Alpha-amino Group Research Articles

Effect of Area Specific Mineral Supplementation on Biochemical Profile in Female Black Bengal Goats

To discern the effect of area specific mineral supplementation (ASMS), on some plasma parameters viz. glucose, non-esterified fatty acids (NEFA), alpha amino nitrogen (AAN), alanine transaminase (ALT) and aspartate transaminase (AST), the intensive study was conducted on 24 female Black Bengal goats at around of 4–5 months of age. The animals were divided into four groups viz. Group I (control), II, III supplemented with 0, 1 and 2% area specific mineral supplementation, respectively. Whereas, in another group (Group-IV), commercial mineral mixture fortified concentrate was given. Blood samples were collected at monthly interval and estimated five prime plasma parameters. Present study revealed that plasma glucose concentration was in normal range and differed significantly (P < 0.05) in groups. Highest plasma glucose concentration was observed in group IV and lowest in control group. Whereas, NEFA differed significantly in different groups. Plasma AAN level was higher in Group IV followed in Group III, II and I respectively. AAN did not differ significantly in groups. Plasma ALT and AST level differed significantly but highest Plasma ALT and AST level observed in Group II. Present study revealed that ASMS improved plasma biochemical profile in Black Bengal goats.

M-path: a compass for navigating potential metabolic pathways.

Construction of synthetic metabolic pathways promises sustainable production of diverse chemicals and materials. To design synthetic metabolic pathways of high value, computational methods are needed to expand present knowledge by mining comprehensive chemical and enzymatic information databases. Several computational methods have been already reported for the metabolic pathway design, but until now computation complexity has limited the diversity of chemical and enzymatic data used. We introduce a computational platform, M-path, to explore synthetic metabolic pathways including putative enzymatic reactions and compounds. M-path is an iterative random algorithm, which makes efficient use of chemical and enzymatic databases to find potential synthetic metabolic pathways. M-path can readily control the search space and perform well compared with exhaustively enumerating possible pathways. A web-based pathway viewer is also developed to check extensive metabolic pathways with evaluation scores on the basis of chemical similarities. We further produce extensive synthetic metabolic pathways for a comprehensive set of alpha amino acids. The scalable nature of M-path enables us to calculate potential metabolic pathways for any given chemicals.

New roles for old modifications: emerging roles of N-terminal post-translational modifications in development and disease.

The importance of internal post-translational modification (PTM) in protein signaling and function has long been known and appreciated. However, the significance of the same PTMs on the alpha amino group of N-terminal amino acids has been comparatively understudied. Historically considered static regulators of protein stability, additional functional roles for N-terminal PTMs are now beginning to be elucidated. New findings show that N-terminal methylation, along with N-terminal acetylation, is an important regulatory modification with significant roles in development and disease progression. There are also emerging studies on the enzymology and functional roles of N-terminal ubiquitylation and N-terminal propionylation. Here, will discuss the recent advances in the functional studies of N-terminal PTMs, recount the new N-terminal PTMs being identified, and briefly examine the possibility of dynamic N-terminal PTM exchange.

Effect of Drying Methods on Odorous Compounds and Antioxidative Activity of Gelatin Hydrolysate Produced by Protease from B. amyloliquefaciens H11

Gelatin hydrolysates with antioxidative activity produced by protease from Bacillus amyloliquefaciens H11 with different hydrolysis times were prepared. Alpha-amino group content and antioxidative activities increased with increasing hydrolysis time (p < 0.05). When gelatin hydrolysate prepared with hydrolysis time of 3 h (GH-3H) was subjected to freeze drying and spray drying, the powder obtained from spray drying showed a decrease in antioxidant activity as measured by DPPH and ABTS radical scavenging activities, ferric-reducing antioxidant power, and metal chelating activity. Spray-dried gelatin hydrolysate (GH-3H-SD) showed higher whiteness with lower fishy odor and off-odor associated with fermentation. This was concomitant with the decreases in several odorous compounds in the sample, except for nonanal, which was higher in comparison with the powder obtained by freeze drying. Thus, spray drying could be an effective drying method to improve color and reduce undesirable odor of gelatin hydrolysate.

