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231223s2007 xx ||||| 00| ||eng c |
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|a pubmed24n0574.xml
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|a (DE-627)NLM172263433
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|a (NLM)17713935
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|a DE-627
|b ger
|c DE-627
|e rakwb
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| 041 |
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|a eng
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| 100 |
1 |
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|a Garcia, Ana R
|e verfasserin
|4 aut
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| 245 |
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|a Interactions of L-alanine with alumina as studied by vibrational spectroscopy
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|c 2007
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|a Text
|b txt
|2 rdacontent
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|a ohne Hilfsmittel zu benutzen
|b n
|2 rdamedia
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|a Band
|b nc
|2 rdacarrier
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| 500 |
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|a Date Completed 13.11.2007
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|a Date Revised 21.11.2013
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|a published: Print-Electronic
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|a Citation Status MEDLINE
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|a The interactions of L-alanine with gamma- and alpha-alumina have been investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). L-alanine/alumina samples were dried from aqueous suspensions, at 36.5 degrees C, with two amino acid concentrations (0.4 and 0.8 mmol g-1) and at different pH values (1, 6, and 13). The vibrational spectra proved that the nature of L-alanine interactions with both aluminas is the same (hydrogen bonding), although the groups involved depend on the L-alanine form and on alumina surface groups, both controlled by the pH. For samples prepared at pH 1, cationic L-alanine [CH3CH(NH3+)COOH] displaces physisorbed water from alumina, and strong hydrogen bonds are established between the carbonyl groups of alanine, as electron donors, and the surface Al-OH2+ groups of alumina. This occurs at the expense of alanine dimer dissociation and breaking of intramolecular bonds. When samples are prepared at pH 6, the interacting groups are Al-OH2+ and the carboxylate groups of zwitterionic L-alanine [CH3CH(NH3+)COO-]. The affinity of L-alanine toward alumina decreases, as the strong NH3+...-OOC intermolecular hydrogen bonds prevail over the interactions with alumina. Thus, for a load of 0.8 mmol g-1, phase segregation is observed. On alpha-alumina, crystal deposition is even observed for a load of 0.4 mmol g-1. At pH 13, the carboxylate groups of anionic L-alanine [CH3CH(NH2)COO-] are not affected by alumina. Instead, hydrogen bond interactions occur between NH2 and the Al-OH surface groups of the substrate. Complementary N2 adsorption-desorption isotherms showed that adsorption of L-alanine occurs onto the alumina pore network for samples prepared at pH 1 and 13, whereas at pH 6 the amino acid/alumina interactions are not strong enough to promote adsorption. The mesoporous structure and the high specific surface area of gamma-alumina make it a more efficient substrate for adsorption of L-alanine. For each alumina, however, it is the nature of the specific interactions and not the porosity of the substrate that determines the adsorption process
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|a Journal Article
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|a Research Support, Non-U.S. Gov't
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|a Aluminum Oxide
|2 NLM
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| 650 |
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|a LMI26O6933
|2 NLM
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| 650 |
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|a Alanine
|2 NLM
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| 650 |
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|a OF5P57N2ZX
|2 NLM
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| 700 |
1 |
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|a de Barros, Ricardo Brito
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Fidalgo, Alexandra
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Ilharco, Laura M
|e verfasserin
|4 aut
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| 773 |
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|i Enthalten in
|t Langmuir : the ACS journal of surfaces and colloids
|d 1992
|g 23(2007), 20 vom: 25. Sept., Seite 10164-75
|w (DE-627)NLM098181009
|x 1520-5827
|7 nnns
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| 773 |
1 |
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|g volume:23
|g year:2007
|g number:20
|g day:25
|g month:09
|g pages:10164-75
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|a AR
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|d 23
|j 2007
|e 20
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|h 10164-75
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