Exam 1 AA digestion and analysis Flashcards
Aliphatic AA
Gly, ser, ala, thr, val, leu, ile
Aromatic aa
Phe, tyr, trp
Heterocyclic aa
Trp, pro, hypro
Basic aa
Arg, Lys, his
Sulfur aa
Cys, met
Pepsin breaks cho end of
Aromatic and acidic aa (trp, tyr, phe, asp, glu)
Trypsin breaks cho end of
Lys and arg
Chymotrypsin breaks cho end of
Aromatic aa (phe, tyr, trp)
Elastase breaks cho end of
Aliphatic aa (ser, ala, val, leu, ile, thr, gly)
Carboxypeptidase A breaks end of chain cho end of
Aromatic aa(phe, tyr, trp)
Carboxypeptidase B breaks end of chain cho end of
Basic aa (Lys, his, arg)
Essential AA
HILLMA PheTrpThreVa CysTyr
+ gly and pro for chicken
B transport system
Dipolar alpha aa, depends on Na gradient and requires energy
B° + transport system
Dipolar alpha AA, basic aa and cys. Requires energy
b ° + transport system
Dipolar alpha aa, basic and cys. Same as B° + but does not depend on Na gradient and does not require energy
X- AG transport system
Acidic aa, depends on na gradient, also uses K and uses energy
y+ transport system
Basic aa, does not depend on na gradient or other ions or energy
IMINO transport system
IMINO acids, uses Na gradient, also Cl and uses energy
Beta transport system
Beta aa, uses na gradient, Cl and energy
What’s the N content in SBM protein?
18.5, using the 6.25 factors overestimates CP in it
Key steps of Kjeldahl
Digest sample using concentrated sulfuric acid and heat,
Cu and K sulfates as catalysts,
forms ammonium sulfate
treated with 50% sodium hydroxide
ammonia is trapped in boric acid
then titrated with HCl
Key steps of combustion method
Sample is introduced to pressurized tube and combusted with pure oxygen at min of 950 C
The products (NOx, N2, CO2, H2O and O2) are allowed to equilibrate
An aliquot is sampled and carried by He through a series of reagents to remove H2O, CO2 and excess O2
The N products that remain are converted to N2 when heated in the presence of N catalyst reagents
He is used to carry the isolated N2 through thermal conductivity detector that measures N
how are samples on average hydrolyzed prior to AA analysis? and for free AA
with HCl at 110 C for 24 hours in vacuum, for analysis of free AA they must be ultrafiltrated
What are the AA that cannot be digested in the conventional way for AA analysis?
Ile and Val require 48-72h
Sulfur AA Met and Cys are prone to partial oxidation so they must be treated before hydrolysis
Gln and Asn are converted to Glu and Asp, so must be converted to stable derivatives
Trp is completely destroyed and requires base hydrolysis (sodium hydroxide)
what are the possible AA analysis methods?
gas chromatography (GC), high performance liquid chromatography (HPLC), Ion exchange chromatography (IEC), and capillary electrophoresis (CE)
What are the main characteristics of GC analysis of AA?
AAs must be converted to their volatile derivatives such as HFB isobutyl and then separated in columns. It’s not much use in animal nutrition studies, and require complex derivatization and purification
What are the main characteristics of HPLC analysis of AA?
Largest advances in AA analysis. AAs are reacted with reagents to form fluorescent or UV-absorbing derivatives that are separated in the column, derivatizing agent can be DABS-Cl, FMOC, PITC. due to errors results should be replicated and reported with error ranges
What are the main characteristics of IEC analysis of AA?
AA are separated in a column, mixed with a derivatization agent, passed through a reaction coil and passed through a fluorometric or spectrophotometric detector.
Requires expensive instrumentation and columns, has complex mobile phases and has low sensitivity
