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1.
Substrate specificity of the acyltransferase activity of the lipase (EC 3.1.1.3) fromCandida parapsilosis CBS 604 was studied in aqueous media. The specificity toward both acid and alcohol parts of a large number of acylglycerols
and aliphatic esters was investigated. This lipase showed a high activity in the presence of esters with long-chain fatty
acids and particularly unsaturated fatty acids with acis-Δ9 double bond. It was observed that the activity profile depended not only on the alcohol part of the acyl ester, but also
on the temperature of the reactant medium. The best lipid substrates had their melting point between −40 to +20°C, 14 to 18
carbon atoms in the acyl group and 1 to 4 carbon atoms in the alkyl group. The enzyme, defined as an acyltransferase in a
previous paper, showed a high affinity for primary and secondary alcohols with a short carbon chain (1 to 5 carbon atoms)
as acyl acceptors. The influence of free alcohols in the reactant medium on the hydrolysis and alcoholysis activities of the
enzyme is discussed. Two phenomena seem to be involved, depending on the alcohol: competition with water for the acyltransfer
reaction and lipid substrate dilution when the alcohol places at the oil/water interface. 相似文献
2.
Douglas G. Hayes Robert Kleiman 《Journal of the American Oil Chemists' Society》1996,73(11):1385-1392
Lesquerolic acid was and α,Ω-diol esters were synthesized via immobilizedRhizomucor miehei lipase-(Lipozyme) catalyzed esterification of lesquerolic acid and alcoholysis of lesquerella oil. For each wax ester synthesis,
when alcohol substrate was present at a slight (ca. 20%) stoichiometric excess and water content was kept low, over 94% of
the hydroxy acyl groups were esterified. The extent of reaction and the ratio of monoester to diester produced for α,Ω-diol
reactions was controlled by the solubility of diol in the medium. This latter quantity increased as alcoholysis proceeded
due to the formation of partial glycerides and monoesters, which increased the polarity of the medium. Alcoholysis reactions
were significantly slower when the medium diol content was above saturation. As the diol chainlength increased, diol solubilization
decreased, the ratio of monoester to diester decreased, and the extent of hydrolysis increased. Alcoholysis reactions involving
either fatty alcohols or diols suffered from acyl migration, which lowered the purity of lesquerolic acid esters. Several
lesquerolic acid esters, synthesized on a preparative scale and purified via column chromatography, were evaluated for their
properties: density, viscosity, and melting point. Potential applications for lesquerolic acid esters are discussed. 相似文献
3.
Yanis Caro Fabrice Turon Pierre Villeneuve Michel Pina Jean Graille 《European Journal of Lipid Science and Technology》2004,106(8):503-512
We have examined the possibility of producing analogs of medium‐chain triglycerides (MCT) from copra oil, i.e. a triacylglycerol mixture with a high content of medium‐chain fatty acid moieties (C6–C10). A two‐step enzymatic process was used in which copra triacylglycerols were first split with papain lipase by alcoholysis with an alkyl alcohol and then subjected to interesterification with the alkyl esters recovered using papain lipase. Effects of temperature, water activity content, substrate ratio, biocatalyst amount, and alcohol chain length were also investigated. On the one hand, the sn‐3 stereoselectivity of the lipase in the alcoholysis of copra oil with butanol has permitted a direct enrichment of caproic, caprylic and capric moieties in the synthesized butyl esters. Thus, in the batch reactor, the reaction led to about 31% conversion of the oil after 24 h, and the content of C6–C10 acids in the synthesized esters increased from about 16% in the starting oil to almost 42%. A similar enzymatic alcoholysis in a packed‐bed column bioreactor gave 31% conversion of the oil after 120 min of reactor residence time. The reaction was also very selective because the C6–C10 fatty acyl groups represented about half of the newly formed butyl esters, whereas they accounted for only 16% of total fatty acids in the starting oil. On the other hand, the transesterification of the alkyl esters recovered (highly enriched in C6–C10 fatty acyl groups) with native copra oil directly led to an increase in the content of MCT in the oil, from 18 mol‐% at the beginning of the reaction to 61 mol‐% of MCT after a time period of 72 h in the batch reactor. 相似文献
4.
