Johan Ariff Mohtar
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Preferred name
Johan Ariff Mohtar
Official Name
Mohtar, Johan Ariff
Alternative Name
Mohtar, J. A.
Mohtar, Johan Ariff
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Scopus Author ID
56119103200
Researcher ID
FMF-3163-2022

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Structural and mechanical variations of major ampullate silk spun by Malaysian Nephila pilipes spider

2023 , Nurul Ain Harmiza Abdullah , Ku Syahidah Ku Ismail , Khadijah Hanim Abdul Rahman , Saiful Bahari Bakarudin , Johan Ariff Mohtar , Mohd. Mustafa Al Bakri Abdullah , Boon Yin Khoo

Major ampullate (MA) silk is a natural biomaterial, spun by spiders with exceptional mechanical characteristics. Most researchers who studied MA silk structure were primarily interested in the properties of a dragline thread that protrudes from the spider’s spigot when being chased by its predator. Apart from the dragline, the MA silk fibers may also be found in three pivot threads of the orb web known as the mooring, framework, and radial. However, it is currently uncertain whether the MA silk in these threads has properties similar to the dragline thread. Thus, this work attempted to compare the properties of MA silk fiber in the mooring, framework, radial, as well as the dragline threads. The MA silk fibers in mooring thread were found to exhibit significant quantity of MA fibers (12 ± 5.0 fibers per thread), thickness diameter (11.7 ± 0.6 μm), and supercontraction effect (high swelling ratio of 18.6), with an outstanding combination of strength (4464 MPa) and toughness (875 MJ/m3), outperforming the dragline thread. Positive correlation was found between the diameter of MA fibers and supercontraction effect and between the number of MA fibers and tensile strength. These findings might be modeled as a fundamental guide in silk spinning for future synthetic MA silk fiber development with extraordinary mechanical performance.

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Induction of Apoptosis of Melanoma Skin Cancer Cells by Atmospheric Plasma Jet

2023-01-01 , Abdullah Z. , Siti Khadijah Za'aba , Mohammad Taufiq Mustaffa , Saidin N.A. , Johan Ariff Mohtar

The apoptotic effect is an important issue in cancer treatment. To achieve this goal, an atmospheric plasma jet (APJ) was set up for use on cultured cells in a temperature-controlled environment. Melanoma skin cancer and normal skin cells were targeted with this device. Following a 5 s plasma exposure, there was a 67% cell death in melanoma skin cancer cells compared with 5% in normal skin cells as measured after 24 h. When the treatment time was increased to 15, a 98% cell death was reported for melanoma skin cancer cells, which was 80% greater than the cell death in normal skin cells. Our observations further indicate that this preferential cell death is largely due to apoptosis. It shows that an APJ is a selective device in the induction of apoptosis in cancer and normal cells. APJ was shown to affect cells directly and indirectly through a plasma-activated medium (PAM). In direct treatment, cells were exposed to plasma while suspended in a culture medium, and in indirect treatment, cells were added to a culture medium previously acti-vated by plasma treatment. PAM was able to induce cell death 29% higher than direct treatment as measured after 48 h. The depth of the growth medium is also one of the factors in the induction of apoptosis of cancer cells. The growth medium protected the cells from plasma exposure. The result shows that the low level (0 mm) of growth medium will cause more cell death as compared with the high level (2 mm) of growth medium. Apoptotic behavior of skin cancer cells was de-duced from the fact that treated cells initially grew and died 12 h following the treatment, while untreated cells continued to grow and proliferate.

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DNA barcoding of common Malaysia spiders using the Cytochrome Oxidase I (COI) gene

2020 , Ahmad Mukhlis Abdul Rahman , Kek Chian Koay , Johan Ariff Mohtar , Anwardi Jamil , Mohd Mushahril Abdul Shukor , Nurul Ain Harmiza Abdullah

For the last twenty years, many newly described spiders were collected from Malaysia and in fact, more than 11,000 species were recorded in Peninsular Malaysia as well as in Sabah and Sarawak states. Scientists have put an immense effort on untangling the spider biology from its physical structure and behavior to silks and venoms. However, working with spiders is impeded by the difficulties in species identification via solely morphological methods. Thus, DNA barcoding is an alternative technique that employs standard fragment to facilitate species identification. Isolation of genomic DNA from three Malaysian spiders were performed using NucleoSpin® DNA insect extraction kit. Amplification of reference mitochondrial cytochrome oxidase I (COI) gene employing PCR with two set of primers followed by the DNA sequencing and validation through phylogenetic analysis were carried out. The commercial extraction kit was effective for the recovery of good quality of intact genomic DNA band as indicated by the integrity analysis. Both set of primers successfully amplified 100% of the samples with approximately 600 – 700 bp of PCR products. The obtained sequences (610 bp to 692 bp) were compared with the sequences available in Gene Bank. BLAST and phylogenetic analysis revealed that the analyzed individual samples belong to Nephila pilipes, Neoscona nautica and Crossopriza lyoni, respectively. Phylogenetic analysis provided unique insight into the evolutionary relationship of each analyzed sample. This study aids in an accurate identification of the selected local spider species at molecular level using the COI gene.

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