium hydroxide and ammonia resulted in better fermentability using Saccharomyces cerevisiae than detoxification with sodium hydroxide. The results from the experiments with the inhibitor cocktail indicated that the positive effects of alkali treatment are difficult to explain by removal of the inhibitors only and that possible stimulatory effects on the fermenting organism warrant further attention.

Acetic Acid↗

Influence of thioketo substitution on the properties of uracil and its noncovalent interactions with alkali metal ions: threshold collision-induced dissociation and theoretical studies.

Experimental and theoretical studies are carried out to determine the influence of thioketo substitution on the properties of uracil and its noncovalent interactions with alkali metal ions. Bond dissociation energies of alkali metal ion-thiouracil complexes, M(+)(SU), are determined using threshold collision-induced dissociation techniques in a guided ion beam mass spectrometer, where M(+) = Li(+), Na(+), and K(+) and SU = 2-thiouracil, 4-thiouracil, 2,4-dithiouracil, 5-methyl-2-thiouracil, and 6-methyl-2-thiouracil. Ab initio electronic structure calculations are performed to determine the structures and theoretical bond dissociation energies of these complexes and provide molecular constants necessary for thermodynamic analysis of the experimental data. Theoretical calculations are also performed to examine the influence of thioketo substitution on the acidities, proton affinities, and A::SU Watson-Crick base pairing energies. In general, thioketo substitution leads to an increase in both the proton affinity and the acidity of uracil. 2-Thio substitution generally results in an increase in the alkali metal ion binding affinities but has almost no affect on the stability of the A::SU base pair. In contrast, 4-thio substitution results in a decrease in the alkali metal ion binding affinities and a significant decrease in the stability of the A::SU base pair. In addition, alkali metal ion binding is expected to lead to an increase in the stability of both single-stranded and double-stranded nucleic acids by reducing the charge on the nucleic acid in a zwitterion effect as well as through additional noncovalent interactions between the alkali metal ion and the nucleobases.

Journal Article↗