Wax esters were isolated from commercial orange roughy (Hoplostethus atlanticus) oil by column chromatography and fractionated by argentation thin layer chromatography. Following transesterification, the
resultant fatty acid methyl esters and fatty alcohols were analyzed by gas chromatography. both acyl- and alkyl-moieties were
mainly of the monoene structure within the 16∶1–22∶1 range. After derivatization, the positions of the double bonds of even
numbered fatty acid and fatty alcohol isomers were located by chromatography-mass spectrometry and compared.
Results of these positional analyses indicate that the primary desaturation reactions takes place in the Δ9 position of pre-existing
(C14 to C24) acyl chains. It is proposed that acyl components from 18∶1 are subjected to chain elongation to form a mixture of 24∶1 isomers
as the final product. Apart from the 24∶1 acyl moiety of the wax esters, in which the double bond was almost exclusively in
the Δ15 position, de novo biosynthetic reactions on acids and alcohols appear to yield related acyl- and alkyl-moieties of
resynthesized wax esters. 相似文献
5.
Marine fish have an absolute dietary requirement for C20 and C22 highly unsaturated fatty acids. Previous studies using cultured cell lines indicated that underlying this requirement in
marine fish was either a deficiency in fatty acyl Δ5 desaturase or C18–20 elongase activity. Recent research in turbot cells found low C18–20 elongase but high Δ5 desaturase activity. In the present study, the fatty acid desaturase/elongase pathway was investigated
in a cell line (SAF-1) from another carnivorous marine fish, sea bream. The metabolic conversions of a range of radiolabeled
polyunsaturated fatty acids that comprised the direct substrates for Δ6 desaturase ([1-14C]18∶2n−6 and [1-14C]18∶3n−3), C18–20 elongase ([U-14C]18∶4n−3), Δ5 desaturase ([1-14C]20∶3n−6 and [1-14C]20∶5n−3), and C20–22 elongase ([1-14C]20∶4n−6 and [1-14C]20∶5n−3) were utilized. The results showed that fatty acyl Δ6 desaturase in SAF-1 cells was highly active and that C18–20 elongase and C20–22 elongase activities were substantial. A deficiency in the desaturation/elongation pathway was clearly identified at the level
of the fatty acyl Δ5 desaturase, which was very low, particularly with 20∶4n−3 as substrate. In comparison, the apparent activities
of Δ6 desaturase, C18–20 elongase, and C20–22 elongase were approximately 94-, 27-, and 16-fold greater than that for Δ5 desaturase toward their respective n−3 polyunsaturated
fatty acid substrates. The evidence obtained in the SAF-1 cell line is consistent with the dietary requirement for C20 and C22 highly unsaturated fatty acids in the marine fish the sea bream, being primarily due to a deficiency in fatty acid Δ5 desaturase
activity. 相似文献
6.
Ran Ye Sang-Hyun Pyo Douglas G. Hayes 《Journal of the American Oil Chemists' Society》2010,87(3):281-293
Saccharide–fatty acid esters, important biobased and biodegradable emulsifiers in foods, cosmetics, and pharmaceuticals, were
produced with high yields and productivity via immobilized Rhizomucor miehei lipase-catalyzed esterification in solvent-free systems at 65 °C. Preliminary experiments demonstrated high rates of reaction
occurred in the presence of acetone near or above its boiling point, due to the formation of 10–200 μm suspensions of saccharide
particles. Subsequently, a two-step process was developed to produce a solvent-free supersaturated solution of 1.5–2.0 wt%
saccharide that remained stable for ≥10–12 h. The solvent-free suspensions were used in a bioreactor system at 65 °C, consisting
of a reservoir open to the atmosphere that contained molecular sieves, a peristaltic pump, and a packed bed bioreactor, operated
under continuous recirculation. At 10 h intervals, suspensions were re-formed by treating the substrate/product mixture with
additional acyl acceptor and applying strong agitation. Using this system and approach, a product mixture containing 88% fructose
oleate was formed, of which 92% was monoester, within 6 days. This equates to a productivity of 0.2 mmol h−1 g−1, which is similar to values reported for synthesis in the presence of solvent. 相似文献
7.