INFLUENCE OF SULPHUR AND CARBOFURAN NEMATICIDE ON ROOT-KNOT NEMATODE AND THE PERFORMANCE OF SOME SUGAR BEET VARIETIES IN SANDY SOIL

Two field trials were carried out in Nubaryia region, El BeheiraGovernorate, Egypt throughout two successive seasons of 2012/2013 and2013/2014 to examine the response of five multigerm varieties of sugarbeet (Beta vulgaris, sacchrifera L.) as affected by agricultural sulphur(100 kg/fed.), and nematicide, furan (carbofuran10% G) at 13 kg/fed onroot knot nematode, Meloidogyne incognita under naturally infected withit. A split-split plots design was used, where sulphur treatments in mainplots, the nematicide, in the sub-plots, and sugar beet varieties were sownin the sub-sub- plots. Results obtained cleared that number of galls/ plantsignificantly affected by sulphur treatments, this finding was true in bothgrowing seasons at the two studied age i.e. 3-momth or 6- month.Application of 100 kg sulphur reduced the values of galls from 15.6 to 9.0in the 1st age corresponding 38 to 25 in the 2nd age. The percent ofreduction amounted by 73.33% and 52.0% at age 3 and 6 monthsrespectively. Once more, the differences between sulphur treatments didnot reach the level of significant in respect to their effect on galls numberin the 2nd seasons of both ages. Concerning carbofuran (C) influence, theresults showed that the used nematicide compound significantly reducedthe percent values of gall’s number, the amount of reduction reached to140 and 152 % in the 1st and 2nd seasons at age of 3- month corresponding172 and 226.4 % in 6- month age in the 1st and 2nd season respectively.This result may be indicating to the high specificity against nematode.Regarding the different combination between the studied factors, it couldbe noted that the 1st and 2nd order interaction were significantly effected onthe values of gall’s number/ root in both seasons whether at 3-momth or 6-month ages. Once more by the end of growing season (six months), thevalues of egg masses significantly affected by the individual studiedfactors. Application of 100 kg sulphur significantly reduced the values ofeggmasses/root. As for, the influence of carbofuran nematicide on eggmasses, the available data appeared highly response to carbofuran inrespect to its effect on egg masses in the two growing seasons, usingcarbofuran et a reduction in this trait amounted by 113.33 and 137.5% inthe 1st and 2nd seasons respectively. Belong to varietal difference in respectto egg masses, the collected results showed sugar beet variety Gloriserecorded the lowest value of this trait in both seasons. This finding may beassured the gen make up role in its influence on varieties with respect to their resistance against nematode infection. The most effect interaction wasthat between sugar beet varieties and each of sulphar treatment andnematicide. Sugar beet root fresh weight, root diameter and sugar yield/fedincreased significantly at the studied rates of nematicide and sulphur in the1st and 2nd seasons. Root yield had the same trend in the 2nd season only.Sucrose% and sugar extractable% significantly increased at the rates ofnematicide and sulphur treatments in both seasons, respectively. Glorisevariety cleared the significant superiority over all the other tested ones insucrose%, without significant variance with lilly variety. The interactionbetween the used rates of sulphur and carbofuran nematicide had the sameeffect on root diameter in both seasons. Sulphur treatment at developedroot quality and reduced the impurity of juice of sugar beet and increasedroot growth as well as carbofuran nematicide did. Alpha amino nitrogen insugar beet roots was significantly influenced by sulphur and carbofurannematicide interaction in both seasons. Potassium, sucrose and extractablesugar percentages and percentage extractability of root juice weresignificantly recorded impacts by the interaction between varieties andsulphur levels in both seasons.

Cuso4 -amine redox-initiated radical polymerization of methyl methacrylate mediated by a CuCl2 complex: Homogeneous reverse ATRP

Kinetic results of CuSO4/2,2'-bipyridine(bPy)-amine redox initiated radical polymerization of methyl methacrylate (MMA) at 70 to 90 °C in dimethylsulfoxide suggest that such initiation is characteristic of a slow rate and a low initiator efficiency, but tertiary amines exhibit a relatively higher rate. UV-Vis spectroscopy confirms the alpha-amino functionality of PMMA chains. CuCl2/bPy successfully mediates the redox-initiated radical polymerization of MMA with aliphatic tertiary amines in a fashion of slow-initiated reverse atom transfer radical polymerization (ATRP), i.e. both the initiator efficiency of aliphatic tertiary amines and the average molecular weight of PMMA increase gradually, while the molecular weight distribution remains narrow but become broader with the conversions. As the PMMA chains contain alpha amino and omega C-Cl moieties, UV-induced benzophenone-initiated radical polymerization and CuICl/bPy-catalyzed ATRP initiated from PMMA lead to block copolymers from terminal functionalities. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2562-2578

Biochemical, textural, microbiological and sensory attributes of gutted and ungutted sutchi catfish (Pangasianodon hypophthalmus) stored in ice.

