Final answer:
Histone H1 is the nucleosome protein associated with the linker DNA between nucleosomes, helping in the compaction of chromatin.
Step-by-step explanation:
The nucleosome protein found in the linker DNA between nucleosomes and not part of the nucleosome core is histone H1. The core nucleosome consists of an octamer of histones, which includes two copies each of histone H2A, histone H2B, histone H3, and histone H4. This core is where DNA wraps around approximately 1.65 turns. In contrast, histone H1 is involved in the higher-order structure and is located on the outside of the nucleosome core, linking DNA to the nucleosome. Histone H1 thus helps to compact the chromatin into higher order structures necessary for the organized packing within the nucleus.