Label-free, simultaneous quantification of starch, protein and triacylglycerol in single microalgal cells

Table 1 The 13 reference Raman bands that are highly correlated with starch, protein and TAG contents in Chlamydomonas reinhardtii CC124 during the process of nitrogen depletion

Component	Raman bands (cm⁻¹)	R ²	Assignments
Starch	478	0.6976	C–C–C deformation
	865	0.9300	C–C–H and C–O–C deformations
	940	0.8895	C–O stretching; C–O–C and C–O–H deformation; α-helix C–C backbone
	1049	0.8308	C–O and C–C stretching; C–O–H deformation
	1127	0.8862	C–O and C–C stretching; C–O–H deformation
Protein	1003	0.7638	Phenylalanine ring breath; carotene C–H bending
	1586	0.9105	Phenylalanine
	1610	0.8850	C=O stretching of protein amide I; –NH₂
Triacylglycerol^a	972	0.8438	ν (C–C) wagging
	1265	0.8783	Alkyl=C–H
	1441	0.8974	Alkyl C–H₂ bend
	1658	0.7721	Allyl C=C stretches
	2851	0.8902	C–H₂, C–H₃ asymmetric and symmetric stretches

Correlation coefficient (R ²) between averaged intensity of the Raman bands derived from SCRS and the corresponding quantitative trait shown
^aCorrelation coefficients calculated based on post-1d datasets, since the TAG content of C. reinhardtii cells during the first day of nitrogen depletion was very low