Pangasianodon hypophthalmus (sutchi catfish) is a fresh water catfish extensively being cultured in the South East Asian countries in the recent years. The present study provides the first report on the effects of gutting on the quality characteristics of aquacultured sutchi catfish stored in ice. pH of whole ungutted and gutted catfish didn't show significant difference (p > 0.05) during ice storage period. Total Volatile Base Nitrogen (TVB-N), Alpha Amino Nitrogen (AAN), Free Fatty Acids (FFA) and Thio Barbituric Acid Reactive Substance (TBARS) were lower in gutted fish compared to whole ungutted fish at any particular day during ice storage. However, gutted fish expressed higher rate of primary lipid oxidation than ungutted fish. Textural degradation of the fish muscle as indicated by hardness, cohesiveness, springiness and chewiness was lower in gutted fish. Results of sensory evaluation revealed that gutting has significantly improved the sensory quality of the fish. However, microbiological analysis revealed higher Total Plate Count (TPC) and Enterobactereaceae count in gutted fish. The shelf life of gutted and whole ungutted sutchi cat fish as determined by microbiological analysis was 16-18days and 18-20days respectively while storage in ice.

EFFECT OF SOWING DATES AND PHOSPHORUS FERTILIZER ON ROOT ROT AND QUALITY OF SOME SUGAR BEET VARIETIES

The present investigation was carried out at the experimental farm of Malawi Agricultural Research Station, El-Minia Governorate, Egypt during 2009/2010 and 2010/2011 seasons to investigate the effect of sowing dates (15th October, 30th October and 15th November) and phosphorus fertilizer (0, 15 and 30) kg P2O5 /fed on root rot disease incidence, yield and its quality of three sugar beet varieties i.e. Farida, Kawemira and Montibianco. A split-split plot design with three replications was used, sowing dates were allocated in the main plots, phosphorus fertilizer was assigned in the sub plots while, sugar beet varieties were distributed in the sub- sub plots. The results revealed that sowing date15th October significantly reduced root rot disease incidence and increased all quality parameters, i.e. sucrose ,sex, Na, K, alpha amino N,SLM and extractability percentages except purity % as well as productivity traits (top and root yields ) in the two growing seasons. The above varieties of sugar beet significantly differed in all studies traits in the two growing seasons. Phosphorus fertilizer significantly effected on all studies traits in both seasons, except sugar yield and (root yield and root fresh weight ) in the first season only. Planting Kawemira sugar beet variety when received 30 kg P2O5 / fed in 15th October significantly increased yields of root and top (ton/fed) in the second season.

Nutritional Assessment of Some Traditionally Processed Hill-Stream Fishes of Manipur with Special Reference to n-3 Fatty Acids

Traditionally, smoke-dried hill-stream fishes are an important part of the diet of the people of Manipur, India. The nutritional values of the processed fishes were studied. The proximate composition, protein digestibility, and fatty acid composition of hill-stream fishes Neolissochilus stracheyi, Labeo pangusia, Semiplotus manipurensis, Schizothorax sp., and Ompok sp. were determined. The mean values of protein, lipid, ash, and moisture ranged from 31.20 to 72.58%, 6.36 to 18.73%, 4.32 to 5.33%, and 10.14 to 16.25%, respectively. The protein digestibilities were high (75.56–97.65%), and alpha amino nitrogen liberated during in vitro tests was highest (19.34 mg/g) in L. pangusia in pepsin and trypsin phase. The n-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid were highest in L. pangusia, followed by S. manipurensis. The study shows that the processed hill-stream fishes have different food values, and some are a good source of highly digestible protein and also contain a good amount of essential fatty acids that may be beneficial for brain development and optimal health.

Arginyltransferase ATE1 Catalyzes Midchain Arginylation of Proteins at Side Chain Carboxylates In Vivo

Arginylation is an emerging posttranslational modification mediated by Arg-tRNA-protein-transferase (ATE1). It is believed that ATE1 links Arg solely to the N terminus of proteins, requiring prior proteolysis or action by Met-aminopeptidases to expose the arginylated site. Here, we tested the possibility of Arg linkage to midchain sites within intact protein targets and found that many proteins invivo are modified on the side chains of Asp and Glu by unconventional chemistry that targets the carboxy rather than the amino groups at the target sites. Such arginylation appears to be functionally regulated, and it can be directly mediated by ATE1, in addition to the more conventional ATE1-mediated linkage of Arg to the N-terminal alpha amino group. This midchain arginylation implies an unconventional mechanism of ATE1 action that likely facilitates its major biological role.