Inhibition of the hormone-sensitive lipase in adipose tissue by long-chain fatty acyl coenzyme A 总被引:1,自引:0,他引:1
The effects of free fatty acids and fatty acyl esters of coenzyme A and carnitine on the activity of a hormone-sensitive lipase
preparation made from pigeon adipose tissue were determined. Oleic acid (100 μM) resulted in a 40% inhibition of lipase activity
A more potent inhibition of lipase activity was seen with long-chain fatty acyl CoA compounds. The concentration required
for half-maximal inhibition with oleoyl CoA and palmitoyl CoA was 25–40 μM, whereas palmitoyl carnitine stimulated lipase
activity. Activated lipase preparations (preincubated with Mg2+, ATP, cyclic AMP and protein kinase) were 4–6 times more sensitive to inhibition by oleoyl CoA than were nonactivated preparations.
An increase in cellular levels of fatty acyl coenzyme A could, therefore, contribute to the feedback inhibition of lipolysis
in adipose tissue. 相似文献
8.
The presence of long chain acyl:CoA synthetases in mammalian microsomes and mitochondria has been established previously by
Aas (Biochim. Biophys. Acta 231, 32–47 [1971]). The presence of a plasma membrane-associated enzyme was investigated in rat hepatocyte plasma membranes,
where an enzyme exhibiting high activity and with a preferred substrate of 18-carbon chain length was discovered. The results
are consistent with the presence of a single enzyme. The effect of the degree of unsaturation of the fatty acid substrates
was not as pronounced as that arising from the length of the carbon chain. The pattern of substrate preference of the enzyme
was ω3 polyenoic fatty acids >ω6 polyenoic acids >ω9 monoenoic acids > saturated acids. This may relate to the similar substrate
preference pattern exhibited by the fatty acyl desaturase enzymes. The role played by long chain acyl:CoA synthetase in hepatocyte
metabolism is uncertain, but it may relate to the incorporation of polyenoic fatty acids from the circulation into cell membranes
and the trapping of other fatty acids within the cell for further metabolism. 相似文献
9.
Euglena gracilis, a unicellular phytoflagellate, can accumulate a large amount of medium-chain wax esters under anaerobic growth conditions.
Here we report the identification and characterization of two genes involved in the biosynthesis of wax esters in E. gracilis. The first gene encodes a fatty acyl-CoA reductase (EgFAR) involved in the conversion of fatty acyl-CoAs to fatty alcohols and the second gene codes for a wax synthase (EgWS) catalyzing esterification of fatty acyl-CoAs and fatty alcohols, yielding wax esters. When expressed in yeast (Saccharomyces cerevisiae), EgFAR converted myristic acid (14:0) and palmitic acid (16:0) to their corresponding alcohols (14:0Alc and 16:0Alc) with
myristic acid as the preferred substrate. EgWS utilized a broad range of fatty acyl-CoAs and fatty alcohols as substrates
with the preference towards myristic acid and palmitoleyl alcohol. The wax biosynthetic pathway was reconstituted by co-expressing
EgFAR and EgWS in yeast. When myristic acid was fed to the yeast, myristyl myristate (14:0–14:0), myristyl palmitoleate (14:0–16:1), myristyl
palmitate (14:0–16:0) and palmityl myristate (16:0–14:0) were produced. These results indicate EgFAR and EgWS are likely the
two enzymes involved in the biosynthesis of medium-chain wax esters in E. gracilis. 相似文献
10.
Hydroxy fatty acid (HFA) esters of long-chain alcohols, such as hydroxy stearates, have potential applications from lubricants
to cosmetics. These esters were synthesized enzymatically to overcome the problems associated with chemical processes. An
immobilized lipase, Rhizomucor miehei, was employed as catalyst in the esterification reaction between hydroxy-stearic acid as a source of HFA and monohydric fatty
alcohols (C8–C18). The yields of esters were in the range of 82–90% by conducting the reactions at 65±2°C, 2–5 mm Hg pressure, and 10% lipase
concentration. The products were analyzed by infrared spectroscopy, and some of their analytical characteristics were determined. 相似文献
11.
Cetane numbers (C#) for the homologous series of straight-chain, saturated n-alcohols, C5−C12 and C14, were determined according to ASTM D 613. Measured C# ranged from 18.2–80.8 and increased linearly with carbon number (CN).
