Kjeldahl Determination of Nitrogen without Distillation.

Hashmi, M. H.; Ali, Ehsan; Umar, Muhammad

doi:10.1021/ac60188a031

Cited by 22 publications

(12 citation statements)

References 15 publications

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“…Sugars were determined according to the method of Dubois et al (39). Esters were determined by the method of Snyder and Stephens (40), long-chain bases by the method of Lauter and Trams (41), glycerylethers by the method of Hanahan and Watts (42), and nitrogen according to the method of Hashmi et al (43). Mild alkaline hydrolysis (deacylation) was performed with NaOH (1.2 N) as described previously (21).…”

Section: Methodsmentioning

confidence: 99%

Sphingophosphonolipids, phospholipids, and fatty acids from aegean jellyfish Aurelia aurita

Kariotoglou¹,

Mastronicolis²

2001

Lipids

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The goal of this study is to elucidate and identify several sphingophosphonolipids from Aurelia aurita, an abundant but harmless Aegean jellyfish, in which they have not previously been described. Total lipids of A. aurita were 0.031-0.036% of fresh tissue, and the lipid phosphorus content was 1.3-1.7% of total lipids. Phosphonolipids were 21.7% of phospholipids and consisted of a major ceramide aminoethylphosphonate (CAEP-I; 18.3%), as well as three minor CAEP (II, III, IV) methyl analogs at 1.3, 1.1, and 1.0%, respectively. The remaining phospholipid composition was: phosphatidylcholine, 44.5%, including 36.2% glycerylethers; phosphatidylethanolamine, 18.6%, including 4.5% glycerylethers; cardiolipin, 5.6%; phosphatidylinositol, 2.6%; and lysophosphatidylcholine, 5.0%. In CAEP-I, saturated fatty acids of 14-18 carbon chain length were 70.8% and were combined with 57.3% dihydroxy bases and 23.4% trihydroxy bases. The suite of the three minor CAEP methyl analogs were of the same lipid class based on the head group, but they separated into three different components because of their polarity as follows: CAEP-II and CAEP-III differentiation from the major CAEP-I was mainly due to the increased fatty acid unsaturation and not to a different long-chain base, but the CAEP-IV differentiation from CAEP-I, apart from fatty acid unsaturation, was due to the increased content of hydroxyl groups originated from both hydroxy fatty acids and trihydroxy long-chain bases. Saturated fatty acids were predominant in total (76.7%), polar (83.0%), and neutral lipids (67.6%) of A. aurita. The major phospholipid components of A. aurita were comparable to those previously found in a related organism (Pelagia noctiluca), which can injure humans.

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Section: Methodsmentioning

confidence: 99%

Sphingophosphonolipids, phospholipids, and fatty acids from aegean jellyfish Aurelia aurita

Kariotoglou¹,

Mastronicolis²

2001

Lipids

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“…Each extracted band of residual lipids was used for analytical methods and 1 H-NMR spectroscopy. Total phosphorus (33), esters (47), nitrogen (20), and glycerol (30) analysis was performed as described previously. Deacylation (27,54) was also performed in 0.1 ml of NaOH (1.2 N) in 50% (vol/vol) methanol at 45°C for 20 min.…”

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confidence: 99%

Coordinated Regulation of Cold-Induced Changes in Fatty Acids with Cardiolipin and Phosphatidylglycerol Composition among Phospholipid Species for the Food Pathogen Listeria monocytogenes