Influence of Some Process Parameters on Defined Characteristics of Sorghum Beer during Very High Gravity Fermentation

This study was carried out to investigate the influence of some process parameters on defined characteristics of sorghum beer during very high gravity fermentation. The yeast (Saccharomyces uvarum)was pitched in very High Gravity Wort from two varieties (red and white) of sorghum (Sorghum bicolor). Changes in some process parameters like pH, specific gravity, percentage alcohol by volume, free amino nitrogen, total reducing sugar, total nitrogen and total protein were investigated over a period of 5 days of fermentation. Results showed that pH values decreased as fermentation proceeded with increased total acidity while alcohol contents of the fermenting wort increased from the first day to the fifth day of fermentation. There were observed decrease in specific gravity, total reducing sugar, free amino nitrogen (FAN), Percentage total nitrogen and Percentage total protein from first day to the fifth day of fermentation. The red sorghum had a lower pH, higher specific gravity and alcohol content than the white sorghum. This showed that Saccharomyces uvarum can grow well in very high gravity sorghum wort and pH, specific gravity, free alpha amino nitrogen is an important aspect of the wort for yeast fermentation.

Abstract 024: Metabolomics and Incident Hypertension in African Americans from the Atherosclerosis Risk in Communities (ARIC) Study

Introduction: Development of hypertension is influenced by genes, environmental effects and their interactions, and the human metabolome is a measurable manifestation of gene x environment interaction. We explored the metabolomic antecedents of hypertension in a sample of African Americans (AAs) in the ARIC study. Methods: We examined 896 (565 females, aged 45-64 years) baseline normotensives, whose serum metabolome was measured by gas chromatography-mass spectrometry/ liquid chromatography-mass spectrometry. The analyses presented here focus on 204 metabolites having high 4-6 week intra-individual repeatability (reliability coefficients ≥ 0.60). We used principal-components analyses (PCA) to identify patterns in these metabolomic data. Weibull parametric models considering interval censored data were used to assess the hazard ratio of developing hypertension. The analyses adjusted for age, gender, leisure-time physical activity, smoking status, alcohol intake, diabetes status, BMI, and estimated glomerular filtration rate in the full model. An additional model adjusted for the previous variables plus baseline systolic and diastolic BP. We used a modified Bonferroni correction accounting for the correlations among metabolites to determine statistical significance (p &lt;3.9×10-4) in the analysis of association between an individual metabolite and hypertension. Results: During 10-years of follow-up, 38% of baseline normotensives developed hypertension (N=344; incidence rate: 63.94 per 1000 person-years). Each SD of baseline 4-hydroxyhippurate, a product of gut microbial fermentation, was associated with 17% higher risk of hypertension (p=2.5×10-4), which remained significant after adjusting for baseline BP (p=3.8×10-4). PCA showed three interpretable metabolomic patterns: sex steroids, alpha amino acids and branched-chain amino acids. The sex steroids pattern mainly consisted of androstenediol and pregnendiol disulfate, and it was significantly associated with risk of incident hypertension independent of all factors in the full model (highest versus lowest quintile HR, 1.72; 95% CI, 1.05 to 2.82; p for trend=0.03). Stratified analyses suggested this association was consistent in both genders. Conclusions: In our study of ARIC AAs with 204 reliable metabolites, one metabolite (4-hydroxyhippurate) and one pattern of sex steroids were identified as biomarkers of incident hypertension independent of measured traditional risk factors. Metabolomic analyses such as these may identify novel biomarkers or pathways in the etiology of hypertension and point to new prevention strategies.

Synthesis and Characterization of a Lipidic Alpha Amino Acid: Solubility and Interaction with Serum Albumin and Lipid Bilayers

