We always remember the most important research in our life since we find it was the critical step toward successful academic and scientific career. For me it was the first paper published in 1991 while I was a student in PhD program. Actually, it was published in a very important international journal as shown below. I do not know if you remember that important paper you published?
Zakaria Al-Hassan (Al-Qodah), Viara Ivanova, Elena Dobreva, Ivan Penchev ., Non-porous magnetic supports for cell immobilization, Journal of fermentation and bioengineering 71 (2), 114-117, 1991