The phrase "adjacent portion of" is correct and usable in written English.
It can be used to describe a part of something that is next to or adjoining another part.
Example: "The adjacent portion of the wall showed signs of water damage."
Alternatives: "neighboring section of" or "contiguous area of".
When PFN1 is co-crystalized with actin, the N-terminus of the helix and adjacent portion of the loop sit in a surface pocket of actin.
The sparsely populated High Plains region, encompassing the Panhandle and a small adjacent portion of northwestern Oklahoma, offers a marked contrast.
Valois, historic region of France that gave its name to the second line of the Capetian dynasty; it corresponds to the southeastern quarter of the modern département of Oise, with an adjacent portion of Aisne.
And like the 1960 Chilean quake, the Indonesian quake increased stresses nearby: it was followed, just three months later, by an 8.7-magnitude quake on an adjacent portion of the fault zone.
It extends from the extreme southeastern portion of Andhra Pradesh into the adjacent portion of Tamil Nadu state and has a length of about 30 miles (50 km) and a width of 3 to 10 miles (5 to 16 km).
Contrast-enhanced computed tomography (CT) revealed abnormal thickening of the gallbladder wall, which appeared to invade the adjacent portion of the liver.
Some layers also cover adjacent portions of North Africa and the Middle East.
Explorations in northern Canada and adjacent portions of Greenland and Alaska [map] / James White.
The UES is composed of the inferior pharyngeal constrictor, the cricopharyngeus, and adjacent portions of the cervical esophagus.
G. Woolworth Colton's railroad, township & distance map of New England : with adjacent portions of New York, Canada & New Brunswick.
In 1972 Kuala Lumpur was designated a municipality, and in 1974 this entity and adjacent portions of surrounding Selangor state became a federal territory.