The lipidic α-amino acid with 11 carbons in the alkyl lateral chain (α-aminotridecanoic acid) was synthesized via multicomponent hydroformylation/Strecker reaction, which is a greener synthetic approach to promote this transformation relative to previously described methods. Its solubility and aggregation behavior in aqueous solutions was characterized, as well as the interaction with lipid bilayers. Lipidic amino acids are very promising molecules in the development of prodrugs with increased bioavailability due to the presence of the two polar functional groups and nonpolar alkyl chain. They are also biocompatible surfactants that may be used in the food and pharmaceutical industry. In this work we have conjugated the lipidic amino acid with a fluorescent polar group (7-nitrobenz-2-oxa-1,3-diazol-4-yl), to mimic drug conjugates, and its association with serum proteins and lipid bilayers was characterized. The results obtained indicate that conjugates of polar molecules with lipidic α-amino acid, via covalent attachment to the amine group, have a relatively high solubility in aqueous solutions due to their negative global charge. They bind to serum albumin with intermediate affinity and show a very high partition coefficient into lipid bilayers in the liquid-disordered state. The attachment of the polar group to the lipidic amino acid increased strongly the aqueous solubility of the amphiphile, although the partition coefficient into lipid membranes was not significantly reduced. Conjugation of polar drugs with lipidic amino acids is therefore an efficient approach to increase their affinity for biomembranes.

Protein N-terminal Acetyltransferases Act as N-terminal Propionyltransferases In Vitro and In Vivo

N-terminal acetylation (Nt-acetylation) is a highly abundant protein modification in eukaryotes catalyzed by N-terminal acetyltransferases (NATs), which transfer an acetyl group from acetyl coenzyme A to the alpha amino group of a nascent polypeptide. Nt-acetylation has emerged as an important protein modifier, steering protein degradation, protein complex formation and protein localization. Very recently, it was reported that some human proteins could carry a propionyl group at their N-terminus. Here, we investigated the generality of N-terminal propionylation by analyzing its proteome-wide occurrence in yeast and we identified 10 unique in vivo Nt-propionylated N-termini. Furthermore, by performing differential N-terminome analysis of a control yeast strain (yNatA), a yeast NatA deletion strain (yNatAΔ) or a yeast NatA deletion strain expressing human NatA (hNatA), we were able to demonstrate that in vivo Nt-propionylation of several proteins, displaying a NatA type substrate specificity profile, depended on the presence of either yeast or human NatA. Furthermore, in vitro Nt-propionylation assays using synthetic peptides, propionyl coenzyme A, and either purified human NATs or immunoprecipitated human NatA, clearly demonstrated that NATs are Nt-propionyltransferases (NPTs) per se. We here demonstrate for the first time that Nt-propionylation can occur in yeast and thus is an evolutionarily conserved process, and that the NATs are multifunctional enzymes acting as NPTs in vivo and in vitro, in addition to their main role as NATs, and their potential function as lysine acetyltransferases (KATs) and noncatalytic regulators.

Studies on Hepato and Renal Toxicity of Cadmium on Normal and Protein Malnourished Rats

Cadmium is an established toxic metal with its ability to accumulate in blood, liver and kidney. It adversely affects the renal cortex and ultimately leads to the renal failure. It has been reported that deficiency of certain dietary components affects cadmium toxicity. Present study was designed to evaluate the cadmium toxicity (50 ppm in drinking water) in protein malnourished group (8%) and on normal protein (21%) diet groups. It was found that Cd exposure led to marked elevation in alkaline phosphatase, acid phosphatase, glutamic pyruvic transferase, glutamic oxaloacetic acid transferase with significant increase in protein malnourished group (p 0.005). Same trend of result was noted in urinary concentration of alpha amino acid, albumin, total protein and glucose. Results were more significant (p 0.001) in malnourished animals. However, hepatic and renal enzymes showed depletion in all groups. There was marked increase in serum enzymes GOT, GPT, alkaline phosphatase, acid phosphatase in low protein diet + Cd (p 0.001). Hence present findings strongly support that protein under-nutrition predisposes the organism to the deleterious effects of cadmium toxicity.

Amino acid-accepting ketosynthase domain from a trans-AT polyketide synthase exhibits high selectivity for predicted intermediate

The trans-acyltransferase (AT) polyketide synthases are a recently recognised group of bacterial enzymes that generate complex polyketides. A prerequisite for re-engineering these poorly studied systems is knowledge about the substrate specificity of their components. In this work, KS domain 1 from the bacillaene polyketide synthase has been shown to possess high specificity towards 2-amidoacetyl intermediates, which are derived from incorporation of alpha amino acids into the polyketide chain. N-Acetylcysteamine (SNAC) analogues of full-length substrates were synthesised and incubated with the KS1 domain. The natural glycine-derived acyl–SNAC was found to acylate KS1 with highest efficiency, as evidenced by mass spectrometry (MS). An alanine variant was also incorporated, but its valine equivalent was not, which indicated limited tolerance of substitution at the α-position. Substrate analogues without an amine or amide nitrogen substituted on the 2-position were not accepted by KS1 at the standard assay concentration of 0.5 mM. Moreover, removal of Asn-206 from the active site of KS1 by site-directed mutagenesis reduced kcat/Km by a factor of approx. 2. This residue is conserved in most known 2-amidoacetyl-accepting KS domains from trans-AT PKSs and we postulate an important interaction between Asn-206 and the amide nitrogen of the substrate.