Mastronicolis

Arvanitis

Karaliota

et al. 2008

Appl Environ Microbiol

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We present here the structural identification of four phospholipid (Phl) classes in Listeria monocytogenes, the fatty acid (FA) composition for each individual Phl species, and a description of cold-induced FA changes. Cardiolipin (48.5%) and phosphatidylglycerol (18.1%) are dominated by anteiso-FA, and the previously recognized branched FA chain shortening by cold was observed singularly in these Phls. Phosploaminolipid (19.9%) and phosphatidylinositol, (9.1%) are significantly different, containing significant amounts of straightchain FA. These findings are supported by nuclear magnetic resonance analysis.The bacterium Listeria monocytogenes, one of the leading causes of food-borne illness (15), can adapt to cold and salinity (9,10,31,46,53) and can survive even on dust or flakes of organic material (34). Listeria is characterized by Ͼ85% branched-chain fatty acids (FA), anteiso-15:0 (a-15:0) and anteiso-17:0 (a-17:0). Cells grown in the cold (5°C) contain significantly less a-17:0 than those grown at higher temperatures (4,8,37,43,44,57). A cryotolerance element of Listeria is also its ability to use cryoprotectant osmolytes (31), a property shared by other organisms (2, 3, 12, 21, 23). The critical role of odd numbered anteiso-FA in influencing the lower-temperature growth limits has recently been reported (14,19,25). We have reported previously (39) that Listeria spp. can be cold adapted by an increased content (30%) of neutral lipids (NL) among total lipids (TL) and an increase in the a-15:0/a-17:0 FA ratio (FAr) of TL, polar lipids (PL), and NL (10-, 10-, and 7-fold, respectively), as well as by an increase in FAr (38) for each NL subclasses 1,2-diglyceride, 1,3-diglyceride and free FA (6-, 5-, and 8-fold, respectively).This study is a continuation (35, 36) of an investigation for the structural characterization of the major phospholipid (Phl) classes of L. monocytogenes, in order to (i) elucidate the isolation and quantification of each of class (cells at 30°C), (ii) evaluate the cold temperature (5°C) effect on each individual Phl class FA composition, and (iii) confirm the findings by 1 H-nuclear magnetic resonance (NMR) analysis.

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“…A value of k 1a (eq 14) of (2.3 ± 1.7) × 10 -3 M -1 s -1 was determined from our five data points (buffer free) from p[H + ] 3.6 to 7.4 (Table ). The dotted line in Figure from pH 7 to 14 is obtained by using a p K a value of 8.80 for HOBr and eq 17, where k 1b (eq 16) is evaluated as (6 ± 4) × 10 -7 M -1 s -1 from literature values at pH 12−14. ,,, A value for the k 1ab (eq 15) term was estimated to be 2.3 × 10 -4 M -1 s -1 from an extrapolation of general-base-assisted rate constants (to be discussed). The solid line plotted in Figure shows this predicted contribution from pH 10 to 12.…”

Section: Resultsmentioning

confidence: 99%

“…Literature values for k 1 and k 2 are shown in Table . − The reaction involving [Br(III)] in eq 2 is generally regarded as being faster than that of eq 1. Reported activation energies for eq 1 are 58 ± 3 kJ/mol in 1 M H 2 SO 4 15 and 81.2 kJ/mol 11 and 95 ± 2 kJ/mol in base.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Hypobromous Acid Disproportionation

Beckwith

Margerum

1997

Inorg. Chem.

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The kinetics of aqueous hypobromous acid disproportionation are measured at 25.0 degrees C from p[H(+)] 0.2 to 10.2. The reactions are second order in HOBr with a maximum rate at pH 3-8. The rate of disproportionation decreases significantly above pH 8 as OBr(-) forms. Another suppression observed below pH 3 is attributed to the reversibility of initial steps in the decomposition. The rate expression is given by -d[Br(I)]/dt = n{(c/(c + [H(+)])k(1a) + k(B)[B])[HOBr](2) + k(1b)[OBr(-)](2)}, where k(1a) = 2 x 10(-)(3) M(-)(1) s(-)(1), k(B)[B] is a general-base-assisted pathway, k(1b) = 6 x 10(-)(7) M(-)(1) s(-)(1), n is a stoichiometric factor that ranges from 2 to 5, and c is a ratio of rate constants that is equal to 0.03 M. Decomposition is catalyzed by HPO(4)(2)(-) (k(B) = 0.05 M(-)(2) s(-)(1)) and by CO(3)(2)(-) (k(B) = 0.33 M(-)(2) s(-)(1)). Above pH 8, the first observable product is BrO(2)(-) (initially n = 2). Below pH 4, n = 5 due to Br(2) and BrO(3)(-) formation. From pH 4 to 7, n varies from 5 to 3. A detailed mechanism is presented.

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Kjeldahl Determination of Nitrogen without Distillation.

Cited by 22 publications

References 15 publications

Sphingophosphonolipids, phospholipids, and fatty acids from aegean jellyfish Aurelia aurita

Sphingophosphonolipids, phospholipids, and fatty acids from aegean jellyfish Aurelia aurita

Coordinated Regulation of Cold-Induced Changes in Fatty Acids with Cardiolipin and Phosphatidylglycerol Composition among Phospholipid Species for the Food Pathogen Listeria monocytogenes

Kinetics of Hypobromous Acid Disproportionation

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