Regression analyses developed equations that related various physical properties or molecular characteristics of these alcohols
to calculated C#. The degree of relationship between measured and calculated C# was expressed as R2. The decreasing order of the precision with which these properties correlated with C# was: boiling point (bp)>melting point
(mp)>CN>heat of combustion (HG)>refractive index (n20
D)>density (d). This ranking was based upon R2 (0.99–0.96) and the Average % error (2.8–7.2%). C# were also determined for straight-chain homologs of saturated methyl esters
with CN of 6, 10, 12, 14, 16 and 18. C# ranged from 18.0–75.6 and increased curvilinearly with CN. Equations were also developed
that related physical properties of these esters to C#. The precision with which these properties correlated with C# was:
bp>viscosity (V)>heat of vaporization (HV)>HG>CN>surface tension (ST)>mp>n20
D>d. R2 ranged from 0.99 for bp to 0.98 for d. Equations for the alcohols were linear or quadratic, while equations for the esters
were linear, quadratic or cubic based upon statistical considerations that included a Student’s t-test. With related physical
properties and these equations, accurate predictions of C# can be made for saturated n-alcohols and methyl esters. 相似文献
12.
Sharon A. Spurvey S. P. J. Namal Senanayake Fereidoon Shahidi 《Journal of the American Oil Chemists' Society》2001,78(11):1105-1112
Oils containing both n−3 and n−6 fatty acids have important clinical and nutritional applications. Lipase-catalyzed acidolysis
of seal blubber (SBO) and menhaden oils (MO) with γ-linolenic acid (GLA) was carried out in hexane. The process variables
studied for lipase-catalyzed reaction were concentration of enzyme (100–700 units/g of oil), reaction temperature (30–60°C),
reaction time (0–48 h), and mole ratio of GLA to triacylglycerols (TAG) (1∶1 to 5∶1). Two lipases chosen for acidolysis reaction
were from Pseudomonas species (PS-30) and Mucor miehei. Lipase PS-30 was chosen over Mucor (also known as Rhizomucor) miehei to catalyze the acidolysis reaction owing to higher incorporation of GLA. For the acidolysis reaction, optimal conditions
were a 3∶1 mole ratio of GLA to TAG, reaction temperature of 40°C, reaction time of 24 h, and an enzyme concentration of 500
units/g of oil. Under these conditions, incorporation of GLA was 37.1% for SBO and 39.6% for MO. 相似文献
13.
Effects of dietary vegetable oil on atlantic salmon hepatocyte fatty acid desaturation and liver fatty acid compositions 总被引:5,自引:0,他引:5
Fatty acyl desaturase activities, involved in the conversion of the C18 EFA 18∶2n−6 and 18∶3n−3 to the highly unsaturated fatty acids (HUFA) 20∶4n−6, 20∶5n−3, and 22∶6n−3, are known to be under
nutritional regulation. Specifically, the activity of the desaturation/elongation pathway is depressed when animals, including
fish, are fed fish oils rich in n−3 HUFA compared to animals fed, vegetable oils rich in C18 FFA. The primary aims of the present study were (i) to establish the relative importance of product inhibition (n−3 HUFA)
vs. increased substrate concentration (C18 EFA) and (ii) to determine whether 18∶2n−6 and 18∶3n−3 differ in their effects on the hepatic fatty acyl desaturation/elongation
pathway in Atlantic salmon (Salmo salar). Smolts were fed 10 experimental diets containing blends of two vegetable oils, linseed (IO), and rapeseed oil (RO), and
fish oil (FO) in a triangular mixture design for 50 wk. Fish were sampled after 32 and 50 wk, lipid and FA composition of
liver determined, fatty acyl desaturation/elongation activity estimated in hepatocytes using [1-14C]18∶3n−3 as substrate, and the data subjected to regression analyses. Dietary 18∶2n−6 was positively correlated, and n−3
HUFA negatively correlated, with lipid content of liver. Dietary 20∶5n−3 and 22∶6n−3 were positively correlated with liver
FA with a slope greater than unity suggesting relative retention and deposition of these HUFA. In contrast, dietary 18∶2n−6
and 18∶3n−3 were positively correlated with liver FA with a slope of less than unity suggesting metabolism via β-oxidation and/or desaturation/elongation. Consistent with this, fatty acyl desaturation/elongation in hepatocytes was significantly
increased by feeding diets containing vegetable oils. Dietary 20∶5n−3 and 22∶6n−3 levels were negatively correlated with hepatocyte
fatty acyl desaturation. At 32 wk, 18∶2n−6 but not 18∶3n−3 was positively correlated with hepatocyte fatty acyl desaturation,
wheres the reverse was true at 50 wk. The data indicate that both feedback inhibition through increased n−3 HUFA and decreased
C18 fatty acyl substrate concentration are probably important in determining the level of hepatocyte fatty acyl desaturation
and that 18∶2n−6 and 18∶3n−3 may differ in their effects on this pathway. 相似文献
14.