Change of the Alpha Amino Nitrogen of Tartary Buckwheat Beer during the Process of Mashing and Its Process Optimization

To analysis the effect of 4 diastatic technical parameters (the ratio of water and materials, pH, the diastatic temperature of stageIand stageII) on α-amino nitrogen content of wort, the response surface method is applied and the mathematical model of the four parameters above influencing α-amino nitrogen content was established. The results showed that the optimum technical conditions were as follows: the ratio of water to raw materials was 4:1, the diastatic temperature of stageI was 62°C and the diastatic temperature of stageII was 72°C, the pH was 5.35. Under the optimum technical conditions condition, the αamino nitrogen content of wort in beer was 188.2 mg/L.

Recombinant granulocyte colony-stimulating factor (filgrastim): Optimization of conjugation conditions with polyethylene glycol

In order to create an active pharmaceutical substance of the drug with prolonged action the modification of recombinant human granulocyte colony-stimulating factor GCSF (filgrastim) with polyethylene glycol (PEG, M 21.5 kDa) was conducted. A method for preparation of PEG-filgrastim designed for the development and scaling-up of the technological process of production was described. Modification of proteins with PEG was performed by selective covalent attachment of the molecule alpha-methyl-PEG-propionaldehyde to the alpha-amino group of the N-terminal methionine amino acid residue of the recombinant GCSF. The conditions of the reaction, which provide the desired product yield at least 85% of the total protein, also high protein concentration in the reaction mixture (more than 9 mg/mL) and reduce consumption of PEG in terms of terminal alpha-amino group of the protein was chosen. The data of RP HPLC and MALDI-mass spectrometry showed that the produced drug modified by the N-terminal residue and contains no more than 10% of products with a high degree of modification.

Synthesis of a diaminopropanoic acid-based nucleoamino acid and assembly of cationic nucleopeptides for biomedical applications

In this work, we report a synthetic approach to a Fmoc-protected nucleoamino acid, based on L-diaminopropanoic acid, carrying the DNA nucleobase on the alpha-amino group by means of an amide bond, suitable for the solid-phase synthesis of novel nucleopeptides of potential interest in biomedicine. After ESI-MS and NMR characterization this building block was used for the assembly of a thymine-functionalized nucleopeptide, composed of nucleobase-containing L-diaminopropanoic acid moieties and underivatized L-lysine residues alternated in the backbone. Circular dichroism studies performed on the cationic nucleopeptide and adenine-containing DNA and RNA molecules suggested that the thymine-containing peptide is able to interact with both DNA and RNA. In particular, a significant conformational variation in the RNA structure was suggested by CD studies. Human serum stability assays were also conducted on the cationic nucleopeptide, which was found to be highly resistant to enzymatic degradation.

Influence of a gamma amino acid on the structures and reactivity of peptide a3 ions

Collision-induced dissociation of protonated AGabaAIG (where Gaba is gamma-amino butyric acid, NH2–(CH2)3–COOH) leads to an unusually stable a3 ion. Tandem mass spectrometry and theory are used here to probe the enhanced stability of this fragment, whose counterpart is not usually observed in CID of protonated peptides containing only alpha amino acids. Experiments are carried out on the unlabelled and 15N-Ala labeled AGabaAIG (labeled separately at residue one or three) probing the b3, a3, a3-NH3 (a3*), and b2 fragments while theory is used to characterize the most stable b3, a3, and b2 structures and the formation and dissociation of the a3 ion. Our results indicate the AGabaA oxazolone b3 isomer undergoes head-to-tail macrocyclization and subsequent ring opening to form the GabaAA sequence isomer while this chemistry is energetically disfavored for the AAA sequence. The AGabaA a3 fragment also undergoes macrocyclization and rearrangement to form the rearranged imine–amide isomer while this reaction is energetically disfavored for the AAA sequence. The barriers to dissociation of the AGabaA a3 ion via the a3→b2 and a3→a3* channels are higher than the literature values reported for the AAA sequence. These two effects provide a clear explanation for the enhanced stability of the AGabaA a3 ion.