A fractal scaling analysis of the SARS-CoV-2 genome sequence

An approach based on fractal scaling analysis to characterize the organization of the SARS-CoV-2 genome sequence was used. The method is based on the detrended fluctuation analysis (DFA) implemented on a sliding window scheme to detect variations of long-range correlations over the genome sequence regions. The nucleotides sequence is mapped in a numerical sequence by using four different assignation rules: amino-keto, purine-pyrimidine, hydrogen-bond and hydrophobicity patterns. The originally reported sequence from Wuhan isolates (Wuhan Hu-1) was considered as a reference to contrast the structure of the 2002-2004 SARS-CoV-1 strain. Long-range correlations, quantified in terms of a scaling exponent, depended on both the mapping rule and the sequence region. Deviations from randomness were attributed to serial correlations or anti-correlations, which can be ascribed to ordered regions of the genome sequence. It was found that the Wuhan Hu-1 sequence was more random than the SARS-CoV-1 sequence, which suggests that the SARS-CoV-2 possesses a more efficient genomic structure for replication and infection. In general, the virus isolated in the early 2020 months showed slight correlation differences with the Wuhan Hu-1 sequence. However, early isolates from India and Italy presented visible differences that led to a more ordered sequence organization. It is apparent that the increased sequence order, particularly in the spike region, endowed some early variants with a more efficient mechanism to spreading, replicating and infecting. Overall, the results showed that the DFA provides a suitable framework to assess long-term correlations hidden in the internal organization of the SARS-CoV-2 genome sequence.

Note. Mesquite gum (Prosopis juliflora) and maltodextrin blends as wall materials for spray-dried encapsulated orange peel oil / Nota. Mezclas de goma de mezquite (Prosopis juliflora) y maltodextrina como material encapsulante de aceite esencial de naranja secado por aspersion

The performance of mesquite gum and maltodextrin mixtures in the preparation of encapsulated orange peel oil was evaluated. Emulsions of orange peel oil were prepared using an emulsifier for mulated with 1:4, 2:3, 3:2 and 4:1 (w/w) ratios of maltodextrins:mesquite gum solutions (30 %) and spray dried with a laboratory unit. The highest rate of oil encapsulation, 84.6 %, was achieved with the 3:2 ratio of maltodextrin:mesquite. Results showed no statistical difference ( p ≤ .05) in flavor intensity between samples prepared with all mesquite:maltodextrins mixtures and microcapsules made with gum Arabic only as wall material. The mixtures provided acceptable oil retention and could be an economic alternative to conventional encapsulating agents.