Biology subjects

Jafarpour, A.

Publications and source records attributed to Jafarpour, A..

5 recordsLinked to original sources

bioRxiv2022

Bioinformatically predicted emulsifying peptides and potato protein hydrolysate improves the oxidative stability of microencapsulated fish oil

The aim of this study was to investigate the potential of potato proteins and peptides as emulsifiers in the microencapsulation of fish oil by spray-drying. Microcapsules were produced using a potato protein extract, and fractions enriched in patatin and protease inhibitors. Furthermore, bioinformatically predicted emulsifier peptides from abundant potato proteins and a hydrolysate, obtained through targeted proteolysis of the extract, were investigated. During 28 days of storage at 25{degrees}C, peptides and hydrolysate exhibited better emulsifying properties and higher encapsulation efficiencies compared to native proteins and sodium caseinate. Significant differences (p < 0.05) were observed in the peroxide value (PV) and secondary volatile oxidation products between the microcapsules produced with peptides and native proteins. Microcapsules produced with peptides and hydrolysate showed the highest oxidative stability, not exceeding a PV of 10 meq/kg oil, and with concentrations of volatiles below the odor threshold in oil for five of the six studied compounds. These results show the emulsifying potential of potato peptides and hydrolysate for use in microencapsulation of hydrophobic bioactive ingredients such as fish oil.

bioengineering↗

bioRxiv2022

Multiple memory systems for efficient temporal order memory

We report the distinct contribution of multiple memory systems to retrieval of the temporal order of events. The neural dynamics related to retrieval of movie scenes revealed that recalling the temporal order of close events elevates hippocampal theta power, like that observed for recalling close spatial relationships. In contrast, recalling far events elevates beta power in the orbitofrontal cortex, reflecting recall based on the overall movie structure.

neuroscience↗

bioRxiv2022

Targeted hydrolysis of native potato protein: A novel route for obtaining hydrolysates with improved interfacial properties

Peptides and protein hydrolysates are promising alternatives to substitute chemical additives as functional food ingredients. In this study, we present a novel approach for producing a potato protein hydrolysate with improved emulsifying and foaming properties by data-driven, targeted hydrolysis. Based on previous studies, we selected 15 emulsifier peptides derived from abundant potato proteins, which were clustered based on sequence identity. Through in silico analysis, we determined that from a range of industrial proteases (Neutrase (Neut), Alcalase (Alc), Flavorzyme (Flav) and Trypsin (Tryp)), Tryp was found more likely to release peptides resembling the target peptides. After applying all proteases individually, hydrolysates were assayed for in vitro emulsifying and foaming properties. No direct correlation between degree of hydrolysis and interfacial properties was found. Tryp produced a hydrolysate (DH=5.4%) with the highest (P<0.05) emulsifying and foaming abilities, good stabilities, and high aqueous solubility. Using LC-MS/MS, we identified >10,000 peptides in each hydrolysate. Through peptide mapping, we show that random overlapping with known peptide emulsifiers is not sufficient to quantitatively describe hydrolysate functionality. While Neut hydrolysates had the highest proportion of peptides with target overlap, they showed inferior interfacial activity. In contrast, Tryp was able to release specifically targeted peptides, explaining the high surface activity observed. While modest yields and residual unhydrolyzed protein indicate room for process improvement, this work shows that data-driven, targeted hydrolysis is a viable, interdisciplinary approach to facilitate hydrolysis design for production of functional hydrolysates from alternative protein sources.

biochemistry↗

bioRxiv2019

Event segmentation reveals working memory forgetting rate

We encounter the world as a continuous flow and effortlessly segment sequences of events into episodes. This process of event segmentation engages working memory (WM) for tracking the flow of events and impacts subsequent memory accuracy. WM is limited in how much information is retained (i.e., WM capacity) and for how long the information is retained (i.e., forgetting rate). It is unclear which aspect of WM limitations affects event segmentation. In two separate experiments with multiple tasks, we estimated participants WM capacity and forgetting rate in a dynamic context and evaluated their relationship to event segmentation. The results across tasks show that individuals who reported more movie segments than others (fine-segmenters) have a faster decaying WM. A separate task assessing long-term memory retrieval reveals that the coarse-segmenters have better recognition of temporal order of events in contrast to the fine-segmenters who performed better at free recall. The findings show that event segmentation employs dissociable memory strategies and depends on how long information is retained in WM.

neuroscience↗

bioRxiv2018

Orbitofrontal cortex, dorsolateral prefrontal cortex, and hippocampus represent the magnitude of event saliency

Two primary functions attributed to the hippocampus and prefrontal cortex network are retaining the temporal and spatial associations of events and detecting deviant events. It is, however, unclear how these two functions converge onto one mechanism. Here, we tested whether increased activity with perceiving salient events is a deviant detection signal or contains information about the event associations by reflecting the magnitude of deviance (i.e., event saliency). We also tested how the deviant detection signal is affected by the degree of anticipation. We studied regional neural activity when people watched a movie that had varying saliency of a novel or an anticipated flow of salient events. Using intracranial electroencephalography from ten patients, we observed that high-frequency activity (50-150 Hz) in the hippocampus, dorsolateral prefrontal cortex (dorsolateral PFC), and medial orbitofrontal cortex (OFC) tracked event saliency. We also observed that medial OFC activity was stronger when the salient events were anticipated than when they were novel. These results suggest that dorsolateral PFC and medial OFC, as well as the hippocampus, signify the saliency magnitude of events, reflecting the hierarchical structure of event associations.

neuroscience↗