Specificity means {HEAD ~ the ability} of the membrane to selectively bind or filter certain species from {TAIL ~ complex mixtures} 
Specificity means { HEAD ~ the ability } of the membrane to selectively bind or filter certain species from { TAIL ~ complex mixtures }
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL