Detection of 4-hydroxy-2-nonenal adducts of turkey and chicken myoglobins using mass spectrometry

4-Hydroxy-2-nonenal (HNE), an unsaturated aldehyde generated by peroxidation of polyunsaturated fatty acids, is highly reactive and destabilizes myoglobin (Mb) redox state, affecting meat colour. Our objective was to characterise the adduction of HNE to turkey and chicken Mbs using tandem mass spectrometry (MS/MS). Turkey and chicken oxymyoglobins (OxyMbs) were incubated with HNE at 25 °C, pH 5.8 or 7.4. MetMb formation was greater in the presence of HNE than controls (p < 0.05). Electrospray ionisation-Q-TOF mass spectrometry of HNE-reacted Mbs revealed covalent adduction of HNE to both turkey and chicken Mbs via Michael addition. LC–ESI-MS/MS of chicken Mb reacted with HNE identified covalent adduction of histidine (His) residues 64 and 93 at pH 7.4, whereas at pH 5.8 only His 64 was adducted. These results suggest that HNE accelerates chicken OxyMb oxidation in vitro by covalent modification at histidine residues.     

Rapid coverage of regions of interest for environmental monitoring

Intelligent Service Robotics - We present a framework for rapidly determining regions of interest (ROIs) from an unknown intensity distribution, particularly in radiation fields. The vast majority...     

Assessing Low Redox Stability of Myoglobin Relative to Rapid Hemin Loss from Hemoglobin

Bovine myoglobin (Mb) auto‐oxidized 11‐fold faster at pH 5.7 compared to bovine hemoglobin (Hb). Replacement of Ser(F7) in bovine Mb with positively charged or large apolar residues decreased auto‐oxidation rates (2‐ to 4‐fold) in comparison with wild‐type Mb (P < 0.05). However, the same substitutions increased hemin loss rate (15‐ to 28‐fold), indicating that hydrogen bonding between Ser(F7) and the heme‐7‐propionate is critical for stabilizing protoporphyrin in the globin. The anchoring of Ser(F7) to the heme‐7‐propionate in the proximal pocket of Mb is suggested to expose the distal pocket to solvent molecules that accelerate auto‐oxidation. The rate of hemin loss from metHb at pH 5.7 was 68‐fold faster compared to metMb. The ability of Ser(F7) and His(FG3) in Mb to form stabilizing contacts with the heme‐7‐propionate maintains hemin within the globin whereas Leu(F7) and Leu(FG3) of Hb cannot form stabilizing contacts which results in low hemin affinity. MetHb promoted lipid oxidation more effectively in washed muscle at pH 5.7 compared to metMb (P < 0.05). The greater ability of bovine metHb to promote lipid oxidation is likely due to its enhanced rate of hemin dissociation compared to bovine metMb.     

FE Modeling of FRP-Repaired Planar Concrete Elements Subjected to Monotonic and Cyclic Loading

In this paper, a nonlinear finite-element model is developed for the analysis of plane stress members, such as RC beams and walls, strengthened either unidirectionally or bidirectionally with fiber-reinforced polymer (FRP) composites and subjected to either monotonic or cyclic loading. The model takes into account the effects of the bonded interface between the FRP and concrete while allowing slippage in each direction. A two-dimensional membrane contact element is developed to model the effects of local bond-slip with debonding failure between the FRP and concrete capable of being captured. The model has been incorporated into a finite-element program for the analysis of RC members subject to plane stress with verification against test data of FRP-strengthened RC joints, beams, and walls. The numerical results show good agreement with the experimental data for both load-displacement responses and for the overall failure mechanisms.     

The effects of HNE on ovine oxymyoglobin redox stability in a microsome model

The effect of 4-hydroxy-2-nonenal (HNE), a secondary lipid oxidation product, on ovine myoglobin (Mb) redox stability was investigated. HNE increased oxymyoglobin (OxyMb) oxidation under all pH/temperature conditions studied. Mono-, di- and tri-HNE adducts were detected by ESI-Q-TOF MS analysis. Sites of adduction, His 120, His 25 and His 65, were determined by ESI–CID–MS/MS analysis. The relationship between ovine Mb (with/without HNE) and lipid oxidation was also studied in a microsome model in the presence of α-tocopherol. Surprisingly, preincubation of Mb with HNE did not affect subsequent Mb redox stability in the microsome model (P < 0.05). Microsomes with elevated concentrations of α-tocopherol delayed lipid and Mb oxidations relative to controls. HNE-treated ovine Mb caused greater lipid oxidation compared to control ovine Mb in control microsomes (P < 0.05). This study demonstrated an interaction between ovine Mb oxidation and lipid oxidation.     

Effects of lactate on ground lamb colour stability and mitochondria-mediated metmyoglobin reduction

Previous research suggests that lactate’s colour stabilizing effect in beef is through NADH production and antioxidant activity. However, no research has assessed lactate’s role in lamb colour. Hence, our objectives were to evaluate the effects of lactate on lamb surface discolouration, oxygen consumption, and metmyoglobin reduction. In experiment 1, lactate (final meat concentration = 2.5% w/w) was added to ground lamb (n = 20 carcasses) and patties were stored for 3 days at 1 °C in PVC packaging. Surface colour (CIE L∗ and a∗) and metmyoglobin reducing activity of ground lamb patties were measured. Addition of lactate improved colour stability and metmyoglobin reducing activity (p < 0.05). In experiment 2, mitochondria were isolated from lamb longissimus muscle (n = 3). Addition of lactate–LDH–NAD to mitochondria resulted in significant oxygen consumption and metmyoglobin reduction compared with mitochondrial controls without lactate (p < 0.05). Lactate can improve the colour stability of lamb, possibly by increasing metmyoglobin reducing activity.