First, the Definition of Gluten:

Gluten is a protein found in Rye, Wheat, Oats, Barley & Triticale. ("Gliadin" is part of the gluten structure. Gliadin is present in varying amounts in these grains. The combination of gliadin and glutenen makes gluten.) This protein gives structure, elasticity and sponginess.

Gluten Flour:

Also called "vital wheat gluten flour", "instant gluten flour", "pure gluten flour", and "vital wheat gluten" depending on vendor and manufacturer. This is flour with the starch and bran removed. Gluten is the natural protein in the wheat endosperm which, when combined with water, forms a taffy-like dough. This retains the gas and steam from baking. Bob's Red Mill vital wheat gluten flour – and any other brand of vital wheat gluten flour (such as Hodgson Mill) is 75 to 80% protein. This yields approximately 24 grams of carbohydrate per cup. The process of keeping mostly the protein constituents of the wheat and very little of the starch makes this product useful in low-carbohydrate baking and cooking.

I have never tried it but am told it is absolutely dreadfull!