Lipase-catalyzed alcoholysis of soy phospholipids was investigated to simultaneously make lysophospholipids and fatty acid
esters of individual alcohols. Alcoholysis was carried out by stirring a mixture of soy phospholipids and individual alcohols
in equimolar proportions with 10% (by weight of reactants) Mucor miehei lipase at 55°C for 24 h. The products were isolated by column chromatography after removal of the lipase. Lysophospholipids
(in 69–78% molar yield) were obtained from soy phospholipids, and the yield of esters of various alcohols also conformed nearly
with theoretical yields. 相似文献
15.
Our previous isolation of branched-chain fatty acid (BCFA) methyl esters from lanolin was improved and scaled up. Also, oleate
esters of isopropanol, oleyl alcohol and normal alcohols of 1–12 carbons chain lengths were prepared. Esters were made by
interesterification with sodium alcoholates and by esterification with Candida antarctica lipase. It proved easier to obtain pure esters by the enzymatic synthesis. Melting points and viscosities over the range
of 0–70 °C were determined in order to better identify potential lubricant targets that might be produced by genetically modified
oilseed crops. Isopropyl and butyl oleate have melting points of −33 and −32 °C, respectively and viscosities that range from
~17 cp (0 °C) to ~2.5 cp (70 °C). They should have suitable stability for lubricants. BCFA esters had viscosities similar
to their straight chain analogs. Viscosities increased with alcohol chain length and decreased with temperature. The dependence
of viscosity on temperature was fit with an equation based on Erying’s rate equation. Some esters with branched acid or branched
alcohol moieties, and some oleate esters might be utilized as biolubricants or biofuels on the basis of their melting points
and viscosities. 相似文献
16.
Fatty acyl groups (16∶1 and 16∶0) liberated from purified sulfoquinovosyl diacylglycerols produced by the unicellular marine
microalga,Heterosigma carterae (formerlyH. akashiwo), were converted to either the corresponding alcohols or methyl esters. Nicotinate derivatives of the alcohols were examined
by combined gas chromatography/mass spectrometry, and the methyl esters were examined by nuclear magnetic resonance (NMR)
spectroscopy after separation by high-performance liquid chromatography. Three different hexadecenoyl fatty acyl groups were
identified, one of which wascis 13-hexadecenoyl (16∶1n−3). Both the configuration and the n−3 position of the double bond in thecis 13-hexadecenoyl moiety were unequivocally established by NMR analysis of the corresponding methyl ester. The nicotinate derived
from the alcohol of the 16∶1n−3 fatty acyl moiety gave a characteristic fragmentation series in the electron impact msss spectrum
which, by careful interpretation, was consistent with, but not unambiguous for, the assigned location of the double bond.
Tandem mass spectrometry experiments on a sulfoquinovosyl monoacylglycerol containing thecis 13-hexadecenoyl group in thesn-2 position, using negative-ion liquid secondary ion mass spectrometry, also gave a fragmentation pattern which was consistent
with the positional assignment of the double bond. 相似文献
17.
Marianne Lilja Hallberg Daobin Wang Magnus Härröd 《Journal of the American Oil Chemists' Society》1999,76(2):183-187
Wax esters were transesterified from fatty acid methyl esters of rapeseed and a fatty alcohol (1-hexadecanol, 16:0). The amounts
of both the substrates were fixed to 0.1 mmol and an immobilized enzyme, Lipozyme, was used as catalyst. The experiment was
performed following a statistic central composite design with five variables. The enzyme/lipid ratio was varied between 0.3–0.9
of the substrate weight and the enzyme was equilibrated to different water activities varying from 0.11 to 0.44. A temperature
range of 50–80°C was investigated and the reaction time lasted up to 40 min. A solvent, isooctane, constituted 0–30% of the
substrate weight. The first experimental series was performed in small closed test tubes. In the second series the caps of
the test tubes were off to evaporate the methanol produced during the reaction. The highest initial reaction rate was 9.6
gwax esters/genzyme · h. It appeared when: the enzyme/lipid ratio was low, 0.3, the temperature was high, 80°C; no isooctane was present; and
the water activity was below 0.11. The initial reaction rate was independent of the caps on the test tubes. With the large
amount of enzyme the yield of wax esters was above 70% after 10 min in both experimental series. In the reaction with caps,
the reaction reached equilibrium at 83% after 20 min at 80°C. However, without caps the continuous evaporation of methanol
increased the equilibrium constantly, and after 40 min at 80°C a yield of 90% was reached. 相似文献
18.
Bernard Freedman Royden O. Butterfield Everett H. Pryde 《Journal of the American Oil Chemists' Society》1986,63(10):1375-1380
Transesterification of soybean oil (SBO) and other triglycerides with alcohols, in the presence of a catalyst, yields fatty
esters and glycerol. Di- and monoglycerides are intermediates. Reactions are consecutive and reversible. Rate constants have
been determined for each reaction with a computerized kinetic program. The effects of the type of alcohol, 1-butanol or methanol
(MeOH); molar ratio of alcohol to SBO; type and amount of catalyst; and reaction temperature on rate constants and kinetic
order were examined. Forward reactions appear to be pseudo-first order or second order depending upon conditions used. Reverse
reactions appear to be second order. At a molar ratio of MeOH/SBO of 6:1, a shunt reaction was observed. Energy of activation
was determined for all forward and reverse reactions under a variety of experimental conditions from plots of log k vs 1/T.
Values ranged from 8–20 kcal/mol.
1Presented at the AOCS meeting in Philadelphia, PA, May, 1985.
2 Deceased. 相似文献
19.
This study has utilized radiolabeled analogues of arachidonic acid to study the substrate specificity of elongation of long-chain
polyunsaturated fatty acids. Human umbilical vein endothelial cells were incubated for 2–72 hr in medium supplemented with
0.9–2.6 μM [14C]fatty acid, and cellular glycerolipids were analyzed by gas-liquid chromatography with radioactivity detection. Elongation
of naturally occurring C20 polyunsaturated fatty acids occurred with eicosapentaenoate (20∶5(n−3))>Mead acid (20∶3(n−9))>arachidonate (20∶4(n−6)). Chain
length markedly influenced the extent of elongation of 5,8,11,14-tetraenoates (18∶4>19∶4>20∶4>21∶4); effects of initial double
bond position were also observed (6,9,12,15–20∶4>4,7,10,13–20∶4. Neither 5,8,14- nor 5,11,14–20∶3 was elongated to the extent
of 5,8,11–20∶3. Differences between polyunsaturated fatty acids were observed both in the initial rates and in the maximal
percentages of elongation, suggesting that the content of cellular C20 and C22 fatty acids may represent a balance between chain elongation and retroconversion.
Umbilical vein endothelial cells do not exhibit significant desaturation of either 22∶4(n−6) or 22∶5(n−3). By contrast, incubation
with 5,8,11,14-[14C]18∶4(n−4) resulted in formation of both [14C]20∶5(n−4) and [14C]22∶5(n−4). The respective time courses for the appearances of [14C]22∶5(n−4) and [14C]20∶5(n−5) suggests Δ6 desaturation of [14C]22∶4(n−4) rather than Δ4 desaturation of [14C]20∶4(n−4). 相似文献
20.
The alcoholysis reaction has been applied to the preparation of highly unsaturated alkyl esters from menhaden oil. This reaction
proceeded very rapidly, and nearly quantitative yields were obtained with virtually, no loss in double-bond structure. The
formation of esters was studied, using straight- and branched-chain alcohols having 1–6 carbon atoms. The reactions were monitored
by the technique of thin-layer chromatography (TLC). Maximum conversion of straight-chain esters was found to be a linear
function with respect to the number of carbon atoms in the alcohol. Reaction time varied from 2 min for methanol to 60 min
for n-hexanol. Branched-chain alcohols reacted more slowly than did the corresponding straight-chain compounds.
This reaction was found to be applicable to laboratory and large scale preparations of highly unsaturated alkyl esters.
Presented at the AOCS meeting, St. Louis, Mo., 1961. 相似文献